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This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0/).

This paper proposes a synthesis of the taxonomy, phylogeny, palaeogeographic distribution, regional biostratigraphy, and palaeobiogeographic faunal development of Carboniferous fusuline foraminifers. They appeared in the latest Tournaisian and comprised a small-sized, morphologically conservative taxonomic group during the Mississippian. Fusulines became larger and prevailed in Pennsylvanian foraminiferal assemblages. Carboniferous fusulines consist of Ozawainellidae, Staffellidae, Schubertellidae, Fusulinidae, and Schwagerinidae, in which 95 genera are considered as valid taxonomically. Upsizing their shells throughout the Pennsylvanian is likely related to symbiosis with photosynthetic microorganisms, which was accelerated by the acquisition of a keriothecal wall in Late Pennsylvanian schwagerinids. Regional fusuline succession data from 40 provinces provide a refined biostratigraphy, enabling zonation and correlation with substage- or higher-resolution precision in the Pennsylvanian. Their spatio-temporal faunal characteristics show that fusulines had a cosmopolitan palaeobiogeographic signature in Mississippian time, suggesting unrestricted faunal exchange through the palaeoequatorial Rheic Ocean. After the formation of Pangaea, Pennsylvanian fusulines started to show provincialism, and their distributions defined the Ural–Arctic Region in the Boreal Realm, Palaeotethys, Panthalassa, and North American Craton regions in the Palaeoequatorial Realm, and Western Gondwana and Eastern Peri-Gondwana regions in the Gondwana Realm. The Western Palaeotethys and East European Platform Subregions maintained higher generic diversity throughout the Pennsylvanian.

Fusulines are literally defined as a Carboniferous–Permian multi-chambered benthic foraminiferal group, which essentially possesses calcareous microgranular planispiral tests. Their size is from less than 1 mm (minute in size) to over several centimetres (gigantic), and the test shape is also variable, such as discoidal, lenticular, spherical, oval, fusiform, elongate fusiform, and cylindrical. They comprised the first group of larger foraminifers that appeared in the history of foraminiferal evolution (e.g. BouDagher-Fadel 2008; Simmons 2020). Fusulines are usually found in shallow marine limestone formed in tropical/subtropical environments. Phylogenetically, they comprise a large, monophyletic group and first appeared in the latest Tournaisian of the earliest Carboniferous (Early Mississippian). After flourishing nearly 100 million years, fusulines became extinct at the end of the Permian, together with many other Paleozoic-type shallow-marine dwellers. Thus, this microfossil group is one of well-known victims involved in the disaster of the P–T boundary mass extinction.

The Carboniferous Period corresponds to the early half of the entire evolutionary history of the fusuline foraminifers. In the Mississippian, they all were just conservative small taxa among the entire foraminiferal fauna. Fusulines from that interval exhibit less morphological diversity compared to coeval non-fusuline foraminifers, and almost all of them had lenticular shells with homogeneous or only weakly differentiated spirotheca. After the Mid-Carboniferous boundary, the increase of shell length (coiling axis) in association with the formation of conspicuous skew coiling in the early volutions and the resultant upsizing of shells led to a new clade called the Fusulinidae, which flourished over the Early and Middle Pennsylvanian. Fusulines became a major part of the biota that inhabited various shallow-marine environments in the tropical/subtropical belt. After the rapid decline of this family at around the Middle–Late Pennsylvanian boundary, the family Schwagerinidae arose, and they dominated the foraminiferal fauna during the rest of the Carboniferous and much of the Permian. The phylogenetic evolutionary history of Carboniferous fusulines briefly outlined here is the result of a vast amount of palaeontological and biostratigraphic studies carried out during nearly two centuries, which almost completely overlap the history of research on Carboniferous chronostratigraphy (Lucas et al. 2021). These studies done over a long period of time in various areas of the world also established a robust biostratigraphic framework using fusulines for regional and global correlation.

In this paper, after briefly introducing a chronostratigraphic framework generally used in this geological period, Carboniferous palaeogeography is investigated first. Two palaeomaps in Mississippian and Pennsylvanian time slices are proposed as base maps to understand Carboniferous fusuline distribution and palaeobiogeography, by gathering information from global and regional palaeogeographical studies as well as detailed regional palaeotectonic investigations. As a result, six palaeobiogeographical regions in three fundamental realms (Boreal, Palaeoequatorial and Gondwana) are recognized in Pennsylvanian time, whereas in the Mississippian fusulines generally show more cosmopolitan palaeobiogeographical distributions. Then, all the fusuline genera so far reported from the Carboniferous are scrutinized to clarify their taxonomic validity and phylogenetic relationship. Up to the present, Carboniferous fusulines have been reported from the Arctic region in the north (80°05′N at Ward Hunt Island; Thompson 1961) to Patagonia in the south (50°22′S at Isla Guarello in the Madre de Dios Archipelago; Douglass and Nestell 1976), with more variable localities and sections of their abundant occurrences in the lower and middle latitudinal areas in the present-day geographical configuration. These are arranged into a total of 40 provinces, and regional fusuline successions in respective areas through the Carboniferous are carefully examined and summarized, while paying attention to their original palaeogeographical positions in Carboniferous time and, in particular, their regional palaeotectonic development after that. In the last section of this paper, a palaeobiogeographical faunal development of Carboniferous fusuline foraminifers over time is outlined, and the generic assemblage in each time segment is characterized.

Since the early part of the nineteenth century when Conybeare and Phillips (1822) first introduced this chronostratigraphic term for the typical coal-bearing succession in Britain, the stratigraphy and palaeontology of the Carboniferous System have been investigated in various areas of the world. In the late 1800s, several stages adopted today in the standard Carboniferous chronostratigraphic scheme, except for the Bashkirian and Kasimovian, were established in this geological system through studies in the Western Europe and Moscow areas, and by the mid-1900s the above-mentioned two stages were also brought into the Carboniferous basic subdivisions. There are three historical type regions where Carboniferous strata have been investigated intensively during nearly two centuries of research in view of chronostratigraphy and biostratigraphy; they are Western Europe, the Russian Platform, and North America (see compilation in Aretz et al. 2020 and Lucas et al. 2021). These regions have developed their own regional chronostratigraphic/chronologic units, some of which are now in global use to comprise the standard Carboniferous chronostratigraphic scale. At present, the Carboniferous System is formally subdivided into two subsystems, the Mississippian (Lower Carboniferous) and the Pennsylvanian (Upper Carboniferous) in which a total of seven ‘global’ stages are recognized (Fig. 1).

Fig. 1.

Chronostratigraphic framework of the Carboniferous mainly used in this study (adapted from Aretz et al., 2020). Abbreviations in chronostratigraphy: Miss./Mississip., Mississippian; Pennsyl., Pennsylvanian; L., Lower; M., Middle; U., Upper; low., lower; mid., middle; up., upper.

Fig. 1.

Chronostratigraphic framework of the Carboniferous mainly used in this study (adapted from Aretz et al., 2020). Abbreviations in chronostratigraphy: Miss./Mississip., Mississippian; Pennsyl., Pennsylvanian; L., Lower; M., Middle; U., Upper; low., lower; mid., middle; up., upper.

As for substages (subages) in the seven Carboniferous stages (ages), those shown in Figure 1 are primarily used in this study. They are based on subdivisions established in the type areas of the respective stages. For the Tournaisian and Visean, two substages in the former and three substages in the latter are recognized in ‘Dinantian’ sections of the type Namur–Dinant Basin in southern Belgium. These Belgian substages are strongly linked to the Mississippian Foraminiferal Zones (MFZ) established by Devuyst and Hance in Poty et al. (2006), which are known to have wide applicability and correlation potential in many Mississippian sections in Eurasia, although their utility potential in the type North American Mississippian is still challenging. Thus, this Western European subdivision has high utility to calibrate stratigraphic occurrences of Early Carboniferous fusulines, although they occur only in latest Tournaisian and younger strata. The four Serpukhovian substages were mainly derived from the regional chronostratigraphic subdivision of the Moscow Basin, with the supplemental Zapaltyubian substage originating from the corresponding Donets Basin succession, for the missing uppermost Serpukhovian interval in the type Moscow area. The subdivision of the Bashkirian is based on data from the South Urals where this stage is generally divided into six substages. The Tashastian of the upper Bashkirian was also spelled as the Tashastinian in some papers (e.g. Leven et al. 2006), which probably came from the term Tashastinsky Horizon (e.g. Semichatova et al. 1979). Herein the former spelling, Tashastian, is adopted, which is also used in Aretz et al. (2020), because of the name of the type area, Tashasty. In this study, I essentially follow the Bashkirian subdivision and substage names and definition used in Ivanova (2008), who described a detailed foraminiferal (mainly fusuline) succession of the entire Bashkirian of the Urals under this chronostratigraphic framework. For the remaining three Pennsylvanian stages, the Moscovian, Kasimovian, and Gzhelian, fundamental substage divisions established in the Moscow Syneclise, are widely used in Carboniferous fusuline studies. Following Alekseev et al. (2004), four substages in the Moscovian, three substages in the Kasimovian, and four substages in the Gzhelian are applied in this study. As in Figure 1, a conventional subdivision using adjectival lower/middle/upper (and early/middle/late as well) is also used in parallel with particular substage (subage) names as necessary.

The Carboniferous was the time of the formation of the supercontinent Pangaea, which resulted in the closure of the palaeoequatorial Rheic Ocean between the Laurussia (in the north) and Gondwana (in the south) continents at around the Mid-Carboniferous boundary. This significant plate-tectonic event strongly affected the distribution, dispersion, palaeobiogeography, and evolution of fusuline foraminifers. Especially in the Pennsylvanian after the formation of united Pangaea, fusulines started showing provincialism and formed several distinctive palaeogeographical regions, as a result of the then global continental configuration, especially related to the closure of the palaeoequatorial seaway.

In the following section in this study, I review the Carboniferous fusuline faunal successions along with the biostratigraphy of a total of 40 areas in the world, according to their palaeo(bio)geographical attributes. For illustrating the distribution (palaeopositions) of these fusuline-bearing areas and the extent of palaeobiogeographical domains, two palaeogeographical reconstruction maps at the Middle/Late Mississippian (c. 340–330 Ma) and Middle/Late Pennsylvanian (around 310 Ma) are prepared in this study (Fig. 2). These maps were adopted from Scotese (2001) and Domeier and Torsvik (2014), and slightly modified based mainly on Şengör et al. (1984) for the Mediterranean region, on Heubeck (2001) and Huang et al. (2018) for NE Asian blocks, on Ueno (2006) for the SE Asian blocks, on Colpron et al. (2007) and Colpron and Nelson (2009) for the western North American terranes, on Keppie (2004) for the Mexican terranes, and on Lawver et al. (2011) and Davydov (2016) for the northern polar region. During Mississippian time, fusulines did not show strong provincialism. They made up a more or less cosmopolitan fauna in generic composition, although the number of fusuline genera itself was still not many during this time interval. Fusulines were mainly distributed within the then lower to lower middle latitudes (Fig. 2a). After closing the palaeoequatorial Rheic Ocean at around the Mid-Carboniferous boundary, however, the unique Pangaean palaeogeography produced regional separation of fusuline faunas quickly. Some fusuline genera had restricted geographical distributions, and the faunal composition became differentiated accordingly.

Fig. 2.

Palaeogeography and fusuline palaeobiogeography in two time slices of the Carboniferous, with locations (locs 40) where fusuline faunal successions are described in this study. (a) Palaeogeographical map in Middle–Late Mississippian time (c. 340–330 Ma). (b) Palaeogeographical map in Middle–Late Pennsylvanian time (around 310 Ma), with subdivisions of fusuline palaeobiogeographical realms/regions. Base map adopted from Scotese (2001) and Domeier and Torsvik (2014), and slightly modified based on Şengör et al. (1984) for the Mediterranean region, Heubeck (2001) and Huang et al. (2018) for NE Asian blocks, Ueno (2006) for SE Asian blocks, Colpron et al. (2007) and Colpron and Nelson (2009) for western North American terranes, Keppie (2004) for Mexican terranes, and Lawver et al. (2011) and Davydov (2016) for northern polar region. The Eastern Peri-Gondwanan Region in the Middle/Late Pennsylvanian palaeogeographical reconstruction map (b) includes provinces of the future Gondwanan Tethyan Region in the Permian by Zhang and Wang (2018). 1: Western North American terranes (1a: insular terranes derived from the Arctic region, 1b: several Intermontane terranes once detached from ancestral cratonic North America and developed as an island arc system in Pennsylvanian time). Note that the Panthalassan Cache Creek Terrane is not included in these terranes; 2: Yukon Territory; 3: Arctic Alaska; 4: Arctic Canada (Canadian Arctic Archipelago); 5: Greenland; 6: Taimyr; 7: Barents shelf; 8: Timan–Pechora; 9: Urals; 10: Moscow Syneclise; 11: Kazakhstan Block; 12: Central Asia (Tianshan and Darvaz); 13: Precaspian Basin; 14: Donets Basin; 15: Carnic Alps; 16: Central and Western European basins; 17: Cantabrian Mountains; 18: Maritimes Basin in eastern North America; 19: Northern Africa (Maghreb); 20: Apulian Platform and Variscan relicts in the Dinarides; 21: Turkey; 22: Iran; 23: Tarim Basin; 24: Eastern Tianshan; 25: Mongolian Block; 26: North China (including the Korean Peninsula); 27: Primorye; 28: Japan; 29: South China; 30: Indochina; 31: Mid-oceanic Palaeotethys; 32: Canadian Cordillera; 33: intracratonic basins in the US; 34: Mexico; 35: Mid-oceanic Panthalassa (35a: Akiyoshi; 35b: Yayamadake/Futagoyama; 35c: Cache Creek); 36: Southern Patagonia; 37: South American basins; 38: Sibumasu and Baoshan blocks (future Cimmerian continent); 39: Australia; 40: Timor.

Fig. 2.

Palaeogeography and fusuline palaeobiogeography in two time slices of the Carboniferous, with locations (locs 40) where fusuline faunal successions are described in this study. (a) Palaeogeographical map in Middle–Late Mississippian time (c. 340–330 Ma). (b) Palaeogeographical map in Middle–Late Pennsylvanian time (around 310 Ma), with subdivisions of fusuline palaeobiogeographical realms/regions. Base map adopted from Scotese (2001) and Domeier and Torsvik (2014), and slightly modified based on Şengör et al. (1984) for the Mediterranean region, Heubeck (2001) and Huang et al. (2018) for NE Asian blocks, Ueno (2006) for SE Asian blocks, Colpron et al. (2007) and Colpron and Nelson (2009) for western North American terranes, Keppie (2004) for Mexican terranes, and Lawver et al. (2011) and Davydov (2016) for northern polar region. The Eastern Peri-Gondwanan Region in the Middle/Late Pennsylvanian palaeogeographical reconstruction map (b) includes provinces of the future Gondwanan Tethyan Region in the Permian by Zhang and Wang (2018). 1: Western North American terranes (1a: insular terranes derived from the Arctic region, 1b: several Intermontane terranes once detached from ancestral cratonic North America and developed as an island arc system in Pennsylvanian time). Note that the Panthalassan Cache Creek Terrane is not included in these terranes; 2: Yukon Territory; 3: Arctic Alaska; 4: Arctic Canada (Canadian Arctic Archipelago); 5: Greenland; 6: Taimyr; 7: Barents shelf; 8: Timan–Pechora; 9: Urals; 10: Moscow Syneclise; 11: Kazakhstan Block; 12: Central Asia (Tianshan and Darvaz); 13: Precaspian Basin; 14: Donets Basin; 15: Carnic Alps; 16: Central and Western European basins; 17: Cantabrian Mountains; 18: Maritimes Basin in eastern North America; 19: Northern Africa (Maghreb); 20: Apulian Platform and Variscan relicts in the Dinarides; 21: Turkey; 22: Iran; 23: Tarim Basin; 24: Eastern Tianshan; 25: Mongolian Block; 26: North China (including the Korean Peninsula); 27: Primorye; 28: Japan; 29: South China; 30: Indochina; 31: Mid-oceanic Palaeotethys; 32: Canadian Cordillera; 33: intracratonic basins in the US; 34: Mexico; 35: Mid-oceanic Panthalassa (35a: Akiyoshi; 35b: Yayamadake/Futagoyama; 35c: Cache Creek); 36: Southern Patagonia; 37: South American basins; 38: Sibumasu and Baoshan blocks (future Cimmerian continent); 39: Australia; 40: Timor.

In Pennsylvanian time, three basic palaeobiogeographical realms can be recognized, which more or less reflected palaeolatitudinal climatic belts at that time; they are the Boreal, Palaeoequatorial, and Gondwana realms, corresponding broadly to the northern temperate/subtropical, equatorial tropical/subtropical, and southern temperate palaeoclimatic belts (Fig. 2b). The Boreal Realm consists of the Ural–Arctic Region, which corresponds to the Arctic and the East European Platform (Russian Platform). The Palaeoequatorial Realm can be subdivided into the Palaeotethys Region (including the eastern Pangaean shelves and the mid-oceanic Palaeotethys), the North American Craton Region (interior basins of western Pangaea), and the Panthalassa Region (corresponding to the pelagic realm of the Panthalassa Ocean). The Gondwana Realm is composed of the Western Gondwana Region (interior basins of South America) and the Eastern Peri-Gondwana Region (northern part of eastern Gondwana facing the Palaeotethys). The former region has been often combined with the palaeoequatorial North American Craton Region to form the composite ‘Midcontinent–Andean Realm’, which extended from the northern lower/middle to southern higher middle palaeolatitudes, in some previous studies (e.g. Ross and Ross 1985; Ross 1992). Due to their different fusuline faunal development and taxonomic diversity, these two are better separated into different palaeobiogeographical realms and regions in this study. The Eastern Peri-Gondwana Region was not very conspicuous palaeobiogeographically in terms of fusuline occurrence during the Carboniferous. But, it includes some palaeobiogeographical provinces, such as the Sibumasu and Baoshan in today's SE Asia and Yunnan, which eventually developed into a peculiar fusuline palaeobiogeographical domain called the Gondwanan Tethyan Region during the Permian (Zhang and Wang 2018). In summary, six palaeogeographical regions in total are recognized during the Pennsylvanian in this study. In them, the Ural–Arctic and Palaeotethys regions can be further separated into two subregions; the Arctic and the East European Platform in the former and the Western Palaeotethys and the Eastern Palaeotethys in the latter, as noted in the later section.

Since the introduction of the first fusuline genus Fusulina by Fischer de Waldheim (1829), and the first species Fusulina cylindrica and F. depressa described by Fischer de Waldheim (1830), approximately 350 genera and more than 7000 species have been proposed for this foraminiferal group (World Foraminifera Database: Hayward et al. 2021). Among many taxonomic works in the history of fusuline study, Thompson (1948) provided the first comprehensive ‘textbook’ to compile and describe fusuline genera established by that time, in which fusulines were allocated to a family rank and a total of 49 genera were collected. With regard to the higher taxonomy of fusulines, with the rising of the taxonomic rank of Foraminifera to the rank of phylum or subphylum, that of fusuline foraminifers has also been upgraded from a traditional superfamily category to an order or superorder rank (Rauzer-Chernousova and Fursenko 1959; Thompson 1964; Rozovskaya 1975; Loeblich and Tappan 1987; Sheng et al. 1988; Rauzer-Chernousova et al. 1996; Gaillot and Vachard 2007; Vachard et al. 2010, 2013; Vachard 2016; Vachard in Krainer et al. 2019).

In this study, I essentially follow Vachard et al.’s (2010) view of the taxonomic rank of the fusulines (thus, order Fusulinida) and consider that they form a single monophyletic clade. Table 1 shows a systematic structure of the family and higher taxa in the order Fusulinida. Nine families are recognized in this foraminiferal group, and they can be further bundled into three superfamilies. Figure 3 illustrates the chronological ranges and supposed phylogenetic relationship of the fusuline families. As in this figure, Carboniferous fusulines consist of five families.

Fig. 3.

An overview of the higher taxonomy and phylogenetic relationship of families in the fusuline Foraminifera. Abbreviations of geological ages: Tn, Tournaisian; Vi, Visean; Se, Serpukhovian; Ba, Bashkirian; Mo, Moscovian; Ka, Kasimovian; Gz, Gzhelian; As, Asselian; Sa, Sakmarian; Ar, Artinskian; Ku, Kungurian; Ro, Roadian; Wo, Wordian; Ca, Capitanian; Wu, Wuchiapingian; Ch, Changhsingian.

Fig. 3.

An overview of the higher taxonomy and phylogenetic relationship of families in the fusuline Foraminifera. Abbreviations of geological ages: Tn, Tournaisian; Vi, Visean; Se, Serpukhovian; Ba, Bashkirian; Mo, Moscovian; Ka, Kasimovian; Gz, Gzhelian; As, Asselian; Sa, Sakmarian; Ar, Artinskian; Ku, Kungurian; Ro, Roadian; Wo, Wordian; Ca, Capitanian; Wu, Wuchiapingian; Ch, Changhsingian.

Table 1.

Systematic structure of the family and higher taxa in the order Fusulinida, used in this study

Order Fusulinida von Möller, 1878 
 Superfamily Fusulinoidea von Möller, 1878 
  Family Ozawainellidae Thompson and Foster, 1937 
  Family Schubertellidae Skinner, 1931 
  Family Boultoniidae Skinner and Wilde, 1954 
  Family Fusulinidae von Möller, 1878 
  Family Schwagerinidae Dunbar and Henbest, 1930 
 Superfamily Neoschwagerinoidea Dunbar and Condra, 1927 
  Family Verbeekinidae Staff and Wedekind, 1910 
  Family Neoschwagerinidae Dunbar and Condra, 1927 
 Superfamily Staffelloidea Miklukho-Maklay, 1949 
  Family Staffellidae Miklukho-Maklay, 1949 
  Family Thailandinidae Toriyama and Kanmera, 1968 
Order Fusulinida von Möller, 1878 
 Superfamily Fusulinoidea von Möller, 1878 
  Family Ozawainellidae Thompson and Foster, 1937 
  Family Schubertellidae Skinner, 1931 
  Family Boultoniidae Skinner and Wilde, 1954 
  Family Fusulinidae von Möller, 1878 
  Family Schwagerinidae Dunbar and Henbest, 1930 
 Superfamily Neoschwagerinoidea Dunbar and Condra, 1927 
  Family Verbeekinidae Staff and Wedekind, 1910 
  Family Neoschwagerinidae Dunbar and Condra, 1927 
 Superfamily Staffelloidea Miklukho-Maklay, 1949 
  Family Staffellidae Miklukho-Maklay, 1949 
  Family Thailandinidae Toriyama and Kanmera, 1968 

This superfamily consists of five families (Fig. 3). Of them, the Ozawainellidae contains the first fusuline genus (the root stock of all fusulines), Eoparastaffella, which appeared in the latest Tournaisian of the early Carboniferous (Early Mississippian). Members of this family are usually small and discoidal or lenticular in shape. Some genera and species can be good biostratigraphic markers, but others are usually morphologically conservative and long-ranging. Ozawainellids are abundant in the Mississippian and the early part of the Pennsylvanian, but subsequently the families Fusulinidae and Schwagerinidae (with larger spherical, oval, fusiform, and elongate fusiform shells) became prevalent, and the importance of ozawainellids in the fusuline fauna, as well as in the entire foraminiferal fauna, diminished. This family continued to occur until the end of the Permian.

The Schubertellidae appeared in the early Bashkirian, almost at the same time as the first representative of the Fusulinidae. It originated from a lenticular ozawainellid (Plectostaffella), or as a lesser possibility from an earliest subglobose fusulinid (Semistaffella). Except for some genera, especially those found in the Permian, schubertellids remained small- to moderate-sized, and usually did not proliferate in local fusuline assemblages during the Carboniferous. In the early Permian, this family gave rise to an important lineage, which later founded the superfamily Neoschwagerinoidea (Vachard et al. 2013).

In many fusuline taxonomic works, boultoniids are often regarded as constituting part of the schubertellids, and thus were assigned to the Boultoniinae in the Schubertellidae or to the Boultoniidae in the Schubertelloidea (Loeblich and Tappan 1987; Rauzer-Chernousova et al. 1996; Gaillot and Vachard 2007; Vachard in Krainer et al. 2019). In this taxonomy, I recognized the Boultoniidae as a discrete family from the Schubertellidae, based on the following features: (1) boultoniids generally show a much more glassy test wall under the microscope than schubertellids, which probably suggests that the former (boultoniids) have a slightly different wall composition (possibly in mineralogy) from the latter, and (2) boultoniids consistently have much stronger septal fluting than do schubertellids. The Boultoniidae was derived from the Schubertellidae at around the Carboniferous–Permian boundary, so it is essentially restricted to the Permian. This family was more diversified in younger Permian time, especially during the Capitanian and Lopingian (late middle–late Permian).

The Fusulinidae was the most successful fusuline family in the Carboniferous and produced a number of genera that became major elements in Early–Middle Pennsylvanian fusuline faunas of the world. Most fusulinid genera have high (or relatively good) biochronological value and are useful for making refined biostratigraphy and regional/inter-continental correlation. This family was derived from the Ozawainellidae in the early Bashkirian (Early Pennsylvanian) and flourished by the end of the Moscovian (Middle Pennsylvanian). Some genera survived until the early Permian, but after the Moscovian–Kasimovian boundary time they were less diversified, and their occurrence became rare. Fusulinids are the first fusuline group that can be called ‘larger foraminifers’. They acquired large, fusiform to elongate fusiform shells by extending their coiling axis (thus extending their chambers laterally to form a shell with its axial length larger than shell diameter so that the shell length/diameter ratio was over 1.0) and by increasing the number of volutions (thus increasing the number of chambers during their whole life). Increase of shell size in the fusuline foraminifers is generally supposed to be related to the endosymbiosis of photosynthetic microorganisms (such as photosymbiotic algae and/or cyanobacteria: Ross 1972; Vachard et al. 2004a), as in the modern benthic larger foraminifers (Haynes 1965; Hallock 1985), but the detailed mechanism at this stage of upsizing the shell in the Fusulinidae has not been clearly explained. Nevertheless, it could also be related to the acquisition of some endophotosymbiotic microorganisms within their tests because shells of fusulines in this family started to develop clearly differentiated spirotheca. They also sometimes show even a porous feature in the spirotheca, which is finer than but structurally essentially similar to the keriothecal structure in the Schwagerinidae. Keriotheca is considered to be a shell microstructure for housing symbiotic algae or cyanobacteria (Vachard et al. 2004a). Genera in the family Fusulinidae usually have three- or four-layered spirotheca, consisting of primary layers (protheca including ‘diaphanotheca’ or lower thicker homogeneous layer) covered by secondary epithecal layer(s) (upper tectorium and lower tectorium). Septal folding is also common, which is considered to contribute to making a chamber of greater volume.

The Schwagerinidae is the other fusuline family in the Carboniferous that accomplished increasing shell size to the stage of larger foraminifers. Schwagerinid genera developed a characteristic keriothecal structure in their spirotheca, which likely functioned for housing photosynthetic symbiotic algae or cyanobacteria, as mentioned above (Vachard et al. 2004a). Septal folding to various degrees (but usually moderately to strongly fluted) is also characteristic of most genera of this family. As noted later, this family is considered to have arisen from two different phylogenetic stocks in Fusulinella in the family Fusulinidae, at the beginning of the Kasimovian. During the Late Pennsylvanian (latest Carboniferous), the Schwagerinidae superseded the Fusulinidae as the prevailing element of the fusuline fauna. Some 30 genera are known in this family in the latest Carboniferous, but its major diversity occurred in the Permian, and more than twice the number of genera are known during early–middle Permian time. There is no major extinction event known in this family at the Carboniferous–Permian boundary.

The superfamily Staffelloidea is characterized by having innately recrystallized shells to various degrees, and an aragonitic shell mineralogy has been suggested for some of the completely sparitized genera (Vachard et al. 2010; Vachard and Hance in Hance et al. 2011). It is a long-lived fusuline group, started almost at the beginning of fusuline history and sustained until its extinction at the end of the Permian. It consists of two families (Fig. 3). In the Carboniferous, only the Staffellidae is known to occur, and it comprised six genera. They are morphologically conservative, and most of them are small and lenticular, or rarely subspherical, in shape. Their biostratigraphic value is usually not very significant, even at the species level.

The other family recognized in the Staffelloidea is the Thailandinidae, which has been less known among fusuline researchers because specimens of this family were reported only in a few papers that deal with material from Thailand. It is essentially of Permian age and includes two genera, Thailandina and Neothailandina, both established by Toriyama and Kanmera (1968) based on materials from Central Thailand (as their generic names show). Due to their completely recrystallized shells, details of shell features are not well preserved, but these two genera likely possessed parachomata. Moreover, Neothailandina seems to have a shell structure like the transverse septula seen in the Neoschwagerinidae, based on some type material. Toriyama and Kanmera (1968) established the subfamily Thailandininae to accommodate these two peculiar fusuline genera and originally assigned it to the Neoschwagerinidae. Afterwards, Kobayashi et al. (2010) argued that Thailandina and Neothailandina are just recrystallized (diagenetically sparitized) Misellina and neoschwagerinids, verbeekinids, and Parafusulina-like schwagerinids, respectively, and rejected the validity of these two genera and Thailandininae. Recently, Ueno (2021) reexamined the type materials by Toriyama and Kanmera (1968) and clarified that Thailandina and Neothailandina do not represent recrystallized specimens of other known fusulines but are better treated as discrete taxonomic entities. He salvaged the taxonomic validity of Thailandina and Neothailandina.

Two families, Verbeekinidae and Neoschwagerinidae, constitute this superfamily (Fig. 3). The oldest genus of the Verbeekinidae, Brevaxina, was derived from the schubertellid genus Pamirina (Leven 1970, 2010; Ueno 1991a; Vachard et al. 2013) at about the earliest Kungurian. Thus, the Neoschwagerinoidea is a descendant of the Schubertellidae (Fig. 3), contrary to the traditional view of ozawainellid affinity (Leven 1970, 2010; Ueno 1991a, c). The first neoschwagerinids (Cancellina, Maklaya) branched off from the verbeekinids (Misellina) in the middle Kungurian. These two families very much flourished in the Tethys and Panthalassa regions, and they have very high biostratigraphic resolution during the late early to middle Permian. The taxonomy and phylogeny of neoschwagerinoideans have been studied by many students of fusulines (e.g. Ozawa 1970; Leven 1982).

Morphologically, neoschwagerinoideans are characterized by having parachomata in their shells, and both families show marked tendencies toward shell gigantism. Increasing shell size is considered to be achieved in two ways. They correspond to one of the two taxonomic groups in fusulines that developed a permanent keriothecal structure. The keriotheca in neoschwagerinoideans and that seen in schwagerinids originated differently; the former was inherited from the ZarodellaLevenellaPamirina lineage in the Schubertellidae and the other from the FusulinellaProtriticites/Obsoletes lineage in the Fusulinidae. Moreover, the former, which is herein referred to as the Neoschwagerinoidea-type keriotheca, is generally finer than the latter, although they show a close similarity in basic architecture. As the schwagerinid keriotheca is considered to be related to the housing of photosynthetic symbiotic algae or cyanobacteria (Vachard et al. 2004a), the Neoschwagerinoidea-type keriotheca would also have the same function (based on the size of alveoli in the keriotheca, cyanobacteria are more likely in the Neoschwagerinoidea). Moreover, the Neoschwagerinidae developed a peculiar set of septula in their shell construction, and, by this feature, neoschwagerinids increased the strength of their shell structure. The development of septula helped upsizing the shell volume structurally. These biotic interactions and architectural renovations were the main reasons for neoschwagerinoideans to have developed voluminous shells as larger foraminifers and was key to their success in the history of fusuline evolution.

Carboniferous fusulines are composed of five out of the total of nine fusuline families (Fig. 3). In the following section, the taxonomic constitution of Carboniferous fusuline genera in each family is summarized, and the major framework of their phylogenetic evolution used in this study is outlined.

The Ozawainellidae consists of two subfamilies in the Carboniferous: the Eostaffellinae and Ozawainellinae. The Eostaffellinae includes the stem genus of the fusuline Foraminifera, which is Eoparastaffella.

Family OzawainellidaeThompson and Foster, 1937 

Subfamily Eostaffellinae Mamet in Mamet et al., 1970 

EoparastaffellaVdovenko, 1954 ( = EoparastaffellinaVdovenko, 1971a; = Palaeoparastaffella Wu in Wu et al., 1998); EostaffellaRauzer-Chernousova, 1948b ( = IkensieformisOrlova, 1997; = ParamillerellaThompson, 1951); PseudonovellaKireeva, 1949 [ = PseudoacutellaVachard, Krainer and Lucas, 2013 (pro AcutellaOrlova, 1997, preoccupied by the brachiopod genus AcutellaLyashenko, 1973)]; EostaffellinaReitlinger, 1963 ( = ?EoplectostaffellaPostoyalko, 1990); Seminovella Rauzer-Chernousova in Rauzer-Chernousova et al., 1951; NovellaGrozdilova and Lebedeva, 1950; PlectostaffellaReitlinger, 1971 ( = VarvariellaOrlova, 1997); VaristaffellaKulagina and Sinitsyna, 2003; MillerellaThompson, 1942; RectomillerellaLiêm, 1974; Plectomillerella Brazhnikova and Vdovenko in Aizenverg et al., 1983.

Eoparastaffellina was separated by Vdovenko (1971a) as a subgenus of Eoparastaffella, in having a subspherical to broadly ovoid, involute shell with broadly rounded periphery and slightly concave umbilici. Vachard (2016) suggested Eoparastaffellina to be the most ancestral stock of the fusuline foraminifers, and Vachard et al. (2019) recognized the broadly rounded periphery of this taxon as an ancestral character. Although Vachard and Arefifard (2015) legitimated Eoparastaffellina as a distinct genus, Devuyst and Kalvoda (2007) had earlier concluded that Eoparastaffellina cannot be characterized properly at present, and, consequently, argued that the concept of that taxon is not clearly defined. This latter view is followed in this study, and the former genus is synonymized into the latter. Hance (1997) and Devuyst et al. (2003) suggested that subspherical to broadly ovoid, involute forms of Eoparastaffella with broadly rounded periphery, for which Vdovenko (1971a) named Eoparastaffellina, tend to occur in older strata (in the latest Tournaisian) in the ‘EoparastaffellinaEoparastaffella lineage’ of Vachard and Arefifard (2015). They constituted a primitive form-group of Eoparastaffella, probably bridging with an ancestral dainellin genus (Hance 1997; Cózar and Vachard 2001). Palaeoparastaffella is also synonymized with Eoparastaffella. It is a poorly defined genus, established by Wu in Wu et al. (1998) based on materials from the Tournaisian–Visean boundary interval of South China. When this genus was proposed, Wu in Wu et al. (1998) illustrated only the holotype of the type species (E. shifendongensis Wu in Wu et al., 1998) and some other poorly sectioned specimens of two unspecified and one qualified species, in Palaeoparastaffella. Thus, the taxonomic characterization of this genus is very vague. Based on these illustrated specimens, at least the type species likely has common shell features of Eoparastaffella. Thus, Palaeoparastaffella is considered as superfluous taxonomically.

With regard to the taxonomy of Eoparastaffella and some genera that are supposed to be phylogenetically related to it, Vachard and Arefifard (2015) introduced the subfamily Eoparastaffellinae and included it in the superfamily Staffelloidea (thus, the Staffellidae in this study). More recently, Vachard and Le Coze (2021) raised it to a family and transferred it to the superfamily Loeblichioidea Cummings, 1955 (nomen translat. Vachard and Hance in Hance et al., 2011). Consequently, their taxonomy has excluded Eoparastaffella from the fusuline Foraminifera. The Eoparastaffellidae includes, besides the type genus, Eoparastaffellina, Bozorgnites Cózar, Vachard and Le Coze in Vachard et al., 2019 (pro BozorgniellaCózar and Vachard, 2001, preoccupied by the nummulitid genus BozorgniellaRahaghi, 1973), KlubonibeliaConil, 1980, Neoparadainella Vdovenko in Brazhnikova and Vdovenko, 1973, Paradainella Brazhnikova in Aizenverg, 1971, and PojarkovellaSimonova and Zub, 1975. According to Vachard and Le Coze (2021), the grounds for the need of this family are that these mentioned taxa having a granular wall (and also a weakly differentiated wall with a ‘luminotheca’) would be linked phylogenetically and could constitute a family transitional between the Dainellidae Cózar and Vachard, 2001 (nomen translat. Vachard and Hance in Hance et al., 2011) and the Eostaffellidae, thus connecting the Endothyrida Fursenko, 1958 and Fusulinida. As in the generic composition, however, the Eoparastaffellidae seems to be a jumble family, which includes varied genera showing too diverse morphological features in gross shell profile and coiling pattern. Among them, Eoparastaffella (and its junior synonym Eoparastaffellina) is distinguishable from others in having a (sub)planispiral lenticular shell, and this diagnosis is shared with the earliest fusulines (Eostaffella). In this study, I regard the Eoparastaffellidae/Eoparastaffellinae to be unnecessary and, as in the traditional fusuline taxonomy, Eoparastaffella is considered as the most primitive genus of the fusuline Foraminifera.

Pseudoacutella was introduced as a replaced name for AcutellaOrlova, 1997, which was preoccupied by the brachiopod genus AcutellaLyashenko, 1973. Its type species, Eostaffella grozdilovaeMaslo and Vachard, 1997 (a replacement name of Eostaffella acutaGrozdilova and Lebedeva, 1950, due to the homonymy with E. mosquensis var. acutaRauzer-Chernousova, 1948a) shares basic morphological features with the type species of Pseudonovella, Novella (Pseudonovella) irregularisKireeva, 1949, such as a slender lenticular shell with 3–3.5 volutions and a large spherical proloculus relative to the shell size. Pseudonovella and Pseudoacutella have similar stratigraphic ranges and are known to occur commonly in the Bashkirian and Moscovian. Although there are some subtle differences, such as the shape of the periphery (horse shoe in Pseudonovella and carinate in Pseudoacutella; Vachard et al. 2013) and the feature of chamber involution at umbilical regions, they are considered to form a single generic entity in the Pennsylvanian eostaffellin taxonomy. Pseudoacutella is regarded as a junior synonym of Pseudonovella in this study.

Eoplectostaffella, established by Postoyalko (1990) as a subgenus of Eostaffella, is herein provisionally regarded as the same as Eostaffellina. In the original proposal of this taxon, it is noted that Eoplectostaffella is characterized by mixed characters of Eostaffellina and Plectostaffella. However, its type species, Eostaffella (Eoplectostaffella) acuminulataPostoyalko, 1990, obtained from the upper part of the Serpukhovian, has almost identical shell features as some Eostaffellina species found in the same interval. Thus, the introduction of Eoplectostaffella is probably superfluous.

Ikensieformis is treated in this taxonomy just as a morphological group within Eostaffella, which possesses an acute periphery and almost straight lateral slopes. Van Ginkel (2010) separated Eostaffella and Paramillerella based mainly on their supposedly different phylogenetic origin, and more practically on their different stratigraphic occurrences; Eostaffella is mainly in the Mississippian, whereas Paramillerella is in the Pennsylvanian. This view is not supported by tangible data, so, as in Loeblich and Tappan (1987), the latter is considered as a junior synonym of the former.

In this taxonomy, I treated Varvariella as a junior synonym of Plectostaffella. It was introduced by Orlova (1997) as a subgenus of Plectostaffella, with Eostaffella varvariensisBrazhnikova and Potievska, 1948 as the type species. She pointed out several morphological differences such as the general shell shape and the shape of periphery, the degree of expansion of the volution, and the degree of deviation of the coiling axis, between Varvariella and Plectostaffella. However, all these differences are not significant in view of the genus-group diagnosis and are regarded as merely corresponding to differences in species. Thus, Varvariella is not necessary in the eostaffellin taxonomy.

When Gaillot and Vachard (2007) established the genus Neomillerella with N. mirabilisGaillot and Vachard, 2007 from the late Permian (Lopingian) as the type species, in the family Eostaffellidae (thus Eostaffellinae in this study), they included in this genus Early Pennsylvanian Millerella japonica, M. gigantea, and M. yowarensis described by Kanmera (1952) and Ota (1971) from Japan, together with some other early Permian species. Neomillerella is a questionable taxon, consisting of species from variable ages that lack evident phylogenetic relations. These Early Pennsylvanian forms that have been combined with Neomillerella in the original description should be reassigned to Eostaffella, or as a lesser possibility to Pseudoendothyra. Neomillerella is possibly retained as a late Permian monotypic genus in the Ozawainellidae.

Subfamily OzawainellinaeThompson and Foster, 1937 

OzawainellaThompson, 1935 ( = MoscoviellaMiklukho-Maklay, 1952).

Ozawainella is the only genus in this subfamily that occurs in the Carboniferous. This genus is distinguished from eostaffellin genera by having a larger shell, thicker secondary deposits (chomata), and peculiar septa that bend anteriorly (not perpendicular to the spiral wall), curve slightly (in falciform), and are narrowly spaced.

The type species of Moscoviella, Ozawainella mosquensis Rauzer-Chernousova in Rauzer-Chernousova et al., 1951 from the Moscow Syneclise, is one of the typical species of the named genus known in the Moscovian of the Ural–Arctic and Palaeotethys regions (e.g. Rui et al. 1991; Ivanova 2008; Orlov-Labkovsky and Bensh 2015). The junior synonymy of Moscoviella with Ozawainella is indisputable.

Through the early history of their evolution during the Mississippian, the fusuline foraminifers showed lower generic diversification, and only a few genera are known in this interval. In latest Tournaisian–Visean times they include Eoparastaffella, Eostaffella, and Pseudoendothyra, of which the first two are included in the Eostaffellinae of the Ozawainellidae, and the last one is assigned to the Pseudoendothyrinae in the Staffellidae in this study. To date, variable ideas on the supra-generic taxonomy and phylogenetic relationship of these genera, and in addition on the origin (ancestral stock) of the fusuline foraminifers, have been proposed, but these issues related to the early evolution of fusulines are still controversial among students, except a widely accepted understanding that the first fusuline genus is Eoparastaffella (or Eoparastaffellina in some studies) (Vdovenko 1964; Mamet et al. 1970; Rozovskaya 1975; Hance 1997; Maslo and Vachard 1997; Devuyst and Kalvoda 2007; van Ginkel 2010; Vachard and Hance in Hance et al. 2011; Vachard et al. 2013; Vachard and Arefifard 2015; but not Vachard and Le Coze 2021 as noted already). Of them, two major hypotheses are as follows (Fig. 5): (1) The first fusulines, Eoparastaffella (including Eoparastaffellina in some studies), appeared in the latest Tournaisian, is a pseudoendothyrin genus, and it directly gave rise to Pseudoendothyra in the next step of evolution that happened sometime in the early part of the late Visean (Vdovenko 1964; Brazhnikova and Vdovenko 1973; Rauzer-Chernousova 1985). Eostaffella having an ozawainellid microgranular (low-magnesian calcite) wall, on the other hand, was derived from the earliest pseudoendothyrin lineage (namely Eoparastaffella) in the early Visean, and it newly created the family Ozawainellidae (Vachard et al. 2013; Vachard and Arefifard 2015; Fig. 5a). In this scenario, the family Staffellidae, supposedly having a high-magnesian calcite and/or aragonite shell mineralogy originally, is the founder of all fusuline foraminifers, and the microgranular wall, which is widespread in later major fusuline genera, is a derivative character. (2) It is known that in younger forms of Eoparastaffella occurring in the lower Visean, the wall tends to be thinner and its microgranular feature becomes more distinct (Devuyst et al. 2003). These characters incipiently suggest an intimate (direct) phylogenetic relationship between Eoparastaffella and Eostaffella. Moreover, Hance (1997) noted, based on data from Western European material, that whereas Eoparastaffella and Eostaffella have transitional forms in the upper part of the lower Visean (Moliniacian) (Conil and Naum 1977; Conil et al. 1980), those between Eoparastaffella and Pseudoendothyra are never found. The last occurrence of Eoparastaffella in the late Moliniacian or early Livian slightly but distinctly predates the first occurrence of Pseudoendothyra in the early Warnantian. Therefore, in this second model, Eoparastaffella is the first ozawainellid genus (Devuyst and Kalvoda 2007), and, soon after its appearance, Eoparastaffella gave rise to Eostaffella in the earliest Visean. Then, Pseudoendothyra (the first pseudoendothyrin and staffellid genus) came from Eostaffella sometime in the late Visean (Hance 1997; van Ginkel 2010; Fig. 5b). As described elsewhere in the later part of this paper, some studies from Timan–Pechora, the Urals, Western European basins, and the Precaspian Basin documented the occurrence of Eoparastaffella from middle Visean strata (Brazhnikova and Vdovenko 1973; Kostyzova 1997; Brenckle and Milkina 2003; Vachard et al. 2018b), and also the first Pseudoendothyra from the middle Visean (e.g. Makhlina et al. 1993; Brenckle and Milkina 2003). But, there is as yet no report that clarified an unequivocal stratigraphic overlap between the last Eoparastaffella and the first Pseudoendothyra. There still seems to exist a minor stratigraphic gap between the ranges of these two genera. Moreover, Tournaisian dainellin foraminifers that have been considered as the most potential ancestral taxon of Eoparastaffella (Hance 1997; Cózar and Vachard 2001) do not show a Pseudoendothyra-like wall.

Fig. 4.

Stratigraphic ranges and phylogeny of ozawainellid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). Abbreviations of geological ages: Serpukhov., Serpukhovian; Kas., Kasimovian; Desmoines., Desmoinesian; Mis., Missourian.

Fig. 4.

Stratigraphic ranges and phylogeny of ozawainellid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). Abbreviations of geological ages: Serpukhov., Serpukhovian; Kas., Kasimovian; Desmoines., Desmoinesian; Mis., Missourian.

Fig. 5.

Two hypotheses for the phylogeny and evolution of early fusulines. (a) A model proposed by Vachard et al. (2013) and Vachard and Arefifard (2015). In this model, the first fusuline genus Eoparastaffella is a staffellid taxon and the ozawainellid genus Eostaffella was derived from the staffellid lineage immediately after the rise of the fusuline foraminifers. Another staffellid genus, Pseudoendothyra appeared later directly from Eoparastaffella. (b) An alternative model that the fusuline foraminifers started with the ozawainellid genus Eoparastaffella and, immediately after its appearance, this genus gave rise to Eostaffella in the same family. The staffellid lineage commenced with Pseudoendothyra later, derived from Eostaffella (Hance, 1997; van Ginkel, 2010). The model (b) is adopted in the taxonomy in this study. Abbreviation of geological age: Tour., Tournaisian. MFZ denotes Mississippian Foraminiferal Zones established by Devuyst and Hance in Poty et al. (2006).

Fig. 5.

Two hypotheses for the phylogeny and evolution of early fusulines. (a) A model proposed by Vachard et al. (2013) and Vachard and Arefifard (2015). In this model, the first fusuline genus Eoparastaffella is a staffellid taxon and the ozawainellid genus Eostaffella was derived from the staffellid lineage immediately after the rise of the fusuline foraminifers. Another staffellid genus, Pseudoendothyra appeared later directly from Eoparastaffella. (b) An alternative model that the fusuline foraminifers started with the ozawainellid genus Eoparastaffella and, immediately after its appearance, this genus gave rise to Eostaffella in the same family. The staffellid lineage commenced with Pseudoendothyra later, derived from Eostaffella (Hance, 1997; van Ginkel, 2010). The model (b) is adopted in the taxonomy in this study. Abbreviation of geological age: Tour., Tournaisian. MFZ denotes Mississippian Foraminiferal Zones established by Devuyst and Hance in Poty et al. (2006).

In this study, the second scenario is adopted because of the similarity of walls between Eoparastaffella and Eostaffella (which is, on the other hand, different from that of typical Pseudoendothyra appearing first in the later part of the Visean) and the biostratigraphic data that Eostaffella occurred in the earliest Visean, but the first occurrence of Pseudoendothyra is later. The first fusuline foraminifer, Eoparastaffella, appeared in the latest Tournaisian (MFZ8 of Poty et al. 2006; latest Ivorian) as the first eostaffellin (thus ozawainellid) genus, and Eostaffella evolved from it at the beginning of the Visean. By the mutation of wall composition that happened in Eostaffella in younger Visean time, this genus gave rise to Pseudoendothyra, which established a new long-lasting clade (Staffellidae) in the fusuline foraminifers. With respect to the ancestral root stock of fusulines, Hance (1997) and Cózar and Vachard (2001) suggested a possible dainellin origin, and I consider herein that Paradainella, especially P. dainelliformis, is most likely (Fig. 5b).

In the Ozawainellidae, several genera appeared from Eostaffella during the later part of the Serpukhovian. They include Eostaffellina and Plectostaffella, and the latter soon gave rise to Plectomillerella and Varistaffella (Fig. 4). The latter three genera started developing slight deviation of the coiling axis and, together with it, the expansion of shell length (coiling axis) had commenced to form thickly lenticular to subspherical shells in the PlectostaffellaVaristaffella lineage in the earliest Bashkirian. Soon after that, Plectostaffella gave rise to Semistaffella, which is the earliest genus of the family Fusulinidae. Moreover, Eostaffella was ancestral to several other small lenticular genera in the Bashkirian, such as Millerella and Pseudonovella. They occur abundantly in Bashkirian and Moscovian strata (e.g. Rauzer-Chernousova et al. 1951; Ueno in Fohrer et al. 2007; van Ginkel 2010), but diminished in the Late Pennsylvanian. Pseudonovella extended up at least to the earliest Permian (Asselian) (Yarahmadzahi and Vachard 2014), whereas Eostaffella likely survived only to the end of the Carboniferous (Vachard and Krainer 2001).

The origin and ancestral genus of Ozawainella (thus Ozawainellinae) are still not very clear. This genus was documented first from the Akavassian (Severokeltmian) in the lower Bashkirian and became more common in the Askynbashian (Prikamian) and further in the upper Bashkirian, based on data from the type Bashkirian in the Urals and the Donets Basin of Ukraine (Aizenverg et al. 1963; Brazhnikova et al. 1967; Kulagina et al. 2001; Nikolaev 2005; Ivanova 2008). Ozawainella generally has larger shells with denser secondary deposits (laterally extending chomata), which are the key characters to separate the genus from most of discoidal eostaffellins, when observed in axial sections. But, a more important distinctive feature is peculiar septa that are thin, anteriorly bending falciform, and spaced narrowly in sagittal sections (see the specimen on pl. 3, fig. 18 of Putrya 1956, illustrating a sagittal section of Ozawainella angulata, as a typical example). Somewhat similar, relatively narrowly spaced, falciform septa are seen in some eostaffellins, such as Millerella (Thompson, 1944; Groves 1983) and Pseudonovella, including ‘Pseudoacutella’ synonymized herein (author's unpublished data from the Donets Basin, eastern Ukraine). In the phylogenetic scheme in this study, I provisionally consider that Ozawainella was derived from Millerella or Pseudonovella, sometime in the early Bashkirian (Fig. 4).

MediocrisRozovskaya, 1961 has been traditionally treated as a member of primitive fusulines and appeared in many publications that studied Mississippian and Early–Middle Pennsylvanian fusuline taxonomy, as a distinct genus in the Ozawainellidae or Eostaffellidae/Eostaffellinae (Mamet et al. 1970; Vdovenko 1971b; Brazhnikova and Vdovenko 1973; Rozovskaya 1975; Bird and Mamet 1983; Loeblich and Tappan 1987; Groves 1988; Sheng et al. 1988; Ueno in Fohrer et al. 2007; van Ginkel 2010). Several other phylogenetically related genera such as Chomatomediocris Vdovenko in Brazhnikova and Vdovenko, 1973, Plectomediocris Brazhnikova and Vdovenko in Aizenverg et al., 1983, EndostaffellaRozovskaya, 1961, and ZellerinellaMamet, 1981 (pro ZellerinaMamet and Skipp, 1970a, preoccupied by the lepidopteran ZellerinaTorre and Callejas, 1958) have been also related to fusulines in some cases. Mediocris has a minute discoidal, planispiral shell with distinct lateral fillings in the chambers and first appeared in the latest Tournaisian (MFZ8: Poty et al. 2006; Vachard and Hance in Hance et al. 2011) or just at the beginning of the Visean (van Ginkel 2010), and ranged to the late Moscovian (Ueno et al. 1994). Although in these above-mentioned studies, Mediocris has been regarded as a member of the Ozawainellidae, this traditional view is now challenged. At its supposed first occurrence around the Tournaisian–Visean boundary interval, there are only two genera known in fusulines; they are Eoparastaffella and Eostaffella as discussed above. However, Mediocris is morphologically quite far from these two early ozawainellid genera and thus, it is difficult to construct the phylogenetic relationships among them. As in Rauzer-Chernousova et al. (1996), Vachard and Hance in Hance et al. (2011), and Vachard and Le Coze (2021), Mediocris (and its related genera mentioned above) is now better classified as a taxon in the order Endothyrida, probably in the subfamily Endostaffellinae Loeblich and Tappan, 1984, or, if necessary, Mediocrinae Vachard and Hance in Hance et al., 2011.

The Staffellidae appeared in the later part of the Visean, and the Pseudoendothyrinae and Staffellinae are recognized in the Carboniferous. Staffellids are characterized by having variously recrystallized tests, which suggest innate aragonitic shell mineralogy (Vachard et al. 2010).

Family StaffellidaeMiklukho-Maklay, 1949 

Subfamily Pseudoendothyrinae Mamet in Mamet et al., 1970 

PseudoendothyraMikhailov, 1939 ( = ParastaffellaRauzer-Chernousova, 1948b; = ShouguaniaLin, 1981); Volgella Reitlinger in Reitlinger and Melnikova, 1977; ParastaffelloidesReitlinger, 1963 ( = StaffelloidesLiêm, 1976); PalaeoreichelinaLiêm, 1974.

Shells of pseudoendothyrins are slightly recrystallized, though not so much as the staffellins described next, and usually vaguely differentiated with a thin, sometimes unclear, translucent layer in the middle, which is sometimes referred to as ‘diaphanotheca’ or ‘luminotheca’ (Cózar 2002). The poorly preserved nature of pseudoendothyrin shells suggests that they had different shell composition from coeval ozawainellids, which exhibit microgranular darker walls. Pseudoendothyrins may have high-magnesian calcite shells, which made their preservation poorer by the eluviation of Mg during diagenesis.

Parastaffella has been used as a valid genus by some Russian scholars (Shlykova 1951; Rauzer-Chernousova 1985; Makhlina et al. 1993; Rauzer-Chernousova et al. 1996). However, as in Loeblich and Tappan (1987), Parastaffella (type species: Parastaffella struveiRauzer-Chernousova, 1948b, non Fusulinella struveivon Möller, 1879) is an objective junior synonym of Pseudoendothyra, as they have the same type species, F. struveivon Möller, 1879. Brenckle (2005) summarized the intricate taxonomic history on Parastaffella and concluded that the naming of the genus and its type species P. struvei done in Rauzer-Chernousova (1948b) are considered to be valid nomenclatural acts, thus Parastaffella is potentially retained as a valid genus. But even in this case, it seems unreasonable to separate these genera based on slightly rounded (in Pseudoendothyra) and slightly keeled (in Parastaffella) peripheries. In any case, Parastaffella is regarded as a junior synonym of Pseudoendothyra in this study, aside from whether the synonymy is objective or subjective. Shouguania established by Lin (1981) shares many essential shell features with Pseudoendothyra, and is not regarded as a valid genus and included in the latter.

Volgella and Parastaffelloides, and also early Permian PalaeostaffellaLiêm, 1966, all have spherical/subspherical shells with a wall composition similar to Pseudoendothyra, but appeared at separate times. Volgella is restricted to the late Serpukhovian (Protvian); Parastaffelloides occurs from mainly Moscovian–early Kasimovian strata; and Palaeostaffella is in the late Cisuralian (early Permian) (Reitlinger and Melnikova 1977; Kobayashi 2017, 2019). Pseudoendothyra gave rise to such spherical groups several times repeatedly; they are treated as distinct taxa in this study because these genera that resemble each other in spherical pseudoendothyrins have separated chronostratigraphic ranges and no direct phylogenetic relationship is proposed to each other. Staffelloides is a poorly known genus originally described from the lower Moscovian(?) of Vietnam (Liêm 1976). It has a recrystallized spherical shell, and is probably a junior synonym of Parastaffelloides.

Subfamily StaffellinaeMiklukho-Maklay, 1949 

StaffellaOzawa, 1925; NankinellaLee, 1934 ( = ReitlingerinaRauzer-Chernousova, 1985).

Staffellids usually have strongly recrystallized shells, suggesting their original aragonitic mineralogy. As for the distinction between Staffella and Nankinella, Thompson's (1948) conventional concept is followed here, stating that Staffella possesses a rounded periphery, whereas Nankinella has an angular periphery. As noted by Groves (1991), however, these distinctions could be somewhat arbitrary in view of taxonomy, and the conceptual limits separating these two genera vary considerably among authors.

Reitlingerina is a poorly designated genus from Bashkirian and Moscovian strata and sometimes appeared in the Russian literature (Rauzer-Chernousova et al. 1996; Baranova et al. 2014). Its type species, Fusulinella bradyivon Möller, 1878, was illustrated originally as stylized drawings, so that detailed characters of this taxon are not clear. Nevertheless, it seems to have a largely recrystallized shell with a somewhat angular periphery and undifferentiated wall. These features more or less coincide with those of Nankinella, and thus Reitlingerina is provisionally synonymized with Nankinella in this study.

Six genera are recognized in the family Staffellidae during the Carboniferous. Phylogenetic transitions among genera in this family during the Carboniferous are relatively simple and uneventful. As noted already, the first staffellid genus is Pseudoendothyra, the founder of the name-crowned subfamily, and was derived from Eostaffella sometime in the late Visean or in the later part of the middle Visean based on data from the Moscow Syneclise and Western Europe (Fig. 5). This genus was a stem taxon of all Carboniferous staffellid genera. In the later part of the Mississippian, Pseudoendothyra gave rise to Volgella, which possesses a homeomorphic feature with the Moscovian Parastaffelloides in having subspherical-spherical shells. Palaeoreichelina, seen in the early part of the Pennsylvanian, is considered as a specialized branch from Pseudoendothyra and developed a peculiar uncoiled stage in the later part of its ontogeny. An important renovation of shell composition occurred in the Bashkirian. The Staffellidae started forming their shells with aragonite, and the two genera, Staffella and Nankinella, having this type of shell mineralogy, appeared almost simultaneously in the latest Bashkirian (Groves 1991; age calibrated based on Groves et al. 2007) or slightly older (Zhang et al. 2010). Early representatives of the staffellin lineage are documented mainly from the lower Atokan in the North American craton, but information on this phylogenetic group from Eurasia is weak.

Fig. 6.

Stratigraphic ranges and phylogeny of staffellid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). See Figure 4 for the abbreviations of geological ages.

Fig. 6.

Stratigraphic ranges and phylogeny of staffellid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). See Figure 4 for the abbreviations of geological ages.

The Schubertellidae is restricted, in the Carboniferous, to the Pennsylvanian. It is rather a morphologically conservative group among the Carboniferous fusuline fauna. One subfamily, the Schubertellinae, is recognized in this geological period.

Family SchubertellidaeSkinner, 1931 

Subfamily SchubertellinaeSkinner, 1931 

SchubertellaStaff and Wedekind, 1910 ( = EoschubertellaThompson, 1937; = SchubertinaMarshall, 1969; = PseudoschubertellaMarshall, 1969); TaitzehoellaSheng, 1951 ( = ?ShachellaZhu, 1995); DouglassitesRead and Nestell, 2018; Fusiella Lee and Chen in Lee et al., 1930; OketaellaThompson, 1951.

There is a long-standing discussion, over 30 years, on the distinction and synonymy between Schubertella and Eoschubertella (Sheng et al. 1988; Groves 1991; Ueno in Fohrer et al. 2007; Davydov 2011; Villa and Merino-Tomé 2016). Because of the practical difficulties to delineate the clear taxonomic boundary between these two groups based on their wall structure and other properties, herein it seems to be better to treat them as the same generic entity and recognize Schubertella as valid in this taxonomy, which has a nomenclatural seniority over Eoschubertella. Schubertina and Pseudoschubertella of Marshall (1969) are considered to be small morphotypes of Schubertella (thus Eoschubertella of some authors), or merely correspond to specimens of Schubertella lacking the outermost volution.

Taitzehoella has long been considered to have an affinity with Profusulinella and has been included in the family Fusulinidae (e.g. Rauzer-Chernousova et al. 1951, 1996). Following Ueno in Fohrer et al. (2007), however, this genus is included in this taxonomy in the Schubertellidae, and Shachella is provisionally regarded as a junior synonym of Taitzehoella. Shachella is characterized by a spirotheca developing fine pores, but this feature is also recognized, though vaguely, in Taitzehoella according to the original description by Sheng (1951).

Douglassites reported recently by Read and Nestell (2018) from the North American upper Virgilian is a unique genus, which has a large (in schubertellids) and slightly inflated shell with rugosity in the outer volution. Judging from a strong similarity between the juvenile part of Douglassites shells and the mature shells of ordinary fusiform Schubertella, the descent of the former genus from the latter is evident. This genus is so far monotypic and is only known in the North American craton and should be considered as a specialized offshoot in the Carboniferous schubertellin clade. Schubertella popensis described by Thompson (1965) can be mentioned here as a candidate for the ancestor of Douglassites sprucensisRead and Nestell, 2018, the type species of the genus, although that Schubertella species was reported from the Panthalassan Cache Creek Terrane.

When Thompson (1951) newly established the genus Oketaella, he suggested its generic affinities to both Triticites and Schubertella. Later, Thompson (1964) included this genus in the Schwagerininae (namely Schwagerinidae in the sense of present taxonomy), and this view was followed by Loeblich and Tappan (1987), Sheng et al. (1988), and Rauzer-Chernousova et al. (1996). Until now nine species have been described under the generic name of Oketaella originally, from North American cratonic basins. Of them, Oketaella battleshipwashensis, O. campensis, O. lenensis, and probably O. waldripensis were established based on juvenile specimens of some schwagerinids. On the other hand, Oketaella inflata, O. oscurensis, and O. earglei from several levels of the Missourian, and O. cheneyi and O. fryei (the type species of the genus) from the Wolfcampian (lower Permian) show schubertellid affinities in various degrees, such as the nature of septa, developmental feature of chomata, coiling pattern, nature of spirotheca with relatively fine alveolar structure, and gross shell morphology. In this taxonomy, Oketaella is provisionally included in the Schubertellidae due mainly to its small shell size and spirotheca having a much finer ‘keriothecal’ structure than the ordinary schwagerinid keriotheca. This genus is essentially a cratonic North American, Late Pennsylvanian–early Permian taxon. There are species reported under the name of Oketaella from China and Japan, but they are all regarded as misidentified juvenile (or semi-mature) shells of some schwagerinids assigned to this genus (such as Oketaella borealis, O. sinensis, and O. fuchengensis by Zhang and Xia in Xia and Zhang 1985 and O. shiroishiensis by Morikawa and Kobayashi 1960).

As has been noted by Ebrahim Nejad et al. (2015), Grovesella established by Davydov and Arefifard (2007) contains species that belong to several distinct lineages, judging from the species composition given in the original description of the genus. Especially, there is a relatively large morphological gap between Pennsylvanian and Permian forms. Ebrahim Nejad et al. (2015) recognized a difference in wall composition between Permian Grovesella, including the type species (G. tabasensisDavydov and Arefifard, 2007) from the early Artinskian and older, Pennsylvanian forms of Grovesella. They noted that the former has a typical schubertellid wall with a slightly lighter lower layer (primatheca of Davydov and Arefifard 2007) and probably was derived from typical Schubertella, but the latter has a microgranular wall. Moreover, there is a tendency in the coiling pattern of Grovesella, that Pennsylvanian forms often show skewness in early volutions whereas Permian ones (including the type species) have almost planispiral (or less skewed) coiling. In this taxonomy, Grovesella is restricted to Permian forms having a typical schubertellid wall with a well-recognized primatheca (thus giving a somewhat glassy occurrence when observed under the microscope), by acknowledging the idea of Ebrahim Nejad et al. (2015). Most Pennsylvanian forms that have been assigned to Grovesella are probably the same as ‘Schubertina’ or ‘Eoschubertella’, and are thus included in Schubertella in this study. Permian Grovesella is an important genus in the Schubertellidae because it is an ancestral stock of Pamirina and all neoschwagerinoideans (Vachard et al. 2013).

Biwaella is an early Permian schubertellid genus, which was established by Morikawa and Isomi (1960) with B. omiensisMorikawa and Isomi, 1960 from central Japan as a type species. It occurred originally in late Artinskian–early Kungurian exotic limestone blocks in Jurassic accretionary complexes of Japan, implying that Biwaella was a Panthalassan genus in late early Permian time. This genus is characterized by having spirotheca with a porous structure, which is sometimes expressed as ‘keriotheca’ but is finer than true schwagerinid keriotheca. In any case, this spirothecal character is diagnostic among schubertellid genera. Davydov (1984, 1990a, 2011) reported several ‘Biwaella’ species from the middle Gzhelian of the Darvaz and Donets Basin, including B.? tshelamtshiensis, B.? ex gr. tchelamchiensis (sic), B. zhikalyaki, and B. poletaevi. They have small, elongate, fusiform shells with small proloculi, often skew-coiled early volutions, only weakly fluted septa at polar regions, small but well recognized asymmetrical chomata, and a rather coarsely porous (true keriothecal) wall in the outermost volution. At a glance in axial section they look like some Biwaella but they are regarded as Triticites species in this study. In true schubertellid Biwaella, such as B. europaea of Kochansky-Devidé and Milanović (1962), B. americana reported by Skinner and Wilde (1965a) and Read and Nestell (2019), and B. omiensis mentioned above, septa are rather short and much widely spaced in cross-section (see Morikawa and Isomi 1960, pl. 54, fig. 5; Kochansky-Devidé and Milanović 1962, pl. 1, fig. 11; Skinner and Wilde 1965a, pl. 13, figs 5–6; Read and Nestell 2019, fig. 1i, for example), like its closely related (descendant) genus ToriyamaiaKanmera, 1956. These diagnostic features can be recognized only in cross-sectioned specimens, but in some original descriptions of those ‘Biwaella’ only axial-sectioned specimens were illustrated. In the above-mentioned ‘Biwaella’ specimens from the Gzhelian a cross-section is shown in ‘B.’ poletaevi by Davydov (2011). That specimen (Davydov 2011, fig. 4C) shows ordinary schwagerinid-type septa. Thus, all these Gzhelian ‘Biwaella’ species of Davydov (1984, 1990a, 2011), all having similar shell profiles in axial sections, are potentially considered as merely ‘undersized’ Triticites species. Dzhenchuraeva and Getman (2007, 2010) described similar small Triticites species from the Middle Tianshan in Central Asia under the name of T. komansuensis (s.s.), T. komansuensis deplanatus, T. perpussilus, and Schwageriniformis? facetus. Davydov (1984) considered that early Permian Sphaeroschwagerina is a schubertellid genus and originated from Gzhelian Biwaella (B.? tshelamtshiensis) via the intermediate genus Dutkevichites. Forke (2002, p. 215) accepted part of this idea about the assumed phylogenetic relationship between Dutkevichites and Sphaeroschwagerina (thus the Biwaella?–DutkevichitesSphaeroschwagerina lineage) but rejected its schubertellid assignment based on the fact that the keriothecal wall of these genera does not differ at all from that of the Schwagerinidae. The present observation, that the schwagerinid-type septa can also be seen in the ‘Biwaella’ species discussed above, is consistent with Forke's (2002) conclusion and supports that Sphaeroschwagerina belongs to the Schwagerinidae. In conclusion, the relevant Carboniferous species that have been identified as ‘Biwaella’ before should be excluded from this genus and are placed in Triticites. True Biwaella in the Schubertellidae is restricted to the early Permian (mainly in the Artinskian–Kungurian), thus this genus is not particularly treated in this paper. This minor schubertellid genus has a rather wide palaeogeographical distribution (Read and Nestell 2019), although its dispersal pathway is not very clear.

Kwantoella also has been usually regarded as a schubertellid genus in major fusuline taxonomic works (Loeblich and Tappan 1987; Sheng et al. 1988; Rauzer-Chernousova et al. 1996; Hayward et al. 2021). Igo and Makabe (1999) clarified that the type species of this genus, K. fujimotoiSakagami and Omata, 1957, occurred in the latest Carboniferous. As noted later in the section on the Schwagerinidae, Kwantoella is redefined as a schwagerinid genus in this study, which probably has a close phylogenetic relationship with Triticites.

In the Carboniferous, the Schubertellidae is restricted to the Pennsylvanian, and its generic diversity was low. Schubertella was the first schubertellid genus and appeared in the middle of the early Bashkirian (Akavassian/Askynbashian) (Kulagina et al. 2001; Ivanova 2008). The most promising hypothesis regarding the descent of schubertellids is that they came from Plectostaffella in the Eostaffellinae (Ozawainellidae), such as P. reitlingerae (Groves et al. 1994; Groves 1997).

Fig. 7.

Stratigraphic ranges and phylogeny of schubertellid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). Genera with ranges indicated by red have palaeobiogeographical distribution restricted to the North American Craton Region. See Figure 4 for the abbreviations of geological ages.

Fig. 7.

Stratigraphic ranges and phylogeny of schubertellid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). Genera with ranges indicated by red have palaeobiogeographical distribution restricted to the North American Craton Region. See Figure 4 for the abbreviations of geological ages.

Taitzehoella is a relatively successful genus during the Moscovian. It first appeared in the Kashirian (late early Moscovian) and is known to occur by the end of the Moscovian (Rauzer-Chernousova et al. 1951, 1996; Makhlina et al. 2001b). This genus has been reported from various Carboniferous basins in Eurasia (Palaeotethys and Russian Platform), but is not known in North America, the Arctic, and Panthalassa. Fusiella also appeared sometime in the later part of the early Moscovian (Makhlina et al. 2001b). It is essentially a small-sized schubertellid, but during the Moscovian–Kasimovian transition there are some distinct species in this genus that have remarkably large shells with a large number of volutions, such as F. rawi, F. lancetiformis, and F. segyrdashtiensis (Villa 1995; Davydov 1997b; Forke and Samankassou 2000; Leven and Davydov 2001; Ueno et al. 2013). Fusiella is a rather minor, long-ranging, biostratigraphically less useful genus extending its stratigraphic occurrence up to the Permian, but these large forms can be good biostratigraphic markers, especially for the Moscovian–Kasimovian boundary interval (Isakova 2013).

There are two schubertellid genera that have been known only from cratonic North America; they are Oketaella and Douglassites. Oketaella appears sporadically in Missourian and Wolfcampian strata, but its main occurrence is in the lower Permian (Thompson 1954; Myers 1967; Wahlman 2013, 2019). The origin of the genus is not clearly explained, but two early forms from the lower Missourian, O. inflata and O. oscurensis, have general similarities to Schubertella, implying a close phylogenetic relationship with the latter genus. Douglassites is one of the largest schubertellids known so far in the Carboniferous and restricted to the upper Virgilian (Read and Nestell 2018). As noted above, this genus is likely derived from Schubertella.

The Fusulinidae is a large taxonomic group that flourished and diversified in the Bashkirian and Moscovian. It consists of six subfamilies: the Pseudostaffellinae, Fusulinellinae, Fusulininae, Wedekindellininae, Eofusulininae, and Hemifusulininae.

Family Fusulinidaevon Möller, 1878 

Subfamily PseudostaffellinaePutrya, 1956 

SemistaffellaReitlinger, 1971 ( = PraesemistaffellaOrlova, 1997); PseudostaffellaThompson, 1942 = Atetsuella Okimura, 1958; ( = QuydatellaLiêm, 1966; = QuasistaffellaSolov'eva, 1986); NeostaffellaMiklukho-Maklay, 1959a ( = TopiliniaIvanova, 2008); HanostaffellaCheong, 1984; XenostaffellaCheong, 1973.

Orlova (1997) established Praesemistaffella as a subgenus of Semistaffella, based on two specimens identified as Semistaffella variabilis in Reitlinger (1971). She newly assigned them to Semistaffella (Praesemistaffella) pseudovariabilisOrlova, 1997. The type species of Semistaffella is Pseudostaffella variabilisReitlinger, 1961, but those two specimens in Reitlinger (1971) are not what were included in the type series of the relevant species. Orlova (1997) noted that Praesemistaffella can be distinguished from Semistaffella in the shell shape (the former is predominantly wide-nautiloid with weak umbilici, whereas the latter is subspherical without umbilici), less developed chomata, and more deviated coiling axis. As in the taxonomic name, she considered this subgenus as an intermediate between ancestral Plectostaffella and Semistaffella. However, the differences are minor and thus can be regarded just as showing differences among species, or even as intraspecific variability in one species, in one genus-group taxon. Herein Praesemistaffella is considered taxonomically the same as Semistaffella.

As discussed in Villa et al. (2021), early Kasimovian Quasistaffella can be synonymized with Pseudostaffella, the latter genus usually prevailed in the younger Bashkirian and early Moscovian interval. When Solov'eva (1986) established Quasistaffella, she described its simple morphology among the pseudostaffellin clade (thus, just like showing reversion), such as very small size and undifferentiated wall composition. Nevertheless, she implicitly admitted that its Kasimovian occurrence can distinguish Quasistaffella from much older Pseudostaffella. Later studies disclosed sporadic but continuous occurrences of Pseudostaffella from the late Moscovian (e.g. Villa et al. 2021), so the problem of the apparent stratigraphic gap of these two genera has been resolved.

Quydatella, originally reported from the late Bashkirian–earliest Moscovian interval of Vietnam, is characterized by a well-developed, prolonged early skew-coiled stage in its ontogeny (Liêm 1966). However, this somewhat bizarre feature seen in Quydatella is considered as merely showing an ultimate trait within morphologically variable Pseudostaffella and has no taxonomic value to separate the former from the latter. As noted in Loeblich and Tappan (1987), Atetsuella, which was established by Okimura (1958) with A. imamurai Okimura, 1958 as the type species, is regarded as a junior synonym of Pseudostaffella.

Topilinia was established with Pseudostaffella topiliniPutrya, 1956 as the type species (Ivanova 2008). It can be regarded as a Neostaffella species having a peculiar oval shell with longer diameter (shell width) than coiling axis (shell length). This somewhat different gross shell morphology in this species looks superficially distinctive, but merely indicates that it is a morphological variant within the genus Neostaffella (most probably in N. ex gr. ozawai).

Subfamily FusulinellinaeStaff and Wedekind, 1910 

StaffellaeformesSolov'eva, 1986; Profusulinella Rauzer-Chernousova and Beljaev in Rauzer-Chernousova et al., 1936 [ = ?DagmarellaSolov'eva, 1955; = SolovievaiaVachard and Le Coze, 2018 (pro Ovatella Solov'eva in Rauzer-Chernousova et al., 1996, preoccupied by the brachiopod genus OvatellaBivona Bernardi, 1832): = Depratina Solov'eva in Rauzer-Chernousova et al., 1996; = KalmykovaellaEktova, 1989; = NeofusiellaEktova, 1989]; Aljutovella Rauzer-Chernousova in Rauzer-Chernousova et al., 1951 ( = Priscoidella Solov'eva in Rauzer-Chernousova et al., 1996; = Tikhonovichella Solov'eva in Rauzer-Chernousova et al., 1996; = Skelnevatella Solov'eva in Rauzer-Chernousova et al., 1996; = Elongatella Solov'eva in Rauzer-Chernousova et al., 1996; = SubaljutovellaIvanova, 2008); Citronites Solov'eva in Rauzer-Chernousova et al., 1996; Fusulinellavon Möller, 1877 ( = NipperellaSolov'eva, 1984; = MoelleritesSolov'eva, 1986; = AnnulofusulinellaWilde, 2006; = Bogushinella Bensh and Orlova in Orlov-Labkovsky and Bensh, 2015), HidaellaFujimoto and Igo, 1955; ObsoletesKireeva, 1950 ( = PraeobsoletesRemizova, 1992); PlectofusulinaStewart, 1958; ProtriticitesPutrya, 1948; KanmeraiaOzawa, 1967 ( = PulchrellaSolov'eva, 1983; = UsvaellaRemizova, 1992); ThompsonellaSkinner and Wilde, 1965b; WaeringellaThompson, 1942.

Solov'eva (in Rauzer-Chernousova et al. 1996) introduced several new genus-group taxa to what have been called ‘species groups’ within Profusulinella and Aljutovella by Rauzer-Chernousova et al. (1951); they are Depratina, Ovatella (but later replaced by the name Solovievaia by Vachard and Le Coze 2018), Priscoidella, Tikhonovichella, Skelnevatella, and Elongatella. After that, these names have been mainly employed by Russian fusuline specialists but seldom are found in works by others. In this taxonomy, these Solov'eva (in Rauzer-Chernousova et al. 1996) taxa are regarded herein as invalid and their generic content is restored to those that were generally assigned before, namely to Profusulinella or Aljutovella. As Rauzer-Chernousova et al. (1951) admitted, these taxa are indeed intra-generic ‘species groups’ recognized based on rather minor morphological differences that are usually considered as showing specific diagnoses within a genus, and their taxonomic boundaries and utility as genus-ranked taxa are quite vague. In fact, Solov'eva (in Rauzer-Chernousova et al. 1996) described short diagnoses of these ‘genera’, but she did not mention their differences from closely related ones. At the moment, there is little benefit to recognizing them as genus-group taxa.

Although several Profusulinella-group genera are regarded as synonyms mentioned above, Staffellaeformes is provisionally retained as valid in this taxonomy. This genus is easily recognized morphologically by having a small, short, oval shell, almost unfluted septa, well-developed chomata, and often early skew coiling. The appearance of oval-shaped Staffellaeformes (thus having a slightly longer axis of coiling than a diameter of shell) from ancestral spherical Pseudostaffella (Figs 8 & 9) may merely show one small change of shell morphology, but it was a significant leap for fusuline evolution because with this evolutionary step it started the upsizing of shells in Carboniferous fusulines and finally resulted in the larger foraminifers.

Fig. 8.

Stratigraphic ranges and phylogeny of fusulinid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). Genera with ranges indicated by red have palaeobiogeographical distribution restricted to the North American Craton Region. 1–3 (in a circle) correspond to three lineages that developed four-layered spirotheca from three-layered one at around the Vereian–Kashirian boundary (early Moscovian), illustrated in Figure 10. See Figure 4 for the abbreviations of geological ages. Note that the Wedekindellininae was derived from Fusulinella in the Fusulininae, and the Hemifusulininae and Eofusulininae came from the ProfusulinellaAljutovella lineage in the Fusulinellinae, which are illustrated separately in the lower part of this figure.

Fig. 8.

Stratigraphic ranges and phylogeny of fusulinid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). Genera with ranges indicated by red have palaeobiogeographical distribution restricted to the North American Craton Region. 1–3 (in a circle) correspond to three lineages that developed four-layered spirotheca from three-layered one at around the Vereian–Kashirian boundary (early Moscovian), illustrated in Figure 10. See Figure 4 for the abbreviations of geological ages. Note that the Wedekindellininae was derived from Fusulinella in the Fusulininae, and the Hemifusulininae and Eofusulininae came from the ProfusulinellaAljutovella lineage in the Fusulinellinae, which are illustrated separately in the lower part of this figure.

Fig. 9.

The genus Profusulinella as a centre of diversification in the family Fusulinidae. During the late Bashkirian and earliest Moscovian, this genus produced several morphological groups and each of them founded a new lineage that evolved later into a new subfamily in the Fusulinidae. Abbreviations of geological ages: B., Bogdanovkian; Sy., Syuranian; Aka., Akavassian; Askyn., Askynbashian; Tash., Tashastian; Asat., Asatauian; Podol., Podolskian; Mya., Myachkovian. Abbreviation of taxonomic (generic) name, Pr., Profusulinella. Specimens illustrated in this figure are from the following data sources: Plectostaffella (P. jakhensis) from Reitlinger (1971); Semistaffella variabilis from Reitlinger (1961); Pseudostaffella antiqua/praegorskyi group (P. antiqua) from Grozdilova and Lebedeva (1950); Staffellaeformes staffellaeformis, Profusulinella parva, Profusulinella prisca, Aljutovella (A. salatovica), Fusulinella (F. paracolaniae), Hemifusulina (H. bocki) from Rauzer-Chernousova et al. (1951); Profusulinella oblonga from Potievskaya (1964); Profusulinella primitiva from Grozdilova and Lebedeva (1954); Profusulinella ovata from Rauzer-Chernousova (1938); Profusulinella rhomboides group (P. pseudorhomboides), Citronites (C. notabilis), Eofusulina (E. triangula) from author's unpublished materials from the Donets Basin, Ukraine; Verella (V. varsanofievae) from Dalmatskaya (1951); Kanmeraia (K. ex. gr. pulchra) from Ueno and Mizuno (1993); Wedekindellina (W. euthysepta) from Dunbar and Henbest (1942); Beedeina (B. lanceolata) from author's unpublished material from the Ichinotani Formation, Hida Marginal Belt, Japan; Hemifusulinella (H. djartassensis) from Rumyantseva (1962); Dutkevichella (D. pseudobocki) from Fohrer et al. (2007).

Fig. 9.

The genus Profusulinella as a centre of diversification in the family Fusulinidae. During the late Bashkirian and earliest Moscovian, this genus produced several morphological groups and each of them founded a new lineage that evolved later into a new subfamily in the Fusulinidae. Abbreviations of geological ages: B., Bogdanovkian; Sy., Syuranian; Aka., Akavassian; Askyn., Askynbashian; Tash., Tashastian; Asat., Asatauian; Podol., Podolskian; Mya., Myachkovian. Abbreviation of taxonomic (generic) name, Pr., Profusulinella. Specimens illustrated in this figure are from the following data sources: Plectostaffella (P. jakhensis) from Reitlinger (1971); Semistaffella variabilis from Reitlinger (1961); Pseudostaffella antiqua/praegorskyi group (P. antiqua) from Grozdilova and Lebedeva (1950); Staffellaeformes staffellaeformis, Profusulinella parva, Profusulinella prisca, Aljutovella (A. salatovica), Fusulinella (F. paracolaniae), Hemifusulina (H. bocki) from Rauzer-Chernousova et al. (1951); Profusulinella oblonga from Potievskaya (1964); Profusulinella primitiva from Grozdilova and Lebedeva (1954); Profusulinella ovata from Rauzer-Chernousova (1938); Profusulinella rhomboides group (P. pseudorhomboides), Citronites (C. notabilis), Eofusulina (E. triangula) from author's unpublished materials from the Donets Basin, Ukraine; Verella (V. varsanofievae) from Dalmatskaya (1951); Kanmeraia (K. ex. gr. pulchra) from Ueno and Mizuno (1993); Wedekindellina (W. euthysepta) from Dunbar and Henbest (1942); Beedeina (B. lanceolata) from author's unpublished material from the Ichinotani Formation, Hida Marginal Belt, Japan; Hemifusulinella (H. djartassensis) from Rumyantseva (1962); Dutkevichella (D. pseudobocki) from Fohrer et al. (2007).

Dagmarella is a poorly defined taxon, occurring in the Moscovian (Solov'eva 1955). As long as the original diagnosis is considered, several different taxonomic entities that should be subsumed in different genera in the family Fusulinidae are likely included in this taxon. The type species has well-developed, broad chomata, a Profusulinella-type three-layered wall, and septal fluting in the axial regions and in the last half volution, and is somewhat similar to Profusulinella rhombiformis nibelensis. In this study, Dagmarella is regarded as a morphological variant in Profusulinella and included in the latter genus taxonomically.

Ektova (1989) established Kalmykovaella with Fusulinella (Neofusulinella) parva Lee and Chen in Lee et al., 1930 ( = Profusulinella parva in current taxonomy) as the type species and included several other subspherical Profusulinella species (such as P. copiosa and Staffellaeformes staffellaeformis) in it. Then, she considered that Kalmykovaella should be subsumed in the Schubertellidae, because she found greater similarities between these subspherical early profusulinellas and ‘eoschubertellas’ ( = Schubertella in this study). However, Profusulinella parva is one of the typical species of this named genus, thus any further discussion is unnecessary. Kalmykovaella is a junior synonym of Profusulinella. In the same article establishing Kalmykovaella, Ektova (1989) described a new genus named Neofusiella (type species: N. asymmetricaEktova, 1989) together with the new subfamily Fusiellinae to accommodate Fusiella, Kwantoella, Waeringella, and this new genus. She further introduced the new family Fusiellidae and included Fusiellinae, Eofusulininae, and Wedekindellininae. Neofusiella occurs in the early part of the late Bashkirian and has an elongate fusiform shell with a Profusulinella-type three-layered spirotheca. Thus, it merely shows one morphological type among Profusulinella, and the type species is very similar to P. oblonga, which is considered to give rise to the Eofusulininae lineage later (Fig. 9). Neofusiella is considered as a junior synonym of Profusulinella, and the introduction of the Fusiellidae and Fusiellinae in the sense of Ektova (1989) is not valid in this fusuline taxonomy.

As noted in Loeblich and Tappan (1987), Nipperella is considered a junior synonym of Fusulinella. That genus was established by Solov'eva (1984) with Fusulinella nipperensisRoss and Sabins, 1965 from Arizona, USA as the type species. However, the basic diagnosis of this genus is the same as that of Fusulinella, and there are only some minor differences seen in it, such as the shape of chomata, the total number of septa, slightly different shell shape, and the thickness of wall. These variabilities are merely intra-generic, suggesting differences of species in Fusulinella, and thus do not warrant Nipperella as a distinct genus. Moellerites proposed by Solov'eva (1986) is also considered as a junior synonym of Fusulinella. According to the original description, this genus is morphologically intermediate between Profusulinella and Fusulinella, but the development of a four-layered spirotheca with incipient diaphanotheca supports its closer affinity to Fusulinella. The gross shell morphology and Kashirian to lower Podolskian occurrence of Moellerites also suggest that it is nothing but comparable to Fusulinella. Annulofusulinella erected by Wilde (2006) has a Fusulinella-like shell but possesses fine pores in the wall of the outer volutions. As has been described by Ueno in Fohrer et al. (2007), however, it is not surprising even if Fusulinella exhibits such a feature of finely perforated spirotheca. Probably, those Fusulinella specimens with fine pores in the spirotheca of the outermost volutions suggest that the spirotheca of at least some advanced Fusulinella species is finely perforated originally, but such fine structure in the wall is not preserved in most cases due merely to diagenetic alteration. In any case, Annulofusulinella can be included in the genus Fusulinella in this taxonomy. Its occurrence from the middle–late Atokan is also consistent with this conclusion.

Bogushinella was established by Bensh and Orlova in Orlov-Labkovsky and Bensh (2015) with Fusulinella oviformisBogush, 1960 as the type species. Several existing species (such as Fusulinella subcylindrica, F. altispiralis, F. fluxa, and F. longiaxialis) that have vague porosity in the wall were included in it. These authors intended to accommodate species that have intermediate features (especially in the spirothecal structure) between Fusulinella and Protriticites, in the genus Bogushinella. As noted above, however, the vague porosity in the wall of Fusulinella would not always be a good diagnosis to separate a new genus-group taxon from that genus. Bogushinella is regarded as a junior synonym of Fusulinella in this study.

The taxonomy and validity of Protriticites, Obsoletes, and Praeobsoletes have been discussed, particularly in connection with the definition of the Moscovian–Kasimovian boundary, by many authors since the introduction of the former two genera (Putrya 1948; Kireeva 1950; Ryazanov 1958a; Volozhanina 1962; Chen’ 1963; Rozovskaya 1975; Davydov 1990b, 1997b, 1999, 2007; Ueno 1991b; Remizova 1992, 1993, 1995, 2004; Davydov and Krainer 1999; van Ginkel and Villa 1999; Forke and Samankassou 2000; Baranova 2005). The taxonomic validity of each genus-rank taxon as well as their generic/subgeneric attribution and hierarchical position in the Linnean taxonomy have been variably recognized. Based on a likely plausible phylogenetic scenario from Fusulinella to early schwagerinid fusulines, Obsoletes gave rise to Triticites whereas from Protriticites having massive secondary epithecal deposits arose the MontiparusRauserites lineage (Davydov 1990b, 1997b). Thus, Obsoletes and Protriticites are better regarded as separate valid genera, upon synonymizing somewhat loosely defined intermediate Praeobsoletes with Obsoletes.

Kanmeraia was introduced by Ozawa (1967) as a subgenus of Pseudofusulinella, to accommodate elongate fusiform species with wider tunnel angles in that genus. In terms of the spirothecal structure of Pseudofusulinella (including Kanmeraia in this study), Skinner and Wilde (1965b, p. 27) stated ‘Spirotheca composed of tectum and diaphanotheca. Chomata deposits commonly spread across inner surface of spirotheca in central part of shell, giving a false appearance of fusulinellid wall structure’, in the description of Kanmeraia prima. However, this description seems to be based on a misunderstanding of the fundamental wall structure seen in the family Fusulinidae. As has been clearly demonstrated by Groves (2005), even four-layered Fusulinella originally formed a two-layered spirotheca consisting of a tectum and diaphanotheca (or lower structureless layer, which has been referred to as primatheca by some authors: Stewart 1970; Davydov and Nilsson 1999). These structures are the primary component of the fusulinid shell wall and are termed protheca (Groves 2005). The protheca is variously covered by secondary deposits called epitheca on either (upper or lower) side, or on both sides, of it. Epithecal deposits are developed on the floors, septa, and ceilings of the chamber, making a four-layered Fusulinella-type wall. In this sense, Kanmeraia clearly has a Fusulinella-type four-layered wall because it develops epithecal deposits in various degrees (see Kanmeraia walls illustrated in Skinner and Wilde 1965b, pl. 5, figs 1–3). This type of wall structure and similar gross shell morphology to Kanmeraia, including fusiform to elongate fusiform shell with almost straight to slightly concave lateral slopes, laterally extending highly asymmetrical chomata, and septal fluting only in the axial regions, are also seen in Pulchrella and Usvaella, which are sometimes found in studies of Moscovian–early Permian fusulines in the Russian Platform, Timan–Pechora, and the Urals (Solov'eva 1984; Remizova 1995, 2004; Makhlina et al. 2001b; Ivanova 2008). These genera were also adopted as valid fusulinid taxa in Rauzer-Chernousova et al. (1996). As in Kobayashi's (2017) arguments, however, Pulchrella and Usvaella are better regarded as synonyms of Kanmeraia based on their common essential shell features.

Waeringella is a poorly known genus described from some cratonic basins in the US, and according to Thompson's (1942) original diagnosis it has a wall consisting of a tectum, lower (less dense) layer, and upper layer (tectorium), thus of a protheca and upper tectorium. Its gross shell morphology is similar to Kanmeraia in having an elongate fusiform shell with slightly concave lateral slopes, well developed asymmetrical chomata and tunnel, weakly fluted septa in the extreme polar regions, and weak axial fillings, except for the above-mentioned three-layered spirotheca lacking a lower tectorium. As noted in the following section, Waeringella seems to be related phylogenetically to Kanmeraia rather than Eowaeringella in the Wedekindellininae. Among the three species of Waeringella from North America, W. bailkeyi and W. chiricahuensis reported, respectively, by Thompson et al. (1950) and Sabins and Ross (1963), are probably included in Kanmeraia based on their diaphanotheca-bearing spirothecal structure. Moreover, there are some Sakmarian Waeringella described by Grozdilova and Lebedeva (1961) and Konovalova (1977) from Timan and other parts of the Russian Platform. As Remizova and Mikhaylova (1996) concluded, they are better referred to Thompsonella. In summary, at the moment Waeringella is monotypic, including only the type species (W. spiveyiThompson, 1942) from the early Virgilian of Texas. Its phylogenetic origin is not very clear.

Although it is not a Carboniferous genus, UralofusulinellaChuvashov, 1980 has been attributed to the family Fusulinellinae (Loeblich and Tappan 1987; Rauzer-Chernousova et al. 1996). It is a short-ranging monotypic taxon restricted to the Artinskian (early Permian) of the Urals, and was proposed originally as a subgenus of Fusulinella. Uralofusulinella has a short fusiform shell, large proloculus compared to the shell size, weakly developed chomata, and almost unfluted septa. Its spirotheca is described as being four-layered, consisting of a tectum, diaphanotheca, and upper and lower tectoria, which is essentially identical to that of Fusulinella. However, the stratigraphically discrete occurrences of Uralofusulinella and Moscovian Fusulinella do not relate them phylogenetically. Uralofusulinella is probably a schubertellid genus, contrary to its generic name, although the large proloculus of this genus is not very common in schubertellids (but see Oketaella described in the section on Schubertellidae).

Subfamily Fusulininaevon Möller, 1878 

BeedeinaGalloway, 1933 ( = Parabeedeina Solov'eva in Rauzer-Chernousova et al., 1996); Putrella Rauzer-Chernousova in Rauzer-Chernousova et al., 1951; BartramellaVerville, Thompson and Lokke, 1956; FusulinaFischer de Waldheim, 1829 ( = SchellwieniaStaff and Wedekind, 1910, a superfluous name for Fusulina; = Kamaina Solov'eva in Rauzer-Chernousova et al., 1996); PseudotriticitesPutrya, 1940; UndatafusulinaLeven, 1998; Quasifusulinoides Rauzer-Chernousova and Rozovskaya in Rauzer-Chernousova and Fursenko, 1959; QuasifusulinaChen, 1934 ( = Epifusulina Chen in Grabau, 1936).

Parabeedeina was erected by Solov'eva in Rauzer-Chernousova et al. (1996), but its type species, Fusulina elegans Rauzer-Chernousova and Beljaev in Rauzer-Chernousova et al., 1940, is a typical Beedeina with a fusiform shell, strongly and regularly fluted septa, four-layered wall, and asymmetrical, well-developed chomata. Moreover, there is no mention as to what shell features of Parabeedeina can be diagnostic to separate it from other related genera, especially from the most similar genus Beedeina. Since Parabeedeina is defined based on the same morphological diagnosis as Beedeina, the former is regarded as a junior synonym of the latter. Kamaina was also introduced by Solov'eva in Rauzer-Chernousova et al. (1996) with the type species Fusulina kamensis Safonova in Rauzer-Chernousova et al., 1951. Unfortunately, she did not explain on what basis the new genus Kamaina can be distinguished from Fusulina. Morphologically, Fusulina kamensis has a larger shell, larger proloculus, and slightly undulating spirotheca, but the overall features do not deviate from the diagnosis of the genus Fusulina. In this study, Kamaina is synonymized with Fusulina.

As noted by Thompson (1948) and Loeblich and Tappan (1987), Schellwienia was proposed as a typical subgenus of Fusulina, thus is a typonym of Fusulina, with Fusulina cylindrica as the type species. It is an illegitimate name nomenclaturally [nomen superfluum, recte Fusulina (Fusulina) of Staff and Wedekind, 1910]. As for Quasifusulina, Grabau (1936, p. 21 footnote) noted ‘the genera Epifusulina and Quasifusulina were both proposed in 1934 by Chen, in a different publication but with the same genotype for both. They are therefore synonyms’. However, the relevant Chen (1934) paper that proposed Epifusulina does not exist, thus Loeblich and Tappan (1987) listed this nomenclatural action as ‘Epifusulina Chen in Grabau, 1936’, which is also followed herein. In any case, QuasifusulinaChen, 1934 is a valid name.

Subfamily WedekindellininaeKahler and Kahler, 1966 

ZellerellaWilde, 2006; ParafusulinellaStewart, 1970; EowaeringellaSkinner and Wilde, 1967a; Wedekindellina Dunbar and Henbest in Cushman, 1933 (pro WedekindellaDunbar and Henbest, 1930, preoccupied by the goniatitid genus WedekindellaSchindewolf, 1928; and pro WedekindiaDunbar and Henbest, 1931, preoccupied by the goniatitid genus WedekindiaSchindewolf, 1925); Parawedekindellina Safonova in Rauzer-Chernousova et al., 1951; FrumentellaStewart, 1958.

Taxonomy and validity (mutual synonymity) of Zellerella, Parafusulinella, and Eowaeringella in this subfamily, and also Waeringella and Kanmeraia, which are included here in the subfamily Fusulinellinae, are complicated. Although all of these are treated as valid genera in this taxonomy, some may be synonymized after further study. Zellerella was established by Wilde (2006) as a typical cratonic North American genus and is known to occur throughout the Desmoinesian. Its morphology is suggestive that the genus was derived from North American elongate fusiform Fusulinella with highly asymmetrical chomata of late Atokan age, such as F. nipperensis reported by Ross and Sabins (1965). As has been suggested by Wilde (2006), Zellerella is a potential ancestral genus of Wedekindellina of early–middle Desmoinesian age, and it also produced Eowaeringella in the early Missourian. In any case, these three are closely related genera occurring mainly from cratonic North America in a particular interval (Desmoinesian–basal Missourian), although Wedekindellina had much wider distribution and is also known in the Arctic and Russian Platform.

Parafusulinella is a rarely known genus reported from cratonic North America, and only two species from the upper part of the lower Desmoinesian have been so far reported, in the original description of the genus (Stewart 1970). Its spirotheca is described as three-layered, consisting of a tectum, diaphanotheca (primatheca), and upper tectorum, but a lower tectorium is sometimes developed, suggesting that it has a spirothecal structure similar to the above-mentioned three genera. Interesting to note, particularly herein, is a striking similarity of gross shell morphology between Parafusulinella species and some species of Zellerella (Z. fusiformis and Z.? sp. B in Wilde, 2006). These Zellerella species occur from the Wedekindellina Zone, which corresponds generally to the lower Desmoinesian in the cratonic North American fusuline biostratigraphy (Wahlman 2019). Parafusulinella is potentially the same as some species of Zellerella, and there may need to be an overall taxonomic reexamination of all the species belonging to these two genera.

It is not clear indeed whether there is a phylogenetic relationship between Eowaeringella and Waeringella. They have somewhat similar gross shell profiles, but the former has larger shells than the latter. Moreover, there is a stratigraphic gap in the occurrence of these two genera. Stewart (1968) concluded that there is little or no phylogenetic relationship between the genera Eowaeringella and Waeringella. If anything, the overall shell features of Waeringella are, at a glance, more similar to those of Kanmeraia. This is one reason why I included Waeringella in the subfamily Fusulinellinae and related these two genera phylogenetically in this taxonomy (Fig. 8).

Subfamily Eofusulininae Rauzer-Chernousova and Rozovskaya in Rauzer-Chernousova and Fursenko, 1959 

EowedekindellinaEktova, 1977; VerellaDalmatskaya, 1951 ( = PseudowedekindellinaSheng, 1958); Eofusulina Rauzer-Chernousova in Rauzer-Chernousova et al., 1951 (= AkiyoshiellaToriyama, 1953; = PostverellaIvanova, 2008); ParaeofusulinaPutrya, 1956; NeofusulinaMiklukho-Maklay, 1963.

For the taxonomy of Verella and Eofusulina and their synonymies, see Ueno and Villa (2018). Although they considered Paraeofusulina as a subgenus of Eofusulina, the former is regarded as an independent genus in this study because of its different (more elongate) gross shell morphology from the latter.

Subfamily HemifusulininaePutrya, 1956 

HemifusulinellaRumyantseva, 1962; DutkevichellaPutrya, 1956; Hemifusulinavon Möller, 1877.

Three hemifusulinin genera are all represented by short to elongate subcylindrical-cylindrical shells with weakly to moderately, regularly fluted septa, well-developed chomata, and a stable tunnel, thus giving an impression that the shell is ‘bilateral’ to a vertical (sagittal) plane passing through the proloculus in the axial section. Dutkevichella is distinguished from Hemifusulinella in having stronger septal fluting, and Hemifusulina is differentiated from Dutkevichella in having further stronger septal fluting and coarse pores in the spirotheca, which are sometimes comparable to the keriothecal structure in schwagerinids.

When establishing the genus Dutkevichella, Putrya (1956) expressed the difference of wall structure between this genus and Hemifusulina by noting that, based on their appearance of wall structure, Dutkevichella had been included in Fusulina before, whereas Hemifusulina had been often attributed to Triticites. His sentence shows well the practical discrimination of the two genera. Both have, by definition, a porous structure in their wall, but that in Dutkevichella is usually faint, and sometimes the diaphanotheca is better expressed in the wall, whereas that of Hemifusulina is usually more robust and better developed. Considering this criterion, Putrya (1956) regarded Fusulina dutkevichi, F. bocki, and F. pseudobocki as Dutkevichella. There are a number of Kashirian and Podolskian ‘Hemifusulina’ reported by Rauzer-Chernousova et al. (1951) and Makhlina et al. (2001b) from the Moscow Syneclise, such as ‘H.’ communis and ‘H.’ vozhgalica. Some, or probably many of them, would be better referable to Dutkevichella after careful re-examination of the wall structure because, according to their description, the diaphanotheca is more clearly expressed in the spirotheca of these species.

The first genus of this family is Semistaffella in Pseudostaffellinae, which came from Plectostaffella in the Ozawainellidae in the early Bashkirian (in Syuranian time) as a consequence of lengthening of the coiling axis and increasing coiling skewness in the early volutions, together with increasing shell diameter (Fig. 9). An idea of the early evolution of the sufbfamily Pseudostaffellinae, from Plectostaffella to Pseudostaffella via Semistaffella, was introduced by Reitlinger (1971). Groves (1988) later demonstrated this hypothesis based on materials from the type section of the Bashkirian Stage, in the Urals. The entire evolutionary and phylogenetic scheme of the Pseudostaffellinae was elaborated in Groves et al. (1994), which is essentially followed in this taxonomy. Pseudostaffellins are characterized by having subspherical to spherical shells with the length of coiling axis not longer than the shell diameter. In most cases, they are circular to vertically elliptical in a section parallel to the coiling axis and through the proloculus, but some show a quadrate profile. This lineage was common during the Bashkirian and Moscovian, and especially Pseudostaffella and Neostaffella constituted important parts of fusuline faunas of these ages in many Eurasian areas. The latter genus, which first appeared in the late Bashkirian, is characterized by a larger shell among pseudostaffellins and is the first fusuline genus that obtained a four-layered wall with a diaphanotheca by developing rich epithecal deposits in the shell (Groves 1988). Hanostaffella and Xenostaffella, which appeared in the late Moscovian, are two morphological variants derived from Neostaffella. These genera have well-developed, depressed umbilici, and the coiling involution became weaker than Neostaffella, finally forming a very distinctive, strongly umbilicated and also slightly depressed vertically, evolute shell in Xenostaffella. Most of the pseudostaffellins disappeared at the end of the Moscovian, but primitive-looking, small forms of Pseudostaffella rarely occur up to the lower Kasimovian, which were sometimes identified as Quasistaffella (Solov'eva 1986; Remizova 1995). They are regarded as mere survivors of Pseudostaffella (Villa et al. 2021). Hanostaffella is also known up to the lower Kasimovian (Ueno et al. 2013).

Pseudostaffella gave rise to Staffellaeformes in the latest early Bashkirian (Askynbashian) and became the founder of the subfamily Fusulinellinae (Figs 8 & 9). It is a morphologically intermediate genus between Pseudostaffella and Profusulinella, and the latter genus soon appeared from Staffellaeformes in the late Askynbashian, or the Tashastian in the late Bashkirian (Kulagina et al. 2001; Ivanova 2008). Profusulinella is an important genus for the evolution and dispersion of the Fusulinidae because it was a ‘centre of diversification’ in the early history of the family. This genus produced a number of morphologically variable lineages (species groups), and they became root stocks of several new subfamilies (Figs 8 & 9). This morphological and phylogenetic diversification occurred during late Bashkirian time, and, by the Kashirian (late early Moscovian), several descendant genera from Profusulinella, such as Fusulinella, Kanmeraia, Eofusulina, Dutkevichella/Hemifusulina, and Aljutovella, became predominant in the Moscovian fusuline fauna, especially in the Palaeotethys and Ural–Arctic regions.

In the subfamily Fusulinellinae, Aljutovella branched off from Profusulinella in the latest Bashkirian, and afterwards it gave rise to a descendant genus Citronites in the Kashirian, which was the direct ancestor of Beedeina in Eurasia. Almost at the same time, Profusulinella produced two other daughter genera, Fusulinella and Kanmeraia. It is interesting to note that these three genera (Citronites, Fusulinella, and Kanmeraia), coming from different phylogenetic stocks in Profusulinella, all had developed the Fusulinella-type four-layered wall consisting of a tectum, diaphanotheca, and upper and lower tectoria (Fig. 10). Moreover, as has been demonstrated by Groves (2005), even among Fusulinella the four-layered wall had evolved in a number of palaeogeographically distinct populations of advanced profusulinellas in North American interior cratonic basins and Eurasia, including the Profusulinella pseudorhomboidesKanmeraia subpulchra transition illustrated in Figure 10. They apparently underwent identical modifications in wall structure at about the same time. This evolutionary process is a good example of the homeomorphism or convergent acquisition of a morphological trait in closely related but distinct lineages within a larger clade, which is often seen in fusuline evolution (Ueno 1992; Groves 1997). The morphological transition from the P. pseudorhomboides group to the K. subpulchra group occurred in the western Palaeotethys (Groves 2005; Fig. 10). Kanmeraia flourished during the Middle–Late Pennsylvanian in mainly the western Palaeotethys and the Ural–Arctic Region (see sections in regional fusuline successions below). Some taxa migrated to the Panthalassa Region in the Moscovian (Kanmeraia itoi, K. taishakuensis, and K. pulchra from the Akiyoshi Limestone in SW Japan: Ueno 1989; Ueno and Mizuno 1993) and to the North American cratonic basins in Virgilian time [such as Kanmeraia bailkeyi ( = Waeringella bailkeyi of Thompson et al., 1950) from the lower Virgilian and K. utahensis of Thompson (1954) at the Pennsylvanian–Permian contact]. This genus was more diversified in Western North American terranes during the early Permian and finally gave rise to Pseudofusulinella as the last genus of this lineage (Skinner and Wilde 1965b, 1966; Ozawa 1967). In the course of the evolutionary development, Kanmeraia probably produced two minor genera in the Late Pennsylvanian, Thompsonella and Waeringella, although the origin of the latter genus is not very clear. Waeringella is probably closer to Kanmeraia phylogenetically rather than the older ZellerellaWedekindellinaEowaeringella lineage that flourished in cratonic North America during Desmoinesian–earliest Missourian time, judging from two pieces of circumstantial evidence; there are slight similarities in gross shell morphology shared by Waeringella and Kanmeraia, and there is a distinct chronological gap between Waeringella and Eowaeringella. North American Waeringella probably exhibits a short-lived peculiar lineage derived from Kanmeraia, which would have migrated from the Ural–Arctic Region. Plectofusulina is a small-shelled variant of Fusulinella developed in cratonic North America, and Hidaella, with its characteristic rugosity in spirotheca, is probably an environmental variant of the latter genus.

Fig. 10.

Evolution from three-layered wall to four-layered one observed in three, coeval, closely related but distinct lineages in the Fusulinellinae. This example is from the lower Moscovian Karaguz section in the Donets Basin, Ukraine. The development of a four-layered wall in Citronites notabilis (b), Kanmeraia subpulchra (d) and Fusulinella schubertellinoides (f) from their ancestors with a three-layered wall, Aljutovella postaljutovica (a), Profusulinella pseudorhomboides (c) and Profusulinella constans (e), occurred almost simultaneously at the Vereian–Kashirian boundary interval in the early Moscovian. A: species with Profusulinella-type three-layered spirotheca [tectum, lower less dense layer ( = ‘diaphanotheca’), and upper tectorium], B: species with Fusulinella-type four-layered spirotheca (tectum, diaphanotheca, and upper and lower tectoria). See Aizenverg et al. (1975) for limestone numbers in Donets Basin stratigraphy of the Karaguz section.

Fig. 10.

Evolution from three-layered wall to four-layered one observed in three, coeval, closely related but distinct lineages in the Fusulinellinae. This example is from the lower Moscovian Karaguz section in the Donets Basin, Ukraine. The development of a four-layered wall in Citronites notabilis (b), Kanmeraia subpulchra (d) and Fusulinella schubertellinoides (f) from their ancestors with a three-layered wall, Aljutovella postaljutovica (a), Profusulinella pseudorhomboides (c) and Profusulinella constans (e), occurred almost simultaneously at the Vereian–Kashirian boundary interval in the early Moscovian. A: species with Profusulinella-type three-layered spirotheca [tectum, lower less dense layer ( = ‘diaphanotheca’), and upper tectorium], B: species with Fusulinella-type four-layered spirotheca (tectum, diaphanotheca, and upper and lower tectoria). See Aizenverg et al. (1975) for limestone numbers in Donets Basin stratigraphy of the Karaguz section.

Obsoletes and Protriticites are two important genera derived from Fusulinella at the end of the Moscovian. They have started developing a steady-state porous structure in the wall, although a simple porous wall is rarely found, even in Fusulinella (e.g. Ueno in Fohrer et al. 2007). The appearance of Protriticites and Obsoletes marked an important evolutionary step in the Fusulinellinae lineage because their direct descendants founded the family Schwagerinidae, which flourished much in the Late Pennsylvanian–middle Permian (Guadalupian). There are two main ideas with respect to the phylogenetic relationships among Fusulinella, Obsoletes, and Protriticites, and the early evolution of the family Schwagerinidae (Fig. 11). Davydov (1990b, 1997b) considered two separate lineages derived from Fusulinella, which finally led to two distinct taxonomic groups in the early Schwagerinidae; they are MontiparusRauserites from Protriticites and Triticites from Obsoletes, respectively, with intermediate Praeobsoletes in the latter phylogenetic line (Fig. 11a). The last genus is regarded as a junior synonym of Obsoletes in this study. On the other hand, van Ginkel and Villa (1999) synonymized Obsoletes in Protriticites (Fig. 11b), showing a more ‘mosaic-like’ evolutionary development pattern from Fusulinella to Montiparus (and to Rauserites) and Triticites (Fig. 11b). In this phylogenetic scheme they treated Obsoletes as showing one type of species group in Protriticites. These two ideas superficially look very different, at least taxonomically, but they both supposed a basically similar evolutionary development between Fusulinella and early schwagerinid genera. In this study I treat Obsoletes and Protriticites as independent, following a conventional view mainly formulated by Davydov (1990b, 1997b), after synonymizing somewhat loosely defined Praeobsoletes in the former genus and also admitting that in actual specimens it sometimes is difficult to make a clear-cut boundary between Protriticites and Obsoletes. Moreover, this treatment ultimately approves polyphyly of the Schwagerinidae, in which this descendant family was derived from two closely related but distinct lineages within a larger clade (including Protriticites and Obsoletes, and their ancestral Fusulinella, all in the Fusulinellinae). Protriticites was also found in the late Desmoinesian of the western United States (Wahlman et al. 1997), without having its ancestral lineage there, suggesting migration from the Ural–Arctic Region (Villa et al. 2003; Villa and Wahlman 2007).

Fig. 11.

Two hypotheses showing the early phylogeny and evolution of the family Schwagerinidae during the latest Moscovian and Kasimovian. (a) Phylogenetic reconstruction between Fusulinella in the Fusulinidae and early schwagerinid genera (Triticites, Montiparus, and Rauserites) proposed by Davydov (1990b, 1997b). (b) Phylogenetic model from Fusulinella to early schwagerinid genera proposed by van Ginkel and Villa (1999) (modified from fig. 2 of van Ginkel and Villa, 1999). Arrows indicate supposed evolutionary pathways between genera and among several morphology-diagnostic species groups within Protriticites (including Obsoletes and Praeobsoletes). Abbreviation of geological age: Dorog., Dorogomilovian.

Fig. 11.

Two hypotheses showing the early phylogeny and evolution of the family Schwagerinidae during the latest Moscovian and Kasimovian. (a) Phylogenetic reconstruction between Fusulinella in the Fusulinidae and early schwagerinid genera (Triticites, Montiparus, and Rauserites) proposed by Davydov (1990b, 1997b). (b) Phylogenetic model from Fusulinella to early schwagerinid genera proposed by van Ginkel and Villa (1999) (modified from fig. 2 of van Ginkel and Villa, 1999). Arrows indicate supposed evolutionary pathways between genera and among several morphology-diagnostic species groups within Protriticites (including Obsoletes and Praeobsoletes). Abbreviation of geological age: Dorog., Dorogomilovian.

As noted above, Beedeina is considered to be derived from Citronites in Eurasia, which occurred sometime in the Kashirian (Vachard et al. 2013). In North American intracratonic basins, the Fusulinella iowensis group is regarded as an intermediate species group connecting (North American) Fusulinella and (North American) Beedeina, and the Fusulinella iowensis Zone was located in the Atokan and Desmoinesian boundary interval (Wahlman 2013, 2019). This brings to mind the result of Groves (2005), who recognized a potential polyphyletic origin of Fusulinella. The origin of Beedeina in Eurasia and North America needs further examination. In Eurasia there are several genera that originated from Beedeina. Putrella is an early taxon that originated from Beedeina (or possibly from Citronites directly) in about the late Kashirian. Pseudotriticites has a gross shell morphology very similar to some elongate Beedeina, but developed porous structure in the wall, and it appeared in the latest Moscovian in the Palaeotethys Region. Bartramella is known only in North American cratonic basins, and was probably derived from North American species of Beedeina in the latest Desmoinesian, which corresponds to about the Moscovian–Kasimovian boundary. In the Fusulininae, Fusulina, Quasifusulinoides, and Quasifusulina made an important lineage, which started in the early Podolskian, and was derived from Beedeina. The second genus of this line characterizes the Moscovian–Kasimovian boundary interval, and the last genus extended its range to the early Permian. Undatafusulina is a specialized collateral genus in this lineage, developing characteristic rugosity in its wall and restricted to the Podolskian of Central Asia (Leven 1998). Leven (1998) included Fusulina tumulosa described by Ryazanov (1958b) in this genus, but that species probably has no phylogenetic relationship with the type species of Undatafusulina, U. asiatica described by Leven (1998).

The Wedekindellininae lineage mainly developed in cratonic North America. It was founded with Zellerella, derived from ‘Kanmeraia-like’ Fusulinella (having an elongate rhomboidal shell with well-developed asymmetrical chomata extending to the polar regions) occurring in the southwestern US (such as Fusulinella nipperensis reported by Ross and Sabins 1965). Soon after that it dispersed into several new genera (Parafusulinella, Wedekindellina Frumentella, and Parawedekindellina). Eowaeringella is the last evolved genus from Zellerella in Desmoinesian–Missourian boundary time. Some Wedekindellina migrated into the Ural–Arctic Region, and there it evolved into Parawedekindellina in Podolskian time. The latter genus is rarely found in the Ural–Arctic and the western part of the Palaeotethys regions (e.g. Rauzer-Chernousova et al. 1951; Rumyantseva 1974; Davydov 1997a; Villa and Remizova 2016). The last form of the Wedekindellininae is Parawedekindellina and extended up to the middle Kasimovian.

The Eofusulininae started evolving in late Bashkirian time just after the appearance of Profusulinella (Figs 8 & 9). This lineage probably originated from the Profusulinella oblonga group, which has an elongate fusiform shell among the genus and is known in the Tashastian (Potievskaya 1964). Eofusulinins have predominantly elongate shells among fusulines of late Bashkirian–early Moscovian age. In this subfamily, two early genera (Eowedekindellina and Verella) appeared in the latest Bashkirian (Asatauian). Then, the latter genus produced Eofusulina and Paraeofusulina in the beginning of the Moscovian, and the ultimate end-member genus Neofusulina appeared in the late Kashirian. Neofusulina is considered to have developed multiple tunnels (Leven 1979), which is only known in this genus among Carboniferous fusulines.

The other subfamily is Hemifusulininae consisting of three genera: Hemifusulinella, Dutkevichella, and Hemifusulina (Fig. 8). The first genus is little understood taxonomically and biostratigraphically because what was described by Rumyantseva (1962) from central Uzbekistan is the only material so far reported. This genus appeared in the Kashirian, probably derived from Aljutovella. Two descendants, Dutkevichella and Hemifusulina, were more widespread in the Kashirian to Myachkovian of the Russian Platform and the western Palaeotethys. Baranova and Kabanov (2003) and Khodjanyazova et al. (2014) suggested a strong facies-dependent distribution for hemifusulinins related to their palaeoecology, although their interpretations are very different between being predominant in a deeper distal tempestite facies and having been restricted to a cooler and hyposaline condition. Whichever the case is, these genera tend to form an exclusively monotypic assemblage in strata, showing adaptation to a special environment. Although hemifusulinins are essentially Eurasian forms, there are some Dutkevichella species (or Dutkevichella-like species) known from the middle part of the Desmoinesian in the North American Craton region (Nestell 1989; Wahlman 2013, 2019). They may provide a key for considering correlation by fusulines between the North American Desmoinesian and the type Moscovian, which is usually difficult based on other common genera such as Beedeina.

The Schwagerinidae descended from the Fusulinellinae in the Fusulinidae in the early part of the middle Kasimovian and flourished during the Late Pennsylvanian and the subsequent early–middle Permian. Three subfamilies: the Triticitinae, Schwagerininae, and Rugosofusulininae, are recognized in the Carboniferous.

Family SchwagerinidaeDunbar and Henbest, 1930 

Subfamily Triticitinae Davydov in Rauzer-Chernousova et al., 1996 

TriticitesGirty, 1904 (= GrabauinaLee, 1924; = GirtyinaStaff, 1909; = Eotriticites Da in Da and Sun, 1983; = TumulotriticitesWilde, 2006); FerganitesMiklukho-Maklay, 1959b; LeptotriticitesSkinner and Wilde, 1965a; ThompsonitesBensh, 1987; QuasitriticitesZhuang, 1984; IowanellaThompson, 1957; KansanellaThompson, 1957; DunbarinellaThompson, 1942; KwantoellaSakagami and Omata, 1957 emend. herein; DutkevichitesDavydov, 1984; ‘Likharevitesfide Leven in Leven and Gorgij, 2006b; ‘OccidentoschwagerinaMiklukho-Maklay, 1959c; Schwageriniformis Bensh in Rauzer-Chernousova et al., 1996; TumefactusLeven and Davydov, 2001.

As noted in Loeblich and Tappan (1987), Girtyina and Grabauina are regarded as junior synonyms of Triticites. Eotriticites Da in Da and Sun, 1983 (non EotriticitesWilde, 1984) was established based on deformed specimens that are probably of large, elongate, fusiform Triticites species. Wilde (2006) proposed Tumulotriticites under a somewhat unclear generic diagnosis. It is a monotypic genus, and the type species has a slightly inflated, short, fusiform shell. As he admitted implicitly, this genus can be regarded as Triticites.

Iowanella was described by Thompson (1957) as a subgenus of Kansanella, based on materials from the Midcontinent Missourian. As summarized by Wahlman (2013), Iowanella is a short-ranging genus restricted only to the lower Missourian, whereas Kansanella (s.s.) appeared in the middle Missourian and ranged to the lower Virgilian. Iowanella is a monotypic genus, and only the type species, Triticites winterensisThompson, Verville and Lokke, 1956, has been described so far. It has a thick fusiform shell with well-developed broad chomata. In contrast, Kansanella is characterized by very slender, elongate fusiform shells with small but massive chomata. The earliest Kansanella species in the middle Missourian show more similarities in gross shell morphology to some Triticites species (such as T. ohioensis), which co-occur with Iowanella, than Iowanella itself. These lines of evidence suggest that Iowanella cannot be a direct ancestor of Kansanella, but the latter genus descended from Triticites. Iowanella and Kansanella should be separated as independent genera, and they did not have a direct phylogenetic relationship to each other.

In this study, Thompsonites as proposed by Bensh (1987) is adopted for latest Virgilian–early Wolfcampian North American ‘Schwagerina’ having large elongate fusiform to cylindrical shells and strong septal fluting, such as ‘S.’ campensis, ‘S.pinosensis, S.’ longissimoidea, and ‘S.’ turki (see also Lucas et al. 2015 and Krainer et al. 2017 for the same taxonomic treatment). They have been included in Schwagerina in most major taxonomic and biostratigraphic studies done in North America (e.g. Thompson 1954; Wahlman 2013, 2019 and references therein), but these species are not related phylogenetically to Schwagerina in Eurasia, which is based on the type species Schwagerina princepsEhrenberg, 1842 (see discussion by Dunbar and Skinner 1936 on the taxonomy and nomenclature of this species). Thompsonites is considered to be derived probably from some Leptotriticites species in latest Virgilian (‘Bursumian’) time, such as L. americana and L. hughesensis. Thus, it is an endemic North American genus, as well as Leptotriticites, Iowanella, Kansanella, and Dunbarinella (Fig. 12).

Fig. 12.

Stratigraphic ranges and phylogeny of schwagerinid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). Genera with ranges indicated by red have palaeobiogeographical distribution restricted to the North American Craton Region. Note that Sphaeroschwagerina in the Triticitinae is an early Permian genus. See Figure 4 for the abbreviations of geological ages.

Fig. 12.

Stratigraphic ranges and phylogeny of schwagerinid genera in the Carboniferous (arrow denotes the generic range extending to the Permian). Genera with ranges indicated by red have palaeobiogeographical distribution restricted to the North American Craton Region. Note that Sphaeroschwagerina in the Triticitinae is an early Permian genus. See Figure 4 for the abbreviations of geological ages.

As noted already, Kwantoella has been suggested to have a schubertellid affinity with respect to the supra-generic taxonomy (Thompson 1964; Loeblich and Tappan 1987; Sheng et al. 1988; Rauzer-Chernousova et al. 1996). It is a monotypic, rarely quoted genus, and only the type species Kwantoella fujimotoi described by Sakagami and Omata (1957) has been so far known. Xia and Li in Xia et al. (1986) newly described an elongate fusiform specimen from the lower Permian of Guangxi, South China under the name of Kwantoella longissima, but it has nothing in common with this genus morphologically. Thus, the generic concept of Kwantoella is based entirely on the three type specimens of K. fujimotoi from the Shiraiwa Limestone of Central Japan, which was assigned to the late Gzhelian by the occurrence of Carbonoschwagerina minatoi (Ozawa, 1975; Igo and Makabe 1999). Of the three types, two axial sections show a small, elongate fusiform shell having a moderately large proloculus (compared to its shell size), compactly coiled volutions, septa that are unfluted in the central part of the shell, but weakly fluted in the axial regions, and weak axial fillings. The spirotheca consists of a tectum and less dense lower layer. Later, Igo and Makabe (1999) reported fusulines of the Shiraiwa Limestone and illustrated many more topotype specimens of K. fujimotoi. Their study contributed to a better understanding of the taxonomic content of Kwantoella. With respect to the wall structure, they noted that it consists of a tectum, middle lighter layer, and lower tectorium, and recognized indistinct fine perforation in the middle lighter layer. Igo and Makabe (1999) also described coexisting similar but larger specimens having additional one or two, slightly inflated outer volutions, under the name of Triticites? thalmanni. These larger specimens are probably not assignable to this species, which was originally described together with K. fujimotoi by Sakagami and Omata (1957) under the name of Triticites intermedia but was later replaced with T. thalmanni by Sakagami and Omata (1959) because the original species name was preoccupied by Triticites jigulensis var. intermediaShlykova, 1948. What is interesting to note is a strong similarity between the inner–middle part of ‘T.? thalmanni’ and the entire shell of K. fujimotoi, illustrated by Igo and Makabe (1999). This observation suggests that the types of K. fujimotoi, illustrated by Sakagami and Omata (1957), are not mature specimens but they merely represent pre-mature shells of what Igo and Makabe (1999) called ‘T.? thalmanni’. Because this latter species clearly has a schwagerinid affinity, Kwantoella is not a schubertellid genus but should be included in the Schwagerinidae. Based on the wall structure and some other shell features of this species, the taxonomic diagnosis of Kwantoella as a schwagerinid genus is emended as follows.

Genus KwantoellaSakagami and Omata, 1957, emend. herein

Type species. Kwantoella fujimotoiSakagami and Omata, 1957 ( = Triticites thalmanniSakagami and Omata, 1959,sensuIgo and Makabe, 1999, non Triticites thalmanniSakagami and Omata, 1959 = Triticites intermediaSakagami and Omata, 1957).

Revised diagnosis. Small, elongate fusiform to cylindrical schwagerinid genus with relatively small proloculus, and compactly coiled inner volutions and outer relatively loosely coiled ones. Wall thin and consist of a tectum and lower less dense layer in the inner volutions and of a tectum and fine keriotheca in the outer ones. Septa thin and weakly fluted in the axial regions. Weak axial fillings observed only in the inner volutions. Low chomata present throughout growth.

Remarks. Kwantoella is a genus less known among Carboniferous fusulines. After the introduction by Sakagami and Omata (1957), Xia and Li in Xia et al. (1986) described the second species in this genus, K. longissima, from South China. But this species is not related to the genus. Thus, Kwantoella has been monotypic so far, including only the type species K. fujimotoi from the Shiraiwa Limestone of Central Japan, for which the types were represented by immature specimens. The entire shell features of Kwantoella are well observed in specimens of ‘Triticites? thalmanni’ by Igo and Makabe (1999) from the type locality of K. fujimotoi, which are considered as mature representatives of the relevant species. Triticites aff. pusillus reported by Kanmera (1958) from the Yayamadake Limestone of SW Japan is also probably conspecific with the type species K. fujimotoi.

Kwantoella is distinguished from Triticites by more compactly coiled inner–middle volutions and thinner spirotheca with finer keriotheca. This genus is somewhat similar to Eoparafusulina in its elongate cylindrical shell. The former genus differs from the latter in having a smaller shell, thinner spirotheca and septa, and weaker septal fluting. There is some possibility that late Gzhelian Kwantoella is ancestral to early Permian Eoparafusulina.

Triticites langsonensis and Fusulinella derelicta, both originally described by Saurin (1950) from a limestone at Ky-Lua in the Langson area, northern Vietnam, can be included in this genus. Moreover, Triticites ellipsoidalis established by Toriyama (1958) based on materials from the Panthalassan Akiyoshi Limestone in SW Japan may possibly be subsumed in the emended Kwantoella.

Distribution and age. Panthalassan mid-oceanic seamounts (Shiraiwa, Yayamadake, and probably Akiyoshi limestones, SW Japan); Indochina (Vietnam). Late Gzhelian to early (earliest?) Permian.

Among triticitin genera in this study, Dutkevichites, ‘Occidentoschwagerina’, and ‘Likharevites’ need special annotation from taxonomic, phylogenetic, and nomenclatural viewpoints. As noted already, there are ‘undersized’ Triticites species from late Kasimovian and early–middle Gzhelian strata (e.g. Dzhenchuraeva and Getman 2007, 2010; Dzhenchuraeva et al. 2013), some of which have been assigned earlier to the schubertellid genus ‘Biwaella’, such as ‘B.’? tshelamtshiensis, ‘B.’ zhikalyaki, and ‘B.’ poletaevi from the Gzhelian (Davydov 1984, 1990a, 2011). Biwaella is known to show peculiar, widely spaced septa in cross-section (e.g. Morikawa and Isomi 1960; Kochansky-Devidé and Milanović 1962; Skinner and Wilde 1965a). Since the mentioned Gzhelian ‘Biwaella’ species do not have true Biwaella-type septal features but exhibit schwagerinid-type septa in cross section (see taxonomic remarks in the section on Schubertellidae), they are better assigned to schwagerinids, most probably to Triticites. These ‘undersized’ Triticites are a potential ancestor of Dutkevichites, which finally led to Sphaeroschwagerina in early Permian time (Davydov 1984). In the original description of Dutkevichites, Davydov (1984) included two new species in the genus: D. darvasica (type species) and D. ljangariensis, both from the late Gzhelian of the Darvaz, along with two existing species: Triticites (Ferganites) ramovsi described by Kochansky-Devidé (1969) and T. inopinatus established by Kochansky-Devidé (1959). The latter two species from Montenegro and Croatia are very different from the two Darvaz species. Triticites (Ferganites) ramovsi is referable to the genus Triticites, and T. inopinatus should be included in true Biwaella. The two Darvaz species mentioned above, originally described by Davydov (1984) as new species, show characteristic elongation of the shell and abrupt loose coiling in the outermost volution, but lack obvious shell inflation. He also described the other species in this genus: Dutkevichites? valeriani, which exhibits distinctive inflation of shell in the outer volutions. Later, Forke (2002) further included Occidentoschwagerina alpina from the Carnic Alps, in Dutkevichites. This species also has an inflated shell, which is somewhat similar to D.? valeriani. However, this taxonomic treatment is not reasonable because, as can be seen by the questionable generic assignment of valeriani to Dutkevichites, Davydov (1984) did not particularly mention such shell inflation as a generic diagnosis of that genus originally. Occidentoschwagerina alpina is closely related phylogenetically to Dutkevichites, especially to D.? valeriani, but there is no good reason to include this species in Dutkevichites. Furthermore, the genus Occidentoschwagerina itself also has serious problems with its taxonomy and nomenclature.

As Forke (2002) discussed in detail, the genus Occidentoschwagerina is probably invalid because the type species Fusulina (Schwagerina) fusulinoides, originally established by Schellwien (1898) from pebbles of the Triassic Uggowitz Breccia in the Carnic Alps, is considered to be conspecific with Pseudoschwagerina extensa from the basal Permian of the same region. Thus, Occidentoschwagerina is a junior synonym of PseudoschwagerinaDunbar and Skinner, 1936. This interpretation is rather consistent with the original generic concept proposed by Miklukho-Maklay (1959c), in which he included, besides the type species, Schwagerina fusulinoides of Chen (1934) ( = Occidentoschwagerina cheniMiklukho-Maklay, 1959c) and Pseudoschwagerina texana. The latter two species are also regarded as Pseudoschwagerina presently. Moreover, there is another taxonomic problem with Occidentoschwagerina. Recently, this generic name has been applied mostly to species that have inflated fusiform shells with minute/small proloculi, tightly coiled juvenaria, moderately to strongly and irregularly fluted septa, and expanded outer volutions. ‘Occidentoschwagerinaalpina is a typical form to fit with these features, and other forms such as ‘O.’ chatcalica, ‘O.’ tianshanensis, ‘O.’ sarycumensis, and to some extent ‘O.’ primaeva, ‘O.’ ancestralis, and ‘O.’ konovalovae, often found in the Uralian and Central Asian latest Gzhelian and earliest Permian biostratigraphy, also have been included in this taxonomic group (e.g. Vilesov 1998b, 2000; Orlov-Labkovsky and Bensh 2015). However, this current generic concept is outside of the original diagnosis proposed by Miklukho-Maklay (1959c), which is well represented by the morphological diagnosis of the type species, thus Fusulina (Schwagerina) fusulinoides mentioned above. It is true that there is a distinct taxonomic group that is typically represented by ‘Occidentoschwagerinaalpina and consists of these mentioned ‘Occidentoschwagerina’ species, in the latest Gzhelian and earliest Permian. However, as Forke (2002) emphasized, the diagnosis of the genus must be related to the concept that is best represented by the type species. Therefore, it is not reasonable to use the name Occidentoschwagerina for the taxonomic group typified by ‘O.’ alpina, because this species is unrelated taxonomically to the type species of the genus. In this study these species, which are related to ‘O.’ alpina but are not close morphologically to O. fusulinoides (type species of the genus) are only provisionally included in this genus and always expressed as ‘Occidentoschwagerina’, although authentic Occidentoschwagerina is probably a junior synonym of Pseudoschwagerina. Notwithstanding these taxonomic and nomenclatural issues, ‘Occidentoschwagerina’ is important for triticitin phylogeny because it is considered to connect with Dutkevichites and Sphaeroschwagerina, and also to give rise to ‘Likharevites’.

The genus ‘Likharevites’ is also problematic in view of nomenclature. This generic name has been used to accommodate latest Gzhelian and early Permian Paraschwagerina-like species that have distinct inflation in shells, minute proloculi, tightly coiled juvenaria, and characteristic septal fluting. As Leven in Leven and Gorgij (2006b) admitted, however, ‘Likharevites’ was described in an intra-institutional report, which should be regarded as an unpublished manuscript. Thus, it is regarded as an unavailable name nomenclaturally. Leven in Leven and Gorgij (2006b) tried to formalize the validity of the genus by re-describing the diagnosis, but that action would not be deemed to be valid nomenclaturally, because it lacks explicit indication that the name is intentionally new (ICZN, Article 16; International Commission on Zoological Nomenclature 1999). Although there are many lines of evidence to show that a taxonomic entity defined by those mentioned morphological features indeed exists in latest Gzhelian schwagerinids, the name ‘Likharevites’ cannot be applied to it simply because it is an unavailable taxonomic name nomenclaturally. In this study, as in the case of ‘Occidentoschwagerina’, this generic entity is expressed provisionally as ‘Likharevites’.

Tumefactus and Schwageriniformis are included in the subfamily Triticitinae only from the conventional viewpoint, since these two may be collaterals (sister genera) of this family phylogenetically (Fig. 12). As Forke and Samankassou (2000) suggested, there is a strong phylogenetic relationship between Obsoletes inflatus and Tumefactus expressus in their juvenile features, inflation of the outer volutions, and the development of conspicuous phrenothecae. Thus, Tumefactus is considered to be derived directly from Obsoletes at about the middle of the middle Kasimovian (Leven and Davydov 2001). The origin of Schwageriniformis is not clearly settled. It appeared sometime in the later part of the middle Kasimovian (in the late Montiparus Zone), which is slightly later than Tumefactus (Leven and Davydov, 2001). So far as the timing of their appearance and the gross shell morphology of its early species (such as S. schwageriniformis, S. nanus, and S. perstabilis) are concerned, it is likely that Schwageriniformis also descended directly from Obsoletes but in different timing from Tumefactus, in the later part of the middle Kasimovian. As shown in Figure 12, Tumefactus and Schwageriniformis may not be included in the subfamily Triticitinae strictly in view of their assumed phylogenetic positions directly derived from Obsoletes, although they are usually related to Triticites.

Subfamily SchwagerinidaeDunbar and Henbest, 1930 

MontiparusRozovskaya, 1948 ( = EotriticitesWilde, 1984, non Eotriticites Da in Da and Sun, 1983); KushanellaLeven and Davydov, 2001; CarbonoschwagerinaOzawa, Watanabe and Kobayashi, 1992; DarvasoschwagerinaLeven and Davydov, 2001; RauseritesRozovskaya, 1950; DaixinaRozovskaya, 1949 ( = ?Pseudodaixinoides Getman and Dzhenchuraeva in Dzhenchuraeva and Getman, 2007); BosbytauellaIsakova, 1982 [ = Ultradaixina Davydov in Chuvashov et al., 1986, and Ultradaixina Davydov, 1982MS (nomen nudum)]; JigulitesRozovskaya, 1948; ‘PseudofusulinaDunbar and Skinner, 1931; AnderssonitesSyomina, Solov'eva and Bensh, 1987; Schwagerinavon Möller, 1877; PseudochusenellaBensh, 1987.

In relation to the designation of the type species of Triticites (Montiparus) by Rozovskaya (1948), Wilde (1984) newly proposed the name Eotriticites (non Eotriticites Da in Da and Sun, 1983) to what has been generally regarded as Montiparus, based on von Möller's (1878),Fusulina montipara Ehrenberg. As Loeblich and Tappan (1987) noted in the details of this nomenclatural story, the name ‘Eotriticites’ by Wilde (1984) is superfluous since Rozovskaya (1948) also designated the type species as Fusulina montipara Ehrenberg, sensuMöller (1878) (non Alveolina montiparaEhrenberg, 1854). Finally, the type species of Montiparus is now fixed as Triticites (Montiparus) montiparusRozovskaya, 1948, according to the ICZN, Article 67.13 (International Commission on Zoological Nomenclature 1999).

In late/latest Gzhelian–early Asselian time there is a distinct taxonomic group in the Schwagerininae that has large elongate fusiform to cylindrical shells with regularly and strongly fluted septa and weak to strong axial fillings. It includes such species as Pseudofusulina elegans, P. zarjae, P. ulukensis, P. manjuscula, P. narjanmarica, P. kumasoana, P. volozhaninae, and P. excessa. These species are considered to comprise an independent genus, but they are not related phylogenetically to late early Permian PseudofusulinaDunbar and Skinner, 1931. In this study, they are only provisionally attributed to this genus and expressed as ‘Pseudofusulina’.

Judging from the original species content, Pseudodaixinoides established by Getman and Dzhenchuraeva in Dzhenchuraeva and Getman (2007) seemingly includes several different genera, such as Dutkevitchia? (e.g. for P. cylindricus), Rauserites? (e.g. for P. honestus), and Bosbytauella? (e.g. for P. kalcagaricus). The type species (Pseudodaixinoides pseudoartiensis Anosova, Getman and Dzhenchuraeva in Dzhenchuraeva and Getman, 2007) looks like a Daixina species with a small proloculus, thus this genus is provisionally included in Daixina in this taxonomy.

The name Ultradaixina has been used in some papers to accommodate several species in the Daixina group with inflated and loosely-coiled shells (e.g. Chuvashov et al. 1986; Davydov 1988a, b; Leven 2009). The name was nomenclaturally informally proposed in an unpublished manuscript by Davydov (1982MS: ‘Zonal'nye Yarusnye Podrazdeleniya po Fuzulinidam Verkhnego Karbona Yugo-zapadnogo Darvaza’, Abstract of Dissertation for the Degree of Geological-Mineralogical Sciences, VSEGEI, 20 p.), and it was regarded by the International Commission on Zoological Nomenclature to be unavailable (pers. comm. with V. I. Davydov, 19 February, 2021). Thus, Davydov in Chuvashov et al. (1986) is deemed as the original publication of Ultradaixina, and it is a junior synonym of BosbytauellaIsakova, 1982.

Vilesov (2002) established two ‘pseudofusulinin’ genera: Retijigulites and Lapigerella from the Carboniferous–Permian boundary interval. He considered that these two genera were descended from Jigulites sometime in the late Gzhelian and ranged to the Asselian. As far as their species compositions in the original description are concerned, both genera seem to include species that are not directly related phylogenetically. Thus, their morphological extent and taxonomic validity are unclear and need to be reexamined. Retijigulites and Lapigerella are not treated in the present taxonomy.

Subfamily RugosofusulininaeDavydov, 1980 

RugosofusulinaRauzer-Chernousova, 1937 ( = Rugosofusulinoides Bensh in Rauzer-Chernousova et al., 1996); SchagonellaDavydov, 1980; Ruzhenzevites Davydov in Chuvashov et al., 1986; DutkevitchiaLeven and Shcherbovich, 1978; RugosochusenellaSkinner and Wilde, 1965a; Kahlerella Bensh in Rauzer-Chernousova et al., 1996; Benshiella Leven in Leven and Gorgij, 2009.

Bensh in Rauzer-Chernousova et al. (1996) established Rugosofusulinoides with Rugosofusulina serrataRauzer-Chernousova, 1937 as the type species. However, the distinction between Rugosofusulina and Rugosofusulinoides is quite unclear. As far as the original description of both genera in Rauzer-Chernousova et al. (1996) is examined, there seems to be no important difference at the generic level between them. Rugosofusulinoides is synonymized with Rugosofusulina in this study.

In Benshiella, the nomenclatural treatment and notation of the type species is somewhat confused. When Leven in Leven and Gorgij (2009) established Benshiella he cited the type species as ‘PseudofusulinastabilisRauzer-Chernousova, 1938. Contrary to this citation, the original taxonomic name with the author and year of this species has been quoted as ‘Rugosofusulina stabilisRauzer-Chernousova, 1937’ (e.g. Kahler and Kahler 1966–67; Rozovskaya 1975; Chuvashov et al. 1986; Kobayashi 2017; Hayward et al. 2021). This species (stabilis) was ‘formally’ (with the explicit indication of ‘sp. nov.’ and a description that states in words characters that are purported to differentiate the taxon) proposed in Rauzer-Chernousova (1938) as ‘Pseudofusulina stabilis’. But, before the formal original description of this species was published, Rauzer-Chernousova (1937) was issued earlier in which stabilis was newly combined with Rugosofusulina, established in it and listed as ‘Rugosofusulina stabilis Rauzer-Chernousova’ [but not as Rugosofusulina stabilis (Rauzer-Chernousova)] with a bibliographic reference in the synonymy as ‘1937. Pseudofusulina stabilis Rauzer-Chernousova, Tr. Geol. Inst. Akad. Nauk, T. 7. (in press)’. The priority of the apparent published year [Rauzer-Chernousova (1937) over Rauzer-Chernousova (1938)] would be the basis of ‘Rugosofusulina stabilisRauzer-Chernousova, 1937’ being considered as the original taxonomic and nomenclatural citation of this species, in some papers mentioned above. However, since Rauzer-Chernousova's (1937) nomenclatural action, that she transferred stabilis from Pseudofusulina to Rugosofusulina, was executed upon citing her own ‘in-press’ paper (probably planned to be printed in 1937 originally, but actually published in 1938) in synonymy, the taxonomic concept of stabilis is regarded to have been fixed originally in Rauzer-Chernousova (1938), so Rauzer-Chernousova's (1937) taxonomic and nomenclatural action is deemed merely to make a new combination. Moreover, there is no description of the taxonomic characters of ‘Rugosofusulina stabilis’ in the words in Rauzer-Chernousova (1937). So, Rugosofusulina stabilis in Rauzer-Chernousova (1937) is regarded nomenclaturally as a nomen nudum. In conclusion, Leven's (in Leven and Gorgij, 2009) citation of Pseudofusulina stabilisRauzer-Chernousova, 1938 as the type species of Benshiella is approved nomenclaturally. Obviously, this case is not applicable to Article 13.1.2 of the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature 1999).

The phylogenetic origin of Rugosochusenella is not very clear. I provisionally relate this genus with Rugosofusulina mainly because of the presence of rugosity, although a small/minute proloculus and tightly coiled juvenarium in the former genus are not consistent with Rugosofusulina. If this is not the case, Rugosochusenella may possibly be close phylogenetically to Pseudochusenella, based on the tightly coiled juvenarium and axial fillings.

As noted in the phylogenetic discussion of fusulinid genera, the Schwagerinidae is apparently polyphyletic, descended from two closely related but distinct genera (Protriticites and Obsoletes) in the Fusulinellinae (Fig. 12). One phylogenetic group is represented by the Triticitinae, which is rooted in Obsoletes. The first genus in this lineage is Triticites and it appeared in middle Kasimovian time in the western part of the Palaeotethys Region. North American earliest Triticites species in the early Missourian, which would correspond more or less to the middle–late Kasimovian boundary (Heckel et al. 2007), are considered as immigrants from the Palaeotethys Region because they do not have ancestral evolutionary history in the Desmoinesian–Missourian boundary interval (Villa and Wahlman 2007). Triticites flourished in both cratonic North America and Eurasia (including the Panthalassa palaeobiogeographical region) after that but shows different evolutionary developments. In North American cratonic areas, soon after the migration, Iowanella and Kansanella appeared independently from Triticites in the Missourian. If not, Iowanella was possibly another immigrant taxon coming together with Triticites to the North American palaeobiogeographical domain from Eurasia because there is little morphological similarity between Iowanella and the earliest Triticites in North America. In Virgilian time, Dunbarinella was derived from Kansanella, and another new lineage represented by LeptotriticitesThompsonites arose separately from Triticites (Fig. 12). Representatives of this lineage extended up into the earliest Permian (Wahlman 2013, 2019).

There are three minor genera that probably derived from Triticites, in the Palaeotethys and Panthalassa regions. Ferganites is mainly found in the late Kasimovian–early Gzhelian strata in the Cantabrian Mountains, Carnic Alps, and Central Asia in the northern part of the western Palaeotethys. This genus had a palaeoecological character similar to Monodiexodina in the late early–middle Permian (Ueno 2006), occurring often in a monotypic manner in sandy (arenaceous) limestone or calcareous sandstone and showing adaptation to a near-shore, high-energy, low-salinity environment (Villa and Bahamonde 2001). Another one is a less known genus, Quasitriticites, which was introduced by Zhuang (1984) based on materials from western Guizhou Province, China. It would form a peculiar lineage consisting of species that show shell inflation during their ontogeny (Fig. 13). This genus was locally developed in South China and includes several forms reported by Ueno et al. (2013) from southern Guizhou; they are ‘Carbonoschwagerina’ sp. A, ‘C.’ sp. B, and ‘C.’ sp. C from the Kasimovian–Gzhelian boundary interval, and the second and third species are reassigned herein as Quasitriticites machangensis and Q.? sp. As Ueno et al. (2013) discussed, ‘C.’ sp. B ( = Q. machangensis) and ‘C.’ sp. C (= Q.? sp.) are very similar to some Carbonoschwagerina species in the degree of shell inflation and the development of tightly coiled juvenile volutions (Fig. 13), but the southern Guizhou species are merely Carbonoschwagerina-mimics, which have no direct phylogenetic relationship to true Carbonoschwagerina (see also description of regional fusuline succession of South China). Thus, Quasitriticites (Carbonoschwagerina-mimics of Ueno et al. 2013) is another inflated schwagerinid lineage, distinct from Gzhelian schwagerinin Carbonoschwagerina (Fig. 13). End-members of these genera had accomplished ultimate shell inflation comparable to some early Permian Sphaeroschwagerina (see fig. 17c–e of Ueno et al. 2013 and Fig. 13). The other minor genus probably derived from Triticites is Kwantoella. As discussed above, it has been generally considered as a schubertellid genus in previous fusuline taxonomy but transferred to the Schwagerinidae in this study. Its phylogenetic origin is not very clear but is probably related to Triticites, judging from overall shell morphology.

Fig. 13.

Homeomorphic appearance of inflated schwagerinids (Quasitriticites, Tumefactus, and Carbonoschwagerina) in three distinct lineages during the Kasimovian and Gzhelian. Genera with ranges indicated by red represent inflated schwagerinids, and those indicated by blue are fusulinellins (Fusulinidae). Montiparus is the first schwagerinin genus and Triticites is the first triticitin one. In this phylogenetic scheme, Tumefactus is only provisionally included in the subfamily Triticitinae (see the text for details). Specimens illustrated in this figure are from the following data sources: Quasitriticites machangensis and Q.? sp. from the Zongdi section of Guizhou Province, South China (from Ueno et al. 2013 and author's unpublished data); Tumefactus expressus from the Puentellés Formation of the Cantabrian Mountains, northern Spain (from author's unpublished data); Carbonoschwagerina nipponica from the Akiyoshi Limestone, SW Japan (from Watanabe 1991); Carbonoschwagerina nakazawai from the Atetsu Limestone, SW Japan (from Nogami 1961); Carbonoschwagerina morikawai and C. minatoi from the Yayamadake Limestone, SW Japan (from Kanmera 1958). The Akiyoshi, Atetsu, and Yayamadake limestones have a Panthalassan mid-oceanic atoll origin and the Carbonoschwagerina lineage is characteristically developed there. It is a typical Panthalassan genus, derived from Montiparus matsumotoi, and its evolutionary species succession shown in this figure (nipponica–nakazawai–morikawai–minatoi) is widely utilized for establishing late Kasimovian–Gzhelian biozonation (see section on Mid-oceanic Panthalassa). Quasitriticites machangensis and Q.? sp. in this figure were named ‘Carbonoschwagerina-mimics’ in Ueno et al. (2013) and were identified as ‘Carbonoschwagerina’ sp. B and ‘C.’ sp. C, respectively (see also section on South China). Scale bar is applicable to all specimens. Abbreviations of Kasimovian and Gzhelian substages: Krevya., Krevyakinian; Khamov., Khamovnikian; Dorogo., Dorogomilovian; Dobryatin., Dobryatinian; Pavlovo., Pavlovoposadian; Nog., Noginskian; Mel., Melekhovian.

Fig. 13.

Homeomorphic appearance of inflated schwagerinids (Quasitriticites, Tumefactus, and Carbonoschwagerina) in three distinct lineages during the Kasimovian and Gzhelian. Genera with ranges indicated by red represent inflated schwagerinids, and those indicated by blue are fusulinellins (Fusulinidae). Montiparus is the first schwagerinin genus and Triticites is the first triticitin one. In this phylogenetic scheme, Tumefactus is only provisionally included in the subfamily Triticitinae (see the text for details). Specimens illustrated in this figure are from the following data sources: Quasitriticites machangensis and Q.? sp. from the Zongdi section of Guizhou Province, South China (from Ueno et al. 2013 and author's unpublished data); Tumefactus expressus from the Puentellés Formation of the Cantabrian Mountains, northern Spain (from author's unpublished data); Carbonoschwagerina nipponica from the Akiyoshi Limestone, SW Japan (from Watanabe 1991); Carbonoschwagerina nakazawai from the Atetsu Limestone, SW Japan (from Nogami 1961); Carbonoschwagerina morikawai and C. minatoi from the Yayamadake Limestone, SW Japan (from Kanmera 1958). The Akiyoshi, Atetsu, and Yayamadake limestones have a Panthalassan mid-oceanic atoll origin and the Carbonoschwagerina lineage is characteristically developed there. It is a typical Panthalassan genus, derived from Montiparus matsumotoi, and its evolutionary species succession shown in this figure (nipponica–nakazawai–morikawai–minatoi) is widely utilized for establishing late Kasimovian–Gzhelian biozonation (see section on Mid-oceanic Panthalassa). Quasitriticites machangensis and Q.? sp. in this figure were named ‘Carbonoschwagerina-mimics’ in Ueno et al. (2013) and were identified as ‘Carbonoschwagerina’ sp. B and ‘C.’ sp. C, respectively (see also section on South China). Scale bar is applicable to all specimens. Abbreviations of Kasimovian and Gzhelian substages: Krevya., Krevyakinian; Khamov., Khamovnikian; Dorogo., Dorogomilovian; Dobryatin., Dobryatinian; Pavlovo., Pavlovoposadian; Nog., Noginskian; Mel., Melekhovian.

During the Gzhelian in the western Palaeotethys, some ‘undersized’ Triticites (including those previously attributed to Biwaella in some studies) became a founder of a distinct lineage consisting of Dutkevichites, ‘Occidentoschwagerina’, and ‘Likharevites’ and leading finally to Sphaeroschwagerina in the earliest Permian (Fig. 12). As Davydov (1984) clarified, Sphaeroschwagerina came from Dutkevichites, but, as discussed above, and also by Forke (2002), this lineage should be included in the Schwagerinidae. Dutkevichites is a rarely occurring transitional genus from the ‘undersized’ Triticites in late Kasimovian–middle Gzhelian time to ‘Occidentoschwagerina’ in the latest Gzhelian. The latter genus flourished in the Urals and Central Asia in the Carboniferous–Permian boundary interval, and is considered to finally give rise to Sphaeroschwagerina at the beginning of the Permian (Vilesov 1998a). ‘Likharevites’ represents a lineage probably derived from ‘Occidentoschwagerina’ by accelerating shell inflation.

Tumefactus and Schwageriniformis, which are characterized by weak septal fluting and the inflated tendency of the shell, probably came directly from Obsoletes as discussed in the taxonomic remarks on the Triticitinae. They are not incorporated within a phylogenetic scheme of this subfamily in a strict sense (Fig. 12). In this study they are provisionally included in it, following a conventional view (Rauzer-Chernousova et al. 1996; Hayward et al. 2021). Of these two genera, Tumefactus is peculiar in its distinct shell inflation and is morphologically comparable to other inflated schwagerinids during Kasimovian–Gzhelian time, such as Quasitriticites and Carbonoschwagerina (Fig. 13). This is also a good example of the homeomorphism of a morphological trait (shell inflation in this case) in closely related but distinct lineages within a larger clade (the family Schwagerinidae in this example) in the Carboniferous.

The other large phylogenetic group at the end of the Carboniferous consists of the Schwagerininae and Rugosofusulininae (Fig. 12). The former subfamily started from Protriticites, and the first genus Montiparus appeared in the middle Kasimovian. Kushanella is a minor offshoot, which is rarely found in Central Asia. Carbonoschwagerina also rooted in Montiparus (Watanabe 1991; Ozawa et al. 1992), thus this lineage started in the middle Kasimovian of the Panthalassa palaeobiogeographical region. Although the relationship is not very clear, Darvasoschwagerina was probably a derivative from Carbonoschwagerina judging from the similarity of ontogenetic shell development between them. Both genera became extinct at the end of the Carboniferous.

Rauserites is a direct descendant of Montiparus and appeared in late Kasimovian time. The former genus gave rise to Daixina and Jigulites in the middle Gzhelian. Diversification of this lineage occurred in late/latest Gzhelian time, and Bosbytauella evolved from the Daixina lineage and Schwagerina, Anderssonites, ‘Pseudofusulina’, and Pseudochusenella were derived probably from Jigulites, although detailed phylogenetic relationships among these genera are not very clear. Many of the Gzhelian schwagerinin genera ranged upward to the Asselian, straddling the Carboniferous–Permian boundary.

The Rugosofusulininae is the other subfamily in the Carboniferous Schwagerinidae and flourished in the later part of the Gzhelian. This subfamily shows rugosity in their shell walls. Rugosofusulina is the first genus in this subfamily and was derived from Rauserites at around the Kasimovian–Gzhelian transitional interval. Schagonella branched off from Rugosofusulina in the early Gzhelian, and gave rise to Ruzhenzevites and Dutkevitchia at around the middle–late Gzhelian boundary. The phylogenetic development of this lineage was well demonstrated by Davydov (1988a, b) based on materials from the Darvaz Range in Central Asia. They show different styles of phylogenetic evolution. Schagonella is characterized by the enlargement and elongation of the entire shell and by the development of intense (and partly irregular) septal fluting, whereas Dutkevitchia is characterized by the development of thicker spirotheca, a slightly inflated shell, characteristic juvenarium having dense axial fillings and larger proloculus, and intensely and irregularly fluted septa. Ruzhenzevites maintained a peculiar elongate cylindrical (‘cigar-shaped’) shell feature with moderately and regularly fluted septa during its entire stratigraphic occurrences from the late Gzhelian to middle Asselian. These genera are commonly found in the western Palaeotethys (Central Asia, Donets Basin, Carnic Alps, and Iran) and the South Urals, but Dutkevitchia is also common in North China, and Schagonella and Dutkevitchia were reported from Indochina, as noted in a later section. Compared to the lineage made by Schagonella, Ruzhenzevites, and Dutkevitchia, the phylogenetic relationships among Rugosofusulina, Benshiella, Kahlerella, and Rugosochusenella are not very clear. As noted above, Rugosochusenella may possibly be close to Pseudochusenella in the Schwagerininae. In any case, the diversification of rugosofusulinin genera occurred in the later part of the Gzhelian.

Overall, the Schwagerinidae exhibits a time of higher diversification in the late/latest Gzhelian (Fig. 12). A total of 25 genera are counted in this short interval.

Fusulines have been reported so far from all of the continents except the Antarctic. They are one of the best studied taxonomic groups of upper Paleozoic microfossils. In the following summary their occurrences are sorted out in a total of 40 provinces in six palaeogeographical regions of three fundamental realms–Boreal, Palaeoequatorial, and Gondwana, which more or less correspond to the then palaeoclimatic belts consisting of lower and lower middle latitudes.

Among the three basic palaeogeographical realms, the Palaeoequatorial Realm in the tropical–subtropical belt is the main area of fusuline distribution in the Carboniferous. Based on the continent-ocean configuration of Pennsylvanian time and fusuline faunal content, this realm is subdivided into three palaeobiogeographical regions: the Palaeotethys, North American Craton, and Panthalassa regions (Fig. 2). The Boreal Realm in northern middle latitudes consists of the Ural–Arctic Region and contains several important areas of fusuline distribution during the Carboniferous, such as Arctic Canada, the Urals, and the Moscow Syneclise (Fig. 2). The Gondwana Realm is recognized in the southern middle latitudes and is subdivided into the Western Gondwana Region and Eastern Peri-Gondwana Region (Fig. 2). As noted later, they had developed only less diversified fusuline fauna during much of the Carboniferous.

Table 2 shows palaeobiogeographical composition used in this paper. In the following sections, the fusuline biostratigraphic successions in respective palaeobiogeographical regions are described according to the order of the areas listed in this table.

Table 2.

Palaeobiogeographical architecture in this paper

BOREAL REALM (in northern middle latitudes)
Ural–Arctic Region
  Western North American terranes (Insular and Intermontaine terranes; Loc. 1)
  Yukon Territory (Loc. 2)
  Arctic Alaska (Loc. 3)
  Arctic Canada (including Northwind Ridge and other Arctic localities; Loc. 4)
  Greenland (Loc. 5)
  Taimyr (Loc. 6)
  Barents shelf (Spitsbergen, Novaya Zemlya, Kolguev Island, and others; Loc. 7)
  Timan–Pechora (Loc. 8)
  Urals (Loc. 9)
  Moscow Syneclise (Loc. 10)
PALAEOEQUATORIAL REALM (in tropical–subtropical belts)
Palaeotethys Region
  Kazakhstan (Loc. 11)
  Central Asia (Tianshan; Darvaz Range; Northern Afghanistan; Loc. 12)
  Precaspian Basin (Loc. 13)
  Donets Basin (Loc. 14)
  Carnic Alps (Loc. 15)
  Central and Western European basins (Loc. 16)
  Cantabrian Mountains (including other areas in Iberia; Loc. 17)
  Maritimes Basin in eastern North America (Loc. 18)
  Northern Africa (surface and subsurface basins in the Maghreb; Loc. 19)
  Apulian Platform and Variscan relicts in Dinarides (Loc. 20)
  Turkey (Loc. 21)
  Iran (Alborz; blocks in Central Iran; Sanandaj–Sirjan Zone; Loc. 22)
  Tarim Basin (Tieklik, Altun Mountains, Kalpin, and other subregions; Loc. 23)
  Eastern Tianshan (Loc. 24)
  Southern margin of the Mongolian Block (Loc. 25)
  North China (including the Korean Peninsula and Qilian Belt; Loc. 26)
  Primorye (Loc. 27)
  Japan (South Kitakami and Hida Marginal belts; Loc. 28)
  South China (including Songpan–Ganzi Zone and West Qinling Belt; Loc. 29)
  Indochina (including several Tibetan blocks; Loc. 30)
  Mid-oceanic Palaeotethys (Loc. 31)
North America Craton Region
  Canadian Cordillera (western margin of ancestral North America (Loc. 32)
  Intracratonic basins in the United States (Loc. 33)
  Mexico (Loc. 34)
Panthalassa Region
  Mid-oceanic Panthalassa (Akiyoshi and Chichibu belts: Cache Creek Terrane; Loc. 35)
  Southern Patagonia (Loc. 36)
GONDWANA REALM (in southern middle latitudes)
Western Gondwana Region
  South American basins (Brazilian and Andean basins; Loc. 37)
Eastern Peri-Gondwana Region
  Sibumasu and Baoshan blocks in southeastern Asia (Loc. 38)
  Australia (Loc. 39)
  Timor (Loc. 40)
BOREAL REALM (in northern middle latitudes)
Ural–Arctic Region
  Western North American terranes (Insular and Intermontaine terranes; Loc. 1)
  Yukon Territory (Loc. 2)
  Arctic Alaska (Loc. 3)
  Arctic Canada (including Northwind Ridge and other Arctic localities; Loc. 4)
  Greenland (Loc. 5)
  Taimyr (Loc. 6)
  Barents shelf (Spitsbergen, Novaya Zemlya, Kolguev Island, and others; Loc. 7)
  Timan–Pechora (Loc. 8)
  Urals (Loc. 9)
  Moscow Syneclise (Loc. 10)
PALAEOEQUATORIAL REALM (in tropical–subtropical belts)
Palaeotethys Region
  Kazakhstan (Loc. 11)
  Central Asia (Tianshan; Darvaz Range; Northern Afghanistan; Loc. 12)
  Precaspian Basin (Loc. 13)
  Donets Basin (Loc. 14)
  Carnic Alps (Loc. 15)
  Central and Western European basins (Loc. 16)
  Cantabrian Mountains (including other areas in Iberia; Loc. 17)
  Maritimes Basin in eastern North America (Loc. 18)
  Northern Africa (surface and subsurface basins in the Maghreb; Loc. 19)
  Apulian Platform and Variscan relicts in Dinarides (Loc. 20)
  Turkey (Loc. 21)
  Iran (Alborz; blocks in Central Iran; Sanandaj–Sirjan Zone; Loc. 22)
  Tarim Basin (Tieklik, Altun Mountains, Kalpin, and other subregions; Loc. 23)
  Eastern Tianshan (Loc. 24)
  Southern margin of the Mongolian Block (Loc. 25)
  North China (including the Korean Peninsula and Qilian Belt; Loc. 26)
  Primorye (Loc. 27)
  Japan (South Kitakami and Hida Marginal belts; Loc. 28)
  South China (including Songpan–Ganzi Zone and West Qinling Belt; Loc. 29)
  Indochina (including several Tibetan blocks; Loc. 30)
  Mid-oceanic Palaeotethys (Loc. 31)
North America Craton Region
  Canadian Cordillera (western margin of ancestral North America (Loc. 32)
  Intracratonic basins in the United States (Loc. 33)
  Mexico (Loc. 34)
Panthalassa Region
  Mid-oceanic Panthalassa (Akiyoshi and Chichibu belts: Cache Creek Terrane; Loc. 35)
  Southern Patagonia (Loc. 36)
GONDWANA REALM (in southern middle latitudes)
Western Gondwana Region
  South American basins (Brazilian and Andean basins; Loc. 37)
Eastern Peri-Gondwana Region
  Sibumasu and Baoshan blocks in southeastern Asia (Loc. 38)
  Australia (Loc. 39)
  Timor (Loc. 40)

Regional fusuline successions are described following the order in this table. See Figure 2 for location numbers.

This region extends, in today's geographical configuration, from exotic terranes comprising the northern part of western North America to the East European Platform (Russian Platform), via Arctic Alaska, Arctic Canada, Greenland, and the Barents Sea (Fig. 2). Palaeogeographically, it covered the northern middle latitudes of Laurussia, just around the ‘Northern Forbiddance Line’ of Davydov (2016).

The western Cordillera of North America makes a geological collage composed of deformed continental margin and accreted small blocks (called ‘exotic terranes’) and various kinds of oceanic rocks (Coney et al. 1980). In this region, two types of terranes that more or less retain their inherent and coherent stratigraphy are known to yield Carboniferous fusulines (Ross and Ross 1983). One type is represented by the Quesnellia (Quesnel), Stikinia (Stikine), and some other terranes in the Intermontane belt (Loc. 1b in Fig. 2). Colpron and Nelson (2009) suggested that these terranes have a magmatic arc origin with a continental margin affinity and show geological connections in many ways with the western margin of cratonic North America. These Intermontane belt terranes originally composed the western margin of ancestral North America until they had been detached from the latter by the opening of the Slide Mountain Ocean (back-arc basin) at around Devonian–Carboniferous boundary time. These separated terranes collided again to the western margin of Laurussia at around the Permian–Triassic boundary by the westward subduction of the Slide Mountain oceanic plate, forming an island arc system on the Quesnellia, Stikinia, and Yukon–Tanana terranes. The other type is the Insular terranes including the Wrangellia and Alexander terranes (Loc. 1a in Fig. 2), which are truly exotic to western North America and accreted in the Cretaceous. According to Colpron and Nelson (2009), these two terranes are derived from the Arctic region, and during much of the Pennsylvanian and Permian they had once an outboard (oceanward) location to the Intermontane terranes. These two types of terranes have slightly different features of Carboniferous fusulines, which are summarized below.

Of the two fusuline-bearing Insular terranes, the Wrangellia Terrane fusulines are not studied in detail. Ross and Ross (1983) listed Eostaffella, Schubertella, and Wedekindellina in the Carboniferous fauna from Wrangellia. Fusulines of the Alexander Terrane were investigated by Douglass (1971) and Mamet et al. (1993). Latest Tournaisian to early/middle Bashkirian foraminifers were reported from the Prince of Wales Island area in southernmost Alaska by Mamet et al. (1993). These taxa are mostly non-fusuline smaller foraminifers, but Eostaffella, Eostaffellina, and Pseudoendothyra were identified from latest Visean to early/middle Bashkirian strata. They also noted that the affinity of the fauna is as much Tethyan as North American, so the microfauna forms a bridge between the two palaeobiogeographical domains.

Pennsylvanian fusulines were also reported from the same island by Douglass (1971). The fauna was described and well illustrated, so that it is possible to know its palaeobiogeographical features. Fusulines described from Prince of Wales Island are Millerella aff. marblensis, Ozawainella? sp., Nankinella sp., Staffella aff. powwowensis, Pseudostaffella rotunda, Fusulinella pinguis, F. alaskensis, Beedeina? sp., and Fusulina flexuosa. Of them, Pseudostaffella, Fusulinella, and Fusulina species were all proposed as new taxa in that study. Based on the occurrence data of these fusulines, there are three assemblages recognized from fusulines by Douglass (1971); the Pseudostaffella rotunda, Fusulinella pinguis, and Fusulinella alaskensisFusulina flexuosaBeedeina? sp. assemblages. Of them, P. rotunda is a very large form in this genus and is similar to P. grandis and P. gorskyi reported from younger Bashkirian strata in the eastern part of the Ural–Arctic Region and the western part of the Palaeotethys Region (Grozdilova and Lebedeva 1950, 1960; Rauzer-Chernousova et al. 1951; Brazhnikova et al. 1967; Villa 1995; Nikolaev 2005). Some specimens of this form are also comparable morphologically to ‘advanced’ Pseudostaffella sp. reported by Groves et al. (1994) from upper Bashkirian strata of Ellesmere Island, Canadian Arctic. The Pseudostaffella rotunda assemblage is probably referable to the late Bashkirian. Fusulinella species from Prince of Wales Island are both endemic, but F. pinguis is, as Douglass (1971) argued, somewhat similar to F. timanica described by Rauzer-Chernousova et al. (1951) from the upper Moscovian of the Russian Platform. Thus, a younger Moscovian age is likely for this species. Fusulinella alaskensis found in the third assemblage has a fusiform shell with almost straight to slightly concave lateral slopes and well-developed high and asymmetrical chomata. These features are somewhat reminiscent of Kanmeraia species such as K. eopulchra and K. pulchra, rather than Fusulinella species. The genus Fusulina is essentially Ural–Arctic and Palaeotethyan, and F. flexuosa is somewhat similar to F. kulikiana from the upper Moscovian of the Russian Platform. Moreover, Beedeina? sp. is noteworthy because this species is very similar to what was described as Fusulina ylychensis by Rauzer-Chernousova in Rauzer-Chernousova et al. (1951) from the Myachkovian of the Russian Platform. This species is considered to be neither related to Beedeina nor Fusulina phylogenetically. It is probably in the Kanmeraia lineage but developed stronger septal fluting than ordinary species in this genus. A Myachkovian age is most likely for the Fusulinella alaskensisFusulina flexuosaBeedeina? sp. assemblage. Therefore, it can be concluded that the Alexander Terrane fusuline fauna, especially in Bashkirian–Moscovian time, clearly possesses affinities with those in the Ural–Arctic province. In contrast, there is no obvious faunal influence recognized in this fauna from the coeval cratonic North American fauna.

The palaeobiogeographical features of Insular terrane fusulines concluded above, suggesting a closer linkage to the Arctic to western Eurasian areas, well agree with a hypothesis that in view of the palaeotectonic evolution of northwestern Laurussia, the Insular terranes were derivations from the Arctic (Boreal) region (Colpron and Nelson 2009). A similar suggestion based on the analysis of fusuline fauna was made by Davydov (2016). In that study, he situated the Insular terranes (Wrangellia Terrane) in the middle of the Arctic region close to the Canadian Arctic in a Pennsylvanian palaeomap. But, the recognized faunal similarity does not necessarily mean that the Insular terranes were still in the Arctic location during that time. The interpretation shown in Figure 2 to place the Insular terranes at a little farther west from the Arctic, which is largely dependent on Colpron and Nelson (2009), is not in conflict with the palaeo(bio)geographical reconstruction of western North American terranes proposed by Belasky et al. (2002).

Ross and Ross (1983) noted that the Stikinia Terrane fusuline fauna contains Profusulinella, which is based on their unpublished data. The Carboniferous fusulines from Stikinia are only poorly known so far. Those from the Quesnellia Terrane were reported by Sada and Danner (1974) and Ross and Monger (1978) from British Columbia, Canada. Its Mississippian fauna is known from the Kamloops area in southern British Columbia. Sada and Danner (1974) reported Pseudoendothyra columbiana, Eostaffella spp., and several other smaller foraminifers. This assemblage is referable to the late Visean, or as a lesser possibility to the early Serpukhovian. Then, Ross and Monger (1978) described a Pennsylvanian fauna from the Omineca Mountains in central British Columbia. Although the stratigraphy of their fusuline-bearing strata was not described in detail, it is possible to recognize four age-diagnostic assemblages in their materials. They are the Pseudostaffella paracompressa, P. gorskyi, Profusulinella, and Fusulinella assemblages. The first one contains P. paracompressa, Pseudoendothyra timanica, and Eostaffella and Millerella species. The first species can be included in the primitive group of the genus, and this and similar species occur commonly in the Askynbashian (latest early Bashkirian; Nikolaev 2005; Ivanova 2008). Pseudostaffella gorskyi is a more advanced taxon in this genus and, as noted already in the section on the Insular terranes, this and similar species are characteristic in the late Bashkirian (Rauzer-Chernousova et al. 1951; Villa 1995; Nikolaev 2005; Ivanova 2008). These two assemblages represented by Pseudostaffella species clearly show faunal affinities to those reported from the Ural–Arctic and some parts of the Palaeotethys regions. The next younger Profusulinella assemblage consists of P. prisca, P. arta, P. ovata, and Fusulinella? densa, the last of which was proposed as a new species in Ross and Monger (1978). Although these three Profusulinella species were given taxonomic names that have been originally described and reported widely over the Eurasian region, based on their illustrations, shell morphologies of the Omineca Mountains Profusulinella are not very similar in overall shell features to those in the named species from Eurasia. As Ross and Monger (1978) concluded, this assemblage is referable to some part of the early Moscovian (probably Vereian or early Kashirian), but its palaeobiogeographical affinity is pending. The Fusulinella assemblage contains two new species; F. concava and F. decora. They are associated with Wedekindellina cf. uralica. The latter species, or the genus Wedekindellina itself, shows faunal relationships to both the North American Craton and Ural–Arctic regions. Of the two Fusulinella species, F. concava is very similar to F. alaskensis described by Douglass (1971) from the Alexander Terrane described above. Moreover, as Ross and Monger (1978) admitted, both Fusulinella species share similarities to some degrees in the general shell shape, nature of chomata, and shell growth to Kanmeraia pulchra and K. eopulchra, and are less similar to species in Fusulinella from cratonic North America. As for the age, a late Moscovian age is suggested for this assemblage. Although it is not yet very conclusive, late Moscovian fusulines from the Quesnellia Terrane have, if anything, an Ural–Arctic affinity.

In conclusion, Carboniferous fusuline faunal aspects in the Stikinia Terrane are not yet very clear. In the Quesnellia Terrane, the Bashkirian fusuline fauna clearly shows an affinity to that of the Ural–Arctic Region. The Moscovian fauna is inconclusive but is likely to be of an Ural–Arctic type.

This part of the Ural–Arctic Region corresponds to a parautochthonous part of ancient North America, in the northern part of the Cordillera (Colpron et al. 2007). Thus, it had been a marginal part of the far northwestern corner of Laurussia in the middle latitudes during the Carboniferous (Fig. 2). Little is known about Carboniferous fusulines except for two articles by Ross (1967, 1969). He reported Late? Mississippian to Moscovian fusulines from several localities in the Yukon Territory in Canada just east of the Alaskan border. In total, four age-diagnostic assemblages were recognized in these works. The oldest is said to be represented by Pseudoendothyra britishensis, but this species may belong to Eostaffella. If this is the case, a Visean–Serpukhovian boundary age is likely. The next one is characterized by Pseudostaffella yukonensis, P. spp., Millerella porcupinensis, and Pseudoendothyra keelensis. Of them, P. yukonensis is included in a primitive group of the genus and is similar to P. antiqua and P. paracompressa, suggesting an Akavassian (late early Bashkirian) age. Neostaffella ettrainensis is diagnostic in the third assemblage and associated with Staffella junglensis and Profusulinella cf. copiosa. Neostaffella ettrainensis is morphologically comparable to N. nibelensis, N. latispiralis, N. pseudoquadrata, and N. vozhgalica, all of which are known to occur from the latest Bashkirian and early Moscovian (mainly Asatauian and Vereian; Rauzer-Chernousova et al. 1951; Nikolaev 2005; Ivanova 2008). Thus, this assemblage is potentially assignable to a Bashkirian–Moscovian boundary interval age. Fusulinella crowensis by Ross (1967) and Eowaeringella richardsonensis by Ross (1969) might be closely related taxonomically and should be included in Kanmeraia by their gross shell morphology. They are probably referable to the late (or latest) Moscovian or a slightly younger age. Moreover, Ross (1969) described Wedekindellina cf. cabezasensis from an isolated locality farther to the east of the locality where the Neostaffella ettrainensis fauna was discovered. The stratigraphic relationships of these localities are not known. Wedekindellina cabezasensis was originally described from the Horquilla Limestone of SE Arizona, USA and may belong to Zellerella of Wilde (2006). The Yukon Territory specimens are similar to the types of this species in gross shell morphology, but the former likely has weakly fluted septa, while septa are unfluted in the latter. Though it is not yet conclusive, what Ross (1969) reported as W. cf. cabezasensis from the Yukon Territory is likely a Kanmeraia species, and thus also potentially suggests a late (or latest) Moscovian or even slightly younger age. As described in the following section, there are age-corresponding comparable fusuline assemblages to those seen in the Bashkirian and Moscovian of the Yukon Territory, in the Canadian Arctic (Nassichuk and Wilde 1977; Groves et al. 1994; Rui et al. 1996).

The Carboniferous fusulines in the Yukon Territory range from the later part of the Mississippian to the Moscovian (or slightly younger). The Mississippian assemblage is difficult to appraise palaeobiogeographically, but for the Pennsylvanian assemblage a closer relationship to the Ural–Arctic fauna is evident.

The Arctic Alaska Block was originally exotic to the North American craton (Laurentia), but had been emplaced already to approximately the present position on the northwestern end of Laurussia by the Devonian. Thus, it was in a northern middle latitudinal area during the Carboniferous (Colpron and Nelson 2009; Lawver et al. 2011). Thick, carbonate-dominant strata of Osagean to Atokan (late Tournaisian to Bashkirian) age, called the Lisburne Group, were deposited there, and the group now widely underlies the east–west-directed Brooks Range, extending across Arctic Alaska into Canada. During the 1970s, a series of investigations on foraminiferal biostratigraphy were carried out by B.L. Mamet and his colleagues to establish the chronostratigraphic framework of the group in relationship to petroleum exploration (Armstrong et al. 1970, 1971; Mamet and Mason 1970; Mamet and Armstrong 1972; Armstrong and Mamet 1974, 1975, 1977). These works provided a vast amount of data as to foraminiferal occurrences from the group. Many of them are in the form of species lists in samples collected from many levels. Some key foraminiferal taxa for biostratigraphy were described and illustrated, but many were left unillustrated. Especially, Pennsylvanian fusulines (Pseudostaffella, Eoschubertella = Schubertella, Eostaffella, and Pseudoendothyra) have seldom been shown, except in a few cases where foraminifers were illustrated as part of photomicrographs for microfacies (Armstrong and Mamet 1974, 1975, 1977). Armstrong and Mamet (1977) described and illustrated several early fusulines including Eostaffella species similar to E. mosquensis, Pseudoendothyra britishensis, Millerella pressa, and Pseudonovella aff. carbonica from the upper part of the Mississippian (Chesterian equivalent), and Schubertella yukonensis from the Lower Pennsylvanian (Morrowan and Atokan equivalents).

Then, Harris et al. (1997) and Baesemann et al. (1998) showed the concrete stratigraphic distribution of foraminifers from outcrop and borehole sections in the eastern part of the Brooks Range and also illustrated some key taxa, including major fusulines. According to them, Eostaffella (including E. postmosquensis) and Pseudoendothyra first occur almost at the same time in lower Chesterian levels and both ranged upward to the Pennsylvanian. Thus, in fusulines the late Visean–Serpukhovian in Arctic Canada yields only these two genera. Millerella marblensis and Pseudonovella carbonica appear first in the middle and upper parts of the Morrowan (earliest Pennsylvanian), and their ranges extend to the Atokan. Millerella pressa is restricted in the middle Morrowan. Plectostaffella and Semistaffella successively appear in the late Morrowan, and the occurrence of Pseudostaffella defines the base of the Atokan. Schubertellids first occur at around the Morrowan–Atokan transition. Harris et al. (1997) illustrated Plectostaffella jakhensis, Semistaffella sp., and Pseudostaffella spp., in which some of the Pseudostaffella specimens are possibly identified as P. antiqua. A successive evolutionary change of the Eostaffella postmosquensisPlectostaffellaSemistaffellaPseudostaffella lineage is usually documented in the Urals and Canadian Arctic, and in some sections in the Palaeotethys Region (Reitlinger 1971; Groves 1988; Groves et al. 1994; Ivanova 2008), but is not known in southerly located cratonic North America. Thus, it can be concluded that the fusuline fauna of Arctic Alaska has a linkage with the Ural–Arctic Region in a broad sense.

In the Canadian Arctic Archipelago, Carboniferous fusulines are known from Serpukhovian and younger strata distributed in the Sverdrup Basin. They occur mainly in the Nansen Formation, and the underlying Borup Fiord Formation also yields some forms. In this basin, Thompson (1961) first described and illustrated a few Moscovian fusuline species from Ward Hunt Island. After that, a series of systematic investigation on Carboniferous fusulines were carried out under the mission of the Geological Survey of Canada (Mamet 1974; Nassichuk and Wilde 1977; Rui et al. 1991, 1996; Groves et al. 1994; Rui and Nassichuk 1994). These studies provide the basis of the account below, and their biostratigraphic summary is shown in Figure 14. Moreover, there is documentation of the occurrence of Carboniferous fusulines from the Northwind Ridge in the Arctic Ocean off Arctic Alaska, in the North Chukotka area and Wrangel Island in Far East Russia, and in the New Siberian Archipelago off northern Siberia, all in the Arctic Ocean. Davydov (2016) suggested that the original locations in Pennsylvanian time of these areas were proximal to the then Canadian Arctic, which was close to his ‘Forbiddance Line’, the northern limit of fusuline distribution. Therefore, the occurrences of Carboniferous fusulines from Northwind Ridge, Chukotka/Wrangel Island, and the New Siberian Islands are also briefly noted in this section.

Fig. 14.

Fusuline biostratigraphic successions in the Canadian Arctic Archipelago, Greenland, and Barents shelf (Spitsbergen, Kolguev Island, and Novaya Zemlya) (Locs 4, 5, and 7 in Fig. 2) in the Ural–Arctic Region. The Pseudostaffella cf. antiqua assemblage from Spitsbergen may possibly represent a slightly younger age than the late early Bashkirian (see discussion in the text). Abbreviations of stages and substages: Vise., Visean; Serpukh., Serpukhovian; Mol, Moliniacian; Liv, Livian; War, Warnantian; Tar, Tarusian; Ste, Steshevian; Pro, Protvian; Zap, Zapaltyubian; Bog, Bogdanovkian; Syu, Syuranian; Aka, Akavassian; Ask, Askynbashian; Tas, Tashastian; Asa, Asatauian; Ver, Vereian; Kas, Kashirian; Pod, Podolskian; Mya, Myachkovian; Kre, Krevyakinian; Kha, Khamovnikian; Dor, Dorogomilovian; Dob, Dobryatinian; Pav, Pavlovoposadian; Nog, Noginskian; Mel, Melekhovian. Abbreviations of taxonomic (generic) names: Eo., Eostaffella; Pt., Protriticites; Qf., Quasifusulinoides; St., Staffellaeformes. References for data: see the text for details.

Fig. 14.

Fusuline biostratigraphic successions in the Canadian Arctic Archipelago, Greenland, and Barents shelf (Spitsbergen, Kolguev Island, and Novaya Zemlya) (Locs 4, 5, and 7 in Fig. 2) in the Ural–Arctic Region. The Pseudostaffella cf. antiqua assemblage from Spitsbergen may possibly represent a slightly younger age than the late early Bashkirian (see discussion in the text). Abbreviations of stages and substages: Vise., Visean; Serpukh., Serpukhovian; Mol, Moliniacian; Liv, Livian; War, Warnantian; Tar, Tarusian; Ste, Steshevian; Pro, Protvian; Zap, Zapaltyubian; Bog, Bogdanovkian; Syu, Syuranian; Aka, Akavassian; Ask, Askynbashian; Tas, Tashastian; Asa, Asatauian; Ver, Vereian; Kas, Kashirian; Pod, Podolskian; Mya, Myachkovian; Kre, Krevyakinian; Kha, Khamovnikian; Dor, Dorogomilovian; Dob, Dobryatinian; Pav, Pavlovoposadian; Nog, Noginskian; Mel, Melekhovian. Abbreviations of taxonomic (generic) names: Eo., Eostaffella; Pt., Protriticites; Qf., Quasifusulinoides; St., Staffellaeformes. References for data: see the text for details.

In the Sverdrup Basin of the Canadian Arctic, the oldest fusuline assemblage in the Carboniferous is found in the Borup Fiord Formation and consists of Eostaffella (E. ex. gr. mosquensis), Eostaffellina, and Pseudoendothyra (Mamet 1974; Groves et al. 1994). A broad Serpukhovian age was suggested for them (Fig. 14).

Shallow carbonate deposition became prevalent in the overlying Nansen Formation during the Bashkirian and later part of the Carboniferous. Based mainly on Groves et al. (1994), and in addition to some data by Rui et al. (1996) from the Canyon Fiord Formation of a marginal clastic facies belt, five age-diagnostic fusuline assemblages can be established in the Bashkirian (Fig. 14). Of them, the oldest one is characterized by the concurrent occurrence of Plectostaffella jakhensis and Eostaffella postmosquensis, and this interval also contains Plectostaffella reitlingerae and Pseudoendothyra spp. These species range upward in the succession, and, in the overlying levels, Semistaffella variabilis together with Eostaffellina paraprotvae and Eostaffella pinguis newly appear. These two biostratigraphic intervals, represented by the P. jakhensisE. postmosquensis and S. variabilis assemblages, are correlated to the Syuranian. From this interval and also slightly younger levels of the Sverdrup Basin, Pinard and Mamet (1998) reported the occurrence of several Eostaffella and Eostaffellina species including Eostaffella pseudostruvei, E. proikensis, E. kanmerai, Eostaffellina paraprotvae, and E. ovaliformis. The next younger interval is defined by the occurrence of Pseudostaffella antiqua and contains Schubertella obscura and Millerella spp. It is referable to the Akavassian.

Groves et al. (1994) reported an interesting taxon identified as ‘advanced Pseudostaffella’ from some levels above the occurrence of Pseudostaffella antiqua. As they admitted, this species is possibly assigned to the genus Neostaffella, and the interval designated by this Neostaffella? species is probably already late Bashkirian. Moreover, elsewhere in the Canadian Arctic Archipelago, Rui et al. (1996) recognized a stratigraphic level marked by the occurrence of Pseudostaffella posterior and P. grandis. It may possibly be correlated to the Askynbashian (latest early Bashkirian), which is between the two biostratigraphic intervals characterized by Pseudostaffella antiqua below and Neostaffella? sp. above. It is important to note that in the Canadian Arctic Archipelago, the stratigraphically successive morphological transition in the early evolution of the Fusulinidae, shown by the PlectostaffellaSemistaffellaPseudostaffellaNeostaffella lineage, is recorded in the lower part of the Nansen Formation (Groves et al. 1994).

Above the Bashkirian, there is a distinct level that yields Ozawainella turgida, Neostaffella ettrainensis, Profusulinella prisca, and Eofusulina (Rui et al. 1996; Fig. 14). This assemblage is considered to be already Vereian (basal Moscovian). Kashirian fusulines are not known in Arctic Canada, but the Podolskian is well represented by Hanostaffella paradoxa, Fusulinella alaskensis, F. paracolaniae, Wedekindellina uralica, Beedeina pseudoelegans, and others (Groves et al. 1994; Fig. 14). The small fusuline fauna of Thompson (1961) from Ward Hunt Island is also probably of this age, although its specific composition is apparently different. From the type section of the Nansen Formation, Rui et al. (1991) described rich fusulines and recognized the Wedekindellina lataWedekindellina uralica longa Zone in the lower part of the section. The lower part of this zone is also correlated to the Podolskian. The upper part of the zone is better separated as the Fusulinella subellipticaF. schwagerinoides Zone by the occurrence of the marker species and also Fusulinella rara, and Neostaffella sphaeroidea, and this zone and the overlying Kanmeraia eopulchra Zone are assignable to the Myachkovian (Fig. 14).

Late Pennsylvanian fusulines are not sufficiently understood in this area, but a small assemblage consisting of Triticites sp. ( = Protriticites spp. of Rui and Nassichuk 1994) and Kanmeraia usvae by Rui and Nassichuk (1994) from the type area of the Nansen Formation is probably referable to the late Kasimovian (Fig. 14). Moreover, Nassichuk and Wilde (1977) earlier reported a fusuline succession that consists mainly of schwagerinids with some Kanmeraia species, from Ellesmere Island. They recognized four assemblage zones and originally assigned all of them to the lower Permian. These zones are: in ascending order the Pseudofusulinella thompsoniP. ex gr. usvae, Pseudofusulina plana, Schwagerina whartoni, and Schwagerina paraarctica zones. The lower three zones are herein reinterpreted as the Kanmeraia usvae, Rugosofusulina flexuosaKanmeraia pulchra, and Daixina sokensis zones (Fig. 14). The lower one is considered to be the same age as the TriticitesKanmeraia usvae assemblage reported by Rui and Nassichuk (1994). The second and third are correlated to the early and late Gzhelian, respectively, based on their taxonomic composition.

Fusuline-bearing rock samples were obtained from piston cores from the seafloor on Northwind Ridge off Arctic Alaska. Stevens and Ross (1997) described fusulines from them, including Parawedekindellina cf. pechorica, Kanmeraia spp., and Fusulinella or Beedeina. A broad late Moscovian age is inferred for these fusulines. From the Chukotka area and Wrangel Island in the Arctic region of Far East Russia, Solov'eva (1975) reported Serpukhovian and Bashkirian foraminifers. The Serpukhovian fusulines contain Eostaffella pseudostruvei, E. postmosquensis, E. prisca, E. postproikensis, Eostaffellina paraprotvae, E. subsphaerica, Pseudoendothyra crassa, P. propinqua, P. struvei, and others, and the Bashkirian assemblage consists of Eostaffella pseudostruvei, E. postmosquensis, Ozawainella maximensis, Pseudonovella grozdilovae, Schubertella obscura, Pseudostaffella sp., Profusulinella sp., Pseudoendothyra spp., and others. In the New Siberian Islands, fusulines were reported from two islands: Kotel'ny Island and Zhokhov Island. From the former, Danukalova et al. (2019) reported and illustrated Serpukhovian fusulines including Eostaffellina paraprotvae, Plectostaffella sp., Eostaffella ex gr. postmosquensis, and E. ex gr. pseudostruvei. From the latter island, Davydov (2016) illustrated Millerella symmetrica, Schubertella gracilis, Pseudostaffella cf. kyselensis, P. aff. paracompressa, Staffellaeformes staffellaeformis, Profusulinella aff. prisca, and Eofusulina cf. triangula, and suggested an early Moscovian (Vereian or Kashirian) age. This fusuline assemblage is considered to be of this suggested age broadly, but some key illustrated specimens are too poorly preserved, such as Staffellaeformes, Profusulinella, and Eofusulina species. They are difficult to identify exactly.

In Greenland, fusulines have been reported from the basal sequence of the Carboniferous–Paleogene Wandel Sea Basin succession in the northeastern corner of this large island. In the early stage of investigation, Ross and Dunbar (1962) described diverse fusulines ranging from the early Moscovian to the early (earliest) Permian. They consist mainly of species known from the Eurasian region, but also contain Desmoinesian (Moscovian) Wedekindellina, which occurs also from North American interior basins. Later works by Nilsson (1994) and Davydov et al. (2001) established a solid biostratigraphic framework of Greenland fusulines upon which the following account is based (Fig. 14). In Davydov et al. (2001) they referred to biostratigraphic units in the study section as biozones, but it is difficult to settle the exact zonal boundary stratigraphically in view of the fact that fusuline-bearing levels are rather sparse within a thick succession in Greenland. Accordingly, it would be reasonable to treat them as age-diagnostic assemblages, following Nilsson (1994).

The oldest fusuline assemblage in the Carboniferous from Greenland, is represented by Profusulinella prisca, P. timanica, Neostaffella greenlandica, and Paraeofusulina trianguliformis and is referable to the Vereian of the lower Moscovian. Overlying this is an interval characterized by Ozawainella mosquensis, Neostaffella greenlandica, Profusulinella constans, P. ovata, P. rhombiformis, Aljutovella postaljutovica, Citronites notabilis, Beedeina pseudoelegans, Eofusulina binominata, and Paraeofusulina sp. (P. trianguliformis?). A Kashirian age is proposed for this assemblage. In the upper Moscovian, the late Podolskian–early Myachkovian is characterized by such species as Neostaffella cuboides, Fusulinella bocki, Beedeina paradistenta, Wedekindellina dutkevichi, and Kanmeraia eopulchra. The late Myachkovian (latest Moscovian) fusuline assemblage in Greenland is represented by large, elongate fusiform Beedeina species (B. siviniensis and B. nytvica) in association with Kanmeraia eopulchra and Protriticites (P. subschwagerinoides and P. aff. ovatus).

In two assemblages in the Kasimovian, the older one is a Krevyakinian (early Kasimovian) age and Protriticites globulus, P. grozdilovae, and Quasifusulinoides quasifusulinoides are diagnostic. Other species found in this interval are Ozawainella mosquensis, Fusiella lancetiformis, Parastaffelloides pseudosphaeroidea, Fusulinella? sp., Protriticites pseudomontiparus, P. manukalovae, Obsoletes sp., and Kanmeraia pulchra. The middle Kasimovian is characterized by Montiparus, Protriticites, and Obsoletes species such as M. umbonoplicatus, P. pseudomontiparus, P. globulus, O. burkemensis, and O. curtus.

Two assemblages are recognized in the overlying lower Gzhelian. The lower one consists of Rugosofusulina flexuosa, R. elliptica, and R. ovoidea, and the upper one contains Rauserites variabilis, R. postarcticus, Rugosofusulina elliptica, R. triticitiformis, and Kanmeraia annae. The late Gzhelian (latest Carboniferous) fusuline assemblage is characterized by large Daixina species, D. ex gr. sokensis, which includes what were originally identified as D. enormis, D. vasilkovskyi, and Schellwienia postmodesta by Davydov et al. (2001). In addition to this diagnostic species, the assemblage contains various schwagerinids such as Rauserites paraarcticus, Jigulites magnus, Anderssonites pseudoanderssoni, Rugosofusulina praevia, Daixina asiatica, D. minima, and D. tormosensis. Moreover, Quasifusulina kaspiensis is also found in it. Of them, the first two Daixina species were originally named as Schellwienia salebrosa, S. kharjagaensis, and S. subundulata, the third Daixina species was identified as S. aff. modesta, and R. praevia was reported as S. ulukensis by Davydov et al. (2001). The Daixina ex gr. sokensis assemblage is also common in the latest Carboniferous of the Canadian Arctic and Spitsbergen in the Arctic region.

The Taimyr Peninsula in northern Siberia, Russia, is comprised of the Taimyr block, which was allochthonous to both the Siberian craton and Baltica/Laurussia in the Late Paleozoic. The block was in a middle latitudinal position between Novaya Zemlya and the Siberian craton during Mississippian time (Lawver et al. 2011). In this area, the marine lower Carboniferous contains foraminifers, which were investigated by Solov'eva (1967, 1970, 1972). In fusulines, Pseudoendothyra struvei, P. taimyrica, Eostaffella mosquensis, E. postmosquensis, and Eostaffellina paraprotvae were described. They suggest a broad late Visean–Serpukhovian age.

In the Barents shelf off northern Norway and northwestern Russia, solid information on a Middle–Late Pennsylvanian fusuline succession has been obtained from Spitsbergen in the Svalbard Islands. Carboniferous fusulines were also reported from two Russian islands: Novaya Zemlya and Kolguev Island. Moreover, there are distributions of Moscovian to Gzhelian fusuline-bearing strata on the subsurface inner Finnmark Platform, and Bashkirian fusulines were reported from Bear Island far off the coast of Norway.

On Spitsbergen, except for descriptive works by Schellwien (1908) and Staff and Wedekind (1910) carried out at the dawn of palaeontological research on this island, fusuline investigation has expanded since the 1960s (Forbes 1960; Ross 1965a; Igo and Okimura 1992; Nilsson and Davydov 1997; Davydov and Nilsson 1999). Based on these works the Carboniferous fusuline succession is summarized as follows (Fig. 14).

Forbes (1960) reported Pseudostaffella cf. antiqua from the lower part of the Carboniferous section, and this species is apparently the oldest fusuline from the Carboniferous of Spitsbergen. On the Russian Platform, P. antiqua is usually considered to characterize the Akavassian, and to some extent the Askynbashian, of the late early Bashkirian (Groves 1988; Nikolaev 2005; Ivanova 2008), and this stratigraphic distribution is also the case in the Arctic region (Groves et al. 1994; Rui et al. 1996). Thus, there is good potential to refer the P. cf. antiqua assemblage of Spitsbergen to this age, but this assessment needs some annotations because P. antiqua and related, likely primitive species of this genus, range upward to the lower Moscovian. On Novaya Zemlya, as noted later, P. antiqua and similar species occur together with early Moscovian (Kashirian) fusulines such as Neostaffella greenlandica, N. sphaerica, Profusulinella prisca, and Aljutovella? priscoidea. Thus, there are some possibilities that the P. cf. antiqua assemblage from Spitsbergen is also of a younger age than the late early Bashkirian (Fig. 14). Forbes (1960) also reported Kashirian fusulines containing Profusulinella constans and Paraeofusulina species. A comparable assemblage of this age is reported from Greenland (Davydov et al. 2001), which also bears these two forms. Moreover, Forbes (1960) illustrated two specimens of ‘Fusulinella eopulchra,’ but those are probably better identified as Beedeina sp., which could be referable to around the Podolskian.

Fusuline biostratigraphy across the Moscovian–Kasimovian boundary was investigated by Davydov and Nilsson (1999) in the Kolosseum section in central Spitsbergen. They established four biozones in this interval: two in the latest Moscovian (Myachkovian) and two in the Kasimovian. The early Myachkovian biozone is defined by Fusulinella bocki and Wedekindellina uralica, and also contains Neostaffella sphaerica, Beedeina paradistenta, Kanmeraia pulchra, Quasifusulinoides sp., and Parawedekindellina subovata. The late Myachkovian is represented by the Protriticites ex gr. ovatusQuasifusulinoides fusiformis Zone, which also yields Fusiella lancetiformis, Fusulina mosquensis, Quasifusulinoides firmus, Kanmeraia eopulchra, Fusulinella helenae, F. timanica, and others. Elsewhere on Spitsbergen Igo and Okimura (1992) illustrated an unspecified, large, elongate fusiform Beedeina. That form is very similar to B. siviniensis, which was also reported from the late Myachkovian interval on Greenland (Davydov et al. 2001). Igo and Okimura's (1992),Beedeina sp. is also considered to be a faunal component of the Protriticites ex gr. ovatusQuasifusulinoides fusiformis Zone of Davydov and Nilsson (1999). This late Myachkovian biozone is succeeded by the Krevyakinian (early Kasimovian) Protriticites pseudomontiparusObsoletes burkemensis Zone. Fusiella lancetiformis, F. rawi, Quasifusulinoides fusiformis, Kanmeraia pulchra, Protriticites ovatus, P. plicatus, P. globulus, and Obsoletes fusiformis are also found in this zone.

Then, the Khamovnikian is represented by the Montiparus montiparus Zone and several Montiparus species (M. likharevi, M. umbonoplicatus, M. mesopachus) and Protriticites ovoides are contained in this zone. A late Kasimovian fusuline biozone is not settled in Spitsbergen, but in the Gzhelian, Nilsson and Davydov (1997) proposed three zones; each broadly correlated to the early, middle, and late Gzhelian, respectively. The Rauserites rossicus Zone corresponds to the early Gzhelian, and, apart from the marker species, Rugosofusulina flexuosa and R. serrata are listed in the faunal composition. The next is the middle Gzhelian Jigulites jigulensis Zone and Jigulites minor, J. longus, J. procullomensis, J. dagmarae, and J. oviformis are mentioned in the composition. A late Gzhelian zone is characterized by Daixina sokensis, and several other Daixina (such as D. laevis, D. timanensis, D. delicata, D. dualis), Jigulites dagmarae, Anderssonites? acuminulata, and others are associated in this zone. Igo and Okimura (1992) illustrated fusulines from this zone in the Skansen section at Central Spitsbergen. As shown in Fig. 14, early and late Gzhelian fusuline zones are defined by similar markers among the Canadian Arctic, Greenland, and Spitsbergen in the Arctic region.

Ross (1965a) described a fusuline assemblage including Triticites species in the list, from the Tempelfjorden section of central Spitsbergen. This assemblage apparently looks to be Late Pennsylvanian because of the Triticites species, but it is a little difficult to estimate its exact level in the Spitsbergen stratigraphy. Some specimens in the Tempelfjorden fusulines (such as those illustrated on pl. 10, figs. 22–28 of Ross 1965a as Schwagerina anderssoni and a specimen shown on pl. 11, fig. 13 as Triticites pseudoarcticus) are similar to those from the basal Permian of Greenland, reported by Nilsson (1994) as Rugosofusulina arianica and ‘Zigarella anderssoni’ ( = Anderssonites anderssoni), respectively. The Tempelfjorden fusuline assemblage reported by Ross (1965a) is probably already of the early (earliest) Permian.

On Novaya Zemlya, age-scattered fusuline assemblages, summarized in Figure 14, have been reported by Solov'eva (1969) and Nakrem et al. (1991). In the Mississippian, the upper Visean and lower Serpukhovian yield various foraminifers, but they are all non-fusuline smaller foraminifers. In the late Serpukhovian, Solov'eva (1969) illustrated several Eostaffella, Eostaffellina, and Plectostaffella species. Bashkirian fusulines consist of Eostaffella and Pseudoendothyra species in the lower part of the Syuranian–Akavassian interval, and in the upper part includes Pseudostaffella antiqua, Semistaffella variabilis, Plectostaffella, and Eostaffella. Nakrem et al. (1991) studied three localities on Novaya Zemlya and illustrated Pseudostaffella, Neostaffella, Profusulinella, and several other genera. One of their localities, which they called the ‘Lower fusulinid sample’, bears Pseudostaffella paracompressa, P. gorskyi, and Staffellaeformes cf. staffellaeformis. Nakrem et al. (1991) originally assigned this assemblage to the Vereian of the early Moscovian, but the specific composition suggests an age around the Tashastian (late Bashkirian). From the second locality (their ‘Upper fusulinid sample’), the following fusulines were illustrated: Ozawainella cf. mosquensis, Pseudostaffella cf. antiqua, Neostaffella greenlandica, and Profusulinella prisca. They considered this assemblage to be Vereian. Then, the third locality by Nakrem et al. (1991) on Eastern Krestovii Island in Northern Novaya Zemlya yielded Eostaffella mixta, Pseudostaffella sp. (probably P. antiqua), several Pseudoendothyra species, and Aljutovella? priscoidea. The last species is suggestive of a slightly younger age than that of their ‘Upper fusulinid sample’. The Krestovii Island fusuline association is probably age-equivalent to the Neostaffella subquadrataProfusulinella ovata assemblage from Kolguev Island described below. Summarizing the data from Novaya Zemlya, there remain fusuline assemblages ranging from the late Serpukhovian up to the early Moscovian on this island.

Davydov (1997a) reported Moscovian to Gzhelian fusulines from several wells on Kolguev Island between Novaya Zemlya and the Kola Peninsula. He recognized the following six assemblages (Fig. 14): the Neostaffella subquadrataProfusulinella ovata, Parawedekindellina subovata, Hanostaffella paradoxaWedekindellina uralica, Protriticites pseudomontiparus, Kanmeraia aff. usvae, and Daixina robusta assemblages. These are referable, respectively, to the Kashirian, Podolskian, early Myachkovian, Krevyakinian, possibly around late Kasimovian, and late Gzhelian. The observed fusuline succession on Kolguev Island is not continuous chronologically, but it consists of several age-diagnostic assemblages that have more or less comparable ones marked by similar species in other areas of the Arctic (Fig. 14).

On Bear Island between Finnmark of mainland Norway and Svalbard, Gradstein et al. (2013) illustrated three fusuline assemblages of the Bashkirian: the Semistaffella variabilis, Pseudostaffella antiqua, and Staffellaeformes staffellaeformis assemblages, in ascending order. These are correlated, respectively, to the Syuranian, Akavassian, and Askynbashian. The same, or partly the same, fusuline succession as the Bear Island succession is known in the Urals (Kulagina et al. 2001; Ivanova 2008), Timan–Pechora (Nikolaev 2005), and on Ellesmere Island of the Canadian Arctic Archipelago (Groves et al. 1994). Gradstein et al. (2013) also noted the occurrence of late Bashkirian up to Kasimovian fusulines (Neostaffella nibelensis in the late Bashkirian; Profusulinella prisca, P. ovata, Aljutovella postaljutovica, Wedekindellina uralica, Beedeina nytvica, Kanmeraia eopulchra in the Moscovian; and Protriticites sp. in the early Kasimovian) elsewhere from this island, but they were not illustrated.

In addition to these on-land occurrences mentioned above, there are fusuline-bearing Pennsylvanian strata known in boreholes drilled on the inner Finnmark Platform in the offshore Barents Sea. Latest Moscovian to Gzhelian fusulines, including Hanostaffella paradoxa, Fusiella lancetiformis, Protriticites ovatus, Quasifusulinoides quasifusulinoides, Kanmeraia eopulchra, Montiparus paramontiparus, Rauserites stuckenbergi, Jigulites magnus, and Daixina ex gr. sokensis, are found in the species listed in Ehrenberg et al. (2000), but they were not illustrated.

In Timan–Pechora located on the northeastern part of the Russian Platform, Carboniferous fusuline study commenced with Rauzer-Chernousova et al. (1936). After Durkina (1959), Volozhanina (1962), Lebedeva (1966), and Grozdilova (1966) established the basic framework of smaller foraminiferal and fusuline biostratigraphy in this region, Konovalova (1991), Remizova (1995, 2004), Durkina (2002), and Nikolaev (2005) supplemented many particular data to make a detailed biostratigraphic scheme for each Carboniferous stage, on which the Timan–Pechora fusuline succession shown in Figure 15 is based.

Fig. 15.

Fusuline biostratigraphic successions of Timan–Pechora, the Urals, and the Moscow Syneclise on the Russian Platform (Locs 8–10 in Fig. 2) in the Ural–Arctic Region. Abbreviations of stages and substages: Tn., Tournaisian; Ivo, Ivorian, see Figure 14 for others. Abbreviations of taxonomic (generic) names: Bd., Beedeina; Fl., Fusulinella; Ob., Obsoletes; Pt., Protriticites. References for data: see the text for details.

Fig. 15.

Fusuline biostratigraphic successions of Timan–Pechora, the Urals, and the Moscow Syneclise on the Russian Platform (Locs 8–10 in Fig. 2) in the Ural–Arctic Region. Abbreviations of stages and substages: Tn., Tournaisian; Ivo, Ivorian, see Figure 14 for others. Abbreviations of taxonomic (generic) names: Bd., Beedeina; Fl., Fusulinella; Ob., Obsoletes; Pt., Protriticites. References for data: see the text for details.

The oldest fusulines in the Carboniferous in this area came from lower Visean strata. They are Eoparastaffella simplex, E. concinna, E. venusta, E. subglobosa, E. restricta, Eostaffella versabilis, E. nalivkini, and others (Kostyzova 1997). This specific composition in the early Visean assemblage was essentially succeeded by the middle Visean one (Fig. 15). Biostratigraphic data of late Visean and Serpukhovian foraminifers are available from Durkina (1959, 2002). The late Visean assemblage consists of various Eostaffella and Pseudoendothyra such as Eostaffella mosquensis, E. prisca, E. paraparva, E. parastruvei, E. rotunda, E. oblonga, E. ikensis, E. proikensis, E. tenebrosa, Pseudoendothyra struvei, P. sublimis, P. schlykovae, and P. candida (Durkina 1959). Detailed foraminiferal biostratigraphy of the Serpukhovian in this area was reported by Durkina (2002), and its early part (Tarusian and Steshevian) is characterized by a fusuline assemblage containing Eostaffella proikensis, E. ikensis, E. tenebrosa, E. mosquensis, E. pseudostruvei, E. oblonga, Eostaffellina eoparaprotvae, E. vischerensis, E. aperta, E. schartimiensis, Pseudoendothyra illustria, P. propinqua, and P. ornata as major elements. Eostaffellina protvae, E. paraprotvae, and Plectostaffella varvariensis appear first in the Steshevian. The late Serpukhovian fusuline assemblage essentially has the same generic and somewhat similar specific composition, but Plectostaffella became more dominant. Eostaffella postproikensis, E. mirifica, Eostaffellina mira, Plectostaffella irregularis, P. bogdanovkensis, P. asymmetrica, P. minima, Pseudoendothyra kremenskensis, and P. parasphaerica are new faunal elements of the late Serpukhovian assemblage.

Nikolaev (2005) carried out detailed fusuline biostratigraphic work for the Bashkirian and proposed a zonation with substage-level resolution (Fig. 15). Particular listing of species from each zone is in Nikolaev (2005), and, instead, an overall character of the Bashkirian fusuline succession is summarized below. The earliest Bashkirian (Bogdanovkian) assemblage still consists of the ozawainellid genera Eostaffella, Eostaffellina, and Plectostaffella, which ranged upward from the upper Serpukhovian. In the following Syuranian the first fusulinid (pseudostaffellin) genus Semistaffella appeared in the fusuline assemblage. The next Akavassian is characterized by typical, somewhat primitive, small Pseudostaffella species such as P. antiqua, P. compressa, and P. proozawai. The first Schubertella also appears in the upper part of this interval. In the Askynbashian the first entry of Staffellaeformes is observed at the base, and Ozawainella also occurs first in the upper part of this interval.

The Tashastian in the late Bashkirian is defined by the Pseudostaffella gorskyi and Ozawainella pararhomboidalis zones, and Staffellaeformes continuously comprises an important part of the assemblage. Moreover, the first occurrence of Profusulinella species (P. parva, P. primitiva, and P.? praeovata) is recorded in the upper part of the Tashastian. Nikolaev (2005) described Pseudostaffella ozawaiformis from the Ozawainella pararhomboidalis Zone in the upper Tashastian. This taxon is likely a Neostaffella species judging from the gross shell morphology, but the first occurrence of certain Neostaffella is marked by N. nibelensis, N. dutkevichi, N. vozhgalica, and N. subquadrata from the Staffellaeformes tashliensis Zone of the upper Asatauian. In the lower part of the Asatauian (Aljutovella nibelensis Zone), several Aljutovella species (A. tikhonovichi, A. nibelensis, A. cybaea) and Profusulinella pararhomboides newly appeared in the fusuline fauna. Overall, the Bashkirian fusuline succession reported by Nikolaev (2005) is similar to that observed in the Urals, which is described in the next section.

The Moscovian–Gzhelian interval of Timan–Pechora is represented by six regional ‘horizons’; they are the Volongsky, Il'sky, and Sul'sky horizons for the Moscovian, the Burkemsky and Odesky horizons for the Kasimovian, and the Aiyubinsky Horizon for the Gzhelian, respectively. Remizova (1995, 2004) documented a continuous Moscovian–early Permian fusuline succession in the Malaya Pokayama section located in the northern part of the Pechora region. The following summary of fusuline succession from the Moscovian and the younger strata, schematized in Figure 15, was compiled by combining her faunal description with additional data by Volozhanina (1962), Lebedeva (1966), Grozdilova (1966), and Konovalova (1991) from other parts of the Timan–Pechora region.

The lower Moscovian (Volongsky horizon) is composed of two biostratigraphic intervals. The lower, correlated to the Vereian, is characterized by Schubertella pauciseptata and Neostaffella subquadrata and also yields Eostaffella mutabilis, Ozawainella umbonata, O. mosquensis, Pseudostaffella timanica, P. gorskyi, Neostaffella larionovae, N. vozhgalica, and Profusulinella prisca. The upper Volongsky horizon corresponds to the Kashirian and is defined by Aljutovella? priscoidea. Beside this species, the following fusulines are found in this interval: Schubertella obscura, Neostaffella parasphaeroidea, Taitzehoella atelica, and Profusulinella timanica. In the Il'sky horizon of the Podolskian, Neostaffella ozawai and Ozawainella mosquensis are the characteristic species, and other species found include Ozawainella angulata, O. praestellae, Schubertella acuta, Taitzehoella librovitchi, Neostaffella rostovzevi, N. formosa, Wedekindellina uralica, Parawedekindellina subovata, Fusulinella volozhaninae, F. bocki, Beedeina elegans, and B. samarica. The uppermost Moscovian is referred to as the Sul'sky horizon, and its lower part, correlated to the lower Myachkovian, is characterized by the occurrence of Beedeina elegans, although this species also occurs in the underlying Il'sky horizon in Timan (Lebedeva 1966). Other constituent species from the lower Myachkovian interval are Schubertella mjachkovensis, Neostaffella umbilicata, N. sphaeroidea, Fusulinella bocki, F. timanica, Wedekindellina dutkevitchi, Parawedekindellina ellipsoides, P. pechorica, Kanmeraia pulchra, Fusulinella kumpani, F. pseudobocki, and F. vozhgalensis. The late Myachkovian (late Sul'sky Horizon) contains the Obsoletes burkemensis assemblage. It is described in detail by Remizova (1995), and, besides the marker species, the assemblage consists of Fusiella typica, F. lancetiformis, Neostaffella cuboides, Fusulinella pseudoschwagerinoides, F. helenae, F. vozhgalensis, F. ovoides, Wedekindellina sera, W. grandis, W. thompsoni, Protriticites sphaericus, P. ex gr. pseudomontiparus, P. ovatus, Obsoletes pauper, Kanmeraia pulchra, and many other species.

The lower Kasimovian (Krevyakinian) is referred to as the Burkemsky horizon in the Timan–Pechora regional stratigraphy. Protriticites pseudomontiparus and Obsoletes obsoletus, in association with Ozawainella mosquensis, Pseudostaffella postparadoxa, Fusulinella pseudobocki, F. solovievae, Wedekindellina sera, Parawedekindellina porrecta, Kanmeraia usvae, Quasifusulinoides fusulinoides, Pseudotriticites makarichiensis, P. concinnus, Protriticites ovatus, P. nikitovkensis, P. jucundus, P. rotundatus, P. aquilus, P. semichatovae, P. plicatus, Obsoletes burkemensis, O. timanicus, O. concinnus, O. kireevae, and many other species were listed by Konovalova (1991) and Remizova (1995, 2004). The Odesky horizon represents a regional middle–late Kasimovian interval in Timan–Pechora, and the lower part is marked by Montiparus montiparus and the upper by Rauserites quasiarcticus. The former assemblage also contains Fusiella lancetiformis, Parawedekindellina tscherlichaensis, Protriticites pseudomontiparus, P. rotundatus, Quasifusulinoides fusiformis, Kanmeraia usvae, K. mesopachys, Montiparus umbonoplicatus, M. subcrassulus, M. sinuosus, M. mesopachus, M. paramontiparus, and others. The latter, correlated to the Dologomilovian, includes the following species: Schubertella kingi, Quasifusulina longissima, Schwageriniformis schwageriniformis, Triticites simplex, T. noinskyi, T. shikhanensis, T. acutus, T. explanatus, T. incomptus, Rauserites petschoricus, R. venustus, Rugosofusulina prisca, R. pleiomorpha, and R. triticitiformis.

The Aiyubinsky horizon represents the Gzhelian succession, which can be divided nominally into three fusuline intervals. In most previous studies, however, the lower and middle Gzhelian is collectively referred to as the ‘zone of Rauserites rossicus and Jigulites jigulensis’, ‘zone of Rauserites stuckenbergi and Jigulites jigulensis’, or ‘zones of Rauserites rossicusR. stuckenbergi and Jigulites jigulensis’ (Konovalova 1991; Remizova 1995, 2004). The lower portion of this stratigraphic interval, which corresponds to the Dobryatinian and Pavlovoposadian, is the zone of Rauserites rossicus, and contains Schubertella kingi, R. parairregularis, and R. stuckenbergi. The upper, the zone of Jigulites jigulensis, is marked by the occurrence of Schubertella longiformis, Quasifusulina longissima, Kanmeraia cf. kozhymiensis, Triticites longiformis, Rauserites stuckenbergi, Jigulites longus, J. dagmarae, J. intermedius, Rugosofusulina praevia, and several others. The late Gzhelian contains large fusiform Daixina species typically represented by D. sokensis. In addition to this, Daixina rozovskayae, D. zsui, D. aquilonae, D. timanensis, D. recava, and D. ruzhencevi are also of this kind. In this late Gzhelian part, Quasifusulina longissima, Benshiella stabilis, Triticites complicatus, Jigulites jigulensis, J. volgensis, Rugosofusulina praevia, and Daixina robusta also occur.

In the Urals, Carboniferous strata are distributed on both sides of the Main Uralian Fault running in a north–south direction in the middle of the mountain range, which is the main divide in the Uralian geology. To the west of the fault, the section consists of continental margin sediments of the East European Platform (Baltica) including the Pre-Uralian Foredeep, which was filled finally with a gently deformed, thick pile of flysch having an easterly provenance. To the east of the Main Uralian Fault is an oceanic sector of the Uralides, including the Tagilo–Magnitogorskian zone, which represents an island arc system developed along the western margin of the composite Kazakhstan Block (Puchkov 2009). In this zone several important Carboniferous sections (such as the Bolshoi Kizil and Verkhnyaya Kardailovka sections) are situated. These two areas on both sides of the Main Uralian Fault belong to different tectonic domains, but during Carboniferous time they already came closer geographically before and during the Uralian orogen since Bashkirian time. Thus, all of the information of fusuline succession from these areas is summarized here as the Ural province collectively (Fig. 15).

Information of the Tournaisian–Visean boundary foraminifers came from Postoyalko (1975) and Kulagina et al. (2018). The former author reported foraminiferal assemblages from the Pester'kovsky, Ilychsky, and Druzhninsky horizons (correlated broadly to the latest Tournaisian to the early Visean) of the western slope of the Urals. The latest Tournaisian contains Eoparastaffella ovalis, E. iniqua, E. lenticulare, E. restricta, and E. lenevkensis, while the early Visean bears E. simplex, E. interiecta, E. subglobosa, E. fabacea, and several other Eoparastaffella species along with Eostaffella prisca, E. ordinata, and E. versabilis. Then, Kulagina et al. (2018) designated the Eoparastaffella rotunda Zone in the uppermost Tournaisian and the E. simplex Zone in the lower Visean (Fig. 15). Middle Visean up to earliest Bashkirian shallow-marine sections are distributed on both western and eastern slopes in the South Urals (Grozdilova and Lebedeva 1954; Ivanova 1973; Kulagina 1988; Kulagina and Gibshman 2002; Nikolaeva et al. 2009; Pazukhin et al. 2010; Kulagina et al. 2014). Middle–late Visean fusulines include Eostaffella mosquensis and Pseudoendothyra struvei in the middle Visean, and E. mosquensis, E. prisca, E. proikensis, E. ikensis, E. tenebrosa, E. parastruvei, Pseudoendothyra struvei, P. concinna, and others in the late Visean (Fig. 15).

The Serpukhovian foraminiferal (including fusuline) succession is well presented in the Kugarchi, Muradymovo, and Bolshoi Kizil sections in the South Urals (Kulagina 1988; Kulagina et al. 1992, 2014; Kulagina and Gibshman 2002). The early Serpukhovian fusuline assemblage consists of Eostaffella mirifica, E. pseudoovoidea, several Eostaffella species that ranged up from the Visean (such as E. mosquensis and E. proikensis), and Eostaffellina decurta. The late Serpukhovian one contains Eostaffella postmosquensis, E. mirifica, E. pseudoovoidea, several other Eostaffella species, Eostaffellina actuosa, E. ex gr. paraprotvae, Plectostaffella jakhensis, P. varvariensis, and P. orbiculata (Fig. 15).

Ivanova (2008) made a comprehensive summary of the Bashkirian and Moscovian fusuline biostratigraphy of the Urals based on vast data from northern to southern domains of this large mountain range. In the Bashkirian, she established six fusuline zones that have a resolution of substage-level correlation (Fig. 15). In the Bashkirian stratotype in the South Urals, Groves (1988) described the foraminiferal succession while focusing mainly on the early evolution of pseudostaffellins. In the South Urals, Kulagina et al. (2001) also carried out a very detailed biostratigraphic work on Bashkirian foraminifers. Moreover, Chuvashov et al. (1984) reported Pennsylvanian biotic successions from the eastern slope of the Urals. There is sufficient quantity and quality of biostratigraphic information on fusulines in the Ural province. In this part, Bashkirian fusuline succession is summarized based mainly on Ivanova (2008) with supplemental information from other studies mentioned above as necessary.

The Bogdanovkian (the earliest Bashkirian) is marked by the Plectostaffella bogdanovkensis Zone. Eostaffella postmosquensis, E. mirifica, Millerella uralica, Eostaffellina ovoideaformis, Plectostaffella nauvalia, and P. orbiculata are associated in this zone. The Syuranian corresponds to the Semistaffella variabilisS. minuscularia Zone, which contains, besides these two markers, the following fusulines: E. postmosquensis, E. pseudostruvei, P. varvariensis, P. varvariensiformis, P. jakhensis, P. lukensis (which is somewhat similar to Plectomillerella by Brazhnikova and Vdovenko in Aizenverg et al. 1983), and Semistaffella primitiva. The first occurrence of the genus Semistaffella is recognized in this interval. Groves (1988) reported the first Semistaffella from the base of the Akavassian in the Bashkirian stratotype section, but actually it had appeared in the Syuranian (or Kamennogorian) already (Kulagina et al. 2001). The Akavassian is marked by the entry of the first Pseudostaffella, and Ivanova (2008) designated this interval the Pseudostaffella antiqua Zone, which is further divided into the lower P. antiqua Subzone and the upper P. grandis Subzone. In the P. antiqua Zone (s.l.) several small primitive Pseudostaffella, such as P. paracompressa, P. sofronizkyi, and Varistaffella varsanofievae, are characteristic, and it also yields Eostaffella mutabilis, Plectostaffella bogdanovkensis, Semistaffella variabilis, S. minor, and the first Schubertella species. The Staffellaeformes staffellaeformisPseudostaffella praegorskyi Zone of Askynbashian age is the next younger fusuline zone. Millerella uralica, the first Ozawainella species (O. tingi and O. umbonata), Semistaffella primitiva, P. antiqua, P. grandis, P. turbulenta, P. shidaliensis, and P. proozawai along with these two zonal markers occur in this zone. The first occurrence of the genus Staffellaeformes is important to recognize this fusuline zone.

In the late Bashkirian, the Pseudostaffella gorskyiOzawainella pararhomboidalisProfusulinella primitiva Zone was advanced as a Tashastian fusuline biozone of the South Urals. It also contains Eostaffella mutabilis, Millerella uralica, Ozawainella aurora, O. paratingi, Varistaffella korobezkikh, Schubertella mosquensis, Pseudostaffella posterior, P. paracompressa, P. turbulenta, P. praegorskyi, P. proozawai, and Staffellaeformes staffellaeformis. The latest Bashkirian, Asatauian fusuline assemblage denotes the entry of three new genera: Verella, Aljutovella, and Neostaffella, two of whose representative species make the Verella spicataAljutovella tikhonovichi Zone. There were diversified species in this zone, and, besides the marker fusulines, the following species were listed: Pseudonovella grozdilovae, Ozawainella rhomboidalis, O. ovata, O. pararhomboidalis, O. tingi, O. alchevskiensis, Pseudostaffella gorskyi, P. posterior, Neostaffella subquadrata, Staffellaeformes tashliensis, S. staffellaeformis, S. bona, Profusulinella parva, P. chernovi, P. convoluta, P. oblonga, P. pararhomboides, P. rhomboides, P. prisca, P. ovata, P. subovata, P. eoprisca, Aljutovella cybaea, A. fallax, A. nibelensis, A. bashkirica, Verella varsanofievae, V. ivanovae, and V. plicata. An important feature of the Bashkirian fusuline succession in the Urals is that the continuous evolutionary succession represented by the EostaffellaPlectostaffellaSemistaffella PseudostaffellaNeostaffella lineage has been well recognized in this province (Groves 1988).

The entire Moscovian fusuline succession of the Urals was described in detail by Chuvashov et al. (1984) and Ivanova (2008). In the latter monograph, a total of nine fusuline zones were established in the Moscovian (Fig. 15). Here, general features of fusulines in each Moscovian stage are described based on Ivanova (2008). Concerning the base of the Moscovian, Kulagina (2008, 2009) suggested a possibility to subdivide the Vereian into the Profusulinella prisca Zone (lower) and the Aljutovella aljutovica Zone (upper) and to put the Bashkirian–Moscovian boundary at the base of the former. However, it would not be very promising to use the species P. prisca in the ‘Depratina’ lineage (Kulagina 2009) for the definition of the base-Moscovian because there are always practical problems with the recognition of this species. This taxon is also identified as P. cf. prisca and P. ex gr. prisca on many occasions, and, moreover, separation of this species from P. praeprisca also is not easy. All the latter taxa (cf. prisca, ex gr. prisca, and praeprisca) occur in the latest Bashkirian (e.g. Kulagina 2009). For defining the Bashkirian–Moscovian boundary in the Urals, as has been suggested by Ivanova (2015), the VerellaEofusulina lineage seems to be more practical in the present circumstances.

Ivanova (2008) defined the Vereian as the Profusulinella priscaAljutovella aljutovica Zone. The major fusulines in this zone are Pseudonovella grozdilovae, Ozawainella alchevskiensis, Pseudostaffella gorskyi, P. composita, P. conspecta, Neostaffella pseudoquadrata, Schubertella mosquensis, Profusulinella parva, P. paratimanica, P. polasnensis, P. prisca, P. rhomboides, P. nytvica, P. ovata, Aljutovella aljutovica, A. subaljutovica, A.? dagmarae, A. elongata, A. cybaea, A. skelnevatica, Paraeofusulina trianguliformis, and Eofusulina triangula. Profusulinella and Aljutovella are dominant, and Eofusulina and Paraeofusulina are diagnostic in the Vereian assemblage. The Kashirian is allocated to the Aljutovella? priscoidea and Kanmeraia subpulchraBeedeina schellwieniFusulinella schubertellinoides zones. The former zone corresponds to the Tsninsky horizon (Tsninian) of the Moscow Basin (Solov'eva 1986). Fusulines found in these Kashirian zones include Ozawainella tingi, O. mosquensis, O. digitalis, O. praestellae, Neostaffella latispiralis, N. larionovae, N. khotunensis, N. confusa, Schubertella pauciseptata, S. pseudoglobulosa, Taitzehoella prolibrovichi, Profusulinella paratimanica, P. subovata, P. znensis, Aljutovella saratovica, A.? priscoidea, A. postaljutovica, Beedeina schellwieni, B. bona, Eofusulina triangula, E. rasdorica, E. pullata, Paraeofusulina trianguliformis, Fusulinella schubertellinoides, and Kanmeraia subpulchra. In the lower levels of the Kashirian, which corresponds to the Tsninian, Profusulinella and Aljutovella, together with Eofusulina and Paraeofusulina, prevailed in the assemblage, as in the underlying Vereian, but Fusulinella, Kanmeraia, and Beedeina came into the assemblage in the later part of the Kashirian.

The Podolskian has three zones: the Fusulinella colaniae, Fusulinella vozhgalensis, and Fusulina kamensisPutrella brazhnikovae zones. These contain Neostaffella umbilicata, N. rostovzevi, N. sphaeroidea, N. ozawai, N. topilini, Schubertella mjachkovensis, Taitzehoella perseverata, Fusulinella colaniae, F. paracolaniae, F. borealis, F. propria, F. vozhgalica, F. pseudobocki, F. mosquensis, Kanmeraia eopulchra, Wedekindellina uralica, W. thompsoni, Parawedekindellina subovata, P. pechorica, Fusulina kamensis, F. chernovi, Beedeina elegans, B. kirovi, B. pseudoelegans, B. ozawai, B. dunbari, Putrella brazhnikovae, P. donetziana, and others. In this interval Beedeina, Fusulinella, and large Neostaffella were dominant in the assemblage, and the occurrences of Wedekindellina and Putrella marked some particular horizons. Then, the Fusulinella bocki and Fusulina cylindrica zones comprise the lower part of the Myachkovian. The following fusulines were listed from this interval: Ozawainella stellae?, Fusiella typica, Fusulinella vozhgalensis, F. bocki, F. pseudobocki, F. pseudoschwagerinoides, Kanmeraia pulchra, Fusulina cylindrica, F. mosquensis, Beedeina elegans, Putrella donetziana, Dutkevichella kashirica, D. truncatula, D. communis, and Hemifusulina bocki. Hemifusulinin species are only known from the Myachkovian in the Urals. This stratigraphic distribution is in contrast to the Moscow Syneclise in which this group first appeared in the Kashirian. Considering the supposed palaeoecology of hemifusulinin genera (Baranova and Kabanov 2003; Baranova et al. 2014; Khodjanyazova et al. 2014), it could be attributed merely to some environmental control. Ivanova (2008) assigned the late Myachkovian to the Obsoletes burkemensis Zone, and it contains Kanmeraia stshugorensis ( = ?K. ozawai), K. stricta ( = ?K. condensa), Fusulina domodedovi, F. mjachkovensis, and F. uralica, as well as the zonal marker.

The Late Pennsylvanian fusuline succession was investigated in the Pechorian Pre-Urals of the Chernyshev Ridge and the western slope of the Northern and Subpolar Urals by Mikhaylova (1974). The overall fusuline succession has similarity to that of the adjoining Timan–Pechora province, in sharing the occurrences of some species that have peculiar shell morphology, such as Kanmeraia species with a very elongate fusiform shell (K. usvae in Mikhaylova 1974 and K. plicata in Remizova 1995) and spherical Triticites (T. subschwagerinoides: Grozdilova 1966; Mikhaylova 1974). In the South Urals, Einor (1979) described stratigraphically important fusuline species from the Kasimovian–Gzhelian of the western slope of the Urals and the Pre-Uralian Foredeep. This palaeontological atlas gives geochronological (stratigraphic) ranges of all the illustrated species, in the framework of standard biostratigraphic zonation in the Urals shown in Figure 15. Thus, Einor (1979) provides good basic data to take an overview of fusuline succession during Kasimovian–Gzhelian time in the South Urals. Concerning the late Gzhelian Daixina sokensis Zone (C3E), Chuvashov et al. (1986) further divided it into the D. sokensis Zone (early part of the late Gzhelian: Noginskian) and the Daixina robustaBosbytauella bosbytauensis Zone (later part of the late Gzhelian: Melekhovian) based on data from the sections in the South (southernmost) Urals and the Darvaz in Central Asia. Data from the South Urals in Chuvashov et al. (1986) were also utilized in making the following summary. This late Gzhelian zonation has also been applied in recent studies carried out in the Middle Urals, but Bosbytauella bosbytauensis is not found there (Chuvashov et al. 1986; Vilesov 2000).

According to Einor (1979), the lower part of the Kasimovian (C3A1), designated as the Protriticites pseudomontiparusObsoletes obsoletus Zone, bears Kanmeraia usvae, K. pulchra, and Protriticites globulus together with the two zonal markers. The Montiparus montiparus Zone of the middle Kasimovian (Khamovnikian: C3A2) is characterized by the occurrence of Montiparus species (M. montiparus, M. umbonoplicatus, M. sinuosus, M. rhombiformis, M. solidus), Triticites petschoricus, and T. whitei ( =?Schwageriniformis). The late Kasimovian (C3B) is referred to as the Rauserites quasiarcticusTriticites acutus Zone, which is widely used in the Late Pennsylvanian fusuline zonation of the Russian Platform. Occurrence of various Triticites and Rauserites species, such as T. simplex, T. dictyopholus, T. noinskyi, R. pseudoarcticus, R. oryziformis, along with the two marker species, and Schwageriniformis schwageriniformis, is the basic feature of this interval.

The lower Gzhelian (C3C) is marked by the Rauserites stuckenbergi Zone, and contains Kanmeraia plicata, Quasifusulina sp. Triticites shikhanensis, T. dictyopholus, T. communis, T. noinskyi, T. voskresenikus, T. samaricus, Rauserites paraarcticus, R. rossicus, R. bashkiricus, R. stuckenbergi, Rugosofusulina prisca, and others. Except for the zonal species, R. rossicus is important for correlation in the Russian Platform and the Palaeotethys regions. The Jigulites jigulensis Zone denotes the middle Gzhelian (C3D). This species is commonly found in many Russian Platform sections (Fig. 15). The constituent species of this zone are Triticites communis, Jigulites jigulensis, J. dagmarae, Daixina parasokensis, and D. volgensis. In the South Urals, Ferganites ferganensis was documented by Chuvashov et al. (1986) in the correlated middle Gzhelian Daixina ruzhencevi Zone. In general the late Gzhelian Daixina sokensis Zone (C3E) in the Urals is known to be diagnostic by containing large Daixina species such as D. atypica, D. admirabilis, and D. sokensis (Zolotova et al. 1977). Einor (1979) mentioned the occurrence of the following species from this zone: Quasifusulina eleganta, Triticites nagadakensis, T. pegmatus, Rauserites pseudoarcticus, R. paraarcticus, Jigulites jigulensis, Daixina volgensis, D. ruzhencevi, D. uralica, D. sakmarensis, Rugosofusulina egregia, Dutkevitchia complicata, and Benshiella stabilis. In addition to these, Rozovskaya (1952) described Rugosofusulina uralensis, which was later reassigned to Schagonella (Chuvashov et al. 1986).

As mentioned already, the late Gzhelian D. sokensis Zone in the South Urals is divided into two parts. The lower part is the redefined Daixina sokensis Zone (s.s.) and the upper part is the Daixina robustaBosbytauella bosbytauensis Zone (Chuvashov et al. 1986). The former zone, corresponding to the Noginskian, generally has a biostratigraphic definition similar to the D. sokensis Zone (s.l.) and large Daixina such as D. sokensis, D. enormis, D. recava, D. vasilkovskyi occur characteristically in this redefined interval. The Daixina robustaBosbytauella bosbytauensis Zone of Melekhovian age is defined by the occurrence of Daixina species having slightly inflated globular (short fusiform) shells, such as D. robusta and D. vozhgalensis, and Bosbytauella with a characteristically inflated shell and large proloculus, including B. postsokensis, B. postgalloway, and B. dashtidzhumica (Chuvashov et al. 1986). The latter genus is an ultimate end-member of the Daixina lineage, restricted to the latest Gzhelian (Davydov 1988a, b; Fig. 12). In the South Urals the Daixina robustaBosbytauella bosbytauensis Zone was established based on studies in the Nikol'sky and Aidaralash sections on both sides of the Russia–Kazakhstan border; the latter section contains the GSSP at the base of the Asselian (thus the base of the Permian; Davydov et al. 1994, 1998). In this Melekhovian fusuline zone, other associated species are Dutkevitchia expansa, D. tachygrada, Benshiella stabilis, Anderssonites paraanderssoni, Rugosochusenella pseudogregaria, Pseudochusenella zarjae, P. paraervinensis, ‘Likharevitessartauensis, ‘L.’ paranitida, and several ‘Occidentoschwagerina’ species (‘O.’ ancestralis, ‘O.’ primaeva, ‘O.’ sarykumensis, and ‘O.’ alpina). In the Middle Urals, the Daixina robustaBosbytauella bosbytauensis Zone has been settled nominally, but because the latter marker species does not occur in that area (Chuvashov et al. 1986, p. 51), the ‘Occidentoschwagerinaancestralis and ‘O.’ konovalovae zones were designated alternatively to exhibit the equivalent interval (Vilesov 2000).

As one of the significant properties of Gzhelian fusulines in the Urals, it is important to note that the genus Bosbytauella is only found in its southern (or southernmost) part. Considering the distribution of this genus in Central Asia (Bensh 1962; Chuvashov et al. 1986; Orlov-Labkovsky and Bensh 2015), the Carnic Alps (Forke et al. 1998), and the Donets Basin (Davydov et al. 1992), the southernmost part of the Ural province from which Bosbytauella was reported would be better regarded as an area in the Ural–Arctic Region that affected a strong faunal influence from the palaeoequatorial Palaeotethys Region in view of fusuline palaeobiogeography during late Carboniferous time.

The Moscow Syneclise covers the west-central part of the Russian Platform (East European Platform), and the Moscow Basin is at its centre. It is one of the classical regions in the world for the study of the Carboniferous and provides the type areas of four Carboniferous stages (Serpukhovian, Moscovian, Kasimovian, and Gzhelian). A large number of taxonomic and biostratigraphic works on Carboniferous fusulines has been carried out since the early nineteenth century (Einor 1996). Alekseev et al. (1996) made a good diagrammatic summary of sedimentation records in the Moscow Syneclise and illustrated that Carboniferous strata in this area consist of three depositional packages with the Moscow Basin as the depocentre. The first one corresponds to the early Tournaisian, which is the continuation from the underlying latest Devonian (Famennian) succession and was terminated before the first appearance of the fusuline foraminifers in the late/latest Ivorian. The second depositional package broadly corresponds to the Visean and Serpukhovian. Fusuline-bearing carbonate succession ranges from the middle part of the Visean up to the late (but not latest) Serpukhovian (Makhlina et al. 1993). After a large hiatus recognized over the entire Bashkirian, sedimentation resumed at the beginning of the Moscovian and continued to the end of the Carboniferous, although some upper parts may have been eroded out. Shallow-marine carbonates showing various sedimentary facies are the main rock type in this third succession, except for the base of the Moscovian (Alekseev et al. 1996; Kabanov 2003; Kabanov et al. 2006; Baranova et al. 2014). Thus, information on the fusuline succession in the Moscow Syneclise consists of two parts; one is from the Visean–Serpukhovian interval and the other is from the Moscovian–Gzhelian.

Makhlina et al. (1993) made a comprehensive study of the lower Carboniferous (Visean–Serpukhovian) foraminiferal biostratigraphy of the Moscow Syneclise. The oldest foraminiferal assemblage they reported was contained in the upper part of the Tulian regional substage, which corresponds to the middle Visean (Livian). Fusulines found in this interval are Eostaffella mosquensis, E. ovoidea, Pseudoendothyra candida, and a few others. The late Visean fusulines are also composed entirely of two genera: Eostaffella and Pseudoendothyra, but specific composition changed within the faunal succession. The early part of the late Visean (corresponding mainly to the Aleksinian regional substage) is characterized by Eostaffella proikensis; the middle part (Mikhailovian) is defined by Eostaffella ikensis; and the latest Visean (Venevian) is marked by Eostaffella tenebrosa (Fig. 15). In addition to these marker species, Eostaffella mosquensis, E. ovoidea, Pseudoendothyra struvei, and P. angulata occur almost throughout the late Visean. Moreover, it is noteworthy that Makhlina et al. (1993) listed Eostaffellina (E. ex gr. protvae and E. aff. paraprotvae) in the Venevian interval.

For the Serpukhovian of the Moscow Basin, two sections at the stratotype Zabor'e Quarry and the reference Novogurovsky Quarry contributed to make up the standard foraminiferal succession of the type area (Gibshman 2003; Gibshman et al. 2009). Two early Serpukhovian substages (Tarusian and Steshevian) broadly correspond to the Pseudoendothyra globosa Zone and Eostaffellina decurta Zone, respectively (Fig. 15). In these zones, Eostaffella parastruvei occurs throughout, but E. proikensis, E. ikensis, and E. tenebrosa, which are characteristic in the late Visean, disappear in the Tarusian. Eostaffella mirifica and E. obesa are new elements that appeared in this substage. Moreover, the entry of Eostaffellina paraprotvae is recognized in the middle part of the Steshevian. The lower Serpukhovian succession is followed by the relatively thin Protvian, which is attributed to the Eostaffellinaprotvae’ Zone (Fig. 15). Other fusulines in this interval are Eostaffellina subsphaerica, E. schartimiensis, and E. umbilicata. The Zapaltyubian is not present in the type Serpukhovian area.

The marine Bashkirian is not developed in the Moscow Basin and the surrounding region, but, after the Bashkirian, shallow-marine sedimentation persisted until the end of the Carboniferous. These strata in the Moscow Syneclise are the bases for establishing three Upper Carboniferous stages that are recognized as parts of the international chronostratigraphic scale: the Moscovian, Kasimovian, and Gzhelian (Aretz et al. 2020; Lucas et al. 2021). Rich records of fusuline faunal succession are preserved in these sections. In the Moscovian, a monographic work by Rauzer-Chernousova et al. (1951) was a landmark of fusuline research, which has remained a strong influence for later studies on the same discipline done over the world. Based on this and many other works, Moscovian stratigraphy, biostratigraphy, and faunal characteristics of the Moscow Syneclise were summarized by Makhlina et al. (2001a, b) in the form of a two-volume monograph. In this achievement they recognized 14 fusuline zones in the Moscovian–early Kasimovian (Krevyakinian) interval (Fig. 15). Makhlina et al. (2001b) provided detailed ranges of nearly 180 fusuline species, and an overall idea of the Moscovian fusuline succession of the Moscow Syneclise is available in that article, which is summarized below.

In the lower Vereian Aljutovella aljutovica Zone (Fig. 15), there are a number of species whose first appearances elsewhere in the Russian Platform extend down to the uppermost Bashkirian, such as Profusulinella parva, P. pararhomboides, Aljutovella tikhonovichi, A. skelnevatica, and A. cybaea. The Vereian fusuline assemblage is dominated by Profusulinella, Aljutovella, and Neostaffella. The Profusulinella arta Zone was established in the upper Vereian (Fig. 15). The lower Kashirian also includes many species of Profusulinella, Aljutovella, and Neostaffella that range upward from the upper Vereian. The Aljutovella? priscoidea Zone defines the lower part of the Kashirian (Fig. 15), and Eofusulina triangula, which is important to designate as the lowest Moscovian elsewhere in Eurasia (Ivanova 2008; Nemyrovska et al. 2010), occurs in this level. This assignment suggests that the entry of Eofusulina in the Moscow Syneclise does not show the evolutionary first appearance of this taxon. It is important to note for biostratigraphy the first occurrence of the schubertellid genus Taitzehoella near the base of the Kashirian. Fusulinella, Citronites, Beedeina, Kanmeraia, Dutkevichella, and probably Hemifusulina appear first in the middle–late Kashirian, and, along with relatively large Neostaffella (such as N. umbilicata and N. sphaeroidea), these genera characterize the middle–upper Kashirian interval. Of them, the hemifusulinin genera (Dutkevichella and Hemifusulina) need some attention for biostratigraphic interpretation because their distributions and occurrence are strongly controlled by sedimentary facies and environment (Baranova and Kabanov 2003; Baranova et al. 2014; Khodjanyazova et al. 2014). Moreover, the taxonomy of Dutkevichella and Hemifusulina in the Kashirian would need extensive revision based on their wall structure. Citronites was derived from some Aljutovella, and immediately after its first appearance the former genus gave rise to Beedeina (Fig. 8). The middle Kashirian is important for fusuline diversification in Moscovian time because there appeared from different phylogenetic stocks in ‘profusulinellas’ some important fusulinid genera: Fusulinella, Beedeina, and Kanmeraia, which flourished in the later part of the Moscovian (Fig. 8). Fusiella also marked its first appearance in the middle of the Kashirian. Based on these distributions of major fusulines, the following three zones were established in the middle–late Kashirian: the Dutkevichella moelleriBeedeina pseudoelegans, Fusulinella praecolaniaeKanmeraia subpulchra, and Dutkevichella vozhgalica zones in ascending order (Fig. 15).

The appearance of Putrella brazhnikovae and some other species (Beedeina elegans and several Dutkevichella such as D. volgensis, D. dutkevichi, D. polasnensis, and D. rjasanensis) defines the base of the Podolskian. The Putrella brazhnikovae Zone was settled in the lower part of this regional substage (Fig. 15). Moreover, Wedekindellina occurs in the early Podolskian section. The presence of this genus is important for correlation to other sedimentary basins in the Arctic and farther to cratonic North America. During Podolskian and early Myachkovian time, Fusulinella and Beedeina were diversified in the Moscow Syneclise, and several different compositions of species in these genera along with facies-dependent Dutkevichella/Hemifusulina species can be the bases to designate particular fusuline intervals. Some of these species have relatively short stratigraphic occurrence (Makhlina et al. 2001b). In the middle part of the Podolskian the genus Fusulina, represented by F. pankouensis and F. innae in the Moscow region, first appears, and the genus became common in fusuline assemblages by the end of the Moscovian. In the late Podolskian, Fusulina chernovi is characteristic. These Fusulinella, Beedeina, and Fusulina species allow the establishment of the Fusulinella colaniaeBeedeina ulitinensis and Fusulina chernovi zones in the middle–upper Podolskian (Fig. 15). Other important elements of the Podolskian fusuline assemblages are Taitzehoella (such as T. librovitchi and T. perseverata) and Neostaffella species, especially of large forms with a quadrate shell outline such as N. cuboides, N. rostovzevi, and N. larionovae.

The lower part of the Myachkovian is characterized by the occurrence of Fusulinella bocki, a well-known species with a large, slightly inflated shell and massive chomata, on which the Fusulinella bocki Zone was established in the lower Myachkovian (Fig. 15). However, it needs some annotation to F. bocki because this species (or its species group) is often variously interpreted taxonomically among fusuline students, and similar forms may also be reported from lower levels. Hanostaffella paradoxa, several other Fusulinella species (F. pseudobocki, F. vozhgalensis, F. helenae, and F. fluxa), and Beedeina (B. elegans and B. samarica) are also common in the early Myachkovian interval. The middle Myachkovian is represented by the Fusulina cylindrica Zone (Fig. 15). Several other species of Fusulina (F. mosquensis, F. domodedovi, F. quasicylindrica, F. mjachkovensis, and F. pakhrensis) and Fusulinella (F. bocki and some small forms such as F. podolskensis, F. kumpani, and F. pseudoschwagerinoides) characterize this interval. Late Myachkovian (latest Moscovian) fusulines contain species that extended their ranges from the middle Myachkovian, and Obsoletes burkemensis (and also O. pauper according to Goreva et al. 2009b) and Protriticites ovatus newly joined in the assemblage. Based on this, the Protriticites ovatus Zone was settled in the upper Myachkovian. Goreva et al. (2009b) reported a fusuline succession of the Domodedovo quarry in the south of Moscow city, which was designated as the neostratotype of the Myachkovian. They identified more numbers of species from the Myachkovian interval, but the fundamental biostratigraphic framework by them is almost the same as that summarized by Makhlina et al. (2001b).

Rozovskaya (1950) earlier established the basis of Kasimovian–Gzhelian fusuline biostratigraphy in the Moscow Syneclise. Since that time a number of works have been carried out in this region on Kasimovian and Gzhelian fusulines, and their faunas as well as species were described from outcrop and borehole sections (e.g. Syomina 1961; Makhlina et al. 1975; Rozovskaya 1975; Makhlina and Isakova 1997; Alekseev et al. 2009, Goreva et al. 2009a, b). Until now, there is no published comprehensive study for the Kasimovian and Gzhelian fusulines of the Moscow Syneclise, similar to Makhlina et al.’s (2001a, b) monographs for the Moscovian. In these former two stages, Alekseev et al. (2004) recognized a total of 10 fusuline biozones, which are shown in Fig. 15 

In the Moscow Basin, early–middle Kasimovian strata are well exposed in the Afanasievo quarry to the SE of Moscow city, which is regarded as the neostratotype of the Kasimovian stage (Goreva et al. 2009a). That section provides good information on the fusuline succession of Krevyakinian and Khamovnikian times. Moreover, the aforementioned Moscovian neostratotype Domodedovo section also has a good outcrop showing a lower Krevyakinian interval. In the Afanasievo section, the lower part of the Krevyakinian (Suvorovo Formation) contains only one level that yields fusulines, and Protriticites subschwagerinoides, Fusulinella kljasmica, and F. ex gr. pseudobocki were identified from it (Goreva et al. 2009a). The same interval in the Domodedovo section has a better occurrence of fusulines, and a slightly more diversified assemblage was reported, including F. lancetiformis, F. typica, Schubertella mjachkovensis, Ozawainella mosquensis, and Obsoletes sp. (Goreva et al. 2009b). In the upper Krevyakinian (Voskresensk Formation) in the Afanasievo section the following species were identified by Goreva et al. (2009a): Fusiella lancetiformis, Fusulina quasicylindrica, F. pakhrensis, F. mosquensis, Protriticites pseudomontiparus, P. subschwagerinoides, Obsoletes ex gr. obsoletus, O. magnus, and others. Of these Krevyakinian fusulines, F. lancetiformis is characteristic in having a relatively large, very elongate fusiform shell in the genus. This, and similar species having especially large and elongate shells in Fusiella, such as F. rawi and F. segyrdashtiensis, have been reported from an early–middle Kasimovian interval (Villa and van Ginkel 2000; Leven and Davydov 2001; Forke et al. 2006; Ueno et al. 2013), and these morphologically peculiar Fusiella could be an auxiliary marker for approximating the position of the Moscovian–Kasimovian boundary. As in Alekseev et al. (2004), these data allow establishment of the Obsoletes sp.–Fusiella lancetiformis Zone and the Protriticites subschwagerinoidesObsoletes obsoletus Zone in the Krevyakinian (Fig. 15).

Khamovnikian strata are also well exposed in the upper part of the Afanasievo section (Neverovo Formation). The fusuline assemblage is represented by Montiparus (M. montiparus, M. subcrassulus, and M. paramontiparus) and is associated with Protriticites pseudomontiparus, P. subschwagerinoides, P. subovatus, Quasifusulina longissima, Q. eleganta, and Q. dagmarae. Moreover, elsewhere in the Moscow Syneclise, Rozovskaya (1950) described Montiparus umbonoplicatus, M. sinuosus, M. reticulatus, and M. rhombiformis. The Montiparus montiparus Zone, which is widely correlatable in Eurasia, was established in the Khamovnikian in this region (Fig. 15).

With respect to post-Khamovnikian (post-middle Kasimovian) strata in the Moscow Syneclise, various kinds of schwagerinids contributed to constructing the basic zonation, and a total of seven regional zones were recognized in Alekseev et al. (2004). They are reassessed here as five zones (Fig. 15). This zonation is also essentially applicable, with some minor modifications, to the Timan–Pechora and Ural provinces. Fusuline species consisting of the Dorogomilovian (C3B) assemblage were described by Rozovskaya (1950, 1975), and they include Montiparus sinuosus, Schwageriniformis schwageriniformis, S. mosquensis, Triticites irregularis, T. zhukovskiensis, T. devexus, T. crispus, T. absimilis, and Rauserites variabilis. Although Alekseev et al. (2004) subdivided the Dorogomilovian into two biozones (the Rauserites quasiarcticusSchwageriniformis mosquensis Zone in the lower and the Triticites irregularisTriticites acutus Zone in the upper), the available published data allow recognition of one biozone, which is herein named the Triticites irregularisSchwageriniformis mosquensis Zone, based on the above-mentioned species from the C3B interval (Fig. 15).

In the early Gzhelian (Dobryatinian) there are two biozones: the Rauserites rossicusRauserites paraarcticus and Rauserites stuckenbergi zones recognized in Alekseev et al. (2004). Lower Gzhelian fusuline data of the Moscow Syneclise are available from Rozovskaya (1950) and Alekseev et al. (2009); the latter reported the lithostratigraphy and fossil successions of the Gzhelian stratotype at Gzhel in Moscow city. These studies listed the following fusulines from the lower Gzhelian (C3C): Triticites dictyopholus, T. paraschwageriniformis, R. paraarcticus, R. stuckenbergi, R. rossicus, R. postarcticus, R. condensus, Jigulites? procullomensis, Quasifusulina longissima, Q. ultima, and Q. eleganta. Because detailed stratigraphic distribution of fusulines has not been documented throughout the early Gzhelian, except for its lower part (Alekseev et al. 2009), it is difficult to subdivide the Dobryatinian into several fusuline zones in the present circumstances. Thus, the single Rauserites rossicusRauserites stuckenbergi Zone is suggested here for the early Gzhelian fusuline zone (Fig. 15), instead of two zones by Alekseev et al. (2004). Middle Gzhelian (Pavlovoposadian: C3D) fusulines of the Moscow Syneclise were reported by Rozovskaya (1950) and Makhlina et al. (1975). They identified Rauserites paraarcticus, R. condensus, Jigulites jigulensis, J. dagmarae, J. intermedius, J. longus, J. formosus, J. mucronatus, and Rugosofusulina flexuosa. Thus, as in Alekseev et al. (2004), the Jigulites jigulensis Zone is appropriate for the biostratigraphic unit of the Pavlovoposadian in the Moscow Syneclise.

Alekseev et al. (2004) showed two fusuline zones in the late Gzhelian: the Daixina sokensis Zone for the Noginskian and the Daixina robustaBosbytauella bosbytauensis Zone for the Melekhovian. The Noginskian fusuline assemblage was reported by Makhlina et al. (1975), and the following species were listed in it: Jigulites volgensis, J. jigulensis, J. longus, J. bona, Daixina sokensis, and D. baituganensis. Makhlina et al. (1975) identified Anderssonites anderssoni in the Noginskian assemblage, but that specimen is probably assignable to Jigulites magnus, based on its gross shell morphology, which was described originally by Rozovskaya (1950) from this interval. Moreover, Noginskian fusulines were also investigated by Makhlina and Isakova (1997) in the Kovrov area about 200 km ENE of Moscow. They identified the following species: Quasifusulina longissima, Triticites sphaericus, T. morkvashensis, Rugosofusulina praevia, Jigulites volgensis, J. dagmarae, J. jigulensis, Daixina sokensis, D. baituganensis, D. fragilis, and others. These species encompass the Noginskian fusuline assemblage in the Daixina sokensis Zone (Fig. 15). In the same paper studying Noginskian fusulines, Makhlina and Isakova (1997) established the Melekhovian substage of the latest Gzhelian overlying the Noginskian. They illustrated fusuline species from the type Melekhovian interval, which comprised a very peculiar assemblage. The following species were originally listed by Makhlina and Isakova (1997): Daixina sokensis, D. robusta, D. insolita, D. vozhgalensis, D. pomposa, D. fortis, Rugosofusulina stabilis ( = Benshiella stabilis), Pseudofusulina paraanderssoni ( = Anderssonites paraanderssoni), P. pseudoanderssoni (­ = A. pseudoanderssoni), Praepseudofusulina dilligens (assignable to Triticites?, or a new genus?), and several other ‘Pseudofusulina’ species. Of the most interesting and diagnostic in this assemblage is their ‘Daixina insolita’ described by Isakova in Makhlina and Isakova (1997), which has a subglobular inflated shell with a small proloculus, tightly coiled juvenarium, and expanded (loosely coiled) outer volutions, and relatively irregularly fluted septa, thus showing somewhat similar gross shell morphology to Paraschwagerina. This species is probably referable to ‘Likharevites’, which has been reported in uppermost Gzhelian beds in the South Urals, Central Asian Tianshan, and Iran (see sections of these areas in this paper), although as noted in the earlier section in this paper the nomenclatural status of ‘Likharevites’ is questionable (Leven and Gorgij 2006b), and the name is probably unavailable. Alekseev et al. (2004) determined the latest Gzhelian fusuline biozone of the Moscow Syneclise as the Daixina robustaBosbytauella bosbytauensis Zone, but the latter zonal name-bearing species has not been reported from this area so far. Based on Makhlina and Isakova (1997), the Daixina robusta–‘Likharevitesinsolita Zone can be established for the Melekhovian (latest Gzhelian).

The Palaeotethys Region covers the circum-Palaeotethyan Pangaean shelves (mainly western part of the Palaeotethys), except the eastern part of peri-Gondwana, and also shallow-marine areas in several isolated continental fragments dispersed between the Panthalassa and Palaeotethys oceans (eastern part of the Palaeotethys), such as the North China, South China, and Indochina blocks (Fig. 2). Within the Palaeotethys Ocean, moreover, there were oceanic islands that originated by hotspot magma activities, and on these islands atoll-type carbonates with long-term fusuline faunal records were formed. Fusuline faunas in this region generally exhibit a highly diversified, warm-water ‘Tethys-type’ signature to various degrees.

The Kazakhstan Block is known to be composite, consisting of amalgamated microcontinents and intra-oceanic arcs associated with their collisional belts, and forms a huge geological domain called the Kazakhstan collage system (Xiao et al. 2015). The formation of the main part of this complex geological system had completed by the Carboniferous, with only remaining the most southerly (in present-day configuration) Chatkar arc, which faced to the Southern Tianshan Ocean. Kazakhstan here corresponds to the main part of the Kazakhstan collage system and includes the North Tianshan of Bensh et al. in Einor (1996) and further northern and northeastern areas. During Carboniferous time, there were several basins formed within the core part of the Kazakhstan Block (Litvinovitchi et al. in Einor 1996).

Marfenkova (1991) reported foraminifer-bearing Carboniferous successions in Kazakhstan and illustrated key fusulines for biostratigraphy. Besides the Bolshoi Karatau (Karatau Range) section in the Middle Tianshan Zone, she reported fusulines from central-southern Kazakhstan (the Chuiskaya, Dzhezkazganskaya, and Sholakskaya depressions) and eastern Kazakhstan (the Lake Balkhash and Dzhungarskiy Alatau areas). According to Safonova et al. (2017), Carboniferous basins in the latter area were judged to be formed on older (Ordovician–Late Devonian) orogenic basements. Of the two regions, fusulines reported from the central-southern Kazakhstan localities are all small, lenticular forms included in the Eostaffellinae and Pseudoendothyrinae. They occur in strata ranging from the late Visean to earliest Bashkirian. In the late Visean, several Pseudoendothyra species (P. struvei, P. ovata, and P. crassa) were found. The Serpukhovian yielded the following species: Eostaffella beleutica, Eostaffellina protvae, E. paraprotvae, E. subsphaerica, Plectostaffella varvariensis, Pseudoendothyra conspicula, P. compressa, and P. intermedia. From the Bashkirian, Marfenkova (1991) illustrated only two species, Eostaffella postmosquensis and E. minuta, thus its age constraint is not solid, although it is likely early Bashkirian.

The eastern Kazakhstan localities of Marfenkova (1991) show younger fusuline assemblages, corresponding to the late Bashkirian (Tashastian) and early Moscovian (Vereian and Kashirian). Of them, the Tashastian assemblage contains Eostaffella dolixa, Ozawainella pararhomboidalis, O. edita, Pseudoendothyra vischerensis, and Profusulinella primitiva. The Vereian has more variable species, including Eostaffella kashirica, Ozawainella tingi, O. pseudorhomboidalis, Pseudonovella grozdilovae, Neostaffella subquadrata, Profusulinella prisca, P. timanica, P. paratimanica, P. pararhomboidalis, Aljutovella aljutovica, A. elongata, and others. Bogush et al. (1976) also reported fusulines of the same age from the Lake Balkhash area, one of Marfenkova's (1991) localities in eastern Kazakhstan. They recognized the following age-diagnostic species from that locality: Pseudostaffella gorskyi, Staffellaeformes staffellaeformis, S. bisyllaba, Profusulinella rhombiformis, Aljutovella tikhonovichi, A. cybaea, A. skelnevatica, and A.? priscoidea. The Kashirian assemblage from eastern Kazakhstan is characteristic because it consists essentially of Dutkevichella species, such as D. pseudobocki, D. dutkevichi, D. volgensis, D. kashirica, and others. It is probably referable to a post-Tsninian age of the Kashirian.

Fig. 16.

Fusuline biostratigraphic successions in the Tianshan and Darvaz of Central Asia (Loc. 12 in Fig. 2) in the western part of the Palaeotethys Region. Abbreviations of stage and substages, see Figure 14. References for data: see the text for details.

Fig. 16.

Fusuline biostratigraphic successions in the Tianshan and Darvaz of Central Asia (Loc. 12 in Fig. 2) in the western part of the Palaeotethys Region. Abbreviations of stage and substages, see Figure 14. References for data: see the text for details.

Central Asia here corresponds mainly to the Middle and South Tianshan, and the Gissar and Darvaz ranges to the south. Northern Afghanistan north of the Herat suture is also provisionally included in this province. Bensh et al. in Einor (1996) subdivided the relevant region into several, east–west extending geological units with different facies development of the Carboniferous; from north to south the North Tianshan, Middle (Central) Tianshan, South Tianshan, Hissan (Gissar/Hisor)–North Pamirs, and Central and South Pamirs. The first zone is a part of the Kazakhstan Block described already. The last one is south of the Major suture line of Central Asia in Leven (1997), partly including the Herat suture, thus corresponding to the Central Asian peri-Gondwanan domain where Carboniferous fusulines are not known (Vachard and Montenat 1996). In a broad palaeogeographical perspective, the development of Carboniferous successions in these areas between the North Tianshan and Central/South Pamirs was linked with the South Tianshan Ocean (a Central Asian branch of the Palaeotethys; e.g. Xiao et al. 2015) between the Kazakhstan collage system and the Tarim–Karakum composite microcontinents. In the section that follows, the Middle and South Tianshan, including the Gissar Range in the Hissan–North Pamirs Zone, are summarized as the Tianshan in Central Asia, following Orlov-Labkovsky and Bensh (2015). Moreover, in view of practical importance, as it has been regarded as one of standard areas in Eurasia for the Middle–Upper Pennsylvanian fusuline biostratigraphy, the fusuline succession of the Darvaz Range is described separately.

As has been noted in Bensh et al. in Einor (1996) and Orlov-Labkovsky and Bensh (2015), many investigations of Carboniferous fusuline taxonomy and biostratigraphy have been carried out in many sections in this area since the 1960s. These are: in the Middle Tianshan, Bogush and Yuferev (1962) and Marfenkova (1991) on mainly the Mississippian of the Karatau Range, Mikhno and Balakin (1975) on the Mississippian of the Ugamsky Range, Kulagina et al. (1992),Marfenkova,(1991) on the Serpukhovian and lower Bashkirian of the Ugamsky Range, and Dzhenchuraeva and Getman (2007, 2010) and Dzhenchuraeva et al. (2013) on the Mississippian and Late Pennsylvanian of the Dzhamantau (Jamantoo) and Baybichetau (Baibichetoo) ranges; in the South Tianshan, Rumyantseva (1962, 1974) on the Bashkirian and Moscovian of the Kizilkum Range, Bensh (1962) on the Late Pennsylvanian of the eastern Chatkar Range, and Bogush (1963), Bensh (1972), and Dzhenchuraeva (1979, 1993) on the Pennsylvanian of the Alai Range; and in the Gissar Range, Bensh (1969) for the Bashkirian and Moscovian. Moreover, there is a palaeontological atlas published from Uzbekistan (Kim et al. 2007). Orlov-Labkovsky and Bensh (2015) synthesized these data and established the standard foraminiferal (mostly fusuline) biostratigraphy of the Serpukhovian and Pennsylvanian of the Central Asian Tianshan region, covering Uzbekistan, Kyrgyzstan, Kazakhstan, and Tajikistan (Fig. 16). In this summary, the post-Visean Carboniferous fusuline succession is based largely on Orlov-Labkovsky and Bensh (2015). In generalizing the pre-Serpukhovian succession, it is based on data from the Central Tianshan (Bogush and Yuferev 1962; Mikhno and Balakin 1975; Dzhenchuraeva et al. 2013). According to these studies the Tournaisian and Visean are widely distributed in the Tianshan, and these strata contain rich foraminifers. However, they are essentially non-fusuline smaller foraminifers. The oldest fusulines in the Carboniferous are found in the early Visean.

Early Visean fusulines were reported by Dzhenchuraeva et al. (2013). They illustrated only Pseudoendothyra angulata and P. cf. nautiliformis, whereas several others were listed, including Eoparastaffella sp. and Eostaffella prisca. The illustrated two ‘Pseudoendothyra’ species mentioned above are probably better identified as Eoparastaffella ex gr. simplex (Fig. 16). The middle Visean assemblage is more variable and contains Eostaffella constricta, E. mosquensis, E. prisca, Pseudoendothyra arcuata, P. mikhailovi, and several others. Dzhenchuraeva et al. (2013) illustrated some Eoparastaffella species (E. pseudochomata, E. simplex, E. schlykovae, E. verna, and E. ovalis) from this interval, but they are reassigned to Eostaffella or Pseudoendothyra. In the late Visean, the fusuline assemblage is essentially similar in generic composition to that of the middle Visean, but also contains the first Eostaffellina species (Bogush and Yuferev 1962). The following fusulines were illustrated: Eostaffella proikensis, E. ikensis, E. tenebrosa, E. mosquensis, E. parastruvei, E. versabilis, Eostaffellina subsphaerica, Pseudoendothyra illustria, P. kremenskiensis, and others. As in other areas in the Palaeotethys, the Visean is dominated by Eostaffella and Pseudoendothyra in the fusuline fauna in the Central Asian Tianshan. On the other hand, Eostaffellina from the late Visean is noteworthy because this genus usually occurs first in the Serpukhovian. A late Visean occurrence of this genus is also known in the Moscow Syneclise (Makhlina et al. 1993).

Orlov-Labkovsky and Bensh (2015) recognized the following four foraminiferal zones in the Serpukhovian of Tianshan: the Neoarchaediscus regularisBiseriella parva, Eostaffellina protvaeBiseriella minima, Eosigmoilina explicataLoeblichia minimaPlectostaffella primitiva, and Plectostaffella mira obtusaEostaffella turkestanica zones, in ascending order. These correspond respectively to the upper Mashatian, lower Keltemashatian, upper Keltemashatian, and lower Koikebiltauian regional substages. Correlation of these regional chronostratigraphic units to those in the Russian Platform is not easy, but based on Dzhenchuraeva et al. (2013) the first zone (upper Mashatian) is referable to the Tarusian and Steshevian, and the remaining three zones are correlated to the Protvian and Zapaltyubian (Fig. 16). Thus, the early Serpukhovian fusuline assemblage in this region consists of Eostaffella prisca, E. parastruvei, E. infulaeformis, E. mosquensis, E. ex gr. tenebrosa, E. ex gr. vasta, and Pseudoendothyra globosa. The major fusulines from the late Serpukhovian are Eostaffella ovoidea, E. postmosquensis, E. mirifica, E. turkestanica, E. ventricosa, Eostaffellina protvae, E. paraprotvae, E. vischerensis, Plectostaffella primitiva, P. praevarvariensis, P. mira obtusa, P. ex gr. seslavica, and Pseudoendothyra ex gr. struvei.

In the Bashkirian, Orlov-Labkovsky and Bensh (2015) subdivided the strata into seven fusuline zones named the Plectostaffella karsaklensis, Plectostaffella jakhensis, Plectostaffella longiscula, Pseudostaffella antiqua, Pseudostaffella praegorskyi, Ozawainella pararhomboidalisProfusulinella primitiva, and Verella spicataProfusulinella rhombiformis zones, in ascending order (Fig. 16). The first zone is also marked by the occurrence of Plectostaffella bogdanovkensis, P. baisultanica, and P. varvariensis, and contains Eostaffella pseudostruvei, Eostaffellina paraprotvae, and Plectostaffella seslavica. Some Millerella species were also mentioned as elements of this assemblage, but their generic affiliation is somewhat questionable. This zone, situated before the occurrence of Semistaffella and Pseudostaffella, is correlated to the Bogdanovkian ( = earliest Bashkirian). The Plectostaffella jakhensis and P. longiscula zones, defined by the first occurrence of respective zonal name-bearers, are also characterized by the massive occurrence of Eostaffella and Plectostaffella. These zones include Eostaffella postovoidea, E. chomatifera, E. acutiformis, E. ex gr. mosquensis, E. pseudostruvei, E. postmosquensis, Plectostaffella varvariensis, P. baisultanica, P. oksanae, P. verta, P.? rotunda, P. benshae, P. ekaterinae, and many others, as well as Millerella paracarbonica, Eostaffellina nauvalia, Pseudonovella grozdilovae, and Pseudoendothyra tchernjaevae. The most important biostratigraphic feature of these two zones is the first occurrence of Semistaffella (S. pseudovariabilis, S. graciosa, and S. ex gr. primitiva). The occurrence of Semistaffella suggests that the Plectostaffella jakhensis and P. longiscula zones are referable collectively to the Syuranian. The Pseudostaffella antiqua Zone is highlighted by the first appearance of typical Pseudostaffella species, including the zonal name-bearer. The following species were also listed in this zone: Eostaffella chomatifera, E. lyschnianskiensis, Millerella paraumbilicata, Plectostaffella oksanae, Semistaffella variabilis, S. mira, Varistaffella varsanofievae, and Pseudostaffella posterior. Varistaffella korobezkikh, V. irinovkensis, Pseudostaffella compressa, P. uralica, and Ozawainella aurora occur in the upper part of this zone. The Pseudostaffella antiqua Zone is rightly referable to the Akavassian, and, as Orlov-Labkovsky and Bensh (2015) noted, it is a benchmark fusuline biozone, which can be correlated well with the same named zones established over the wide area of the Palaeotethys, Ural–Arctic, and Panthalassa palaeobiogeographical regions. This zone is followed by the Pseudostaffella praegorskyi Zone of Askynbashian age. It is marked by the occurrence of slightly more advanced Pseudostaffella species including P. praegorskyi, P. compressa, P. proozawai, and P. grandis, as well as Eostaffella postmosquensis, Millerella umbilicata, Plectostaffella varvariensis, Semistaffella variabilis, Pseudostaffella antiqua, and Ozawainella rhombiformis. Also, the notable biostratigraphic event seen in this zone is the first occurrence of Staffellaeformes (S. bona, S. minima, and S. staffellaeformis). This is the first occurrence of fusulines that have a shell with a longer axis of coiling than a diameter.

The late Bashkirian starts with the Ozawainella pararhomboidalisProfusulinella primitiva Zone of Tashastian age, in which fusiform and rhombic Profusulinella (such as P. primitiva, P. intermedia, P. oblonga, P. rhomboides, and P. parva) and Ozawainella pararhomboidalis first appeared and became dominant among the assemblage. In addition to these new elements, Eostaffella chomatifera, Plectostaffella varvariensis, Ozawainella rhombiformis, O. pararhomboidalis, Pseudostaffella compressa, P. gorskyi, and Staffellaeformes staffellaeformis, all present already in the preceding zones, continuously occur, and the genus Schubertella (S. ex gr. obscura) also became common in this zone. The succeeding Verella spicataProfusulinella rhombiformis Zone is defined by the first occurrence of the two zonal name bearers, together with Profusulinella pseudorhomboides and Aljutovella tikhonovichi. It is correlated to the Asatauian. Ozawainella pseudorhomboidalis, Pseudostaffella gorskyi, Staffellaeformes bona, and Profusulinella primitiva range upward from the underlying zones. The Verella spicataProfusulinella rhombiformis Zone also marked the first occurrence of the genus Neostaffella (N. nibelensis). Of these fusulines, the genus Verella is important because it is known as a marker of the latest Bashkirian in the Urals and some other areas in the Palaeotethys Region (Sheng 1958; Villa 1995; Ivanova 2008; Nemyrovska et al. 2010; Ueno 2013). In the Gissar Range, there are the Profusulinella rhombiformisProfusulinella intermedia Zone and the Profusulinella convolutaVerella aff. spicata Zone located in the early and late parts of the Asatauian (Bensh 1969). In the late Bashkirian, small lenticular eostaffellin genera (Eostaffella and Plectostaffella) continue to occur as well as rising fusulinellin genera (Staffellaeformes, Profusulinella, and Aljutovella), but the former became much diminished in number and diversity among the fusuline assemblage compared to early Bashkirian times.

The Bashkirian fusuline succession in the Central Asian Tianshan is very similar to those observed in the Urals summarized already (Fig. 15) and also the Donets Basin and Cantabrian Mountains described later (Fig. 17). There are some differences in the choice of the zonal marker species, but these four areas share the same generic and almost the same specific compositions regarding major fusulines in assemblages of the six Bashkirian substages.

Fig. 17.

Fusuline biostratigraphic successions of the Donets Basin, Carnic Alps, and Cantabrian Mountains (Locs 14, 15, and 17 in Fig. 2) in the western part of the Palaeotethys Region. Abbreviations of stages and substages: Tn., Tournaisian; Ivo, Ivorian; see Figure 14 for others. Abbreviations of taxonomic (generic) names: Al., Aljutovella; Bd., Beedeina; Dx., Daixina; Hf., Hemifusulina; Pr., Profusulinella; Ps., Pseudostaffella; Qf., Quasifusulinoides; Rs., Rauserites. References for data: see the text for details.

Fig. 17.

Fusuline biostratigraphic successions of the Donets Basin, Carnic Alps, and Cantabrian Mountains (Locs 14, 15, and 17 in Fig. 2) in the western part of the Palaeotethys Region. Abbreviations of stages and substages: Tn., Tournaisian; Ivo, Ivorian; see Figure 14 for others. Abbreviations of taxonomic (generic) names: Al., Aljutovella; Bd., Beedeina; Dx., Daixina; Hf., Hemifusulina; Pr., Profusulinella; Ps., Pseudostaffella; Qf., Quasifusulinoides; Rs., Rauserites. References for data: see the text for details.

Five fusuline zones, named the Aljutovella aljutovica, Aljutovella? priscoidea, Fusulinella bedakensisKanmeraia subpulchra, Fusulina kamensis, and Fusulinella schwagerinoides zones, were recognized in the Moscovian (Fig. 16). The first zone corresponds to the Vereian. Orlov-Labkovsky and Bensh (2015) noted that various species of Schubertella, Ozawainella, Neostaffella, Profusulinella, Aljutovella, and Eofusulina appear in this zone, and besides the zonal marker Schubertella pauciseptata, Ozawainella umbonata, Neostaffella subquadrata, N. pseudoquadrata, Profusulinella paratimanica, P. ovata, Aljutovella subaljutovica, A. distorta, A. elegans, Eofusulina fusiformis, and E. postfusiformis occur first. In the Gissar Range, the Vereian is further subdivided into the Neostaffella pseudoquadrataAljutovella distorta biformis Zone in the lower and the Pseudostaffella aff. gorskyiAljutovella elegans Zone in the upper (Bensh 1969). The next two zones, the Aljutovella? priscoidea and Fusulinella bedakensisKanmeraia subpulchra zones, comprised the Kashirian in the Tianshan of Central Asia. In the former zone, as well as the named zonal marker, the following species were identified: Ozawainella mosquensis, Neostaffella syzranica, N. rotundata, Profusulinella orbiculata, P. prisca, P. ovata, P. subovata, P. paratimanica, P. nuratovensis, P. parasimplex, Aljutovella cafirniganica, A. saratovica, A. znensis, Eofusulina postspicata, and E. triangula. The fundamental generic composition of this assemblage is the same as the preceding Vereian one, but the specific composition of Aljutovella is more variable. The Aljutovella? priscoidea Zone, before the appearance of Fusulinella and Beedeina, is correlated to the Tsninian part of the Kashirian (Solov'eva 1986). The Fusulinella bedakensisKanmeraia subpulchra Zone is marked by the occurrence of several new generic elements, such as Taitzehoella, Fusulinella, Kanmeraia, and Beedeina. Apart from the two zonal species, this zone yields Ozawainella paratingi, O. ex gr. mosquensis, Neostaffella umbilicata, Taitzehoella prolibrovichi, Profusulinella constans, P. meridiana, P. paratimanica, Aljutovella? priscoidea, Fusulinella paracolaniae, F. bockiformis, Beedeina ex gr. pseudoelegans, B. subdistenta, Eofusulina rasdorica, and E. gissarica. In this zone, Aljutovella was no longer a major element whereas the aforementioned newly appearing genera, especially of the Fusulinidae, became predominant. Although Orlov-Labkovsky and Bensh (2015) did not particularly incorporate that information into their biostratigraphic scheme, the genus Hemifusulinella (including H. djartassensis and several other species) reported by Rumyantseva (1962) from the Turkestan regional stage in Uzbekistan (Kim et al. 2007) is also an element in the Kashirian fusuline assemblage of the South Tianshan area.

The late Moscovian is subdivided into two fusuline zones named the Fusulina kamensis and Fusulinella schwagerinoides zones. These were correlated to the Podolskian and Myachkovian, respectively. The major fusulines in the former zone are Ozawainella vozhgalica, Neostaffella parasphaeroidea, N. sphaeroidea, Fusiella praecursor, Taitzehoella librovitchi, Fusulinella vozhgalensis, F. praebocki, F. bocki, F. timanica, Beedeina pseudoelegans, Fusulina chernovi, Dutkevichella vozhgalica, D. rhombiformis, and D.? bassaensis as well as the zonal marker Fusulina kamensis. Moreover, Parawedekindellina irinae and P. pjatkovia reported by Rumyantseva (1974) from the Lower Alai regional stage in Uzbekistan comprised part of the Podolskian fusuline assemblage in the Fusulina kamensis Zone (Kim et al. 2007). Fusiella, Fusulina, and Parawedekindellina are new generic elements that appeared first in this zone. The uppermost Moscovian is the Fusulinella schwagerinoides Zone and contains, besides the marker species, Ozawainella ex gr. mosquensis, Neostaffella ex gr. larionovae, Fusiella ex gr. typica, Fusulinella mosquensis, F. bocki, F. pseudobocki, F. rara, F. adjuncta, F. altispiralis, F. helenae, F. subcylindrica, Hemifusulina bocki, H. fusiformis, Beedeina paradistenta, B. samarica, Putrella? sp., Fusulina aspera, and F. myachkovensis. As noted above, this zone is generally correlated to the Myachkovian, but it is uncertain whether or not it includes the uppermost part of this substage, which is usually represented by the occurrence of the first Protriticites and Obsoletes ( = Praeobsoletes by some authors) (e.g. Davydov 1997b; Makhlina et al. 2001b). Some ‘Bogushinella’ species of Orlov-Labkovsky and Bensh (2015), which is regarded in this study as a junior synonym of Fusulinella, from the Fusulinella schwagerinoides Zone may include some forms in these genera, connecting Fusulinella and early schwagerinids (see also the Fusulinidae part in the section of ‘Taxonomy and evolutionary history of Carboniferous fusuline genera’).

In the three fusuline zones in the Kasimovian of Orlov-Labkovsky and Bensh (2015), the Protriticites pseudomontiparusObsoletes obsoletus Zone is essentially characterized by four genera: Protriticites, Obsoletes, Quasifusulinoides, and Pseudotriticites, with subordinate Fusulinella that ranged upward from the upper Moscovian. This generic association assigns the present zone to the Krevyakinian. Besides Protriticites pseudomontiparus and Obsoletes obsoletus, the following species can be mentioned as major fusulines: Fusulinella bocki, Protriticites subovatus, P. turkestanicus, P. variabilis, P. grozdilovae, Obsoletes fusiformis, O. inflatus, O. paraovoides, O. vetus, Pseudotriticites asiaticus, Quasifusulinoides juvenatus, and Q. parafusiformis. The generic and some specific composition of this assemblage from the Central Asian Tianshan shows strong resemblance with coeval ones of the Donets Basin, Carnic Alps, and Cantabrian Mountains, especially in the occurrence of Pseudotriticites (Fig. 17), although the ProtriticitesObsoletes association of this age is rather common over the wide area of the Palaeotethys, Panthalassa, and Ural–Arctic regions, as has been summarized in this paper. In the next Montiparus montiparus Zone, which is correlated to the middle Kasimovian (Khamovnikian), there are some surviving Obsoletes (such as O. paraovoides and O. inflatus), but Montiparus, represented by M. paramontiparus, M. umbonoplicatus, and M. karawensis, became predominant among the assemblage. The first Tumefactus (T. expressus), Triticites (T. kurshabensis), and Quasifusulina were marked in this zone. Then, the following Rauserites quasiarcticusFerganites ferganensis Zone coincides with the late Kasimovian (Dorogomilovian) in the Tianshan. The genus Montiparus, especially its large forms such as M. varians, M. alaicus, and M. umbonoplicatus, was still conspicuous in this Dorogomilovian assemblage, although they are not abundant. Rauserites, Rugosofusulina, Schwageriniformis, and Ferganites started to occur in this zone, and includes Rauserites quasiarcticus, R. subrossicus, Rugosofusulina ovoidea, Ferganites ferganensis, and F. isfarensis as representative forms. Moreover, it is noteworthy that in the Tianshan the Dorogomilovian assemblage is characterized by various forms of Schwageriniformis. This genus usually exhibits small and simple shells, typically seen in S. schwageriniformis and S. minor, in other palaeobiogeographical provinces (Rozovskaya 1950). In contrast, those Tianshan Schwageriniformis include large, slightly inflated, or elongate species, such as S. parafusiformis, S. gissaricus, S. burganensis, and S. kairakensis. Tumefactus (T. expressus and T. baisunensis) and Triticites (T. ‘oryziformis’) are the genera ranging up from the lower fusuline biozone. The occurrence of Ferganites in this zone is important for considering correlation and palaeobiogeography/palaeoecology. Ferganites in Dorogomilovian time has been reported from the Carnic Alps and Cantabrian Mountains by Krainer and Davydov (1998) and Villa and Bahamonde (2001), and, according to the latter work, the emergence of this genus is strongly linked to particular sedimentary facies showing a high-energy environment with a relatively low-salinity condition. Thus, the occurrence of Ferganites would be controlled by both chronologic constraint and palaeoenvironmental factors.

According to Orlov-Labkovsky and Bensh (2015), the Gzhelian interval in the Tianshan is subdivided into three fusuline zones; viz. the Rauserites rossicusRauserites stuckenbergi, Daixina asiaticaJigulites corpulentus, and Ruzhenzevites ferganensis zones (Fig. 16). As noted below, however, it is reasonable to recognize the zone characterized by the occurrence of Bosbytauella, ‘Likharevites’, and ‘Occidentoschwagerina’ in the uppermost Gzhelian above the Ruzhenzevites ferganensis Zone.

Two markers in the first zone are often selected as zonal species for the early Gzhelian fusuline biozones established in the Russian Platform and several Palaeotethyan areas (Figs 15,, 16,, 17,, 18), which makes the age assessment of the Rauserites rossicusRauserites stuckenbergi Zone in the Tianshan to the Dobryatinian solid. In addition to Rauserites (R. paraarcticus, R. refertus, R. erraticus, R. bashkiricus, and two zonal marker Rauserites species) and Triticites (T. shortangensis, T. noinskyi, and T. ‘oryziformis’), there are abundant Schwageriniformis (S. schwageriniformis, S. perstabilis, S. nanus, S. parallelos, S. gusanicus, S. perlongus, S. asiaticus) identified in this zone, some of which ranged upward from the late Kasimovian zone. Moreover, Schagonella (S. procera and S. cylindrica) occurs first in this zone. The early Gzhelian age for this assemblage is evident based on the occurrence of combined R. rossicus and R. stuckenbergi, but except Rauserites and Triticites, this faunal composition with predominant Schwageriniformis species is somewhat disparate among fusuline assemblages of this age. The middle Gzhelian is characterized by the occurrence of diversified Daixina and Jigulites, and Schagonella became more conspicuous. The Daixina asiaticaJigulites corpulentus Zone was established to this interval. Schwageriniformis and Triticites also ranged upward from the early Gzhelian zone. Apart from the zonal species, the following species can be mentioned as major fusulines: Schwageriniformis turkestanensis, S. perlongus, Jigulites jigulensis, J. major, J. ex gr. dagmarae, Daixina minima, Schagonella procera, S. cylindrica, S. implexa, and S. orientale. The abundant occurrence of Jigulites in this zone warrants the Pavlovoposadian (middle Gzhelian) age assignment, but prevailing Schagonella is diagnostic because this genus is rarely known outside Central Asia (Davydov 1990a; Ueno et al. 1995; Forke et al. 2006). The Ruzhenzevites ferganensis Zone of the late Gzhelian is characterized by the first appearance of two genera, Ruzhenzevites and Dutkevitchia. Schagonella, Daixina, Triticites, and Schwageriniformis also range upward from the underlying zones. Major fusulines included in this zone are, besides the marker, Triticites pseudorhodesi, T. regularis, Schwageriniformis schwageriniformis, Ruzhenzevites olgae, R. vesiculosa, R. subcylindrica, Dutkevitchia dastarensis, D. complicata, D. lancetiformis, Schagonella implexa, and S. ljakanica. Daixina species (such as D. vasilkovskyi and D.? diafana) are scarce and restricted to the upper part of the zone. Late/latest Gzhelian Ruzhenzevites is also characteristic in the Carnic Alps (Forke 2002), Iran (Gaetani et al. 2009; Leven and Gorgij 2011b), Tarim Basin (Zhao et al. 1984), and Indochina (Charoentitirat and Ueno 1997, 1999).

Fig. 18.

Fusuline biostratigraphic successions in the Alborz Mountains, Central Iran (Tabas, Posht-e Badam, and Yazd blocks), and Sanandaj–Sirjan Zone of Iran (Loc. 22 in Fig. 2) in the western part of the Palaeotethys Region. Abbreviations of stages and substages: Tn., Tournaisian; Kasim., Kasimovian; Ivo, Ivorian; see Figure 14 for others. Abbreviation of taxonomic (generic) name: Bd., Beedeina. References for data: see the text for details.

Fig. 18.

Fusuline biostratigraphic successions in the Alborz Mountains, Central Iran (Tabas, Posht-e Badam, and Yazd blocks), and Sanandaj–Sirjan Zone of Iran (Loc. 22 in Fig. 2) in the western part of the Palaeotethys Region. Abbreviations of stages and substages: Tn., Tournaisian; Kasim., Kasimovian; Ivo, Ivorian; see Figure 14 for others. Abbreviation of taxonomic (generic) name: Bd., Beedeina. References for data: see the text for details.

Orlov-Labkovsky and Bensh (2015) considered the Ruzhenzevites ferganensis Zone to be the youngest Gzhelian biostratigraphic unit in the Central and South Tianshan and placed their overlying Occidentoschwagerina alpinaLikharevites paranitidus Zone in the basal part of the Permian. The latter zone is also characterized by the exclusive occurrence of Bosbytauella bosbytauensis, and is settled just below the first occurrence of Sphaeroschwagerina ( = Schwagerina of Orlov-Labkovsky and Bensh 2015). However, this correlation, to place the Carboniferous–Permian boundary at the base of a zone defined by Bosbytauella bosbytauensis and ‘Likharevites’ species, leaves questions because elsewhere in the Palaeotethys Region and the South Urals, the genus Bosbytauella is known to characterize an uppermost Gzhelian interval corresponding to the Melekhovian (Chuvashov et al. 1986; Davydov et al. 1992; Forke 2002). Moreover, setting the problem of potential nomenclatural unavailability of the genus aside, a latest Gzhelian occurrence of ‘Likharevites’ is not unusual (Chuvashov et al. 1986; Leven and Gorgij 2006b; and see also section on the Moscow Syneclise in reference to the occurrence of ‘Likharevitesinsolita from the Melekhovian by Makhlina and Isakova 1997). Thus, it seems to be more reasonable to correlate the Occidentoschwagerina alpina–‘Likharevitesparanitidus Zone, at least part of it, to the latest Gzhelian. This would be also consistent with the fact that the first Sphaeroschwagerina (Schwagerina of Orlov-Labkovsky and Bensh 2015), which is often regarded as a marker fusuline genus of the Asselian (earliest Permian), appeared in the ‘Schwagerinamoelleri–‘Nonpseudofusulinafecunda Zone next to the O. alpina–‘L.’ paranitidus Zone. Because Sphaeroschwagerina moelleri is not the earliest species of the genus and is often regarded as showing the middle Asselian (Leven and Shcherbovich 1978), the upper part of the O. alpina–‘L.’ paranitidus Zone may contain some basal Permian strata, which corresponds to the early Asselian Sphaeroschwagerina vulgarisSphaeroschwagerina fusiformis Zone widely recognized elsewhere in Eurasia (e.g. Leven and Shcherbovich 1978; Chuvashov et al. 1986; Davydov et al. 1998). It is more plausible to put the Carboniferous–Permian boundary somewhere inside the O. alpina–‘L.’ paranitidus Zone, as Orlov-Labkovsky and Bensh (2015, p. 45) themselves also implicitly admitted. The redefined latest Gzhelian part of the O. alpina–‘L.’ paranitidus Zone is best characterized by the occurrence of Bosbytauella bosbytauensis and ‘Likharevites’ species, and thus should be referred to as the Bosbytauella bosbytauensis–‘Likharevites’ Zone (Fig. 16). It is not advisable to use the name ‘Occidentoschwagerina’ and to include it in the markers of this biozone defined herein. As Forke (2002) has demonstrated in detail and also discussed in the earlier section in this paper, this genus is very probably a junior synonym of Pseudoschwagerina since its type species, Schwagerina fusulinoides described by Schellwien (1898), is considered to be conspecific with Pseudoschwagerina extensa (thus Pseudoschwagerina fusulinoides including P. extensa by Kahler and Kahler 1937 as a junior synonym). Moreover, also as pointed out by Forke (2002), the name ‘Occidentoschwagerina’ is often applied erroneously by later authors (including Orlov-Labkovsky and Bensh 2015) to a distinct fusuline group from latest Gzhelian and Asselian strata, whose generic concept ties with the morphology of ‘Occidentoschwagerinaalpina having a minute proloculus and tightly coiled inner volutions (which is somewhat similar to Paraschwagerina). This modified generic concept, probably rooted in Rauzer-Chernousova (1961), is largely different from the original definition of Occidentoschwagerina proposed by Miklukho-Maklay (1959c) based mainly on its type species.

Because of the current undefined position of the base of the Permian within the ‘Occidentoschwagerinaalpina–‘Likharevitesparanitidus Zone by Orlov-Labkovsky and Bensh (2015), the overall picture of the latest Gzhelian Bosbytauella bosbytauensis–‘Likharevites’ Zone in the Central Asian Tianshan is not very clear. As its broad generic composition, in addition to Bosbytauella (B. bosbytauensis and B. postgallowayi) and ‘Likharevites’ (‘L.’ esetensis and ‘L.’ paranitida) the following genera would be listed according to Orlov-Labkovsky and Bensh (2015): Dutkevitchia (D. bimorpha and several other species), Ruzhenzevites (R. ferganensis), Daixina (D. bipartita and D. ruzhencevi), Rugosofusulina, Rugosochusenella, Triticites, and ‘Occidentoschwagerina’.

The Darvaz has been considered as one of key areas for the study of Middle–Late Pennsylvanian fusuline taxonomy, phylogeny, and biostratigraphy due mainly to several respects that were reported by Davydov (1984, 1988a, b, 1990b). Three researches by Chuvashov et al. (1986), Leven (1998), and Leven and Davydov (2001), done at the Kuhifrush Range in the southwestern Darvaz, established a continuous composite fusuline succession ranging from the Kashirian (early Moscovian) to the late Gzhelian in this area. As a result, detailed biozonation has been established during this interval (Fig. 16).

Leven (1998) investigated the Kuhifrush and the lower part of the Kalaikuhna formations in the Moscovian and divided them into seven zones named, in ascending order, the Aljutovella znensisProfusulinella constans, Citronites splendidaProfusulinella timanica, Citronites reticulatusNeofusulina subtilissima, Putrella brazhnikovaeUndatafusulina asiatica, Beedeina samaricaBeedeina elegans, Fusulinella schwagerinoidesBeedeina darvasica, and Beedeina consobrinaBeedeina dutkevichi zones (Fig. 16). The fusuline assemblage of the first zone is not characterized well, but it contains Taitzehoella prolibrovichi, Dutkevichella volgensis, and the two zonal species; Aljutovella znensis and Profusulinella constans. This zone is correlated to the Aljutovella? priscoidea Zone in the Tianshan described above, although the former does not contain some diagnostic forms found in the latter, such as A.? priscoidea, Neostaffella, and Eofusulina (Orlov-Labkovsky and Bensh 2015). Leven (1998) correlated this zone to the early part of the Kashirian (Tsninian of Solov'eva 1986). In the Aljutovella znensisProfusulinella constans Zone, moreover, Kanmeraia subpulchra ( = Pulchrella eopulchra of Leven 1998) was listed but the occurrence of this species is somewhat questionable. It could possibly be Profusulinella pseudorhomboides, which is common in the Tsninian, instead of Kanmeraia subpulchra.

Overlying the Aljutovella znensisProfusulinella constans Zone is the Citronites splendidaProfusulinella timanica Zone, which is marked by the first appearance of the genera Citronites and Fusulinella [Fusulinella (Moellerites) of Leven 1998]. Leven (1998) originally assigned the species splendida, one of the two zonal markers of the relevant zone, to Hemifusulina with question. Based on the gross shell morphology, it is better referred to the genus Citronites. Same as the underlying Aljutovella znensisProfusulinella constans Zone, the fusuline assemblage of this zone is not very distinctive, and except for the entry of Fusulinella, the generic and some specific composition is similar to the former zone. It consists of the following major fusulines: Taitzehoella prolibrovichi, Profusulinella rhomboides, P. arta, P. parva, P. timanica, Aljutovella postaljutovica, and Kanmeraia subpulchra. In the next Citronites reticulatusNeofusulina subtilissima Zone, Profusulinella (such as P. ovata, P. nytvica, and P. ferganensis), Aljutovella (including A. aljutovica, A. pseudoaljutovica, and A. darvasica), Citronites (C. reticulatus, C. apokensis, and C. panjensis), Fusulinella (F. paracolaniae, F. praebocki, F. schubertellinoides, F. ginkeli, and many other species), and Dutkevichella (such as D. paraelliptica and D. orientalis) became more diversified than in the lower zones. Beedeina represented by B. lanceolata, B. schellwieni, and B. rhomboidalis marked its first appearance. Putrella susini is the first species of this genus in this section. Two eofusulinin species (Eofusulina binominata and Neofusulina subtilissima, the latter of which is one of the zonal name-bearers) are also characteristic of this zone, and they are restricted to it. The Citronites splendidaProfusulinella timanica and Citronites reticulatusNeofusulina subtilissima zones in the upper part of the Kuhifrush and the basal part (Member 1) of the Kalaikuhna formations are referable to the Kashirian above the Tsninian. They are correlated to the Fusulinella bedakensisKanmeraia subpulchra Zone in the Tianshan (Orlov-Labkovsky and Bensh 2015), judging from the fundamental generic and some specific composition.

The Putrella brazhnikovaeUndatafusulina asiatica Zone was located in a relatively thin interval in the basal part of the Kalaikuhna Formation (uppermost part of the Member 1). All Profusulinella, Aljutovella, and Citronites species disappeared below this zone. Instead of these, several Beedeina and Fusulinella species, which are different from those in the underlying zone, such as Beedeina samarica, B. pseudokonnoi, B. elegans, Fusulinella helenae, F. gigantea, F. alvaradoi, F. lata, and F. pseudobocki, as well as the two marker species, marked the first occurrence in the assemblage. Putrella brazhnikovae is known as a marker of the Podolskian in the Urals, Moscow Syneclise, and Donets Basin (Figs 15 & 17). In contrast, Undatafusulina asiatica, characterizing this zone and being restricted to it, is of a monotypic genus established by Leven (1998) and endemic to the Darvaz. The Putrella brazhnikovaeUndatafusulina asiatica Zone was assigned to the Podolskian by Leven (1998). The correlation of this zone to the Tianshan is not straightforward because these two zonal markers are not known there, and the likely correlated zone in the Tianshan is characterized by Fusulina kamensis, which likewise is not known in the Darvaz. Nevertheless, there are some common features in fusuline successions seen in these areas, such as that all Profusulinella, Aljutovella, and eofusulinin taxa disappeared below the zones under discussion. Moreover, both of these zones are succeeded by fusuline zones that are considered to be Myachkovian in a broad sense. The Putrella brazhnikovaeUndatafusulina asiatica Zone in the Darvaz is, therefore, correlated probably to the Fusulina kamensis Zone in the Tianshan, although the contemporaneity of the lower and upper limits of the two zones may be somewhat controversial.

The next three zones: the Beedeina samaricaBeedeina elegans, Fusulinella schwagerinoidesBeedeina darvasica, and Beedeina consobrinaBeedeina dutkevichi zones were established in Members 2 to 4 of the Kalaikuhna Formation and are defined based on the occurrences of different Beedeina species as well as Fusulinella schwagerinoides, respectively. As has been noted already in the preceding section, F. schwagerinoides is a marker species for the Myachkovian of the Tianshan (Orlov-Labkovsky and Bensh 2015). Apart from associated smaller fusulines (consisting mainly of ozawainellid and schubertellid species) and Taitzehoella librovitchi being found throughout the Myachkovian, the following features are important in view of biostratigraphy: Fusulinella and Beedeina are the major elements of the three Myachkovian fusuline assemblages; Parawedekindellina cf. subovata and Fusulina cf. quasicylindrica occurred in the B. samaricaB. elegans Zone; several Fusulina species (including F. cf. cylindrica and F. cf. myachkovensis) were found in the B. consobrinaB. dutkevichi Zone; and Protriticites? sp. appears in the uppermost beds of the B. consobrinaB. dutkevichi Zone. These three Myachkovian zones in the Darvaz are correlated broadly to the Fusulinella schwagerinoides Zone in the Tianshan.

Leven and Davydov (2001) reported the fusuline faunal succession of Members 5 to 7 of the Kalaikuhna Formation, which covers the Kasimovian and lower Gzhelian chronostratigraphically. They established the following five zones in this interval: in ascending order, the Protriticites variabilisObsoletes paraovoides, Montiparus umbonoplicatusTriticites kurshabensis, Tumefactus expressusProtriticites? compactus, and Schwageriniformis fusiformisSchwageriniformis pamiricus zones in the Kasimovian and the Rauserites rossicus Zone in the early Gzhelian (Fig. 16). Leven and Davydov (2001) also recognized in the underlying, uppermost part of the Myachkovian (Member 4) the Obsoletes burkemensisProtriticites ovatus Zone, which was not established in Leven (1998), but the details were not described in that paper. In this summary, the Obsoletes burkemensisProtriticites ovatus Zone, defined somewhat loosely, is also incorporated in the general fusuline succession of the Darvaz (Fig. 16), and provisionally correlated to the Peskovian of the late/latest Myachkovian, above the Beedeina consobrinaBeedeina dutkevichi Zone discussed previously.

In the Protriticites variabilisObsoletes paraovoides Zone, set in the basal part of the Member 5 of the Kalaikuhna Formation, the fusuline assemblage, except for small forms and the two zonal name-bearers, consists of Protriticites plicatus, Obsoletes darvasicus, O. inflatus, O. minutus, and O. aff. ovoides. This zone is correlated to the Krevyakinian, but as Leven and Davydov (2001) admitted, it would correspond to only part of the early Kasimovian in view of its reduced thickness (only 2 m thick) and sedimentary facies represented by oolitic grainstone. Hiatuses may exist below and above the Protriticites variabilisObsoletes paraovoides Zone.

The next Montiparus umbonoplicatusTriticites kurshabensis Zone, corresponding to the lower part of the Member 5 of the Kalaikuhna Formation, is characterized by the massive occurrence of the genera Montiparus, Triticites, Quasifusulinoides, and Quasifusulina. The morphologically very characteristic genus Kushanella, which was established by Leven and Davydov (2001) and is endemic to the Darvaz so far, is also restricted to this zone. Major species in later fusulinids and earliest schwagerinids from this zone are Quasifusulinoides quasifusulinoides, Q. juvenatus, Quasifusulina pseudotenuissima, Montiparus umbonoplicatus, M. sinuosus, M. alaicus, several new species in Montiparus (such as M. kushanicus, M. stuckenbergiformis, and M. citreus), Triticites kurshabensis, T. simplex, T. umbonoplicatiformis, and Tumefactus expressus. In this zone, Protriticites and Obsoletes were eradicated, and Quasifusulinoides/Quasifusulina appeared first. It is also noteworthy to describe the occurrence of Fusiella lancetiformis and F. segyrdashtiensis from this zone. These Fusiella species having noticeably large shells are good auxiliary markers for the early–middle Kasimovian in the Moscow Syneclise (Isakova 2013), Donets Basin (Putrya 1939, 1940; Davydov and Khodjanyazova 2009; author's unpublished data), Carnic Alps (Forke et al. 2006), Cantabrian Mountains (Villa and van Ginkel 2000), and South China (Ueno et al. 2013).

The Montiparus umbonoplicatusTriticites kurshabensis Zone is succeeded by the Tumefactus expressusProtriticites? compactus Zone, which covers the upper half of the Member 5 of the Kalaikuhna Formation. The fusuline faunal composition showed a drastic change across these two zones, in that all Montiparus, Triticites, and Kushanella disappeared and, instead, Schwageriniformis and Tumefactus flourished. Moreover, Protriticites and Obsoletes reappeared in the latter zone, which were completely absent in the former, but were common in the Krevyakinian (early Kasimovian) Protriticites variabilisObsoletes paraovoides Zone situated further below. Protriticites and Obsoletes are predominant in the bottom of the Tumefactus expressusProtriticites? compactus Zone and gradually became rarer upward. Leven and Davydov (2001) described the species compactus, one of the two zonal markers, as a species of the genus Protriticites, but this generic assignment is somewhat questionable because of the poorly defined Protriticites-type spirothecal structure in this taxon and its gross shell morphology. Apart from the two marker species, major fusulines are listed below: Protriticites turkestanicus, P. putrjai, P. formosus, P. plicatus, Obsoletes darvasicus, O. paraovoides, and Tumefactus oblisus. Leven and Davydov (2001) correlated the Montiparus umbonoplicatusTriticites kurshabensis and Tumefactus expressusProtriticites? compactus zones to the Khamovnikian. As they admitted, however, the correlation and age assessment of the latter zone would not be straightforward because of the strong provincialism of Darvaz fusulines in this and the next Schwageriniformis fusiformisSchwageriniformis pamiricus zones. Fusulines of these two zones are dominated by Schwageriniformis that includes many endemic new species. Thus, judging from the fact that Protriticites and Obsoletes, which are usually more common in the Krevyakinian and less common but still known to occur in the Khamovnikian, are predominant only in the lower part of the Tumefactus expressusProtriticites? compactus Zone, it cannot be ruled out as a possibility that the upper/uppermost part of the relevant zone may represent already the lower Dorogomilovian. In a regional biostratigraphic context, these two zones are broadly correlated to the Montiparus montiparus Zone in the Tianshan by Orlov-Labkovsky and Bensh (2015).

The Schwageriniformis fusiformisSchwageriniformis pamiricus Zone was established in Member 6 of the Kalaikuhna Formation, above the broadly late Khamovnikian Tumefactus expressusProtriticites? compactus Zone described above. As seen in the zonal markers, Schwageriniformis species (S. fusiformis, S. minor, S. baisunensis, S. pamiricus, and others) are predominant throughout the zone, with the occurrences of some Ferganites and Rauserites restricted to the upper part. Leven and Davydov (2001, fig. 4) depicted a short interval represented by Ferganites ferganensis in the uppermost part of this zone. This information is also incorporated in the present summary (Fig. 16) as these authors described the predominant occurrence of Ferganites in the upper part of the S. fusiformisS. pamiricus Zone. In the Tianshan, Orlov-Labkovsky and Bensh (2015) established the Rauserites quasiarcticusFerganites ferganensis Zone, to which the Schwageriniformis fusiformisSchwageriniformis pamiricus Zone, including the Ferganites ferganensis interval, is likely correlated. The former zone in the Tianshan is also characterized by the abundant occurrence of Schwageriniformis. Moreover, similar stratigraphic intervals represented by Ferganites were also reported in the late Kasimovian of the Carnic Alps and Cantabrian Mountains (Krainer and Davydov 1998; Villa and Bahamonde 2001) as noted later. The Schwageriniformis fusiformisSchwageriniformis pamiricus Zone in the Darvaz is referable to the late Kasimovian.

In the next Rauserites rossicus Zone corresponding to Member 7 of the Kalaikuhna Formation, fusuline composition had changed largely; most species of Schwageriniformis were eradicated, and Rauserites, including R. rossicus, R. jucundus, R. darvasicus, R. concinnus, and R. fortissimus, and Ferganites (F. ferganensis and F. isfarensis) became predominant. This zone is correlated to the Rauserites rossicusRauserites stuckenbergi Zone of the Tianshan (Orlov-Labkovsky and Bensh 2015) and is referable to the early Gzhelian.

Fusuline-bearing strata covering this interval are also well exposed further upward in the Kalaikuhna Formation. Chuvashov et al. (1986) subdivided them into the following zones: the Schagonella minorSchagonella proimplexa, Schagonella implexa, Dutkevitchia dastarensis, Ruzhenzevites ferganensisRauserites? malkovskyi, ‘Pseudofusulinaelegans, and Bosbytauella bosbytauensisDaixina robusta zones, in ascending order (Fig. 16). This zonation is peculiar because it was based mainly on the rugosofusulinin evolution and designated by Schagonella, Dutkevitchia, and Ruzhenzevites species as zonal markers (Davydov 1988a, b). Chuvashov et al. (1986) described and illustrated many fusulines from the studied interval, thus the data on which this zonation was based are readily available.

In the Schagonella minorSchagonella proimplexa Zone, Daixina baituganensis, Schagonella safetgyrensis, and S. cylindrica occur beside the two zonal name-bearers. The fusuline assemblage of the overlying Schagonella implexa Zone was not well characterized and apart from S. implexa, only S. uralensis was illustrated. These two zones were referred to the middle Gzhelian, and thus are correlated to the Daixina asiaticaJigulites corpulentus Zone in the Tianshan (Orlov-Labkovsky and Bensh 2015). Although the designation of the marker species is very different between the Tianshan and Darvaz zones, there are some similar and identical Schagonella species (S. procera, S. implexa, and S. cylindrica) known in the middle Gzhelian zone of the Tianshan, which support this correlation.

The late Gzhelian is composed of the overlying four biozones in fusuline biostratigraphy. The Dutkevitchia dastarensis Zone marked the first occurrences of the genera Dutkevitchia and Ruzhenzevites. In this zone, large advanced Schagonella (S. gigantea and S. amplissima), Dutkevitchia expansa, Ruzhenzevites praeferganensis, Jigulites corpulensis, and Daixina licharevi were found together with the zonal marker. The overlying Ruzhenzevites ferganensisRauserites? malkovskyi Zone contains, besides these two marker species, Triticites? iohchensis, T.? jakshoensis, Dutkevitchia pjandzhiensis, Ruzhenzevites subcylindricus, R. parasolidus, Daixina vasilkovskyi, D. ex gr. sokensis, D. louensis, ‘Pseudofusulina’ sp. ( = P. ulukensis in Chuvashov et al. 1986), and several others. The next ‘Pseudofusulinaelegans Zone has an assemblage consisting of Dutkevitchia miniouensis, Daixina uralica, D. evoluta, ‘Pseudofusulinaelegans, and others. These three zones were collectively assigned to the Daixina sokensis Zone, which could be more or less referable to the Noginskian (early part of the late Gzhelian). They are correlated to the Ruzhenzevites ferganensis Zone in the Tianshan. The uppermost Gzhelian biozone was named the Bosbytauella bosbytauensisDaixina robusta Zone. In this zone, Bosbytauella is the most diagnostic and morphologically conspicuous element in the fusuline assemblage and includes B. bosbytauensis, B. postsokensis, B. postgallowayi, and B. dashtidzhumica. Daixina and Pseudofusulina? occur constantly, but Dutkevitchia and Ruzhenzevites were not listed in Chuvashov et al. (1986). Instead, Schwagerina (such as S. nux and S. versabile), Benshiella stabilis, Pseudochusenella tumidula, and Rugosochusenella (such as R. paragregaria and R. simplex) appeared in this level. The Bosbytauella bosbytauensisDaixina robusta assemblage shows high generic and specific diversity compared to the zones below. This zone is referable to the Melekhovian and is correlated to the Bosbytauella bosbytauensis–‘Likharevites’ Zone in the Tianshan.

Carboniferous fusulines are known in northern Afghanistan north of the Major suture line of Central Asia in Leven (1997), in several localities of the western South Hindu Kush, and Khwahan in Badakhchan (Lys 1988b; Vachard and Montenat 1996). They are Eostaffella parastruvei from the Visean; Eostaffella pseudostruvei, E. mifirica, Plectostaffella varvariensis, and Pseudoendothyra struvei from the Serpukhovian; E. pseudostruvei, E. postmosquensis, Pseudonovella grozdilovae, Ozawainella pararhomboidalis, Pseudostaffella antiqua, P. gorskyi, Schubertella sp., and others from the Bashkirian; and Taitzehoella aff. librovitchi, Schubertella obscura, Aljutovella postaljutovica, Fusulinella paracolaniae, F. ex gr. bocki, Quasifusulinoides? sp., and others from the Moscovian. These species are also known elsewhere in Central Asia as described previously. In this connection, there are Carboniferous distributions also known in the Central Mountains and the Wakhan south of the Major suture line, and foraminifers have been identified there, but fusulines are not known (Vachard and Montenat 1996).

The Precaspian Basin located in western Kazakhstan is a large Late Paleozoic hydrocarbon field, and Carboniferous foraminifers have been investigated in relationship to subsurface petroleum exploration. Gibshman and Akhmetshina (1990) reported detailed foraminiferal biostratigraphy across the Mid-Carboniferous boundary from several wells in the eastern part of the basin, and Brenckle and Milkina (2003) and Brenckle and Collins (2017) documented an almost continuous foraminiferal succession from the uppermost Devonian into the upper Bashkirian from the Tengiz and Kashagan platforms in the southern part of the Precaspian Basin, except in an interval of erosion and/or non-deposition at the Mississippian–Pennsylvanian boundary in the platform interiors. Akhmetshina et al. (2007) published a comprehensive atlas documenting the entire Carboniferous stratigraphy and foraminiferal succession of the Precaspian Depression, by gathering massive borehole data collected from the southern, southeastern, eastern, and northern marginal parts of the basin (including the data of Gibshman and Akhmetshina 1990).

Essentially, the literature mentioned in the preceding paragraph is utilized to make an outline of fusuline succession in the Precaspian Basin during Mississippian time. Akhmetshina et al. (2007) identified Eoparastaffella rotunda from a latest Tournaisian interval. This species is the oldest fusuline in the Carboniferous succession of the Precaspian Basin. In the Tengiz oil field, uppermost Tournaisian beds are likely missing along the top of the platform. The early Visean is better represented in many oil wells and is represented by an assemblage consisting of Eoparastaffella simplex, E. ovalis, E. rotunda, E. pseudochomata, and E. subglobosa. The first Eostaffella (E. versabilis) also appeared in the later part (Bobrikian) of the early Visean (Akhmetshina et al. 2007). The middle Visean contains Eoparastaffella simplex, E. cf. ovalis, Eostaffella nalivkini, and Pseudoendothyra struvei. The late Visean yields more diversified Eostaffella species: E. mosquensis, E. parastruvei, E. constricta, E. proikensis, E. ikensis, E. tenebrosa, E. ovoidea, and E. raguschensis, together with several Pseudoendothyra species.

Some of these above-mentioned Eostaffella (such as E. constricta, E. ikensis, E. raguschensis, E. parastruvei, and E. proikensis) extended their ranges to the early Serpukhovian. In that interval Eostaffella gruenewaldti, E. mirifica, and two additional genera, Eostaffellina and Plectostaffella, appear first, and, in the late Serpukhovian, the latter two genera became predominant. The late Serpukhovian fusuline assemblage has Eostaffellina protvae, E. paraprotvae, E. subsphaerica, E. actuosa, E. schartimiensis, Plectostaffella jakhensis, along with some Eostaffella coming up from the older levels (such as E. parastruvei, E. proikensis, E. raguschensis, and E. ovoidea). Eostaffella postmosquensis and E. cooperi newly appeared in this interval.

The Bashkirian is well recognized in the Tengiz and Kashagan platforms (Brenckle and Milkina 2003; Brenckle and Collins 2017) but is restricted to its lower part in the marginal Precaspian Basin (Gibshman and Akhmetshina 1990; Akhmetshina et al. 2007). The Bogdanovkian–Syuranian interval (early part of the early Bashkirian) records new entries of Eostaffella chomatifera, Millerella marblensis, Plectostaffella bogdanovkensis, and Semistaffella variabilis, which are accompanied by E. postmosquensis, E. ovoidea, Eostaffellina paraprotvae, Plectostaffella jakhensis, and several others ranging from the Serpukhovian. The Akavassian is characterized by the occurrence of Pseudostaffella antiqua, P. compressa, P. posterior, P. grandis, and others. The next Askynbashian is marked by the first ‘profusulinellas’ such as Staffellaeformes staffellaeformis and Profusulinella ex gr. parva in the Tengiz Platform, but without illustration of specimens (Brenckle and Milkina 2003). In the Kashagan Platform, Profusulinella appeared later, in the late Bashkirian (Brenckle and Collins 2017). In the late Bashkirian, fusulines became predominant among the entire Precaspian foraminiferal fauna. Ozawainella cf. alchevskiensis, O. ex gr. fragilis, O. cf. pararhomboidalis, Profusulinella ex gr. pararhomboides, and Aljutovella? sp. were reported from the late Bashkirian interval (Brenckle and Milkina 2003). The Bashkirian fusuline succession of the Precaspian Basin is essentially similar to those seen in sections in the East European Platform areas (Timan–Pechora and the Urals).

The Moscovian fusuline succession is well documented in the Precaspian Basin. Akhmetshina et al. (2007) recognized eight fusuline biozones in the Precaspian subsurface Moscovian, by simply applying the zonation established in the Russian Platform, without modification, to the Precaspian fusuline succession. They are, in ascending order, the Aljutovella aljutovica, Aljutovella? priscoidea, Fusulinella praecolaniaeKanmeraia subpulchra, Fusulinella colaniae, Fusulina kamensis, Fusulinella bocki, Fusulina cylindrica, and Protriticites ovatus zones. The first zone was correlated to the Vereian; the next two to the Kashirian; the Fusulinella colaniae and Fusulina kamensis zones to the Podolskian; and the last three zones to the Myachkovian. Some zonal marker and biostratigraphically important species were illustrated in Akhmetshina et al. (2007), but others were not shown.

Later, Nikolaev (2011) presented massive information on the Moscovian fusuline succession of the Precaspian Basin. He described more than 150 species belonging to 25 genera from samples collected in various wells (Table 3). That monographic work covers almost the entire fusuline succession of the Moscovian, so it can be the primary information source to understand the complete picture of fusulines of this age in the basin. Characteristics of fusulines in the four Moscovian substages are summarized below. The Vereian assemblage consists of Neostaffella, Profusulinella, Eofusulina, and Paraeofusulina. Superficially, the species diversity was not high in the Vereian, possibly due to sample recovery of this age in the wells. The Kashirian is extensively recognized in the wells studied by Nikolaev (2011). In this interval Profusulinella, Aljutovella, and Neostaffella were diversified, and the first Fusulinella and Beedeina were found. Eofusulina species (including Eofusulina triangula and E. binominata) are also characteristic in the Kashirian as in the Vereian. Nikolaev (2011) described Verella parva and several other Verella species from the Kashirian, but they are all identified as Eofusulina parva in this study, which is characterized by apparently weaker septal fluting in the genus. The Podolskian succession is also well developed in materials that Nikolaev (2011) studied. Fusulinella is especially abundant and diversified, and Beedeina, Fusulina, and Putrella are diagnostic in this interval. Nikolaev (2011) described an interesting species under the name of ‘Fusulinidae incertae sedis.’ This unidentified taxon has a large elongate fusiform shell with strongly and regularly fluted septa forming characteristic high and narrow septal loops. He pointed out some morphological similarities between this species and Putrella brazhnikovae, but, because there is no porous structure observed in the spirotheca in his specimens, he left this form open nomenclaturally. However, the pores in spirotheca may be rather arbitrarily observed in actual specimens of Putrella, largely depending on the preservation of samples. Based on the gross shell morphology and occurrence level (Podolskian, late Moscovian) of this species, it can be treated as a new species in Putrella. The Myachkovian of Nikolaev (2011) is still dominated by Fusulinella in association with Hemifusulina, Fusulina, and Taitzehoella. Thus, what was regarded as the Myachkovian by Nikolaev (2011) probably represents only the lower half of this substage, corresponding to the pre-Obsoletes/Protriticites (pre-Peskovian) Myachkovian (see also Fig. 15, for example).

Table 3.

List of fusulines from four Moscovian substages in the Precaspian Basin (Loc. 13 in Fig. 2)

Vereian
Neostaffella syzranica, Profusulinella integra, P. prisca, P. zhanatanensis, P. carasaica, P. pseudorhomboides, Eofusulina triangula, Paraeofusulina sp.
Kashirian
Pseudostaffella composita, P. gorskyi, Neostaffella ovalis, N. nibelensiformis, N. kamensis, N. pseudoquadrata, N. greenlandica, N. topilini, Schubertella gracilis, S. kulensis, S. acuta, S. magna, Taitzehoella prolibrovichi, T. librovitchi, Staffellaeformes latispiralis, Profusulinella arbejalensis, P. albasensis, P. integra, P. pseudorhomboides, P. ovata, P. biconiformis, P. mutabilis, P. propria, P. kazachstanica, P. meridiana, P. subovata, P. constans, P. prisca, P. parasimplex, P. paraprisca, Aljutovella bashkirica, A. nibelensis, A. tikhonovichi, A. subaljutovica, A. artificialis, A. aljutovica, A. fallax, A. skelnevatica, A. postaljutovica, A. dilucida, A. wagneri, A.? priscoidea, A. complicata, Citronites postcitronoides, C.? isvarica, C.? cafirniganica, Fusulinella lopasniensis, F. bedakensis, F. praecolaniae, F. fallax, Eofusulina triangula, E. parva, E. binominata, Dutkevichella dutkevichi, Beedeina manucalovae, B.? prima
Podolskian
Fusiella eolancetiformis, Neostaffella khotunensis, N. ivanovi, N. umbilicata, N. ozawai, Taitzehoella prolibrovichi, T. librovitchi, Fusulinella praecolaniae, F. subcolaniae, F. fallax, F. elshanica, F. lata, F. bockiformis, F. meridionalis, F. colaniae, F. protea, F. vozhgalensis, F. tokmovensis, F. longa, F. bocki, F. prolifica?, F. pseudobocki, F. ordinata, F. valida, F. pseudoschwagerinoides, Kanmeraia eopulchra, Beedeina pseudoelegans, B. dunbari, B. elegans, B. callosa, Fusulina rauserae, F. chernovi, F. kamensis, F. rossochanica, F. lucida, Putrella gurovi, P. licharevi, P. korobcheevi, P. n. sp. ( = indet. Fusulinidae), Hemifusulina acuta, H. communis, Dutkevichella? samarensis
Myachkovian
Schubertella donetzica, Taitzehoella tumida, Fusiella praecursor, Fusulinella solida, F. bocki, F. oviformis, F. mosquensis, F. schwagerinoides, F. rosdorica, F. pandae, F. rara, F. valida, F. pseudoschwagerinoides, F. adjuncta, F. loresae, Fusulina nytvica, Hemifusulina bock, H. djartassensis
Vereian
Neostaffella syzranica, Profusulinella integra, P. prisca, P. zhanatanensis, P. carasaica, P. pseudorhomboides, Eofusulina triangula, Paraeofusulina sp.
Kashirian
Pseudostaffella composita, P. gorskyi, Neostaffella ovalis, N. nibelensiformis, N. kamensis, N. pseudoquadrata, N. greenlandica, N. topilini, Schubertella gracilis, S. kulensis, S. acuta, S. magna, Taitzehoella prolibrovichi, T. librovitchi, Staffellaeformes latispiralis, Profusulinella arbejalensis, P. albasensis, P. integra, P. pseudorhomboides, P. ovata, P. biconiformis, P. mutabilis, P. propria, P. kazachstanica, P. meridiana, P. subovata, P. constans, P. prisca, P. parasimplex, P. paraprisca, Aljutovella bashkirica, A. nibelensis, A. tikhonovichi, A. subaljutovica, A. artificialis, A. aljutovica, A. fallax, A. skelnevatica, A. postaljutovica, A. dilucida, A. wagneri, A.? priscoidea, A. complicata, Citronites postcitronoides, C.? isvarica, C.? cafirniganica, Fusulinella lopasniensis, F. bedakensis, F. praecolaniae, F. fallax, Eofusulina triangula, E. parva, E. binominata, Dutkevichella dutkevichi, Beedeina manucalovae, B.? prima
Podolskian
Fusiella eolancetiformis, Neostaffella khotunensis, N. ivanovi, N. umbilicata, N. ozawai, Taitzehoella prolibrovichi, T. librovitchi, Fusulinella praecolaniae, F. subcolaniae, F. fallax, F. elshanica, F. lata, F. bockiformis, F. meridionalis, F. colaniae, F. protea, F. vozhgalensis, F. tokmovensis, F. longa, F. bocki, F. prolifica?, F. pseudobocki, F. ordinata, F. valida, F. pseudoschwagerinoides, Kanmeraia eopulchra, Beedeina pseudoelegans, B. dunbari, B. elegans, B. callosa, Fusulina rauserae, F. chernovi, F. kamensis, F. rossochanica, F. lucida, Putrella gurovi, P. licharevi, P. korobcheevi, P. n. sp. ( = indet. Fusulinidae), Hemifusulina acuta, H. communis, Dutkevichella? samarensis
Myachkovian
Schubertella donetzica, Taitzehoella tumida, Fusiella praecursor, Fusulinella solida, F. bocki, F. oviformis, F. mosquensis, F. schwagerinoides, F. rosdorica, F. pandae, F. rara, F. valida, F. pseudoschwagerinoides, F. adjuncta, F. loresae, Fusulina nytvica, Hemifusulina bock, H. djartassensis

Based on Nikolaev (2011) with some taxonomic modifications.

In the Precaspian Basin, the Late Pennsylvanian is seemingly well developed in the subsurface. Izotova and Shchurkin (1984) noted an outline of the Kasimovian and Gzhelian fusuline succession in several wells of the basin, although they did not show the details. Akhmetshina et al. (2007) recognized seven fusuline biozones in the Kasimovian and Gzhelian interval, although, as in the case of the Moscovian, they simply applied the general zonation widely used in the Russian Platform to the Precaspian Basin succession. These biozones are: the Protriticites pseudomontiparusObsoletes obsoletus, Montiparus montiparus, and Triticites acutusRauserites quasiarcticus zones in the Kasimovian and the Rauserites rossicusRauserites stuckenbergi, Jigulites jigulensis, Daixina sokensis, and Bosbytauella bosbytauensisDaixina robusta zones in the Gzhelian. Among these zonal name-bearing species, only Montiparus montiparus and Rauserites quasiarcticus were illustrated in Akhmetshina et al. (2007). Based on their species list of each zone, the early Kasimovian P. pseudomontiparusO. obsoletes Zone is characterized by Kanmeraia pulchra, Protriticites ovatus, P. subschwagerinoides, Obsoletes dagmarae, O. paraovoides, and the two zonal name-bearers. The assemblage of the M. montiparus Zone contains essentially two genera: Montiparus (M. monriparus, M. paramontiparus, M. umbonoplicatus, and others) and Quasifusulina (Q. longissima, Q. tenuissima, and Q. elegans), with subordinate Protriticites pseudomontiparus and Obsoletes obsoletus. In the late Kasimovian T. acutusR. quasiarcticus Zone, the assemblage consists of Triticites acutus, several Rauserites species (such as R. quasiarcticus), Schwageriniformis (S. schwageriniformis, S. mosquensis, and S. nanus), Rugosofusulina (such as R. prisca), Quasifusulina, and Montiparus sinuosus.

In the early Gzhelian, the Rauserites rossicusR. stuckenbergi Zone has an essentially similar assemblage in generic composition to that of the Triticites acutusRauserites quasiarcticus Zone below, except for the absence of Montiparus and Rugosofusulina, and the two zonal name-bearers newly appeared in it. The middle Gzhelian Jigulites jigulensis Zone bears, besides the zonal marker species, Jigulites dagmarae, J. longus, Rauserites rossicus, R. stuckenbergi, and some other species that occurred in the underlying two zones. Of them, Akhmetshina et al. (2007) illustrated J. longus and J, dagmarae, and also J. ex gr. volgensis, which is probably an element of the middle Gzhelian biozone. In the late Gzhelian, Daixina became predominant, including D. sokensis, D. ruzhencevi, D. vasilkovskyi, and D. vozhgalensis. Other species from the D. sokensis Zone are Quasifusulina cayeuxi, Q. longissima, Rugosofusulina aktjubensis, Jigulites jigulensis, and J. longus. The latest Gzhelian fusuline assemblage in the Bosbytauella bosbytauensisDaixina robusta Zone has several new faunal elements, such as Bosbytauella postgallowayi, B. bosbytauensis, Daixina robusta, Anderssonites anderssoni, A. pseudoanderssoni, Benshiella stabilis, and ‘Occidentoschwagerinakokpectensis, in addition to several species ranging up from the underlying D. sokensis Zone. Of these species, Akhmetshina et al. (2007) illustrated several large schwagerinid specimens including Daixina vasilkovskyi.

Previously, Shcherbovich (1969) reported some Late Pennsylvanian fusulines from this area. She described species from the Gzhelian interval, including Quasifusulina caspiensis, Schwageriniformis schwageriniformis, S. parallelos, Triticites immutabilis, Jigulites magnus, Daixina sokensis, D. enormis, D.? tenuiseptata, Benshiella aff. stabilis, and others.

The Donets Basin (Donbass) in eastern Ukraine contains a continuous succession comprising the entire Carboniferous (Aizenverg et al. 1979b). Shallow-marine to paralic sedimentation was prevalent there throughout this geological period, and rich and diverse marine and continental fossils from the Donbass give this basin an important role as a global chronostratigraphic reference section of the Carboniferous System. In the fusuline study, after Schellwien's (1908) classical work, F. S. Putrya substantially pioneered the taxonomic and biostratigraphic research of the Donets Basin (Putrya 1937, 1938, 1939, 1940, 1947, 1956; Putrya and Leontovich 1948), which was followed by Manukalova (1948, 1950a, b, 1956) and Kireeva (1949, 1950). These works mainly treated latest Bashkirian to earliest Gzhelian ‘large’ fusulines from the Limestone I (C24) to Limestone O (C32) suites in the Carboniferous stratigraphic nomenclatural system of the Donets Basin. Shortly after that, Potievs'ka (Potievskaya) (1958, 1964) studied Bashkirian fusulines systematically from the Limestone E (C15) to Limestone I suites. Mississippian foraminifers, including early fusulines, have also started to be described since the 1950s in the Donets Basin. Vdovenko (1954, 1964, 1971a) studied the most primitive fusuline genus Eoparastaffella in these papers. Moreover, several comprehensive monographic and/or atlas-style volumes including Carboniferous fusulines were published occasionally (Brazhnikova et al. 1967; Manukalova-Grebenyuk et al. 1969; Brazhnikova and Vdovenko 1973; Lapkina 1975; Aizenverg et al. 1983; Vdovenko 2001). These volumes are useful to understand a general picture of the Carboniferous fusuline fauna from the Donbass. Since the beginning of this century, Fohrer et al. (2007) and Khodjanyazova and Davydov (2013) carried out more detailed fusuline biostratigraphic studies in some particular sections, and in addition to them some fusuline species were occasionally described from the Donets Basin (Leven and Davydov 2001; Davydov et al. 2008, Davydov 2011). The following summary of fusuline succession of this basin is based on these studies along with the author's own data, mainly from Moscovian sections. These studies allow establishment of an almost uninterrupted fusuline succession from the latest Tournaisian up to the very end of the Carboniferous (Fig. 17).

The early fusuline succession in the Mississippian is reported by Vdovenko (1954), Brazhnikova and Vdovenko (1973), Aizenverg et al. (1983), and Vdovenko (2001). In the Donets Basin, the fusuline succession starts with the Eoparastaffella assemblage consisting of E. interiecta, E. rotunda, E. subglobosa, and E, asymmetrica in the ‘C1va’ interval in the latest Tournaisian (Brazhnikova and Vdovenko 1973; Devuyst and Kalvoda 2007). This assemblage was followed by the early Visean one, in which Eoparastaffella simplex, E. ovalis, and Eostaffella prisca were newly introduced in the faunal elements. The middle Visean contains only Eostaffella mosquensis and E, prisca, but there is a more diversified assemblage in the late Visean. The latter yields Eostaffella mosquensis, E. proikensis, E. ikensis, E. parastruvei, E. ovoidea, E. ex gr. pseudostruvei, Pseudoendothyra struvei, P. angulata, and several other species. It is interesting to note that Vdovenko (2001) newly described Plectostaffella? eovarvariensis from the late Visean [Limestone B suite (C12)]. This species shows deviation of the coiling axis during growth, like that of late Serpukhovian–early Bashkirian Plectostaffella, but according to Vdovenko (2001) it has a slightly lesser degree of deviation than true Plectostaffella. Thus, the generic assignment of this species is somewhat questionable.

In the Serpukhovian, its early segment corresponding to the Tarusian and Steshevian is marked by the occurrence of Eostaffellina ex gr. paraprotvae, Eostaffella proikensis, E. pseudostruvei, E. parastruvei, E. postmosquensis, E. postproikensis, Pseudoendothyra struvei, P. parasphaerica, and P. illustria. The late Serpukhovian assemblage includes Eostaffella postmosquensis, E. ikensis, E. postproikensis, E. pseudostruvei, E. angusta, E. mirifica, Eostaffellina ex gr. optata, E. schartimiensis, Plectostaffella varvariensis, P. bogdanovkensis, P. varvariensiformis, and others. Overall, Eostaffella and Eostaffellina were predominant throughout the Serpukhovian, and Plectostaffella came into the later part. Partly based on these foraminiferal data, the Zapaltyubian stratotype of the uppermost Serpukhovian substage was settled in the Starobeshevo area in the southern part of the Donets Basin (Aizenverg et al. 1979a).

In the Donets Basin, the base of the Bashkirian, thus the Mid-Carboniferous boundary, is placed at limestone D58 upper in the Limestone D suite (C14) by the first appearance of the conodont Declinognathodus noduliferus (Nemyrovskaya et al. 1990; Nemyrovska 1999; Barrick et al. 2021). The earliest Bashkirian (Bogdanovkian; limestones D58 upper–D78) fusulines also have a somewhat similar specific composition as in the late Serpukhovian and consist of Plectostaffella varvariensis, P. varvariensiformis, P. berestovensis, Eostaffellina ex gr. optata, Eostaffella postmosquensis, E. pseudostruvei, E. angusta, E. exilis, and some Millerella species (M. uralica and M. umbilicata). Fusulines from the post-Bogdanovkian part of the Bashkirian were investigated by Brazhnikova et al. (1967), Potievs'ka (1958), and Potievskaya (1964). Moreover, Ueno and Nemyrovska (2008) and Nemyrovska et al. (2010) reported fusuline and conodont composite biostratigraphy of the Limestone I suite (corresponding to the Asatauian) in some sections in the central part of the Donets Basin. According to these works, the Syuranian (limestones E1–E7) assemblage is composed of Eostaffella postmosquensis, E. pseudostruvei, Eostaffellina paraprotvae, Plectostaffella varvariensis, and Pseudonovella acutissima. Brazhnikova et al. (1967) listed ‘Pseudostaffella ex gr. antiqua’, without illustration, in this interval, but it could potentially be Semistaffella. Foraminiferal data from the Limestone E suite are still scarce over the Donets Basin. The Akavassian (limestones E8–E92) is marked by the first unequivocal occurrence of the genus Pseudostaffella (P. antiqua), and its fusuline assemblage also contains Eostaffella postmosquensis, E. pseudostruvei, E. angusta, E. chomatifera, Eostaffellina paraprotvae, E. protvae, Pseudonovella grozdilovae, Ozawainella umbonata, Millerella uralica, M. umbilicata, Plectostaffella varvariensis, Pseudostaffella compressa, P. praegorskyi, and others. The next Askynbashian (entire Limestone F suite: C21) has the entry of Staffellaeformes staffellaeformis and yields Eostaffella pseudostruvei, E. postmosquensis, Eostaffellina protvae, E. paraprotvae, Plectostaffella varvariensis, Ozawainella alchevskiensis, O. umbonata, Seminovella donetziana, Pseudonovella grozdilovae, Millerella umbilicata, Varistaffella varsanofievae, Pseudostaffella antiqua, P. grandis, P. posterior, P. composita, P. praegorskyi, Staffellaeformes bona, and others.

In the late Bashkirian, fusulines that have a longer axis of coiling than diameter (thus having an oval or fusiform shell, which is typically represented by Profusulinella during this relevant time interval) became more conspicuous. The Tashastian (limestones G1–I1) is defined by the occurrence of Profusulinella rhomboides, P. primitiva, Neostaffella subquadrata, and Ozawainella pararhomboidalis. Other associated species are Eostaffella lepida, E. dolixa, Pseudonovella grozdilovae, P. acutissima, Pseudostaffella praegorskyi, P. gorskyi, P. proozawai, P. krasnopolskyi, Ozawainella umbonata, O. plana, O. alchevskiensis, O. rhombiformis, Schubertella obscura, Staffellaeformes staffellaeformis, S. bona, Profusulinella parva, P. oblonga, and many other species. The Asatauian in the Donets Basin broadly equates to the interval between limestone I2 and the base of the Limestone K suite (C25). This succession is well represented in the Malo-Nikolaevka (Malo-Mikolaivka) and Zolotaya sections in the central part of the Donets Basin (Aizenverg et al. 1975; Ueno and Nemyrovska 2008; Nemyrovska et al. 2010). Characteristic in these sections is the occurrence of Verella cf. transiens, and the following species are also associated: Pseudonovella grozdilovae, P. carbonica, Eostaffella rjasanensis, Ozawainella pararhomboidalis, Neostaffella subquadrata, N. khotunensis, Aljutovella skelnevatica, and Profusulinella pseudorhomboides. Brazhnikova et al. (1967) listed many other species from this interval elsewhere in the Donets Basin, such as Pseudostaffella gorskyi, Schubertella obscura, Profusulinella rhomboides, and Aljutovella ex gr. elongata.

In the early times of fusuline research in the Donets Basin, Moscovian fusulines were intensively investigated by Putrya (1937, 1938, 1956) and Putrya and Leontovich (1948), and many species that are important for biostratigraphy of the relevant age were described in these studies. However, most of Putrya's type specimens are probably lost and unavailable now for reexamination. Fortunately, there are a number of good stratigraphic sections that collectively cover the almost entire Moscovian interval of the basin comprising the Limestones K, L (C26), M (C27), and N (C31) suites. They are also promising for the examination of Moscovian fusuline taxonomy and biostratigraphy in the Donets Basin. These include the aforementioned Malo-Nikolaevka and Zolotaya sections (limestones I2–K3), the Karaguz section (limestones K2–L7), the Izvarino section (limestones L4–M1), the Gurkova section (limestones M1–N1), and the Kalinovo composite section (limestones N2–P5). Stratigraphy of these sections was described by Aizenverg et al. (1975), Fohrer et al. (2007), and Ueno and Nemyrovska (2008). Here, the Moscovian fusuline succession is summarized based mainly on the author's unpublished data along partly with the result from Fohrer et al. (2007) for the upper Kashirian and Khodjanyazova and Davydov (2013) for the uppermost Myachkovian (Fig. 17).

In the Donets Basin, the base of the Moscovian is variably placed, at limestone K1 by Putrya (1956), at limestone K3/K4 by Pogrebnyak in Lapkina (1975), at limestone K3 by Aizenverg et al. (1979b), and at limestone K1? by Solov'eva (1986). Although the base-Moscovian GSSP is not yet settled, limestone K1 where the first certain Eofusulina occurs is provisionally regarded as the base of the Moscovian (Ueno and Nemyrovska 2008; Nemyrovska et al. 2010). This basal position coincides with the first occurrence of the conodont Declinognathodus donetzianus, which is considered to be one of potential markers to define the base of the Moscovian (Nemyrovska et al. 2010; Nemyrovska 2017; Barrick et al. 2021). A Vereian succession (limestones K1–K7) with good fusuline recovery is seen in the upper parts of the Malo-Nikolaevka and Zolotaya and the lower part of the Karaguz sections, which were described by Aizenverg et al. (1975) and Ueno and Nemyrovska (2008). Included in this succession are Eostaffella lepida, Pseudonovella grozdilovae, P. donbassica, P. carbonica, Ozawainella pararhomboidalis, O. pseudotingi, O. mosquensis, O. digitalis, Pseudostaffella ex gr. antiqua, Neostaffella subquadrata, Schubertella obscura, Profusulinella pseudorhomboides, Aljutovella postaljutovica, A. aff. tumida, Eofusulina triangula, E. paratriangula, and Paraeofusulina trianguliformis. Of these, Eofusulina and Paraeofusulina are morphologically peculiar among fusulines at this level and can be good and widely applicable markers for the Vereian.

The Kashirian (limestones K8–L8) is well recognized in the upper part of the Karaguz section (Aizenverg et al. 1975) and the Izvarino section (Fohrer et al. 2007). The following fusulines occur in Kashirian beds: Eostaffella lepida, E. brazhnikovae, Pseudonovella grozdilovae, P. acutissima, P. carbonica, Ozawainella digitalis, O. kumpani, O. pseudotingi, O. minima, O. pseudoangulata, O. krasnokamski, O. mosquensis, Schubertella obscura, S. lata, Taitzehoella prolibrovichi, T. librovitchi, Pseudostaffella minutissima, P. compressa, Neostaffella khotunensis, N. ozawai, N. larionovae, Profusulinella constans, P. pseudorhomboides, P. convoluta, Aljutovella postaljutovica, A.? priscoidea, Citronites notabilis, Fusulinella schubertellinoides, Kanmeraia subpulchra, Eofusulina paratriangula, Beedeina schellwieni, Dutkevichella pseudobocki, D. moelleri, D. vozhgalica, and Putrella cf. donetziana. In this study, the lower boundary of the Kashirian is placed provisionally at limestone K8 where Citronites notabilis, the first fusulinellin species having a distinct diaphanotheca in the spirotheca, appears (Fig. 10). It is interesting to note that in the early Kashirian, there happened an evolutionary change in the spirotheca, from the three-layered wall to four-layered one, almost at the same time in some distinct phylogenetic groups in the family Fusulinidae (Fig. 10). In the Kashirian interval of the Donets Basin, Citronites, Kanmeraia, Aljutovella, and several large Neostaffella, together with Eofusulina paratriangula, are characteristic of its lower part. In the upper part, Fusulinella, Beedeina, and Dutkevichella species showed new entries to the assemblage. The boundary between the Kashirian and Podolskian by fusulines is established in the Izvarino section and is placed at limestone M1. Nevertheless, it is worth mentioning that there is a distinct discrepancy between conodonts and fusulines, in correlating the strata of the Limestones L and M suites in the Donets Basin to the international chronostratigraphic scale of the Moscovian (Fohrer et al. 2007).

The Podolskian corresponds to the interval between limestone M1 and limestone M9, and is well exposed in the Gurkova section (Aizenverg et al. 1975). The assemblage includes Eostaffella mutabilis, E. grandis, Pseudonovella grozdilovae, Ozawainella mosquensis, O. stellae, Pseudostaffella krasnopolskyi, Neostaffella ozawai, N. umbilicata, N. syzranica, N. larionovae, N. confusa, Schubertella obscura, S. lata, Taitzehoella prolibrovichi, T. librovitchi, T. perseverata, Fusulinella colaniae, F. pseudocolaniae, Beedeina paraozawai, B. ozawai, B. samarica, Putrella brazhnikovae, and Fusulina? aff. rauserae. The genera Fusulinella, Beedeina, Taitzehoella, and Neostaffella are common elements of the Podolskian fusuline assemblage in the Karaguz section, and the first, likely Fusulina species (F.? aff. rauserae), appears in limestone M6 and Putrella brazhnikovae occurs in limestone M9.

The base of the Myachkovian in the Gurkova section is placed at limestone M10 in this study. Khodjanyazova and Davydov (2013) investigated the same section and suggested to put the base above limestone M10 (thus between limestones M10 and N1). This limestone contains, apart from small fusulines (such as Pseudonovella, Ozawainella, and Schubertella), Fusulinella rara, F. kumpani, Hemifusulina bocki, Beedeina sp., and Fusulina rossoschanica. The association of F. rara, F. kumpani, and H. bocki is characteristic in the early Myachkovian in the Moscow Syneclise (Rauzer-Chernousova et al. 1951; Makhlina et al. 2001b). Fusulina rossoschanica is an endemic species, but its shell features (large cylindrical shell with large proloculus, strongly fluted septa, absence of axial fillings) suggest that this species could possibly be phylogenetically an ultimately advanced member in the Fusulina chernoviF. kamensis lineage. These latter two species are known from late Podolskian strata in the Moscow Syneclise, Samarskaya Luka, and the Urals (Rauzer-Chernousova et al. 1951; Makhlina et al. 2001b). Thus, an early Myachkovian age is more likely for limestone M10, rather than late Podolskian.

Moscovian–Kasimovian transitional strata, between limestone N1 and limestone O2, are well exposed in the topmost part of the Gurkova section and the lower part of the Kalinovo section (Aizenverg et al. 1975). Khodjanyazova and Davydov (2013) described fusulines from the lower part of the Limestone N suite (C31), between limestones N1 and N21. According to them this interval is characterized by Ozawainella krasnokamski, O. vozhgalica, Neostaffella sphaeroidea, Fusiella spatiosa, Taitzehoella perseverata, Fusulinella rara, F. pseudobocki, F. cf. bocki, Hemifusulina bocki, H. stabilis, Beedeina cf. paradonetzica, Fusulina cylindrica, F. innaeformis, F. domodedovi, F. quasifusulinoides, and several others. The stratigraphic interval between limestones N1 to N21, just before the entry of Protriticites, Obsoletes, and Quasifusulinoides in limestone N3, is correlated to the Fusulina cylindrica Zone of the Moscow Basin, so it is of the middle part of the Myachkovian (Makhlina et al. 2001b).

In Kalinovo, limestone N3 consists of several subordinate limestone beds, and the major limestone at the base (limestone N3) contains Pseudonovella sp., Schubertella sp., Quasifusulinoides fusulinoides, and primitive Protriticites identifiable as P. parvus. In overlying limestone N33, the following species are recognized: Eostaffella? sp., Ozawainella cf. krasnokamski, Fusiella spatiosa, Schubertella sp., Pseudostaffella sp., Obsoletes? cf. lamellosus, Protriticites parvus, and P. plicatus. The last species well exhibits a porous feature in a translucent diaphanotheca and is considered as an advanced (typical) form of the genus. These data conclude that limestone N3, which is represented by primitive Protriticites, is better referable to the late/latest Myachkovian (Peskovian) and limestone N33 marks the base of the Kasimovian by fusulines, in the Kalinovo section, and thus is correlated to the Krevyakinian. Putrya (1939) described Pseudotriticites donbassicus from core samples obtained in the eastern outskirts of the Donets Basin. Although its stratigraphic position is not clearly settled in the modern stratigraphic scheme of the Donets Basin, this species is also possibly a faunal element of the Krevyakinian fusuline assemblage of the basin. Among conodonts, the Kasimovian in the Kalinovo section is considered to start with the first appearance of Idiognathodus sagittalis and I. neverovensis at limestone N51 (Barrick et al. 2021). This limestone, which is the next exposed one above limestone N33 and composed of several layers, consists of impure muddy limestone and does not contain large fusulines.

The next fusuline-producing level in the Kalinovo section is represented by limestone O1. This level bears abundant Obsoletes ex gr. obsoletes (O. gapeevi, O. elongatus, and O. magnus) along with Fusiella cf. rawi, Quasifusulinoides juvenatus, Obsoletes? (or Montiparus?) cf. praemontiparus, and also likely primitive Montiparus species. The occurrence of the genus Montiparus suggests that limestone O1 is referable to the Khamovnikian of the middle Kasimovian, but it is probably to the earliest part of the Khamovnikian, close to the Krevyakinian–Khamovnikian boundary. The next limestone O2 is also productive for fusulines and is correlated to the middle Kasimovian (late Khamovnikian). Several typical (and advanced) Montiparus species (M. montiparus, M. umbonoplicatus, and M. subcrassulus) abundantly occur, which are accompanied by Fusiella lancetiformis, Quasifusulinoides parafusiformis, and Triticites sp. Davydov and Khodjanyazova (2009) illustrated Schwageriniformis sp. at this level, but it is probably better referable to Triticites, judging from its gross shell morphology.

In the Kalinovo section, limestones O3–O6 contain Quasifusulina elongata (from limestone O3), Rauserites protorossicus (from limestone O4), Rauserites ofive (from limestone O5), and Schwageriniformis sp. and Rauserites shikhanensis (from limestone O6), among which those from limestones O4 and O5 were described by Davydov et al. (2008). The limestones O3–O6 interval is correlated to the late Kasimovian (Dorogomilovian).

The base of the Gzhelian is placed at limestone O7, which contains abundant Rauserites rossicus. This species is known to mark the base of the Gzhelian at the stratotype of the stage in the Moscow Basin (Alekseev et al. 2009). In the Gzhelian of the Donets, fusuline information is sporadic, but from limestone P2 in the Kalinovo section, which is situated up-section from basal Gzhelian limestone O7, Davydov (1990a), Leven and Davydov (2001), and Davydov (2011) described and/or illustrated Darvasoschwagerina donbasica, Schagonella procera, S. aff. cylindrica, and three ‘undersized’ Triticites: T. zhikalyaki, T. poletaevi, and T. ex gr. tshelamtshiensis. From the overlying limestones P3 and P4 in the Kalinovo section, Davydov (1990a) illustrated Jigulites magnus, J. netchaevi, and Daixina vasilkovskyi. Moreover, elsewhere in the Donets Basin, Davydov (1990a) and Davydov et al. (1992) reported in a borehole section Daixina vasilkovskyi from a level correlated to limestone P4 and Bosbytauella bosbytauensis and several ‘Occidentoschwagerina’ species (including ‘O.’ chatcalica) from an interval between P5 to Q9, respectively. These strata, comprising the Limestones P (C33) suite above limestone P3 and Q (Kartamysh) suite, are better referable to the late/latest Gzhelian in view of the occurrence of advanced Daixina and Bosbytauella (Chuvashov et al. 1986; Davydov 1988a). Leven and Davydov (2001) and Davydov (2011) considered limestone P2 in the Kalinovo section to be early Gzhelian, but the above-mentioned age estimate for limestones P3 and P4 suggests that it is probably already of the middle Gzhelian.

In conclusion, an almost uninterrupted Carboniferous fusuline succession ranging from the late Tournaisian to the late/latest Gzhelian is established in Donets Basin strata (Fig. 17). Thus, the basin has one of the best records for fusuline biostratigraphy in the world. The Donets Basin can be an important source of information when considering the Carboniferous timescale based on this microfossil group.

Most of the Carboniferous fusulines in the Carnic Alps come from a post-Variscan sedimentary cover in the Kasimovian–Gzhelian Auernig Formation and upward succession. Pre-Variscan Carboniferous strata are mainly represented by clastics (Corradini et al. 2015), and foraminiferal occurrence is restricted to some thin carbonate intercalations at a few levels.

After the first description of Carboniferous fusulines from the Carnic Alps by Schellwien (1898), Franz and Gustava Kahler progressed taxonomic and biostratigraphic researches on post-Variscan, Late Pennsylvanian–early Permian fusulines of this region and established their frameworks (Kahler and Kahler 1941, 1982; Kahler 1983; 1985). Upon these studies, Forke et al. (1998, 2006), Krainer and Davydov (1998), Davydov and Krainer (1999), Forke and Samankassou (2000), and Forke (2002) further developed a refined Pennsylvanian fusuline biostratigraphy in this area. The following account for the Carnic Alps fusuline succession is mainly based on the most recent study by Forke et al. (2006), which is schematized in Fig. 17. According to them, Pennsylvanian fusulines are restricted to the Kasimovian and Gzhelian in this area.

Fusulines of this subperiod were reported from several levels in the Carnic Alps (Fig. 17). Amler et al. (1991) and Krainer and Vachard (2015) documented a foraminiferal assemblage of late Visean age (MFZ14 of Poty et al. 2006) from the Kirchbach Limestone within the siliciclastic Hochwipfel Formation. It contains Eostaffella cf. parastruvei. An early Serpukhovian (Steshevian) foraminiferal assemblage was known from exotic limestone clasts of the Badstub Formation distributed in the Nötsch area. Vachard et al. (2018a) identified such fusulines as Eostaffella aff. postproikensis, Eostaffellina cf. paraprotvae, and Pseudoendothyra aff. nodus in that assemblage. Moreover, Krainer and Vachard (2002) reported late Serpukhovian (Zapaltyubian) foraminifers from limestone intercalations of the Erlachgraben and Nötsch formations. In fusulines, Eostaffella chomatifera, E. ex gr. postmosquensis, and Plectostaffella? sp. were identified from the assemblage.

In the Carnic Alps, post-Variscan Carboniferous fusulines came from the siliciclastic/carbonate-alternating Auernig Formation and the overlying predominantly carbonate Schulterkofel Formation (Schönlaub and Forke 2007). The latter formation has often been referred to as the ‘Lower Pseudoschwagerina Limestone’ in previous studies (e.g. Forke et al. 1998). These Carnic Alps strata further extend to the Karavanke Mountains in Slovenia (Forke 2002). In the succession the first post-Variscan fusuline assemblage was found from the base of the Auernig Formation distributed in the Zollnersee–Straniger Alm area (Davydov and Krainer 1999; Forke and Samankassou 2000). The assemblage consists of Ozawainella mosquensis, Fusiella aff. lancetiformis, Schubertella donetzica, Pseudotriticites asiaticus (probably the same as what was identified as Beedeina species by Davydov and Krainer 1999), Quasifusulinoides juvenatus, and Protriticites aff. permicus. An early Kasimovian Krevyakinian age is proposed for this stratigraphic interval based on combined conodont and fusuline biochronology, as well as a comprehensive regional stratigraphic study (Forke and Samankassou 2000).

The middle Kasimovian is divided into two assemblages, which are characterized by primitive and advanced Montiparus species, respectively (Fig. 17). The lower one contains Ozawainella mosquensis, Fusiella cf. rawi, Schubertella donetzica, Montiparus pramollensis, Obsoletes inflatus, and Protriticites aff. ovatus. The upper assemblage consists of Montiparus subcrassulus. The next younger assemblage is found from the ‘Pizzul’ Member of the lower part of the Auernig Formation. It contains Ozawainella cf. kumpani, Quasifusulina eleganta, Tumefactus aff. expressus, and Rauserites ex gr. rossicus. In addition to these species, Ferganites ferganensis and ‘R. rossicus’ reported by Krainer and Davydov (1998) from the very top of the ‘Meledis Formation’, which was correlated to the early Gzhelian by them, are also included in this assemblage. Rauserites ex gr. rossicus from the Carnic Alps is morphologically comparable to Rauserites protorossicus and R. ofive described by Davydov et al. (2008) from the late Kasimovian of the Donets Basin (Fig. 17). Moreover, as noted in the following section, a similar assemblage containing Ferganites and Tumefactus is also known in the late Kasimovian of the Cantabrian Mountains in northern Spain. Thus, the ‘Pizzul’ assemblage is better referred to the late Kasimovian (Fig. 17).

In the upper part of the Auernig Formation, there are sporadic occurrences of fusuline-bearing limestone beds in the ‘Watschiger’, Corona, ‘Auernig’, and Carnizza members, which were eventually clarified to be of the Gzhelian. The first assemblage coming from the ‘Watschiger’/Corona interval consists of Schagonella and Daixina, but details are not reported. This assemblage is possibly referable to around the early–middle Gzhelian boundary age. The ‘Auernig’ and Carnizza members contain the Daixina alpinaDutkevitchia multiseptata and Daixina communis assemblages, respectively. These units contain several species that were originally described by Schellwien (1898) from the Carnic Alps and are frequently seen in later publications, but the types have been lost already. Forke (2007) re-described them based on topotype materials, which helps to understand these species in the modern taxonomic framework. The former assemblage is possibly correlated to the middle–late Gzhelian boundary age. The latter one also contains Triticites cf. immutabilis and two other unspecified Triticites species (Forke 2007). Forke et al. (2006) considered the Daixina communis assemblage to be of the Noginskian in the late Gzhelian.

The Auernig Formation is overlain conformably by the Schulterkofel Formation, and three fusuline assemblages are recognized in the latter. They are the Ruzhenzevites parasolidus, Bosbytauella postgallowayi, and Schwagerina versabilis assemblages (Fig. 17). Found also in the first assemblage are Ruzhenzevites ferganensis, Dutkevitchia expansa, and Quasifusulina cf. paracompacta. The second one contains, besides the marker species, Bosbytauella bosbytauensis, Rugosochusenella pseudogregaria, Benshiella arianica, B. stabilis, B. longa, and Daixina spp. The Schwagerina versabilis assemblage straddles the Carboniferous–Permian boundary. ‘Occidentoschwagerina’ alpina, ‘O.’ n. sp., Benshiella arianica, and Schwagerina? sp. occur together with S. versabilis. Kahler and Krainer (1993) investigated the same Schulterkofel section and identified several more Triticites and Rugosofusulina species from the Ruzhenzevites parasolidus and Bosbytauella postgallowayi interval. The mentioned three assemblages are correlated altogether to the latest Gzhelian (Melekhovian) and are equivalent to the Daixina robustaBosbytauella bosbytauensis Zone in the (Southern) Urals and the Daixina robusta–‘Likharevitesinsolita Zone in the Moscow Syneclise (Fig. 15).

In Central Europe, a Tournaisian–Visean boundary succession at Mokrá in the Moravian Karst area, Czech Republic, provided a good record of the Eoparastaffella assemblage (Kalvoda et al. 2010). The latest Tournaisian interval corresponding to MFZ8 (Poty et al. 2006) contains Eoparastaffella parvula, E. rotunda, and E. vdovenkoae. From strata just above the boundary, which are correlated to the basal Visean MFZ9, the entry of E. simplex was observed, and E. interiecta, E. ex gr. florigena, and several other Eoparastaffella species characterize this interval. In Poland, Głuszek and Tomaś (1993) illustrated Eoparastaffella of early Visean age from the Sudetes Mountains, and a late Visean foraminiferal assemblage including Eostaffella mosquensis, E. ikensis, and Pseudoendothyra bona was reported from nearby Krakow (Soboń-Podgórska 1972; Alexandrowicz and Mamet 1973). In the Lublin Coal Basin in southeastern Poland, late Visean to Bashkirian fusulines consisting of Eostaffella radiata, E. irinae, Pseudoendothyra ornata, P. concinna, Ozawainella alchevskiensis, Pseudostaffella antiqua, P. praegorskyi, Staffellaeformes staffellaeformis, Profusulinella parva, and others occurred in borehole samples (Skompski and Soboń-Podgórska 1980; Dembowski and Porzycki 1988; Skompski et al. 1989).

In Western Europe, an extensive shallow sea covered its northern part during Mississippian time, and foraminifer-bearing Dinantian strata were widely formed there. Today, Dinantian outcrops extend from western Germany to Ireland through Belgium, northern France, and Britain. Devuyst and Hance in Poty et al. (2006) established a standard Mississippian foraminiferal zonation (MFZ) based on foraminiferal biostratigraphic data from Belgium and northern France. This biostratigraphic scheme can be widely utilized for Mississippian biochronology and correlation in Eurasian Carboniferous stratigraphy. In southern Belgium and northern France, Conil and Lys (1964), Mamet (1973), Groessens et al. (1979), and Hance (1988) described and illustrated Tournaisian and Visean diverse foraminifers yielding a few fusulines. Summarizing the occurrences, the Moliniacian (possibly including the latest Ivorian) assemblage consists of Eoparastaffella spp., and Eostaffella parastruvei; the Livian contains Eostaffella mosquensis, E. parastruvei, E. optata, Pseudoendothyra struvei, and P. rossica; and the Warnantian assemblage is composed of Eostaffella proikensis, E. mosquensis, and E. parastruvei.

In the British Isles, a latest Tournaisian–early Visean foraminiferal assemblage characterized by Eoparastaffella was described by Kalvoda et al. (2011) from Ireland. The latest Ivorian (MFZ8) contains Eoparastaffella macdermoti, E. ovalis, E. ex gr. interiecta, and E. florigena together with many other non-fusuline foraminifers. The Moliniacian assemblage consists of Eoparastaffella simplex, E. restricta, E. ovalis, E. ex gr. florigena, E. ex gr. interiecta, and Eostaffella sp. Kalvoda et al. (2021) also reported a rich foraminiferal succession of the Tournaisian--Visean boundary interval, including several Eoparastaffella species, from Britain. Middle–late Visean foraminifers were reported by Conil et al. (1980) and Cózar and Somerville (2004, 2012). They yield such fusulines as Eostaffella parastruvei in the Livian and Eostaffella mosquensis, E. mutabilis, E. proikensis, E. parastruvei, E. pseudostruvei, Pseudoendothyra sublimis, and P. concinna in the Warnantian. Then, Cózar et al. (2010) and Cózar and Somerville (2016, 2020) identified the following fusulines from the Serpukhovian equivalent of Great Britain: Eostaffella postmosquensis, E. mirifica, E. angusta, E. mosquensis, Eostaffellina protvae, E. paraprotvae, E. schartimiensis, Plectostaffella reitlingerae, P. varvariensis, P. varvariensiformis, P. decurta, P. ignorabilis, P. serpuchovia, P. mira, and several others. Basal Bashkirian fusulines are represented by the Plectostaffella assemblage that contains P. bogdanovkensis, P. characticus, P. jakhensis, P. minima, P. asiaticus, and P. varvariensiformis (Cózar and Somerville 2016).

Outside the Western European Dinantian outcrop belt described above, Early Carboniferous foraminifers have been known from the Montagne Noire and the neighbouring Mouthoumet Massif in southern France (Mamet 1968a; Vachard 1977; Vachard et al. 2016, 2018b). Most foraminifers are of non-fusuline taxa, but the following fusuline species were documented by Vachard (1977) and Vachard et al. (2016, 2018b): Eoparastaffella iniqua and E. florigena from the latest Tournaisian; Eoparastaffella simplex, E. iniqua, E. florigena, and Eostaffella spp. from the early Visean; Eoparastaffella simplex, E. vdovenkoae, E, iniqua, Eostaffella parastruvei, E. excavata from the middle Visean; Eoparastaffella ex gr. florigena, Eostaffella ikensis, E. proikensis, E. mosquensis, E. acuta, E. tenebrosa, E. parastruvei, E. excavata, Pseudoendothyra sublimis, P. illustria, P. struvei, and P. angulata from the late Visean; and Eostaffella parastruvei, E. mosquensis, E. ikensis, E. tenebrosa, Pseudoendothyra sublimis, Eostaffellina decurta, E. actuosa, and E. protvae from the early Serpukhovian. It is worthy of a special mention that Vachard et al. (2018b) recognized the occurrence of Eoparastaffella from the middle and even late Visean (Livian and Warnantian) parts of the succession, although the illustrated Eoparastaffella specimens all came from the Moliniacian and Livian.

The Carboniferous strata of the Cantabrian Zone, located in the northern part of the Iberian Massif, had been formed in a large marine foreland basin during the pre- and syn-orogenic phases of the Variscan deformation, which took place by the collision of Laurussia and Gondwana in the late Devonian–Carboniferous (Bahamonde et al. 2015). This mountain area contains the most complete Carboniferous succession in Western Europe. Fusulines from the area are mostly of the Pennsylvanian, but Mississippian assemblages have been reported recently. In the Iberian Peninsula, there are some other fusuline reports, which are also briefly noted in the last part of this section.

The Mississippian is mostly represented by a deeper-marine, thin, condensed cephalopod-bearing succession, but Late Mississippian to earliest Pennsylvanian, foraminifer-bearing shallow-marine platform sediments were discovered in the Alba and Barcaliente formations (and their equivalent local stratigraphic units) in the Picos de Europa area of the eastern Cantabrian Zone (Cózar et al. 2015, 2016b; Sanz-López et al. 2018). These reports indicate latest Visean to early Bashkirian (up to the Syuranian) successive foraminiferal assemblages (Fig. 17).

In the latest Visean only Eostaffella spp. were listed. Early Serpukhovian fusulines are Eostaffella mosquensis, E. ex gr. pseudostruvei, and Eostaffellina decurta?. The late Serpukhovian contains more species, consisting of Eostaffella mosquensis, E. ovoidea, E. oblonga, E. postmosquensis, E. proikensis, E. tenebrosa, E. postproikensis, E. pseudostruvei, Eostaffellina decurta, E. schartimiensis, E. paraprotvae, E. ‘protvae’, E. actuosa, Plectostaffella varvariensis, P. seslavica?, and others. As in many other Palaeotethyan areas, the Serpukhovian fusuline fauna in the Cantabrian Mountains is characterized by dominating Eostaffella and Eostaffellina throughout, and the entry of Plectostaffella marks the late Serpukhovian.

A continuous faunal succession representing each substage is observed in the Bashkirian in the Cantabrian Zone (Fig. 17). The Bogdanovkian fusuline assemblage has not been well characterized in this area, and Eostaffella post mosquensis, E. spp., Plectostaffella jakhensis, P. reitlingerae, P. varvariensis, and P. minima were merely listed in Sanz-López et al. (2018). Then, the Syuranian succession records the first Semistaffella and Ozawainella, and also bears Eostaffella postmosquensis, E. prisca, E. chomatifera?, Eostaffellina paraprotvae, E. decurta, E. actuosa, Plectostaffella bogdanovkensis, P. jakhensis, P. varvariensis, P. varvariensiformis, and several others (Sanz-López et al. 2018).

Since the deposition of Barcaliente strata of late Serpukhovian–early Bashkirian age, complex development of sedimentation in the Cantabrian Foreland Basin had commenced in this region, including the formation of very thick (reaching to c. 8000 m) siliciclastic-dominant foredeep sediments of the Central Asturian Coalfield in a rapidly subsiding proximal sector of the basin, accompanying several large carbonate platforms in the distal area. Merino-Tomé et al. (2017) depicted a schematic image on how the sedimentation of different elements took place spatio-temporally in this large foreland basin. Due mainly to prevailing shallow-marine sedimentation, post-Syuranian fusuline-bearing strata are more widely recognized in various sections and localities showing different stratigraphic features over the Cantabrian Zone, and they developed successive, Akavassian to Asatauian fusuline assemblages (van Ginkel 1965, 1987; Villa 1995; Villa et al. 2001; Villa and Merino-Tomé 2016; Fig. 17). Of them, Akavassian fusulines include several species that are common in the underlying early Bashkirian (such as Eostaffella cf. postmosquensis, Eostaffellina ex gr. protvae, and Plectostaffella cf. jakhensis) but also denote the first occurrence of the genus Pseudostaffella (Pseudostaffella antiqua, P. ex gr. compressa, and P. cf. paracompressa). Then, Staffellaeformes ex gr. staffellaeformis appears first in the next Askynbashian interval, together with Ozawainella ex gr. alchevskiensis and Pseudostaffella grandis.

The Tashastian (early late Bashkirian) shows a more diversified fusuline assemblage characterized by the first occurrence of Profusulinella (P. ex. gr. parva, P. primitiva, P. cf. oblonga, and P. cf. pararhomboides). Other species found are Eostaffella cf. parastruvei, Ozawainella ex gr. aurora, O. aff. paraumbonata, Millerella cf. gruenewaldti, Pseudostaffella ex gr. proozawai, P. ex gr. gorskyi, Staffellaeformes staffellaeformis, and S. staffelloides. In this interval, Pseudostaffella and Profusulinella species are conspicuous among the assemblage, and, in contrast, Eostaffella that had predominated in early Bashkirian time became less abundant. The latest Bashkirian Asatauian is marked by the first appearance of Aljutovella (A. asturiensis, A. nibelensis, A. wagneri, A. lazarensis, A. cf. extensa, A. cf. porrecta, and several other species), Eowedekindellina solovievae, and its descendant Verella (V. spicata and V. transiens). Other species associated in the Asatauian assemblage are Ozawainella cf. pararhomboidalis, O. ex gr. mosquensis, Schubertella ex gr. obscura, Staffella breimeri, Nankinella carmenesensis, Neostaffella cf. latispiralis, Staffellaeformes staffellaeformis, Profusulinella sitteri, P. martinezi, P. ex gr. parva, P. cf. postpararhomboides, P. ex gr. rhomboides, and others.

Villa and Merino-Tomé (2016) assigned the Verella transiens interval to the early Vereian (early Moscovian), in correlating it to the Profusulinella prisca Zone in the South Urals (Kulagina 2008, 2009). As already noted in the preceding section, there are still some uncertainties to correlate the Bashkirian–Moscovian boundary interval using P. prisca, and in this case it might result in making the definition and correlation of the base-Moscovian by fusulines more confused. Moreover, a similar form to V. transiens occurs in the Donets Basin just below the level including the first Eofusulina species together with Declinognathodus donetzianus, which is one of potential marker conodonts for the base of the Moscovian (Ueno and Nemyrovska 2008; Nemyrovska et al. 2010; Nemyrovska 2017; Barrick et al. 2021). Thus, a stratigraphic interval represented by the occurrence of Verella transiens is provisionally regarded as part of the Bashkirian (Asatauian) in this study.

The Moscovian is well developed in the Cantabrian Mountains, and its fusulines have been extensively studied since the middle of the last century (van Ginkel 1965, 1973, 1983; van Ginkel and Villa 1991, 1999; Villa 1995; Villa and van Ginkel 2000; Villa et al. 2015; Merino-Tomé et al. 2020; Villa et al. 2021). In these studies, fusuline biostratigraphy and correlation have been generally considered in a chronostratigraphic framework based on four standard Russian Moscovian substages. They allow establishment of a well-correlated and refined fusuline succession throughout the stage (Fig. 17).

The Vereian assemblage includes variable Profusulinella (P. pseudorhomboides, P. albejalensis, P. cf. parva, P. prisca, and P. posadai), Aljutovella (A. artificialis, A. cybaea, and A. cf. skelnevatica), and eofusulinins (Eofusulina cf. triangula, E. rasdorica, and Paraeofusulina cf. trianguliformis), accompanied by Pseudonovella grozdilovae, Schubertella ex gr. obscura, Ozawainella cf. pararhomboidalis, and Neostaffella subquadrata. Kashirian fusulines are still dominated by Profusulinella (P. pseudorhomboides, P. cf. paratimanica, P. cf. guebleri, P. ovata, P. nytvica, and P. cf. constans) and Aljutovella (A.? cf. priscoidea, A. dilucida, and A. cf. parasaratovica) throughout. Eofusulina cf. triangula and P. cf. trianguliformis, ranging upward from the Vereian, are restricted to the lower part. In the upper part, Taitzehoella prolibrovichi, T. librovitchi, Neostaffella ex gr. parasphaeroidea, Fusulinella ex gr. schubertellinoides, F. ginkeli, F. delepinei, Hidaella kameii, Kanmeraia subpulchra, Dutkevichella ex gr. moelleri, Beedeina bona, and B. ex gr. schellwieni newly appeared in the assemblage. Small fusulines, such as Pseudonovella grozdilovae and Schubertella ex gr. obscura, continuously occur, and Neostaffella cf. topilini is also diagnostic in the Kashirian. In this interval, the lower part still retained some features of the Vereian assemblage, but in the upper part several new genera (Taitzehoella, Fusulinella, Kanmeraia, Hidaella, Beedeina, and Dutkevichella) joined the faunal elements.

In view of the generic composition, the Podolskian fusuline assemblage is somewhat similar to that of the late Kashirian, but Profusulinella and Aljutovella species mostly disappeared at the Kashirian–Podolskian boundary, and Fusulina newly appeared in the late Podolskian. Major constituent species recognized in this interval are Ozawainella stellae, Neostaffella ozawai, Schubertella ex gr. obscura, Fusiella cf. typica, Taitzehoella prolibrovichi, Fusulinella pandae, F. ginkeli, F. ex gr. colaniae, F. ex gr. praebocki, F. cf. pseudobocki, F. ex gr. bocki, Beedeina truyolsi, B. ex gr. schellwieni, B. ex. gr. ozawai, B. ex gr. elegans, Putrella brazhnikovae, Fusulina agujasensis, and F. ex gr. kamensis. Myachkovian strata and fusulines are also well recognized in the Cantabrian Mountains. There are several diagnostic Fusulinella species that are restricted to the early Myachkovian. They are F. alvaradoi, F. loresae, F. branoserae, and F. ex gr. mosquensis. Associated with them are Ozawainella cf. magna, Neostaffella cf. rostovzevi, Taitzehoella perseverata, Putrella species with clear development of porous spirotheca, Pseudostaffella sp., Hemifusulina aff. bocki, Beedeina ex gr. elegans, B. cf. samarica, B. cf. paradistenta, Fusulina aff. pankouensis, and others including smaller forms (such as Pseudonovella, Schubertella, and Fusiella). Hemifusulina mosquiterensis described by van Ginkel (1973) is also probably one of the elements in the early Myachkovian assemblage. Nevertheless, there seems to exist some practical difficulties to distinguish the late Podolskian fusuline assemblage from the early Myachkovian one in the Cantabrian Mountains, as van Ginkel (1965) often noted ‘either top of Podolskian or base of Myachkovian’ in estimating the age of fusuline assemblages of this interval from respective localities.

It has been known by some earlier studies that fusulines representing the Moscovian–Kasimovian transitional interval (late/latest Myachkovian–Khamovnikian corresponding to the Protriticites and Montiparus fusuline genus zones) occur in the Cantabrian Mountains (van Ginkel 1965, 1971; van Ginkel and Villa 1991). However, these authors studied in most cases a short section and/or several isolated localities, which made it difficult to discuss biostratigraphy and faunal succession within a unified stratigraphic scheme. There are not many good sections covering this important interval for fusuline biostratigraphy and evolution in the Cantabrian Mountains. It is due mainly to the reason that, by changing tectonic regimes in the course of the Variscan orogen, from the pre-tectonic to syn-tectonic deformation stages, marine sedimentation became more restricted in the Cantabrian Foreland Basin after late Moscovian time (Merino-Tomé et al. 2017). Subsequently, the Las Llacerias section and sections in the Ándara Massif were examined in detail, and fusuline successions of the relevant time interval were described in them (van Ginkel and Villa 1999; Villa and van Ginkel 2000; Villa et al. 2015; Merino-Tomé et al. 2020; Fig. 17).

In these two sections, the Fusulinella Zone (Fusulinella alvaradoi Subzone) of late Moscovian age, described above, is succeeded by the Protriticites Zone. The taxonomic composition of the latter zone is different between the Las Llacerias and Ándara Massif sections, but the following species can be mentioned as important faunal elements: Ozawainella aff. rhomboidalis, O. ex gr. angulata, Fusiella cf. lancetiformis, Pseudostaffella sp. (‘Quasistaffella’ of Solov'eva 1986), Protriticites grajalensis, P. quasiovoidalis, P. benshae, P. cf. ovatus, P. cf. pseudomontiparus, P. cf. manukalovae, P. aff. vetus, P. aff. globulus, P. ex gr. subschwagerinoides, P. ex gr. grozdilovae, Obsoletus cf. obsoletus, Pseudotriticites cantabricus, P. aff. asiaticus, and Quasifusulinoides parafusiformis. Van Ginkel and Villa (1999) and Villa et al. (2015) considered that within the Protriticites Zone, the first occurrence of ‘typical’ Protriticites defined the base of the Kasimovian. These species show clearer development of porous structure in the spirotheca and are represented by P. cf. pseudomontiparus in the Las Llacerias section and by P. grajalensis, P. cf. manukalovae, and P. ex gr. grozdilovae in the Ándara Massif sections. In view of fusuline palaeobiogeography, the combined occurrence of Protriticites, Pseudotriticites, and Quasifusulinoides is a diagnostic feature in the Protriticites Zone of the Cantabrian Mountains. Co-occurrence of these three genera is also known in Central Asia (Bensh 1972; Orlov-Labkovsky and Bensh 2015), the Carnic Alps (Davydov and Krainer 1999; Forke and Samankassou 2000), and the Donets Basin (Putrya 1939, 1940).

The Protriticites Zone is overlain conformably by the Montiparus Zone. In the latter zone Fusiella rawi, Ozawainella rhombiformis, Montiparus ex gr. umbonoplicatus, M. fischeri, M. paramontiparus, Triticites leciae, Quasifusulina praecursor, Pseudotriticites sp., and others constitute the assemblage. It is worth noting that Triticites (T. leciae) occurs in the uppermost part of the Cantabrian Montiparus interval, suggesting that this level is already very close to the Dorogomilovian. Moreover, the occurrence of Fusiella rawi in the Montiparus Zone, as well as that of F. cf. lancetiformis in the Protriticites Zone, is also important because these large and peculiar Fusiella species are known to characterize the early–middle Kasimovian interval elsewhere in the Palaeotethyan and Russian Platform areas (see sections of the Moscow Syneclise, Donets Basin, Carnic Alps, and Iran).

Details of fusulines in these ages were so far only reported from some sections of the Puentellés Formation distributed in the Covadonga–Arenas de Cabrales area (Picos de Europa Unit) in the eastern part of the Cantabrian Zone (van Ginkel 1971; Villa and van Ginkel 1999; Villa and Bahamonde 2001; Villa and Ueno 2002; Villa et al. 2003; Fig. 17). Reflecting dominating siliciclastic shallow turbidite deposits derived from fan-delta and river-delta systems in front of the growing Variscan hinterland, a unique fusuline assemblage consisting exclusively of Ferganites species (F. martinezi and F. ex gr. ferganensis) was seen in the lower part of the Puentellés Formation. This characteristic monotypic assemblage is interpreted to have been adapted to a near-shore, high-energy, low-salinity environment (Villa and Bahamonde 2001). This type of occurrence seen in cigar-shaped Ferganites resembles closely that observed in the Permian fusuline genus Monodiexodina, which shared a similar shell shape (Ueno 2006). Between the fluvial siliciclastic input phases, autochthonous carbonate deposition was renewed, and a different type of fusuline assemblage composed of dominating Tumefactus expressus (Fig. 13) and rare Quasifusulina sp. and Montiparus sp. was settled in a normal open-marine setting, which is typically represented by algal boundstone. These two, highly contrasted assemblages from the lower part of the Puentellés Formation are referable to the Dorogomilovian (late Kasimovian).

In the upper part of the formation, the sedimentary environment had been changed to a shallow ramp setting characterized by the development of bioclastic shoal, by the ceasing of the clastic supply. This part contains an early Gzhelian, more diverse fusuline assemblage consisting of Quasifusulina longissima, Q. aff. ultima, Ferganites obesus, Rauserites cf. rossicus, R. cf. erraticus, Tumefactus ex gr. expressus, Schwageriniformis?. aff. gusanicus, Triticites aff. acutus, and Jigulites sp. This fusuline assemblage is the youngest and last known in the Cantabrian Mountains.

Outside of the Cantabrian Zone, there are several other fusuline localities known in the Iberian Peninsula, which are briefly noted here. Late Visean–Serpukhovian fusulines were reported by Cózar (1999) from the Guadiato area of southwestern Spain. He recognized five foraminiferal zones in the succession, of which the first three are of the late Visean and the other two are Serpukhovian. Of 15 fusuline taxa recognized, Eostaffella prisca, E. radiata, E. proikensis, E. parastruvei, E. rossica, Pseudoendothyra ornata, P. bona, P. nodus, and P. kremenskensis were found in the late Visean zones. The Serpukhovian zones contain E. kashirica, E. pinguis, and all the aforementioned Eostaffella species that occurred in the late Visean zones, Pseudoendothyra kremenskensis, and Eostaffellina protvae. This taxonomic composition suggests that the upper two zones only represent the early part of the Serpukhovian.

In Teruel province of Aragon, late Moscovian and Kasimovian fusulines were reported and Beedeina?, Ferganites, Triticites, Rauserites, and Quasifusulina were illustrated from there (Villa et al. 1996). A close palaeogeographical contact with younger Carboniferous strata in the Cantabrian Zone was suggested, but details have not been clarified yet.

Little is known of the Carboniferous foraminifers in the Maritimes Basin of Canadian eastern North America, but there are younger Mississippian carbonate strata called the Windsor Group (or Codroy Group), distributed in Newfoundland, Nova Scotia, and New Brunswick. The group contains Visean and Serpukhovian foraminifers (Mamet 1968b, 1970; Jansa et al. 1978; Cózar and Somerville 2021). The Windsor Group fauna consists chiefly of smaller foraminifers, and only Eostaffella (E. ex gr. radiata) and Pseudoendothyra (P. ex gr. ornata) are listed and illustrated among fusulines. Jansa et al. (1978) previously concluded that the foraminiferal fauna from the Windsor Group belongs to the North American Realm, and it lacked Tethyan affinity. A recent study by Cózar and Somerville (2021) challenged this traditional palaeobiogeographical view and they suggested a closer Palaeotethyan affinity to the Middle to Late Mississippian microfossils of the Maritimes Basin. Their conclusion justifies to include this eastern North American province during Mississippian time in the Palaeotethys Region palaeobiogeographically.

Carboniferous basins, in both surface and subsurface, are scattered in the Maghreb of North Africa (Massa and Vachard 1979; Weyant et al. 1985; Lys 1988a). In some of these basins, foraminifers have been a subject of intensive biostratigraphic research (e.g. Lys 1988b; Cózar et al. 2016a). In the account that follows, four major basins from which sufficient lines of Carboniferous fusuline information are available are summarized; they are the Central Meseta in Morocco, the Tindouf Basin straddling over Morocco and Algeria, the Béchar Basin in NW Algeria, and the subsurface succession of Djebel Tebaga in southern Tunisia. In addition to them, Carboniferous fusulines from the western Libyan basins and Illizi Basin in the eastern Algeria/Libya border area are also briefly reviewed.

In Central Morocco, Visean–Serpukhovian strata containing foraminifers are distributed north of the High Atlas. Termier et al. (1975), Vachard and Fadli (1991), Vachard and Tahiri (1991), and Ouarhache et al. (1991) earlier reported their foraminifers. Cózar et al. (2008, 2011) investigated this succession based on densely sampled material from several sections and examined late Visean to earliest Bashkirian foraminiferal biostratigraphy. According to them, fusulines were not found in the Visean there, although in eastern Morocco (Jerada area) late Visean Eostaffella (E. ex gr. mosquensis and E. ex gr. ikensis) was reported (Vachard and Berkhli 1992) as well as in the Tindouf Basin in southern Morocco (see below). In the early Serpukhovian (Zone E1) Eostaffella pseudostruvei and E. cf. exilis were identified, and the late Serpukhovian interval (Zone E2) contained Eostaffella postmosquensis, E. pseudostruvei, Eostaffellinaprotvae’, E. ‘paraprotvae’, Plectostaffella varvariensiformis, and some other species. The Bashkirian fusuline assemblage has a similar specific composition as the late Serpukhovian one. Thus, the Bashkirian part of the section is probably referable to the Bogdanovkian.

The Tindouf Basin (southern Morocco and western Algeria) in the western part of the Saharan Platform bears good foraminiferal records of the Middle Mississippian to earliest Pennsylvanian. After some early studies on Carboniferous foraminifers in this basin (Mamet et al. 1966; Lys 1979), Sebbar et al. (2000) has shown a basic framework of Visean–Serpukhovian foraminiferal biostratigraphy in the Algerian sector of the basin, in which several fusuline species were documented in its late Visean–Serpukhovian succession. Cózar et al. (2014a, b) investigated Carboniferous strata of that basin in southern Morocco, made a composite section of the Tindouf succession, and analysed substage-resolution biostratigraphy and correlation ranging from the late Visean to the early Bashkirian. They listed the following fusulines from the late Visean part of the succession: Eostaffella mosquensis, E. parastruvei, E. proikensis, E. ikensis, and Pseudoendothyra kremenskensis.

In the early Serpukhovian, in addition to late Visean Eostaffella species, there are several new elements coming to the assemblage; they are Eostaffella pseudostruvei, E. postproikensis, E. mirifica, E. acutiformis, E. ovoidea, E. angusta, E. amabilis, Eostaffellina ex gr. decurta, and E. ex gr. ‘paraprotvae’. The late Serpukhovian fusuline assemblage has an essentially similar composition as the early Serpukhovian one, but Eostaffella chomatifera and E. mutabilis have their first occurrence in this interval. The early Bashkirian of the succession is divided into two parts; the lower portion is characterized by the first occurrence of Eostaffella postmosquensis and Plectostaffella species (P. reitlingerae, P. varvariensis, and P. jakhensis). This part is probably correlated to the Bogdanovkian. The topmost interval of the section contains Semistaffella minuscularia, S. variabilis, and S. minor as well as Millerella uralica, Pseudonovella ex gr. carbonica, and Eostaffellina ovaliformis. Judging from the first occurrence of Semistaffella, this part is referable to the Syuranian.

According to Weyant et al. (1985), thick Carboniferous strata ranging from the Tournaisian to the Moscovian underlie the Béchar Basin in NW Algeria. As for foraminifers from the Serpukhovian composed of the El Guelmouna, Ain el Mizab, Djenien, and the lower part of the Tagnana formations, Lys in Weyant et al. (1985) and Sebbar and Lys (1989) listed Eostaffella proikensis, E. pseudostruvei, E. ikensis, E. parastruvei, E. postproikensis, and Pseudonovella grozdilovae, and illustrated the first two species.

Bashkirian sections are well represented by the upper part of the Tagnana, Hassi Kerma, and Oued el Hamar formations, in ascending order, which collectively comprise the Djebel Béchar Limestone. Van Ginkel (1986a, 1989, 1992, 2002) investigated the fusuline succession of this limestone in the Béchar area and described the species present. The succession is characterized by recurring erosional levels and also intercalates siliciclastic beds, thus containing presumable missing fusuline biostratigraphic intervals. The upper Tagnana Formation assemblage (from samples SA11 and SA13 of van Ginkel 2002) is dominated by lenticular ozawainellid taxa including several Millerella species, Eostaffella cf. pseudostruvei, E. chomatifera, Plectostaffella varvariensis, P. jakhensis, and others.

Just above limestone beds containing the upper Tagnana Formation assemblage, a limestone bed of the basal part of the overlying Hassi Kerma Formation (Sample SA17 of van Ginkel 1992) bears Eostaffella ex gr. kashirica, Eostaffellina sp., and Ozawainella paraangulata. As the first Declinognathodus noduliferus occurs much lower than SA13, and the above-mentioned three limestone beds do not contain Pseudostaffella, an interval represented by these three limestones is correlated to the early (earliest) Bashkirian (Bogdanovkian–Syuranian). Higher up the section, two limestone beds (samples SA19 and SA20 of van Ginkel 1992) contain Plectostaffella? sp., Ozawainella paraangulata, Pseudostaffella ex gr. antiqua, P. ex gr. gorskyi, and P. composita hassikermaensis. Van Ginkel (1992) originally suggested an Askynbashian age for this level. From the next higher fusuline-bearing sample (SA21 of van Ginkel 1992), he identified Profusulinella ex gr. parva, Pseudostaffella ex gr. gorskyi?, and P. aff rotunda. Because the fusuline assemblage from the overlying upper part of the Hassi Kerma Formation is assignable to the Asatauian (van Ginkel 1989), the sample SA21 assemblage is considered to be Tashastian. In the upper part of the Hassi Kerma Formation, fusulines consist of Ozawainella ex gr. alchevskiensis, O. cf. umbonata, Varistaffella korobezkikh, Pseudostaffella ex gr. gorskyi, Schubertella cf. obscura, Profusulinella ex gr. parva, P. primitiva, Aljutovella cf. extensa, and Eowedekindellina? sp., along with many other small lenticular ozawainellids and some staffellids (Staffella and Nankinella).

The Hassi Kerma Formation is succeeded by the Oued el Hamar Formation. This formation contains the following fusulines: Ozawainella aff. mosquensis, Semistaffella? sp., Profusulinella convoluta, P. ex gr. pararhomboides, P. ex gr. parva, and Verella cf. prolixa, accompanying with Nankinella, Staffella, and several lenticular ozawainellid species (van Ginkel 1986a). Based on the occurrence of likely Eowedekindellina, Verella, and Aljutovella species, this and the above-mentioned upper Hassi Kerma Formation assemblages are referable to the latest Bashkirian Asatauian. The upper Tagnana to Oued el Hamar stratigraphic succession in the Béchar Basin remains the best complete record of Bashkirian fusuline biostratigraphy among North African basins, although some intervals (the Akavassian and probably some part of the Bogdanovkian–Syuranian) may not be present.

Overlying the Oued el Hamar Formation with conformity is the marine Kenadza Formation in the basal part of the essentially paralic to continental upper group of the Béchar Basin Carboniferous succession. Van Ginkel (1985, 1986b) described Profusulinella becharensis, P. cf. weiningica, Aljutovella cf. succincta, Eofusulina cf. tashlensis, and several other fusulines from near the top of the formation. This Kenadza assemblage, containing Eofusulina, is considered to be Vereian. Higher up the section, strata grade into siliciclastic sediments of the Algerian coal basin in this area. The marine Moscovian is also known to be exposed elsewhere in the Béchar area, at Djebel Mezarif and Djebel Béchar (Lys in Weyant et al. 1985). He showed Profusulinella chernovi, Aljutovella aljutovica ( = ?Profusulinella ovata), Eofusulina triangula, and Parastaffelloides cf. pseudosphaeroidea ( = Staffella? sp.) from the Vereian and Aljutovella postaljutovica and Neostaffella subquadrata from the Kashirian. Lys (in Weyant et al. 1985) also illustrated Fusiella cf. typica as a likely Podolskian fusuline, but the specimen is better referable to Taitzehoella (probably Taitzehoella prolibrovichi). Thus, a Podolskian age is not solid.

To sum up, the Béchar Basin of NW Algeria exhibits an almost continuous fusuline succession from the Serpukhovian up to the earliest Moscovian. Late Moscovian species might exist in this basin.

Djebel Tebaga is famous among fusuline palaeontologists for the middle Permian (e.g. Skinner and Wilde 1967b). Carboniferous fusulines were also reported by Glintzboeckel and Rabaté (1964) and Lys (1988a) from boreholes for petroleum exploration drilled in the Djeffara. They illustrated biostratigraphically important fusulines, including some interesting forms (such as Profusulinella rhomboides, Aljutovella postaljutovica, Eofusulina triangula, Dutkevichella pseudobocki, Triticites aff. plummeri, Biwaella sp. 1, and Pseudoschwagerina sp.).

Later, Ghazzay-Souli et al. (2015) investigated samples of the Bir Mastoura BMT-1 borehole from the Djeffara and made a biostratigraphic analysis, in conjunction with a reexamination of the samples of this borehole and reevaluation of materials reported by Glintzboeckel and Rabaté (1964) and Lys (1988a), of the Djebel Tebaga Carboniferous succession. They recognized the Visean–Serpukhovian with the occurrence of Eostaffella and Pseudoendothyra. The early Bashkirian is marked by Plectostaffella cf. karsaklensis, P. nauvalia, P. ex gr. varvariensis, and Schubertella. The Vereian assemblage yields Profusulinella timanica, P. rhombiformis, P. cf. prisca, Aljutovella postaljutovica, Eofusulina triangula, E. binominata, E. cf. tashlensis, and Paraeofusulina trianguliformis. The Kashirian is exhibited by Neostaffella cf. umbilicata, Fusulinella cf. paracolaniae, Beedeina cf. pseudoelegans, and Dutkevichella spp. Although Ghazzay-Souli et al. (2015) did not recognize a late Moscovian assemblage, Beedeina cf. distenta of Lys (1988a), which was reassigned to B. cf. pseudoelegans by them, may possibly indicate this age. In the Late Pennsylvanian, the taxa are Quasifusulina eleganta, ‘Triticites cf. petschoricus’ of Lys (1988a) (which probably belongs to Montiparus or Rauserites), ‘Biwaella sp.’ of Lys (1988a) (which is re-identified herein as Schwageriniformis cf. schwageriniformis), ‘Triticites aff. plummeri’ of Lys (1988a) (which is also re-identified herein as ‘Likharevites’? sp.), and Pseudoschwagerina sp. and Pseudofusulina cf. firma of Lys (1988a) (both re-identified herein as Darvasoschwagerina cf. donbasica). Fusulines potentially referable to several different ages in the Late Pennsylvanian seem to exist in this list. At least ‘Triticites cf. petschoricus’ and ‘Biwaella sp.’ in the list likely indicate a Kasimovian (or early Gzhelian) age, and the latter two species (in ‘Likharevites’ and Darvasoschwagerina) are considered to show a younger Gzhelian age.

The Carboniferous succession of Djebel Tebaga is important, but information is still fragmentary. Examination of additional materials from other boreholes in the Djeffara is awaited.

Surface and subsurface Carboniferous marine strata, ranging from the latest Tournaisian to the late Moscovian, are known in the western part of Libya. Massa and Vachard (1979) illustrated the following key fusulines for biochronology: Eostaffellina ex gr. paraprotvae from the upper Serpukhovian; Eostaffella chomatifera, E. cf. kanmerai, Pseudonovella grozdilovae lata, and Pseudostaffella antiqua from the lower Bashkirian; and Schubertella ex gr. obscura, Taitzehoella cf. prolibrovichi, Ozawainella pararhomboidalis, and Aljutovella ex gr. tikhonovichi from the lower Moscovian. These Carboniferous sediments continue to the Illizi Basin in eastern Algeria. Lys (in Weyant et al. 1985) reported Eostaffella pseudostruvei from the Serpukhovian; Eostaffella chomatifera and Pseudostaffella antiqua from the Bashkirian; Aljutovella aljutovica and A. elongata from the Vereian; and Taitzehoella librovitchi from the Kashirian of the Illizi Basin.

In Greece, a supposedly late early Bashkirian foraminiferal assemblage was known from the Beletsi area to the north of Athens. It contains Pseudostaffella grandis and Millerella sp. (Clément et al. 1971). This area in the Hellenides belongs to the Apulian Platform (Şengör et al. 1984), which can be restored to marginal peri-Gondwana adjacent to the Taurides Belt in southern Turkey, before the Late Triassic (van Hinsbergen et al. 2020).

Farther to the north, there are two isolated Pennsylvanian fusuline localities known in the Jadar area in northwestern Serbia and the Bükk Mountains in northeastern Hungary. These Carboniferous successions represent Variscan relicts in the Dinarides and are now distributed as nappes and/or displaced tectonic blocks of Dinaric affinity. They form the Jadar–Kopaonik composite nappe of the Dinarides, which is composed of Variscan deformed Devonian–Carboniferous sediments (van Hinsbergen et al. 2020). As depicted by Ebner et al. (2008), the Jadar and Bükk Mountains fusuline localities could be located in the deeper western part of the Palaeotethys Ocean during Carboniferous time.

From these two displaced Variscan successions, various fusulines of Bashkirian to Gzhelian ages were reported by Pajić and Filipović in Filipović et al. (1995) from the Jadar locality. The Bashkirian assemblage contains Eostaffella, Ozawainella, Pseudostaffella antiqua, P. compressa, P. turbulenta, Staffellaeformes staffellaeformis, Profusulinella ex gr. parva, and several others. Moscovian fusulines include Ozawainella pseudorhomboidalis, O. angulata, Taitzehoella librovitchi, Fusiella typica, Neostaffella ozawai, Fusulinella ex gr. pseudobocki, F. ex gr. paracolaniae, and Beedeina?. The Kasimovian is probably represented by Triticites species, and Gzhelian (or Asselian) forms yield Ozawainella, Quasifusulina, Dutkevitchia?, and Bosbytauella?.

In the Bükk Mountains in Hungary, Rozovskaja (1963) described fusulines including Parastaffelloides pseudosphaeroidea, Neostaffella larionovae, N. umbilicata, N. subquadrata, N. sphaeroidea, Fusulinella bocki, F. pseudobocki, Beedeina elegans, B. distenta, Fusulina kamensis, Hemifusulina sp. (originally identified as Dutkevichella moelleri), Quasifusulina elegans, Pseudofusulina pseudojaponica (but this specimen is better subsumed in Dutkevitchia), and Codonofusiella? sp. There are at least two age-diagnostic assemblages included in the Bükk Mountains fusulines; one consists of Parastaffelloides, Neostaffella, Fusulinella, Beedeina, Fusulina, and Hemifusulina, suggesting a late Moscovian age, and the other is represented by Quasifusulina and Dutkevitchia, which is referable to the late Gzhelian, whereas the age of Codonofusiella? sp. left uncertain. In Western Europe, fusulines showing similar generic and specific composition are seen in the Cantabrian Mountains in northern Spain (for the late Moscovian assemblage) and in the Carnic Alps in Austria/Italy (for the Gzhelian assemblage).

In Turkey, Carboniferous fusulines have been documented from the Taurides Belt (southern Turkey), Karakaya Complex in the Sakarya Zone (northern Turkey), and the Istanbul Zone (northwestern Turkey). Turkey and the adjacent areas have a complex tectonic history during the late Paleozoic and later, and various models have been proposed to explain the palaeotectonic and palaeogeographical evolution of the region (Şengör et al. 1984; Göncüoğlu et al. 1997; Okay and Tüysüz 1999), which influences much the interpretation of fusuline palaeobiogeography. In terms of the Carboniferous, the Taurides Belt (and the Anatolides Belt in its western part) formed a northern margin of Pangaea (peri-Gondwana) in the southern marginal Palaeotethys, and the Istanbul Zone belonged to the Moesian Platform along the northern margin of the Palaeotethys (Okay and Tüysüz 1999; Altiner et al. 2000). This view is supported by van Hinsbergen et al. (2020), who reviewed the orogenic architecture and tectonic evolution of the Mediterranean region. In Fig. 2a, the Istanbul Zone is included in Location 21 (Turkey) along the northern margin of Gondwana just for the sake of convenience, although it should actually be located along the southeastern margin of Laurussia.

The Karakaya Complex is variously interpreted in terms of the palaeotectonic setting (Okay and Göncüoğlu 2004). Altiner et al. (2000) clarified that late Permian foraminiferal biofacies characteristics in limestones of the complex show similarities to those of coeval limestone successions in the Taurides, suggesting that the relevant limestones in both the Karakaya and Taurides were originally formed in one single carbonate platform along the southern margin of the Palaeotethys Ocean (thus, northern peri-Gondwana). An essentially similar palaeogeographical setting was supposed also for the Mississippian (Göncüoğlu et al. 2007), along with the southerly subducting Palaeotethyan oceanic plate along the northern margin of the Sakarya magmatic arc. It can be concluded from these studies that a consistent tectono-sedimentary setting developing a large carbonate platform had prevailed during most of the Carboniferous and Permian, along the northern margin of peri-Gondwana in and around today's central and southern Turkey. Thus, limestones bearing Carboniferous fusulines from the Karakaya Complex also constituted a carbonate platform along the peri-Gondwana margin in the westerly deeper part of Palaeotethys. In outlining the palaeobiogeography of Carboniferous foraminifers in this region, Kalvoda (2003) suggested a possibility to locate tectonic blocks that constitute Turkish areas today (his Anatolide–Tauride and Sakarya terranes) to the northern margin of Palaeotethys (thus the southern margin of Laurussia). But this view is not consistent with the recent geotectonic understandings mentioned above.

The Taurides Belt has abundant fusuline records that cover the almost entire Carboniferous. They were reported by Altiner (1981), Okuyucu and Vachard (2006), Dzhenchuraeva and Okuyucu (2007), Okuyucu (2009, 2013), Atakul-Özdemir et al. (2011), Vachard and Moix (2011), and Okuyucu et al. (2018). Of these studies, Altiner (1981) presented continuous biostratigraphic data of Visean to Serpukhovian fusuline succession from the eastern Taurides. In that study, the following species were identified from the Visean: Eoparastaffella simplex, E. ovalis, and Eostaffella nalivkini in the lower Visean (Moliniacian); Eostaffella parastruvei and E. aff. ikensis from the middle Visean (Livian); and E. acuta, E. ovoidea, E. pseudostruvei, Pseudoendothyra concinna, P. illustria, P. struvei, and P. compressa from the upper Visean (Warnantian). The Serpukhovian was divided into two, and E. parastruvei, E. ovoidea, Pseudoendothyra struvei, P. composita, and P. suppressa were listed in the lower Serpukhovian assemblage. The upper Serpukhovian contains such species as Eostaffella postproikensis, Pseudoendothyra struvei, and Eostaffellina paraprotvae. Thus, the Visean and Serpukhovian fusulines from the Taurides belt are mostly of Eostaffella and Pseudoendothyra in their generic composi