UPPER TRIASSIC (NORIAN-RHAETIAN) VARIOSTOMATIDS (FORAMINIFERA), TIMOR-LESTE: SYSTEMATICS, PALEOENVIRONMENTAL, AND BIOSTRATIGRAPHIC IMPLICATIONS Open Access

Foraminiferal studies have been used worldwide to determine the age and paleoenvironments of Triassic sedimentary successions (Table 1). In Timor, most previous studies on the Triassic have used conodonts, palynology, and macrofossils for stratigraphic age determinations (e.g., Beyrich, 1864; Wanner, 1913, 1931, 1956; Welter, 1915; Krumbeck, 1921; Nakazawa & Bando, 1968; Nogami, 1968; Berry et al., 1984; Bird & Cook, 1991; Jattiot et al., 2020; Martini et al., 2000; Charlton et al., 2009; McCartain et al., 2024). Triassic foraminifers have been partly recorded in Timor-Leste and have provided age control for (i) the shallow carbonate-platform facies (viz. Bandeira Group; Haig et al., 2007, 2021a; Haig & McCartain, 2012); (ii) the Halstätt-like Lilu facies of the Bandeira Group (Barros et al., 2022); and some age control together with palynomorphs and conodonts on (iii) the basinal mud facies using siliceous agglutinated foraminifers (Haig & McCartain, 2010). Among Triassic Foraminifera elsewhere, the Genus Variostoma has been an important indicator for biostratigraphic correlation of the deep-water basinal muddy limestone–marl facies in the Middle and Upper Triassic (e.g., Kristan-Tollmann, 1960, 1964; Zaninetti, 1976; Gale et al., 2012c). A diverse assemblage of “Variostoma” is present in the Timorese Upper Triassic.

Variostoma was first described by Kristan-Tollmann (1960), with type species Variostoma spinosum Kristan-Tollmann. The type locality of V. spinosum is in the Middle Triassic (Ladinian) in Pedraces, Italy. The age ranges of species of Variostoma have been revised by Gale et al. (2011, 2012c) based on taxonomic reassessment. Apart from Kristan-Tollmann’s (1960) type material and other specimens described by Tappan (1951), Oberhauser (1960), Kristan-Tollmann (1964, 1973, 1983, 1988), Tollmann & Kristan-Tollmann (1970), Fuchs (1975), Zaninetti (1976), He & Hu (1977), He & Wang (1990), Quilty (1990), Trifonova (1994), di Bari & Baracca (1998), and di Bari & Laghi (1988), most records of Variostoma have been made from random thin sections where three-dimensional test and chamber shapes, changes in orientation of test axis during growth, apertural shape and internal chamber structures cannot be easily interpreted.

There has been major disagreement about aspects of morphology (e.g., wall structure and apertural type) in species of Variostoma. Therefore, the current study focuses on the morphological features of variostomatids based on free specimens found in Timor-Leste’s Upper Triassic. A comparison is made between the Timor species and their European counterparts. This will contribute significantly to age determinations for the Late Triassic interval in Timor (and in adjacent strata on the Northwest Shelf of Australia). The aims are to (1) taxonomically classify the variostomatids found in the Timor Upper Triassic, re-evaluate the generic identifications, and determine the morphological affinities to established European taxa; and (2) from this taxonomic study, draw implications concerning (i) wall composition of the variostomatid tests, (ii) paleogeographic and paleoenvironmental distributions, and (iii) biostratigraphic ranges.

Timor is an island within a young orogenic belt (Fig. 1) known for having some of the most chaotic geology anywhere on Earth due to the great complexity of its geological structure (Hamilton, 1979). The start of the collision between the northwest Australian margin and rifted fragments originating from Sundaland (Nano et al., 2023) has been estimated at about 8 ± 2 Ma based on isotopic analysis (Berry & McDougall, 1986) and stratigraphic ages of the youngest pre-orogenic and the oldest syn-orogenic deposits known so far from Timor (Haig & McCartain, 2007; Haig, 2012).

Recent revisions of the tectonostratigraphy of Timor-Leste recognized four main pre-collision associations which are defined by distinct clusters of stratigraphic units (Haig et al., 2019, 2021a, b; Barros et al., 2022; Nano et al., 2023). Two of the associations (Fig. 2) have Australian/Gondwanan affinity: the East Gondwanan Interior Rift Association (EGIRA) ranging from uppermost Carboniferous to Lower Jurassic, and the Timor–Scott Plateau Association (TSPA) from Upper Jurassic to Lower Miocene (McCartain et al., 2006, 2024; Haig & McCartain, 2007, 2010, 2012; Haig et al., 2007, 2014, 2017, 2021a; Haig, 2012; Davydov et al., 2013, 2014; Barros et al., 2022). In contrast, the Overthrust-Terranes Associations are allochthonous to the Australian Continent and include the Overthrust Ocean Basin Association of Middle Jurassic–Cenozoic age, including the Noni, Waibua, and Ofu pelagite units (Haig & Bandini, 2013; Haig et al., 2019, 2021b; Nano et al., 2023); the Overthrust Lolotoi Metamorphics (Harris et al., 1998; Harris, 2006; Standley & Harris, 2009; and equivalent overthrust metamorphics in West Timor, Berry et al., 2024); Overthrust-Terranes Associations (Volcanic/Siliciclastic), Upper Jurassic (?) to Paleogene including the Palelo (Haulasi) beds and Barique volcanics and associated Eocene limestone units (Haig et al., 2019; Nano et al., 2023); and the Overthrust-Terranes Associations (limestone fatus), Lower Jurassic–lowest Miocene (Nano et al., 2023).

Synorogenic deposits of the latest Miocene to the present day cover the older units in intermontane basins (Haig & McCartain, 2007; Haig, 2012; Duffy et al., 2017). Timor is actively rising, for example as evidenced by coral-reef terraces on the seaward margins of the Baucau and Lospalos plateaus (Cox et al., 2006). The highest known Mid-Pleistocene coral-reef terrace is on top of Laritame Mountain at about 1418 m (Leme, 1968; Haig et al., 2019).

In Timor-Leste, variostomatids are found only in the Aitutu and lower Wailuli groups of the East Gondwana Interior Rift Association (EGIRA). These are basinal facies that were deposited during the Late Triassic in a Gondwanan interior rift basin. The EGIRA Triassic succession in Timor-Leste (Fig. 3) is disrupted by faulting and broad-scale folding (including overturned folding). Formation thickness and internal stratigraphy are difficult to determine because of structural disruptions. Detailed logging of many sections still must be done and the sections stitched together by biostratigraphic correlation. A major step towards this has been achieved by McCartain et al. (2024) who outlined conodont and palynological zones and age determinations. As the detailed internal stratigraphy of all the Triassic units is still uncertain, we have used broad “groups” to designate units rather than formations. In the future, when the stratigraphic successions are better known, formations will be defined.

The Aitutu Group in Timor-Leste was included in the broad Mesozoic series of limestones “Série calcaire” by Gageonnet et al. (1959, fig. 2). Audley Charles (1968) first defined it as the Aitutu Formation, characterized by a rhythmic bedding pattern of radiolarian-rich “calcilutite” (indurated muddy limestone) interbedded with thin shale. He speculated that the unit was at least 1000 m thick. The Aitutu Group (Fig. 3) is now described as mainly a continuous succession, tens of meters thick, of dark grey thin–medium bedded radiolarian-rich indurated muddy limestone, paler when weathered or dolomitized, interbedded with subordinate organic-rich dark grey mudstone, often in the form of paper shale (McCartain et al., 2006; Haig et al., 2007; Haig & McCartain, 2010).

Audley-Charles (1968) found that the Aitutu Group usually contains only sparse macrofossils. In places, the muddy limestone beds are rich in microscopic filaments considered to be derived from pelagic bivalves (perhaps related to halobids). In some places, rare concentrations of the bivalves Halobia and Monotis are present (Audley-Charles, 1968), particularly on the surfaces of the limestone beds. In West Timor, these bivalves, and rare brachiopods (Halorella) and ammonoids are found in similar facies (Martini et al., 2000). Based on a revised conodont and palynomorph biostratigraphy, the age of the Aitutu Group as broadly interpreted by McCartain et al. (2024) ranges from Carnian to Rhaetian (Late Triassic). However, we consider the continuous thick successions of dark-grey radiolarian-rich muddy limestone and very thin friable mudstone to lie mostly within the Norian. In contrast, KIGAM (2013) and Kwon et al. (2014) misinterpreted the age of Aitutu Group and placed it into the Lower and Middle Triassic beneath the Babulu Group which they interpreted as the Upper Triassic. Their age determination was based on a U–Pb zircon age from the Babulu Group, interpreted as early Late Triassic. We know in the area that they mapped the Babulu–Aitutu succession is overturned in several places. The stratigraphic chart of Duffy et al. (2017, fig. 2) shows lateral equivalence of the Aitutu, Cablac, and Babulu “formations”. These correlations were not supported by any data.

Audley-Charles (1968) suggested that the formation was deposited centrally within a quiet-water closed basin. He also suggested that bacteria may have had a role in the precipitation of carbonate cement. In similar facies in West Timor, Martini et al. (2000) and Permana et al. (2014) interpreted deposition on a deep shelf margin to the basin.

The Wailuli Group was included in the Mesozoic “Flysch supérieur” by Gageonnet et al. (1959, fig. 2). Audley Charles (1968) first defined the unit as the Wailuli Formation, mainly calcareous mudstone commonly with dark grey burrow infills (including Zoophycos and Chondrites). In a limited part of the section, grey calcisphere and radiolarian-rich thin to medium-bedded “wackestone” (indurated muddy limestone) are interbedded with friable calcareous grey mudstone (McCartain, 2014). In Audley-Charles’ (1968) type area of the Waililu Formation in the valley of Wailuli River, Upper Permian as well as lower Upper Triassic Mudstone units are present together with uppermost Triassic–Lower Jurassic outcrops of the Wailuli Group (McCartain et al., 2006; Haig et al., 2007; McCartain, 2014). In his reconnaissance mapping of Timor-Leste, Audley-Charles (1968) included large areas now recognized as the Middle to lower Upper Triassic Babulu Group in the Wailuli Group.

Palynological biozonation of the Wailuli Group includes the Ashmoripollis reducta Zone of the Rhaetian (uppermost Triassic) and Corallina torosa Zone of the Lower Jurassic (McCartain et al., 2024). The Wailuli Group probably ranges as high as the Toarcian, but detailed biostratigraphic studies remain to be done.

The uppermost Triassic of the Wailuli Group consists mainly of blue-grey calcareous mudstone extensively bioturbated (with common dark mud-infilled Chondrites and Scalarituba burrows, following Audley-Charles’ 1968 identifications). This facies was interpreted as belonging to a closed quiet-water basin.

The material used in this study was collected during joint field work by researchers from The University of Western Australia (UWA) and the Instituto de Geociência de Timor-Leste (IGTL) and its precursor agencies. The foraminifers are curated in the Earth Science Museum at UWA (Tables 2, 3).

Crushed samples (1–3 kg; in 1–3 cm fragments) of indurated calcareous mudstone (e.g., from the Aitutu Group) were digested in a 7% acetic acid solution to which a buffer of spent acid had been added. The digestion was allowed to progress for 4–5 days. The insoluble sand-size residue was washed over a 150-µm sieve and then dried and examined under a stereomicroscope.

Samples of friable shale (e.g., from interbeds in the Aitutu Group, and from the Wailuli Group) were disaggregated in boiling water with added detergent and washed through 2-mm, 150-µm, and 63-µm sieves. The residues were dried and examined under a stereomicroscope.

Indurated mudstone samples were slabbed, and the cut surfaces etched in 2% HCl acid for 4 minutes. Acetone was used to flood the etched surface and a sheet of acetate film was carefully placed on the flooded surface. After several minutes, when dry, the peel was removed and placed between glass plates. A compound biological microscope with transmitted light was used to examine the peels.

Specimens of variostomatids were picked from the residues using a fine 000 sable-hair brush and placed on gridded cardboard micropaleontological slides. Specimens were photographed using a compound biological microscope and incident (reflected) light. A series of images (about 40) was taken of each specimen, in its same orientation at progressively different focal levels. The final image was obtained by rendering the stack of images using the program Helicon Focus (www.heliconsoft.com, accessed 8 December 2023). Selected specimens were examined, photographed, and analysed under a JEOL JCM-7000 Neoscope SEM (Scanning Electron Microscope) and EDS (Energy-Dispersive Spectrometry) microscope at the Centre of Microscopy, Characterisation and Analysis at UWA.

Variostoma Kristan-Tollmann, 1960, with V. spinosum Kristan-Tollmann, 1960 as type species, has been placed in several families and in some cases different subfamilies (Table 4). Species attributed to Variostoma in the World Register of Marine Species (WoRMS; Hayward et al., 2023) are listed in Table 5. Arguments about the classification of the genus have not arisen from revised descriptions of the type specimens of species but are based mainly on free specimens, but not types, of V. pralongense Kristan-Tollmann, 1960, and V. exile Kristan-Tollmann, 1960 (Fuchs, 1975; di Bari & Laghi, 1998). Gale et al. (2011) contributed to the taxonomic discussion by describing thin sections, mainly in off-centered to slightly oblique views, identified as V. catilliforme Kristan-Tollmann, 1960, V. coniforme Kristan-Tollmann, 1960, V. cochlea Kristan-Tollmann, 1960, V. falcata Kristan-Tollmann, 1973, and V. helicta Tappan, 1951. The revision of the suprageneric classification of Variostoma by Rigaud et al. (2015b) was based mainly on a literature review as well as random thin-sections.

The species that are based on free-specimen holotypes such as V. acutoangulata, V. bilimbata, V. catilliforme, V. cochlea, V. coniforme, V. crassum, V. exile, V. hadrolimbata, and V. helicta (Table 5) are distinct from the holotype of the type species of Variostoma, viz. V. spinosum (Fig. 4), by lacking the large spinose tubercles of the latter species. In other benthic foraminiferal groups, such a difference has warranted generic separation (e.g., in subfamilies Ehrenbergininae, Caucasininae, Epistomariinae, Ammoniinae, and families Ungulatellidae, Discorbidae, Glabratellidae and Calcarinidae, based on the classification of Loeblich & Tappan, 1987). Based on the presence of a large spinose tubercle in a central position toward the periphery on the spiral side of each chamber in at least the final two whorls, Variostoma is a distinct genus with V. spinosum as the only known species.

There is a problem in interpreting the morphological features of the other species that were attributed to Variostoma due to poor preservation of holotypes and (i) uncertainty as to apertural shape and position (see comments by Fuchs, 1975), (ii) the structure of the umbilicus, and (iii) the wall composition. The free specimens from Timor appear to be better preserved than many of the free specimens illustrated and described from elsewhere (see references in Introduction). Many of the diagnostic features cannot be assessed by random thin sections (e.g., those used by Gale et al., 2011). For these reasons, a new genus, Pualacana n. gen., is proposed with Pualacana hortai n. sp. as type species.

Family VARIOSTOMATIDAE Kristan-Tollmann 1963 (nom. correct Loeblich & Tappan, 1964b)

Rigaud et al. (2015b) emended the diagnosis of the family to include tests with internally simple chambers and an umbilical region covered, at least in part, by “laminar deposits”. They divided the family into four subfamilies: Asymmetrininae Brotzen, Cassianopapillariinae Rigaud, Praereinholdellinae Rigaud, Martini & Vachard, and Variostomatinae Kristan-Tollmann. Almost planispiral coiling characterises Asymmetrina biophalica Kristan-Tollmann, type species of Asymmetrina (with holotype of A. biophalica free of matrix), the nominal type genus for the Asymmetrininae. Coarse papillae covering a broad umbilical region characterises Cassianopapillaria laghii (di Bari & Rettori - new name for Papillaria laghii), type species for Cassianopapillaria di Bari & Rettori (with holotype of C. laghii free of matrix) the nominal type genus for Cassianopapillariinae. Rigaud et al. (2015b) included Diplotremina Kristan-Tollmann in the Cassianopapillariinae. As originally interpreted from random thin sections in limestone, Praereinholdella galei Rigaud, Martini & Vachard, type species of Praereibholdella Rigaud, Martini & Vachard (the nominal type genus of the Praereinholdellinae) was characterised by its test having “a dorsal wall extension that partially covers the spiral side and an umbilical wall extension that fills the umbilicus” (Rigaud et al., 2015b, p. 20). Since the original description of Variostoma spinosum Kristan-Tollmann, the type species of Variostoma, nominal and only genus of the Variostomatinae according to Rigaud et al. (2015b), no other detailed description of the type material has been published. The type species has not been shown to have the characters portrayed by Rigaud et al. (2015b) of the subfamily that takes its generic name.

Apart of Diplotremina subangulata Kristan-Tollmann, the species described from Timor-Leste do not fit within the definitions of the Asymmetrininae or Cassianopapillariinae. The status of the Praereinholdellinae (based on random thin sections) and the Variostomatinae remain uncertain until more detailed three-dimensional imaging can be done on the Praereinholdellinae species (either by obtaining free specimens or by serial acetate peels through the test, or by micro-CT scanning) and detailed redescription of the types of Variostoma spinosum (including new topotypes). Subfamilies are not designated here for the Timor variostomatids.

Genus Pualacana n. gen.
Type species: Pualacana hortai n. sp.

After the village of Pualaca in the Municipality of Manatuto Timor-Leste near the type locality of the type species.

A genus of Variostomatidae without tubercles or other ornament on chambers; axis of coiling variable during growth; on ventral (umbilical side) the overlap of chambers covers umbilicus, with either complete overlap of umbilicus by final chambers or partial overlap to form a shallow pseudoumbilicus which is usually excentric beneath the spiral coil; aperture a simple arch, not dendritic, on base of terminal face, with lip or flap on upper side of arch, in some species obscured in pseudoumbilicus.

Taxa newly described from Timor-Leste (Norian–Rhaetian):

• P. hortai n. sp.

• P. xananai n. sp.

• P. sp. cf. cochlea (Kristan-Tollmann, 1960)

Known species transferred to Pualacana with stratigraphic ranges as originally cited. Species described here from Timor-Leste are marked by an asterisk (*).

• Pualacana bilimbata (Hu in He & Hu, 1977): Upper Triassic.

• Pualacana acutoangulata (Kristan-Tollmann, 1973): upper Carnian.

• *Pualacana catilliforme (Kristan-Tollmann, 1960): Norian.

• *Pualacana cochlea (Kristan-Tollmann, 1960): Rhaetian.

• *Pualacana crassum (Kristan-Tollmann, 1960): Norian.

• Pualacana exile (Kristan-Tollmann, 1960): Ladinian.

• Pualacana falcata (Kristan-Tollmann, 1973): Carnian.

• Pualacana hadrolimbata (Hu in He & Hu, 1977): Upper Triassic.

• Pualacana helicta (Tappan, 1951): Upper Triassic.

• Pualacana oberhauseri (Vettorel, 1988): Carnian.

• Pualacana pralongense (Kristan-Tollmann, 1960): Ladinian.

Pualacana n. gen. differs from Variostoma in the lack of tubercles on the periphero-spiral edge of each chamber. These are a prominent feature of V. spinosum Kristan-Tollmann (1960, pl. 7, figs. 1a–7 — 3a–c, holotype; pl. 8, figs. 1a–c; Fig 4a–c herein), the type species of Variostoma. The dendritic aperture described and illustrated for V. spinosum by Kristan-Tollmann (1960) is unlike the simple aperture in Pualacana. The observations of Fuchs (1975), however, demonstrated that previous descriptions of apertures described for Variostoma and related genera require revision. Diplotremina Kristan-Tollmann, 1960 (type species D. astrofimbriata Kristan-Tollmann, 1960, pl. 14, figs. 1–4 — figs. 2a–c holotype) differs from Pualacana in having chambers not overlapping the umbilical region (see also thin-section photographs interpreted to be axial sections of D. astrofimbriata by Premoli-Silva, 1971, pl. 27, fig. 5, pl. 28, fig. 2). Duostomina Kristan-Tollmann, 1960 (type species D. biconvexa Kristan-Tollmann, 1960, pl. 17, figs. 1a–c holotype, 2a–c, pl. 18, figs. 2a–c.) differs from Pualacana in having a straight axis with no overlap of chambers in the umbilical region and an umbilicus infilled by calcareous umbonal deposits.

Paulacana has some characteristics in common with Falsoreinholdella Rigaud, Martini & Vachard, 2015b (type species Falsoreinholdella ohmi Rigaud, Martini & Vachard, 2015b) which was based on random thin sections in limestone. As in Pualacana, Falsoreinholdella lacks umbonate deposits. It was interpreted by Rigaud et al. (2015b) to have umbilical wall extensions that incompletely fill the median umbilicus. However, in the three-dimensional Pualacana successive final chambers, which are variably twisted, either completely cover the umbilicus (as in the type species, P. hortai n. sp.) or partially cover it to form an excentric pseudoumbilicus. The aperture and foramina in F. ohmi were interpreted as rounded openings, but in P. hortai are low arched with an upper lip.

In the synonymies of species from Timor-Leste recorded below, only records of free specimens are included. In the descriptions, the spiral side is referred to as “dorsal” and the umbilical side, “ventral”, because the umbilicus is covered. Species of Pualacana are differentiated by (i) test outline including three-dimensional shapes of the dorsal and ventral sides and the equatorial outline; (ii) the irregularity of the test axis; (iii) the numbers of chambers in the final whorl; (iv) the degrees of prolongation and twisting of the ventral sides of chambers; (v) the degree of overlap of chambers on the ventral side and whether the chambers completely or partially overlap in the central region in adult specimens and whether a pseudoumbilicus is present. Morphological differentiation of species recognized in the Norian–Rhaetian of Timor is illustrated on Figure 5. Pualacana hortai n. sp. is chosen as type species because it is considered to represent the basic morphology of the genus group. Transitional forms between P. hortai and Duostomina turboidea Kristan-Tollmann and between P. hortai and P. crassum were observed in studied assemblages.

Pualacana hortai n. sp.
Fig. 6 

In honour of His Excellency Ramos Horta, President of República Democrática de Timor- Leste.

Holotype: UWA182613 (Figs. 6.1a–d): topotype: UWA182614 (Figs. 6.2a–c) from locality UWA144008: paratype: UWA182615 (Fig. 6.3a–c) from locality UWA144123. All types are from acetic acid-digested residues of carbonate-cemented mudstone in the Aitutu Group and are free of matrix. The species is rare.

Near Pualaca town, east of Pualaca Primary School, Administrative Post for Laclubar, Municipality of Manatuto District, Timor-Leste. GPS location 8.7879°S, 125.9728°E.

A species of Pualacana with low trochospiral coiling about a slightly twisted axis in final growth stage, a biconvex axial profile, and a very slightly lobate almost circular equatorial outline. Aperture a broad basal arch, varying in position along suture, with a distinct lip that extends the dorsal edge of the aperture and diverges into the test toward the ventral side, with a shallow re-entrant of the terminal face of last chamber on the dorsal side of the aperture.

The test is large with equatorial diameters ranging from 0.5 to 1.5 mm. Coiling in the holotype is dextral, other specimens are either sinistral or dextral. In the final whorl there are 13–16 chambers. Initial whorls are obscure but probably number 4–5 whorls in adult specimens. The test is biconvex. The periphery is roundly angled. The sutures are flush on the dorsal side and slightly incised toward the periphery on the ventral side. Sutures are almost straight and radial with some slightly oblique. The terminal face is smooth, slightly convex with a shallow re-entrant toward the dorsal periphery at the inner margin of the apertural arch (Fig. 6.1c). There is a broad area of overlap of final chambers in the central region on the ventral side (e.g., Fig. 6.1b arrow, 6.1c arrow, 4 arrow, 5 arrow b). The umbilicus is not exposed, and a pseudoumbilicus caused by partial overlap of the final chambers is not present. The wall is recrystallized and is composed of minute crystalline silica (see Wall Composition and Preservation). There is no evidence of agglutinated grains. The aperture is a simple arch with a toothplate-like lip along upper margin that diverges into chamber toward the ventral side (e.g., Fig 6.1c). In the holotype (Figs. 6.1), the aperture is located halfway between the umbilicus and periphery. No internal toothplate has been observed. Foramina connecting chambers are simple, remain in the position of the aperture, and have upper margins formed by slightly thickened parts of the septa.

Pualacana hortai n. sp. differs from Pualacana crassum, from the Norian Pötschenkalk, by having final chambers that overlap each other in the umbilical area completely covering the umbilical depression, with no pseudoumbilicus. In P. crassum, the final chambers on the ventral side are more ventrally drawn out and twisted and do not completely overlap, leaving a small pseudoumbilicus. Gradational specimens between P. hortai and P. crassum are present.

Accompanying P. hortai in some samples is a biconvex species of Duostomina with about nine chambers in the final whorl coiled in a regular trochospire, non-overlapping chambers on the ventral side, and the umbilical region infilled by clear umbonal deposits (viz. D. turboidea Kristan-Tollmann, 1960). These forms have a simple basal arched aperture with a flap-like lip on its upper side. Any evolutionary relationship between Duostomina sp. and P. hortai is uncertain.

From within Norian to within Rhaetian (Upper Triassic); precise range not determined.

Pualacana catilliforme (Kristan-Tollmann, 1960)
Figs. 7.2–7.5,
Variostoma catilliforme Kristan-Tollmann, 1960, p. 61, pl. 10, figs. 5, 6, 7a–c (holotype), pl. 11, figs. 1–4.

All illustrated specimens are from a washed residue of a shale interbed (UWA144137) in the Aitutu Group (UWA182618–UWA182621) and are free of matrix. The species is abundant at this locality.

The Timor specimens are like the holotype of Variostoma catilliforme Kristan-Tollmann, 1960 from the Pötschenkalkes, Austria (see type figure reproduced on Fig. 7.1). The species is differentiated from the other Timorese Pualacana (Fig. 5) by (i) a less convex, in some specimens almost flat, dorsal side and a more convex ventral side with the axial height up to about one-half equatorial diameter; (ii) angled peripheral margin and with domed central portion of ventral side; (iii) coiling usually with 2 whorls and with 9–11 chambers in final whorl; (iv) thick spiral and intercameral sutures; (v) ventral portion of each chamber slightly twisted with margins tending to overlap producing a thickened elevated wall around a small shallow pseudoumbilicus. The pseudoumbilicus is slightly excentric in position on the ventral side. Both sinistral and dextral coiling is present.

Norian (Gale et al., 2012c, fig. 2).

Pualacana cochlea (Kristan-Tollmann, 1960)
Figs. 8.2–8.8 

• Variostoma cochlea Kristan-Tollmann, 1960, p. 63, 64, pl. 12, fig. 6, pl. 13, figs. 1–12, pl. 14, figs. 5a–c (holotype)

• Variostoma cochlea Kristan-Tollmann; Kristan-Tollmann, 1964, p. 49, 50, pl. 39, figs. 3–5.

• Variostoma cochlea Kristan-Tollmann; Kristan-Tollmann, 1988, pl. 1, figs. 1–10.

• Variostoma cochlea Kristan-Tollmann; di Bari & Baracca, 1998, p. 129, pl. 3, fig. 8,? 7,? 9.

UWA182622–UWA182628. All figured specimens are from acetic acid-digested residues of carbonate-cemented mudstones (Aitutu Group) and are free of matrix (Samples UWA144442, UWA144344, and UWA144454).

The Timor specimens are like the holotype of Variostoma cochlea Kristan-Tollmann, 1960, from the Pötschenkalkes, Austria (see type figure reproduced on Fig. 8.1). The species is differentiated from other Pualacana (Fig. 5) by (i) its flat broad initial spire; (ii) rapid ventral elongation of chambers in last whorl so that the breadth of final adult chamber is less than one-fourth axial length of chamber; (iv) adult chambers on ventral side are twisted and form a prominent thickened margin around a slightly excentric small but deep pseudoumbilicus; and (v) a flap from one side of pseudoumbilicus partially covers it. Apertural openings are obscure in the Timor specimens. In partly dissected specimens (e.g., Fig. 8.2, 4), a foramen is observed on the ventral side of the chamber lumen. This suggests that an aperture is present, opening into the pseudoumbilicus. Perhaps because of chamber twisting, the inner surface of the chamber is undulated, but no distinct high toothplate appears present. Pualacana cochlea differs from the Middle Triassic (Ladinian) P. exile (Kristan-Tollmann, 1960) and P. pralongense (Kristan-Tollmann, 1960) by having a flatter initial coil, fewer whorls with more ventrally elongate final chambers and a less obtuse ventral profile.

Norian–Rhaetian (Upper Triassic).

Pualacana sp. cf. P. cochlea (Kristan-Tollmann, 1960)
Fig. 9,
cf. Variostoma cochlea Kristan-Tollmann, 1960, p. 63, 64, pl. 12, figs. 6, pl. 13, figs. 1–12, pl. 14, fig. 5a–c (holotype)

One specimen, UWA182629, from an acetic acid-digested residue of a carbonate-cemented mudstone (sample UWA144454) of the Aitutu Group. Free of matrix.

This spindle-shaped test differs from typical P. cochlea in its more acute dorsal side and more drawn-out ventral side. The twisted thickened ventral margins of the final chambers form a narrow and deep pseudoumbilicus with a flap like partial cover (Fig. 9.1b). The aperture apparently opens into the pseudoumbilicus.

Sample UWA144454 lies within the Norian–Rhaetian interval (McCartain et al., 2024).

Pualacana crassum (Kristan-Tollmann, 1960)
Figs. 10.2–10.5,
Variostoma crassum Kristan-Tollmann, 1960, p. 59, 60, pl. 10, figs. 1a–c.

UWA182629. All specimens are from acetic acid-digested residues of carbonate-cemented mudstones of the Aitutu Group and are free of matrix.

The Timor specimens are like the holotype of Pualacana crassum Kristan-Tollmann, 1960 from the Norian, Pötschenkalk, Austria (see type figure reproduced on Fig. 10.1). The species is differentiated from other Pualacana (Fig. 5) by (i) its low spire of about three whorls with gently convex smooth dorsal surface having flush sutures between chambers; (ii) a circular equatorial outline encompassing chambers of the final whorl; (iii) chambers drawn-out ventrally with sutures radial across the broad periphery; (iv) chambers twisting toward the umbilical region and forming a thickened elevated ridge around a small excentric pseudoumbilicus. The aperture is obscure on Timor specimens. Some authors suggested that Trochammina helicta Tappan 1951 is the senior subjective synonym of Variostoma crassum Kristan-Tollmann, 1960 (e.g., Trifonova, 1994; Gale et al., 2011). However, the holotype of T. helicta, Smithsonian National Museum of Natural History Paleobiology Collection USNM PAL 106334, while probably a Pualacana, is very poorly preserved as illustrated by reflected light images available at http://n2t.net/ark:/65665/338e7aa6e-4e98-43c6-a935-9285a98a6b18, and the features considered diagnostic for P. crassum cannot be confirmed from this specimen.

Norian (Upper Triassic; Kristan-Tollmann, 1960).

Pualacana xananai n. sp.
Fig. 11 

In honour of His Excellency Xanana Gusmão, Prime Minister of the República Democrática de Timor-Leste.

Holotype: UWA182635, from locality UWA144137 (Figs. 11.2a–c), topotypes: UWA182634, (Figs. 11.1a–c), and UWA182636 (Figs. 11.3a–c) from locality UWA144137. All specimens are from the washed sand residue of a shale interbed in the Aitutu Group and are free of matrix.

South of Soibada town, Municipality of Manatuto, Timor-Leste. GPS location 8.8889°S 125.9374°E.

A large species of Pualacana with a broad high conical dorsal side and a slightly convex ventral side. Periphery almost circular in equatorial outline. In axial view, the periphery is roundly angled. Chambers coiled in 3–4 whorls with 13–14 chambers in the final whorl. On ventral side, final chambers are twisted and their ventral margins form a very wide, very thick, slightly elevated rim around an excentric pseudoumbilicus. A flap partially covers the pseudoumbilicus.

Trochospiral test with a slightly twisted axis, an elevated broadly conical dorsal side displaying all chambers, and a somewhat depressed slightly convex ventral side with chambers of the final whorl partly obscured. Test equatorial diameter varies from 1.25–1.5 mm, and test axial height from 1.2–1.25 mm. There are 3–4 whorls and 13–14 chambers in the final whorl. Intercameral sutures are flush and slightly bent back. The spiral suture is slightly depressed given a rounded step-like appearance to the dorsal cone in axial view. The chambers gradually increase in size and in the final whorl become higher than broad with the ventral parts of the final chambers twisting and thickening to form a very thick wide rim around a small pseudoumbilicus. The rim is subdued in height above the ventral surface. A small flap partially covers the pseudoumbilicus. The apertural position and shape is obscure and apparently within the pseudoumbilicus.

This species has a very different axial profile from the other species of Pualacana described here (see Fig. 5). It is also one of the largest species of Pualacana found in Timor. It is very rare and, is yet, found in one friable shale sample.

Duostomina tamarinense di Bari & Baracca (1998, p. 128. pl. 2, figs. 1, 4, 5 holotype, 7) resembles P. xananai in test outline but is much smaller (maximum equatorial diameter 0.46–0.60 mm compared to 1.25–1.5 mm for P. xananai) and has fewer chambers in final whorl (chamber numbers not designated in type description, but apparently about 8 in final whorl from figures; compared to 13–14 for the final whorl of P. xananai). di Bari & Baracca (1998) described the ventral side of D. tamarinense as umbonate although this cannot be confirmed in the type figures.

Norian or Rhaetian (Upper Triassic).

OTHER “ROBERTINIDS” ACCOMPANYING PUALACANA IN THE TIMOR NORIAN–RHAETIAN

• Family DUOSTOMINIDAE Brotzen, 1963 

• Genus Duostomina Kristan-Tollmann, 1960 

• Type species: Duostomina biconvexa Kristan-Tollmann, 1960 

Duostomina ranges through the Middle to Late Triassic (Gale et al., 2011, 2012c). In thin sections from shallow-water bioclastic limestones of the Bandiera Group in Timor-Leste, Haig et al. (2021a) recorded Duostomina alta Kristan-Tollmann, D. biconvexa Kristan-Tollmann, D. rotundata Kristan-Tollmann, and D. turboidea Kristan-Tollmann.

• Duostomina turboidea Kristan-Tollmann, 1960 Figs. 12.2–12.4 

• Duostomina turboidea Kristan-Tollmann, 1960, p. 71, 72, pl. 18, figs. 3, 4 (holotype), pl. 19, figs. 1–9.

• Duostomina turboidea Kristan-Tollmann; di Bari & Baracca, 1998, p. 129, pl. 2, fig. 6.

UWA182637–UWA182639. All specimens are from acetic acid-digested residues of carbonate-cemented mudstones of the Aitutu Group and are free of matrix.

Duostomina turboidea differs from Duostomina alta Kristan-Tollmann, 1960 and Duostomina biconvexa Kristan-Tollmann, 1960, by a more rounded periphery and a different axial profile. It differs from Duostomina rotundata (Kristan-Tollmann, 1960) by having a more inflated ventral side and a lower convex spiral side.

Upper Ladinian–Carnian, according to Kristan-Tollmann (1960); extending through Norian–Rhaetian (following Vettorel, 1988, p. 182).

• Diplotremina Kristan-Tollmann, 1960 

• Type species: Diplotremina astrofimbriata

• Kristan-Tollmann, 1960 

Rigaud et al. (2015b) placed Diplotremina within the Cassianopapillariinae of the Variostomatidae. The significance of “papillose lamellae” on the ventral side as a distinguishing feature for subfamilies and families requires further assessment. For this reason, Diplotremina is tentatively retained within the Duostominidae which has regular trochospiral coiling about a straight axis. According to Gale et al. (2011) Diplotremina ranges from Early to Late Triassic. In thin sections of shallow-water bioclastic limestones of the Bandeira Group in Timor-Leste, Haig et al. (2021a) recorded Diplotremina altoconica Kristan-Tollmann, 1960, and D. subangulata Kristan-Tollmann, 1960.

• Diplotremina subangulata Kristan-Tollmann, 1960 Fig. 12.6

• Diplotremina subangulata Kristan-Tollmann, 1960, p. 67, 68, pl. 15, fig. 3 (holotype), 4, pl. 16, figs. 1–5.

• Diplotremina subangulata Kristan-Tollmann; Kristan-Tollmann, 1964, p. 51, 52, pl. 39, figs. 8–10.

• Diplotremina subangulata Kristan-Tollmann; Tollmann & Kristan-Tollmann, 1970, pl. 8, fig. 28.

• Diplotremina subangulata Kristan-Tollmann; Kristan-Tollmann, 1988, pl. 1, figs. 11–14.

• Diplotremina subangulata Kristan-Tollmann; Quilty, 1990, p. 359, pl. 3, figs. 27, 28; pl. 4, figs. 1–3.

UWA182640; specimen from acetic acid-digested residue of a carbonate-cemented mudstone of the Aitutu Group; free of matrix.

The Timor specimens are like the holotype of Diplotremina subangulata Kristan-Tollmann, 1960 from Plackleswiese W Plackles, Hohe Wand NW Wr. Neustadt, Nieder – Österreich, Austria. D. subangulata differs from Diplotremina astrofimbriata and Diplotremina placklesiana by having a biconvex test with a slightly angled periphery and inflated chambers giving a lobate equatorial outline.

Rhaetian according to Kristan-Tollmann (1960); Norian–Rhaetian (Haig et al., 2021a).

Family OBERHAUSERELLIDAE Brotzen, 1963 

Genus Oberhauserella Fuchs, 1967 

Type species. Globigerina mesotriassica Oberhauser, 1960 

• Oberhauserella rhaetica (Kristan-Tollmann, 1964) Figs. 12.8–12.9 

• Globigerina rhaetica Kristan-Tollmann, 1964, p. 166, pl. 39, figs. 13–15.

• Oberhauserella rhaetica (Kristan-Tollmann); Fuchs, 1967, p. 153, pl. 5, fig. 1.

• “Globigerina” rhaetica Kristan-Tollmann; Tollmann & Kristan-Tollmann, 1970, pl. 8, figs. 29a,b.

UWA182641, UWA182642. All specimens are from washed sand residues of friable mudstones of the lower Wailuli Group and are free of matrix.

Oberhauserella rhaetica has a slightly more compressed test than the other Late Triassic species of Oberhauserella described by Fuchs (1967) with a greater number of chambers in final whorl.

Rhaetian (Fuchs, 1967).

Understanding the wall composition of variostomatids (including species now placed in Pualacana; Table 5) has been controversial and has developed with the discovery of well-preserved specimens (e.g., P. pralongese and P. exile from the Upper Triassic of Austria). Kristan-Tollmann’s (1963) description of a calcareous agglutinated wall contrasts with later descriptions by di Bari & Laghi (1998) who identified an aragonitic lamellar perforate wall. Hohenegger & Piller’s (1975) description noted a perforate wall.

The composition of the studied specimens of Pualacana hortai observed in SEM images and with elemental analysis by Energy-Dispersive Spectroscopy, showed that the wall composition of P. hortai had recrystallized by silica in the form of trigonal quartz crystals (Fig. 13). The replacement is uniform through the test and no extraneous agglutinated material is present in the recrystallized wall. Examination of acetate peels of a carbonate-cemented grey mudstone bed in the Aitutu Group (sample UWA144008, Table 2) also contain large recrystallized Pualacana with clear coarse silica grains (Figs. 13.5–13.7). Among other bioclasts accompanying the recrystallized Pualacana are sections of (i) nodosarians, known to have low-magnesium calcitic tests (Sen Gupta, 1999, fig. 2.8), with radial prismatic microstructure preserved suggesting original mineralogy (Figs. 13.9a,b); (ii) ostracod valves, known to be calcitic (Dalingwater & Mutvei, 1990), with homogeneous, not recrystallized, microstructure (Fig. 13.7); and (iii) echinoid spines displaying a non-recrystallized lattice structure (Fig. 13.8) as in original spines of high-magnesium calcite (Smith, 1990).

Therefore, the replaced siliceous tests of Pualacana, that are not agglutinated, are present with other biogenic skeletons, originally calcite, that show original microstructure. This suggests that the Pualacana test was composed originally of a mineral that was not calcite, but probably aragonite that is known to be more susceptible to diagenetic change than calcite (e.g., Sulpis et al., 2022). A ready source of silica in the bed comes from the terrigenous mud content as well as radiolarians, originally opaline silica but usually replaced by calcite. The suggestion made here that the test of Pualacana was originally aragonitic agrees with the determination of original mineralogy for other species of the genus examined by di Bari & Laghi (1998).

Pualacana had a widespread distribution around the Late Triassic Tethyan Ocean (Fig. 14). In Europe, Pualacana is present in the “Pötchenkalke” in the Alps of Austria (Kristan-Tollmann, 1960); Southern Alps, Slovenia (Gale et al., 2011); and in the Dolomites of northern Italy (di Bari & Baracca, 1998). In Asia, species now referred to Pualacana were recorded by Kristan-Tollmann (1984) in the Himalayan region, by Korchagin (2008) in Tajikistan, Himalayan region, and by He & Wang (1990) in Qinghai, China. Kristan-Tollmann (1986a,b) recorded a very poorly preserved species of Pualacana from the Rhaetian Kuta Limestone of Papua New Guinea. Most records were based on observations on randomly orientated tests in thin sections.

Triassic stratigraphic units in Timor resemble in their facies association those of the Hallstatt Basin and adjacent shallow-marine carbonate platform as illustrated by Flügel (2004, fig. 15. 29). Figure 15 shows the facies correspondence of Timor units to those in Hallstatt Basin. Kristan-Tollmann et al. (1987) pointed out the similarities between the Aitutu Formation of Timor and the Pötchen Formation in the Hallstatt Basin. Haig et al. (2021a) showed the close similarity of the Bandeira Group in Timor to limestones of the Dachstein Platform adjacent to the Hallstatt Basin. Barros et al. (2022) demonstrated the similarity between the Lilu facies of the Bandeira Group and the Hallstatt Limestone of the Hallstatt Basin.

Kristan-Tollmann et al. (1987) noted that “Variostoma” species including Pualacana catilliforme are typical of the Pötschen beds in Austria but had not been found in the Aitutu Group (which they regarded as a lithofacies equivalent of the type Pötschen beds) in West Timor. The present study shows that similar Pualacana are present both in Europe and in Timor and demonstrates the wide latitudinal distribution of the species between about 40°N and 40°S in continental basinal facies adjacent to the Tethys Ocean of the Late Triassic (Figs. 14, 15). In Timor-Leste, Pualacana inhabited the basinal facies of the East Gondwana Interior Rift (viz. Aitutu Group and lowermost Wailuli Group). They also exist in the submerged carbonate platform limestone of the Lilu facies (Barros et al., 2022). However, they are absent in the shallow-water carbonate platform limestone of the Bandeira Group (Haig et al., 2021a).

Typical indurated beds of the Aitutu Group (Fig. 16) are better classified as carbonate-cemented mudstone than as wackestone or limestone. The rock type resembles that in carbonate nodules found in organic-rich shale deposits (Pirrie & Marshall, 1991; Marshall & Pirrie, 2013; Tremblin & Haig, 2023). In the carbonate nodules and in the Aitutu Group indurated beds, macrofossils are rare; foraminifera and other microfossils may be scattered through the mud matrix; planktonic radiolarians, minute filaments probably derived from pelagic bivalves, and conodonts are abundant in some Aitutu beds; organic matter including non-skeletal algal derivatives and the fine debris of land plants are common to abundant. Acid-digested residues of the rock give microfossils that remain uncrushed by burial compaction (e.g., Haig & McCartain, 2010, 2012; Tremblin & Haig, 2023), and palynomorph assemblages are well preserved (Playford, 2021; McCartain et al., 2024).

Pirrie & Marshall (1991) suggested that carbonate nodules in organic-rich shale were the product of early diagenetic cementation resulting from bacterial activity (e.g., through methanogenesis where bacteria and archaea oxidize methane ultimately leading to the precipitation of carbonate cement). Audley-Charles (1968, p. 12) noted: “The importance of bacteria as agents of calcium carbonate precipitation in the Aitutu Formation is unknown, but must not be overlooked… .pyrite found throughout the Aitutu Formation may be associated with sulphate-reducing and the denitrifying bacteria that are said to precipitate calcium carbonate in the Black Sea.”

Burchell et al. (1990) described Aitutu-like cyclicity in uppermost Triassic (Rhaetian) facies in the Southern Alps of Northern Italy. They deduced that the carbonate beds in the “marl-limestone couplets” were derived as “relatively pure aragonitic mud from adjacent carbonate platforms.” In Timor-Leste, the Aitutu Group depositional site was adjacent a carbonate platform as evidenced by debris-slide conglomerates composed of clasts derived from the coeval Bandeira Group (McCartain et al., 2024). However, because the Aitutu Group “limestone” beds are better classified as carbonate-cemented mudstones, it seems possible that methanogenesis played a part in the carbonate cementation of these beds following a model suggested in Figure 17. The model shows sedimentary couplets caused by alternating periods of low and high influxes of terrigenous mud from the hinterland coming into the basin as mud plumes in surface waters. These would have resulted from periodic changes in hinterland climate (e.g., rainfall).

The Pualacana species have extremely large tests, very thick walls, and unusual chamber and apertural arrangements compared to other foraminifera found in the indurated carbonate-cemented mudstone beds. In the model presented in Figure 17, it is suggested that at least some of the Pualacana inhabited a flocculent layer at the sea floor surface that may have been in a low-oxygen zone. A similar situation was described for modern Trochammina from a flocculent layer at the mud-water interface by Tremblin et al. (2021, fig. 9).

The distinctive nature of the fossil assemblage (including the unusual morphology of Pualacana) suggests that unusual conditions existed during the deposition of the beds that underwent early diagenetic carbonate cementation. The conditions may have been influenced by the bacterial decay of organic matter in the mud resulting in methane production and perhaps sulfate-driven anaerobic oxidation of methane, resulting in precipitation of carbonate cement. This scenario will have to be confirmed through organic geochemistry (e.g., lipid and δ¹³C) analyses.

In Timor-Leste, Pualacana species are recognised from the Aitutu Group and the lowermost part of the Wailuli Group. The type locality of Pualacana hortai is Norian (within the Alaunian to Sevatian interval) according to palynology outlined by McCartain et al. (2024). According to Kristan-Tollmann (1960), with revisions by Gale et al. (2012c), the range of Pualacana catilliforme is Norian, P. cochlea is Norian–Rhaetian, and P. crassum is Norian. Diplotremina subangulata has a Norian to Rhaetian range (Haig et al., 2021a, Supplementary file 5); Oberhauserella rhaetica is from the Rhaetian (Kristan-Tollmann, 1964). Collectively the species described here suggest a Norian or Rhaetian age.

The stratigraphic ranges outlined above will probably be revised and refined with further biostratigraphic studies using conodonts and palynomorphs (including dinoflagellates) on Timor successions. In the lowermost Wailuli Group (about 11 m above base), Pualacana cochlea and Oberhauserella rhaetica are present where accompanying palynology indicates a Rhaetian age (McCartain et al., 2024). However, P. cochlea is present in many samples containing P. crassum and some samples containing P. catilliforme. It seems likely that P. cochlea ranges downward into at least the Sevatian (late Norian), as indicated by Gale et al. (2012c, fig. 2).

• Variostomatids from the Late Triassic of Timor are placed within the subfamily Variostomatinae that includes two genera: Variostoma based on the V. spinosum that is characterised by spinose chambers; and a new ornamented genus Pualacana that includes many species formerly included in Variostoma.

• Six species of Pualacana are recognised in the Late Triassic (Norian–Rhaetian) of Timor-Leste. Two of these species, P. hortai and P. xananai are new. Among the other species, P. catilliforme, P. cochlea, and P. crassum are well-known from Europe. Pualacana sp. cf. cochlea seems closely related to P. cochlea but with a more spindle-shaped test.

• Other families of the Order Robertinida that are present with Pualacana in the Late Triassic basinal facies in Timor-Leste include duostominids (viz., Duostomina turboidea and Diplotremina subangulata) and oberhauserellids (viz., Oberhauserella rhaetica).

• Many of the Pualacana specimens extracted from carbonate-cemented mudstones of the Aitutu Group in Timor-Leste have recrystallized siliceous tests. Acetate peel examination of the rock sample from which the holotype of P. hortai (type species of Pualacana) was extracted showed the presence of calcitic bioclasts with original microstructure preserved. In contrast, all Pualacana in this sample had recrystallized siliceous walls. This suggests that the Pualacana tests were originally composed of a mineral that was not calcite, but probably aragonite as suggested by some previous studies.

• Pualacana was widely distributed around the Late Triassic Tethyan Ocean between paleolatitudes 40°N to 40°S.

• In Timor-Leste, Pualacana is present only in basinal facies of the Norian–Rhaetian East Gondwana Interior Rift. They are common to abundant in carbonate-cemented mudstone beds of the Aitutu Group and less common in friable calcareous-mudstone of the lowermost Wailuli Group. This facies association is similar to that in the Hallstatt Basin of Austria. Here, the Pötchenkalke is similar to the Aitutu Group.

• As in the Pötchenkalke, the Aitutu Group includes cycles of indurated carbonate-cemented mudstone alternating with friable mudstone. The carbonate-cemented mudstone includes features indicating early diagenetic cementation. A depositional model suggests that the sedimentary couplets resulted from alternating periods of low and high influx of terrigenous mud into the basin (as mud plumes in the surface water). These would have resulted from periodic changes in hinterland climate (e.g., rainfall). The early diagenetic cementation may have been linked to decay of organic matter in the mud producing methane and the oxidation of this by Bacteria and Archaea and subsequent precipitation of carbonate-cement. This needs to be tested through organic geochemistry (e.g., lipid and δ¹³C) analyses.

• In contrast to other foraminifera present in the Late Triassic basinal facies in Timor-Leste, Pualacana species have extremely large tests, very thick walls, and unusual chamber and apertural arrangements. It is suggested that Pualacana may have inhabited a flocculent layer at the seafloor surface and may have lived in a low-oxygen zone.

• Collectively the species described here suggest a Norian or Rhaetian age. Further work is needed in linking the species occurrences in Timor-Leste to the distributions of conodonts and palynomorphs (including dinoflagellates).

We thank the local government authorities of Timor-Leste for permission to access the study area. Edwin M. D. C. O. Fraga, Bernardo N. de Araujo, Martalina L. de F. Monteiro, and David M. da Costa are thanked for their assistance during fieldwork, and Clément Tremblin, who helped us with SEM analyses and discussions on Foraminifera. We acknowledge the facilities and the scientific and technical assistance of Microscopy Australia at the Centre for Microscopy, Characterisation & Analysis, The University of Western Australia, a facility funded by the University, and State and Commonwealth Governments. Dr. Alexandra Suvorova provided very helpful advice on the operation of the Scanning Electron Microscope and EDS facility. Dr. Siri Kellner of the Earth Science Museum at The University of Western Australia is thanked for her curatorial assistance. We also thank the Oceans Institute and Oceans Graduate School, UWA, for providing the laboratory facilities necessary to process data. ISB is grateful to the Instituto de Geociências de Timor Leste for providing funding and logistics for this study. Permission to use Kristan-Tollman’s original figures of holotypes was gratefully received from GeoSphere Austria (these images remain under GeoSphere Austria copyright). Sylvain Rigaud and Luka Gale provided very valuable comments on an earlier version of the manuscript.