Abstract Palaeogeographers, geographers and structural geologists use different well-defined terms to designate continental and tectonic units, whereas biogeographers, palaeobiogeographers and palaeontologists use a wide range of subjective terminologies to describe biogeographical and palaeobiogeographical units. The absence of clear definitions and of rules or guidelines for palaeobiogeographical nomenclature has resulted in frequent misunderstandings and general confusion, in particular when applied to ancient time periods, such as the Palaeozoic. Palaeogeographical and palaeobiogeographical terminology used in Palaeozoic geology and palaeontology is reviewed, and recent attempts to standardize palaeobiogeographical nomenclature summarized. We make a number of proposals for future use of terms to avoid confusion and misunderstandings.

Abstract The phylogeographical evolution and the consequent changing distribution and diversity of rhynchonelliform brachiopods through the Ordovician are linked to the dynamic palaeogeography of the period. The Early Ordovician (Tremadocian and Floian) is characterized by globally low-diversity faunas with local biodiversity epicentres, notably on the South China Palaeoplate; low-latitude porambonitoid-dominated faunas with early plectambonitoid and clitambonitoid representatives, as well as high-latitude assemblages mostly dominated by orthoids, can be recognized, but many taxa are rooted in Late Cambrian stocks. The Early Ordovician displays a steady increase in rhynchonelliformean biodiversity, which was mostly driven by the increasing success of the Porambonitoidea and Orthoidea, but the billingsellids and early plectambonitoids also contributed to this expansion. During the Early to Mid Ordovician (Dapingian–Darriwilian), marine life experienced an unprecedented hike in diversity at the species, genus and family levels that firmly installed the suspension-feeding benthos as the main component of the Palaeozoic fauna. However, this may have occurred in response to an early Darriwilian annihilation of existing clades, some of which had been most successful during the Early Ordovician. New clades rapidly expanded. The continents were widely dispersed together with a large number of microcontinents and volcanic arcs related to intense magmatic and tectonic activity. Climates were warm and sea-levels were high. Pivotal to the entire diversification is the role of gamma (inter-provincial) diversity and by implication the spread of the continents and frequency of island arcs and microcontinents. The phylogeographical analysis demonstrates that this new palaeogeographical configuration was particularly well explored and utilized by the strophomenides, especially the Plectambonitoidea, which radiated rapidly during this interval. The porambonitoids, on the other hand, were still in recovery following the early Darriwilian extinctions. Orthides remained dominant, particularly at high latitudes. Biodiversity epicentres were located on most of the larger palaeoplates, as well as within the Iapetus Ocean. Provincial patterns were disrupted during the Sandbian and early Katian with the migration of many elements of the benthos into deeper-water regimes, enjoying a more cosmopolitan distribution. Later Katian faunas exhibit a partition between carbonate and clastic environments. During the latest Katian, biogeographical patterns were disrupted by polewards migrations of warm-water taxa in response to the changing climate; possibly as a consequence of low-latitude cradles being developed in, for instance, carbonate reef settings. Many clades were well established with especially the strophomenides beginning to outnumber the previously successful orthides, although this process had already begun, regionally, in the mid to late Darriwilian. At the same time, atrypoid and pentameroid clades also began to radiate in low-latitude faunas, anticipating their dominance in Silurian faunas. The Hirnantian was marked by severe extinctions particularly across orthide-strophomenide clades within the context of few, but well-defined, climatically controlled provincial belts. Supplementary material: The individual localities and a reference list for the data sources are provided at: http://www.geolsoc.org.uk/SUP18667

Abstract The northeastern margin of Laurentia formed an important part of the Iapetus Ocean and includes the development of the Franklinian Basin in North Greenland and Arctic Canada. The uninterrupted continental margin bordering the North American craton is represented by well-exposed successions in Northeast and eastern North Greenland, together with Svalbard and Bjørnøya. Physiographically, the northeastern margin of Laurentia during the early Paleozoic history of Greenland was a northward extension of the passive rifted continental margin of the Caledonian continental edge of Laurentia. It was a transform-rifted margin and represents the part of the Laurentian margin that borders the Arctic part of the North Atlantic Ocean. Geologically, the northwestern segment of the continental margin has a somewhat different setting and development from farther south in the Northeast Greenland–Svalbard segment but both regions overlie a thick and extensive package of Neoproterozoic rocks and were affected by the Caledonian orogeny.

Abstract The Neoproterozoic succession of East and North-East Greenland (over 14 000 m thick) includes the Eleonore Bay Supergroup (?Tonian–Cryogenian) and the Tillite Group (Cryogenian–Ediacaran). The upper units of the Eleonore Bay Supergroup consist of shallow to deeper-water carbonates, succeeded by siliciclastic fine-grained sediments (Bedgroup 19) that characterize the top unit of the supergroup. The Tillite Group includes two diamictite-bearing units (Ulvesø and Storeelv formations) of glaciogenic origin and two upper, upwards-shallowing strata (Canyon and Spiral Creek formations) that were deposited during semiarid conditions and concluded the Neoproterozoic depositional cycle. Diamictite is preserved on the craton and compares with the Storeelv Formation (Fm.) of the Tillite Group. Detailed investigations of the diamictite-bearing units (i.e. Ulvesø and Storeelv formations) demonstrate that the lower of the two formations is mainly of marine origin, whereas the upper one has both marine and terrestrial origins. Chemostratigraphic data include analyses on total carbon (TC), total organic carbon (TOC), total sulphur (TS) and δ 13 C. The data set for δ 13 C shows a substantial and abrupt shift towards negative values of ≥10%, from below Bedgroup 19. Low-diversity acritarch assemblages (Cryogenian) are recorded from the Andrée Land and Tillite groups; a thin cherty dolostone unit present above the Storeelv Fm. suggests that the diamictite units are of late Cryogenian age and the upper part of the Tillite Group is Ediacaran. Bedgroup 19 disconformably overlies older carbonates and the unit is a prelude to the succeeding (upper Cryogenian–lower Ediacaran) diamictite sediments of the Tillite Group. A disconformity separates the Tillite Group from the overlying Lower Palaeozoic sediments. Both disconformities are, according to palaeomagnetic data, related to rift–drift episodes that occurred during the late Neoproterozoic. Alternatively, the isotope data suggest that the diamictites were deposited during the late Cryogenian glaciation and the older disconformity may be interpreted as a significant gap developed by the lowering of sea level during an early Cryogenian glaciation.

Abstract During the early to mid-Ordovician, marine life experienced an unprecedented rise in diversity at the species, genus and family levels that firmly installed the suspension-feeding benthos as the main component of the Palaeozoic fauna. The earlier Ordovician was characterized by a wide dispersal of the continents together with a high frequency of microcontinents and volcanic arcs. Magmatic and tectonic activity was intense, climates were warm and sea levels were high. Central to the entire diversification is the role of gamma (inter-provincial) diversity and by implication the spread of the continents and frequency of island arcs and microcontinents. A disparate group of continental fragments and island arcs loosely assigned to the Celtic province contained distinctive shelly faunas that formed a testable biogeographical unit. The Celtic faunas are characterized by a large number of endemic brachiopod taxa, some cosmopolitan forms, and taxa at the beginning or end of their stratigraphical ranges. The associated trilobite faunas are composed largely of wide-ranging genera, a few genera at the start of their stratigraphical range and some recently evolved taxa extending their geographical range. The Celtic province helped provide a burst of gamma diversity during the early stages of the Ordovician Radiation whereas the timing and position of the archipelagos associated with the Celtic province may have provided a mechanism for the diachroneity associated with the diversification.

Abstract During the Arenig-Llanvirn interval a series of radiations across all the major clades, established the Brachiopoda as a major component of the Palaeozoic benthos. Radiations on Baltica and Laurentia during the Arenig formed the basis for two distinct biogeographical provinces with contrasting articulated brachiopod faunas. These platform provinces were supplemented by the marginal Celtic and Toquima-Head provinces; the latter included both marginal and intra-ocean island sites. These marginal and intra-oceanic sites may have served as both ‘cradles and museums’ alternately providing sources for radiations on the platforms and refugia for otherwise relict taxa. Such terranes also partitioned oceanic circulation patterns within the Iapetus Ocean and provided mosaics of rapidly changing, nearshore unstable environments. In contrast to later Ordovician brachiopod faunas, many early Ordovician genera are reported from only one or two sites in the Iapetus region; narrow geographical ranges are characteristic of many taxa. The strong biogeo-graphic differentiation at the generic level is less marked at the familial and higher levels suggesting a series of late Cambrian and early Ordovician migrations prior to the more regional development of the Arenig-Llanvirn brachiopod biofacies across the Iapetus terranes. However, the origination of many brachiopod taxa apparently occurred outside the Iapetus region suggesting that the initial stages of the Ordovician radiations here were first spiked by a series of immigrations.