Chondrichthyan teeth from the Early Triassic Paris Biota (Bear Lake County,Idaho, USA)

A new, diverse and complex Early Triassic assemblage was recently discovered west of the town of Paris, Idaho (Bear Lake County), USA. This assemblage has been coined the Paris Biota. Dated earliest Spathian (i.e., early late Olenekian), the Paris Biota provides further evidence that the biotic recovery from the end-Permian mass extinction was well underway ca. 1.3 million years after the event. This assemblage includes mainly invertebrates, but also vertebrate remains such as ichthyoliths (isolated skeletal remains of fishes). Here we describe first fossils of Chondrichthyes (cartilaginous fishes) from the Paris Biota. The material is composed of isolated teeth (mostly grinding teeth) preserved on two slabs and representing two distinct taxa. Due to incomplete preservation and morphological differences to known taxa, the chondrichthyans from the Paris Biota are provisionally kept in open nomenclature, as Hybodontiformes gen. et sp. indet. A and Hybodontiformes gen. et sp. indet. B, respectively. The present study adds a new occurrence to the chondrichthyan fossil record of the marine Early Triassic western USA Basin, from where other isolated teeth (Omanoselache, other Hybodontiformes) as well as fin spines of Nemacanthus (Neoselachii) and Pyknotylacanthus (Ctenachanthoidea) and denticles have been described previously.     

A late-surviving Triassic protomonaxonid sponge from the Paris Biota (Bear Lake County,Idaho, USA)

Protomonaxonid sponges are a major group of Cambrian and Ordovician fossils in exceptionally preserved (especially Burgess Shale-type) faunas, but are rare thereafter. Rare examples of apparent surviving lineages are known from the late Palaeozoic and Mesozoic, but by this time more derived groups of sponges have generally displaced them in at least shallow-water (shelf depth) ecosystems. The early Spathian (Early Triassic) Paris Biota includes abundant material of a new leptomitid protomonaxonid, Pseudoleptomitus advenus Botting nov. gen., nov. sp., distinguished by having an unbundled longitudinal skeleton and very weak transverse component. This is the first post-Ordovician leptomitid known, and indicates long-term survival of the group in unknown environments. Its occurrence near storm wave base is similar to the preferred environment of earlier examples of the family, suggesting either ecological rarity or taphonomic reasons for their ∼200-million-year absence from later Palaeozoic rocks.     

Deciphering the exceptional preservation of the Early Triassic Paris Biota (Bear Lake County,Idaho, USA)

After the end-Permian mass extinction, the Early Triassic (∼251.9 to 247 Ma) is characterized by several biotic crises that particularly affected marine faunas; accordingly, marine ecosystems from this unstable interval have been often described as heavily depauperate. This assumption, however, may relate to a biased fossil record. The discovery of taphonomic windows, like Konservat-Lagerstätten, in the Early Triassic would help to better understand the composition and diversity of ecosystems at that time. The Paris Biota (Idaho, USA) is a highly diverse fossil assemblage from the earliest Spathian (early late Olenekian, ∼250.6 Ma), indicating a rapid rediversification for many groups after the end-Permian crisis and pointing toward a remarkably complex marine ecosystem ∼1.3 m.y. after the Permian-Triassic boundary. However, its detailed taphonomy has not yet been investigated. Here we present the mineral characterization of four of its most abundant taxa: discinoid and linguloid brachiopods, leptomitid sponges, and caridean shrimps. For this purpose, we combined data from Raman microspectroscopy, Fourier Transform InfraRed spectroscopy, and SEM-EDXS. Although all taxa were preserved in calcium phosphate, the morphology, structuring and size of crystals are highly dissimilar at a nano- to micrometric scale. In brachiopods, the ultrastructure of calcium phosphate shows unorganized bacillary-like crystals, while in crustaceans their size is considerably smaller and round-shaped. Similar small crystals are observed in sponges. However, the ultrastructure of calcium phosphate in sponges exhibits a well-defined preferential orientation. In addition, sponges show some compressed but preserved three-dimensional features, with an inner surface better preserved. Such analyses are essential to understand the taphonomic pathways enabling exceptional preservation. The further comprehension of preservation features would help to understand potential bias on observed diversity signals and their interpretation.     

New thylacocephalans from the Early Triassic Paris Biota (Bear Lake County,Idaho, USA)

Two new genera and species of thylacocephalans (Arthropoda, Thylacocephala), Parisicaris triassica Charbonnier and Ligulacaris parisiana Charbonnier, are described from the early Spathian Paris Biota. These new occurrences are the first reports of thylacocephalans from Triassic rocks in North America. They considerably enlarge the spatiotemporal distribution of these enigmatic arthropods and highlight their relatively high generic richness during the Early Triassic. It also confirms that the Triassic was the taxonomically richest period for Thylacocephala.     

Smithian (Early Triassic) ammonoids from Tulong, South Tibet

Intensive sampling of the Tulong Formation in South Tibet has facilitated the construction of a highly-resolved middle and late Smithian ammonoid succession. The new biostratigraphical sequence comprises the middle Smithian Brayardites compressus beds, Nammalites pilatoides beds, and the Nyalamites angustecostatus beds followed by the late Smithian Wasatchites distractus beds and Glyptophiceras sinuatum beds. This faunal succession correlates very well with that of other Tethyan sequences such as the Salt Range (Pakistan), Spiti (India), Oman and South China. The Smithian faunal sequence from Tulong contains several taxa with broad geographic distribution (e.g., Owenites, Paranannites spathi, Shigetaceras, Wasatchites), thus enabling correlation with faunal successions from areas outside the Tethys (e.g., USA, British Columbia, Arctic Canada, South Primorye, Siberia). Early Smithian ammonoid faunas are almost absent in Tulong because of a preservation bias (absence of carbonate rocks). Five new ammonoid genera (Brayardites, Nammalites, Nyalamites, Shigetaceras, Tulongites) and six new species (Brayardites crassus, Brayardites compressus, Prionites involutus, ?Subflemingites compressus, Tulongites xiaoqiaoi, Urdyceras tulongensis) are described.     

Latest Smithian (Early Triassic) ammonoid assemblages in Utah (western USA basin) and their implications for regional biostratigraphy,biogeography and placement of the Smithian/Spathian boundary

The late Smithian extinction represents a major event within the Early Triassic. This event generally corresponds to a succession of two, possibly three successively less diverse, cosmopolitan ammonoid assemblages, which when present, provide a robust biostratigraphic framework and precise correlations at different spatial scales. In the western USA basin, known occurrences of latest Smithian taxa are rare and until now, have only been documented from northeastern Nevada. Based on these restricted basinal occurrences, a regional zone representing the latest Smithian was postulated but not corroborated, as representative taxa had not yet been reported from outside Nevada. Here we document two new ammonoid assemblages from distant localities in northern Utah, overlying the late Smithian Anasibirites beds and characterized by the unambiguous co-occurrence of Xenoceltites subevolutus and Pseudosageceras augustum. The existence of a latest Smithian zone in the western USA basin is therefore validated, facilitating the identification of the Smithian/Spathian boundary and intra-basin correlation. This zone also correlates with the latest Smithian zone recognized from southern Tethyan basins. Additionally, these new data support other observed occurrences of Xenoceltites subevolutus throughout most of the late Smithian.     

A new brittle star (Ophiuroidea: Ophiodermatina) from the Early Triassic Paris Biota (Bear Lake County,Idaho, USA)

Knowledge on the morphology of Early Triassic ophiuroids is very limited, in spite of the relatively high number of described species. This hampers attempts to use morphology-based phylogenetic analyses in order to explore the early diversification of the ophiuroid modern clades between the latest Paleozoic and the early Mesozoic. Here, a new ophiuroid from the Early Triassic of southern Idaho (USA) is described and assigned to the new taxon Shoshonura brayardi Thuy nov. gen., nov. sp. It is part of an exceptional Early Triassic faunal assemblage recently described as the Paris Biota. On account of the arm morphology and the shape of the arm spines and arm spine articulations, Shoshonura brayardi nov. gen., nov. sp. is considered a basal member of the suborder Ophiodermatina.     

A new holocrinid (Articulata) from the Paris Biota (Bear Lake County,Idaho, USA) highlights the high diversity of Early Triassic crinoids

After the end-Permian crisis and the extinction of their four Paleozoic subclasses, crinoids rapidly recovered. This group is classically believed to have radiated from a small surviving clade and to have diversified during the Middle and Upper Triassic from two lineages. Nevertheless, recent findings suggested that several lineages of crinoids had already diversified during the Early Triassic, and that their diversity has been overlooked. Here we describe a new form of holocrinid, Holocrinus nov. sp., from the earliest Spathian (Early Triassic) of southeastern Idaho (USA). So far, the exceptional completeness of sampled specimens, with skeletal elements of arms and stem in connection, is unique for the Early Triassic. They show that derived morphological features had already evolved ∼1.3 million years after the Permian–Triassic boundary, supporting the scenario of a rapid Early Triassic diversification of crinoids.     

Taxonomy of the proterosuchid archosauriforms (Diapsida: Archosauromorpha) from the earliest Triassic of South Africa,and implications for the early archosauriform radiation

Proterosuchidae is one of the first clades of Archosauriformes (archosaurs and closely related species) to appear in the fossil record, with the richest sample of the group coming from the Lystrosaurus Assemblage Zone (earliest Triassic) of South Africa. Four nominal proterosuchid species were described from South Africa during the twentieth century (Proterosuchus fergusi, Chasmatosaurus vanhoepeni, Chasmatosaurus alexanderi and Elaphrosuchus rubidgei), but interpretations of their taxonomy have been widely disparate. The most recent taxonomic revision concluded that P. fergusi is the only valid species and that the other nominal species are junior subjective synonyms of this taxon. This proposal was based on the interpretation that anatomical differences between the nominal species could be explained as a result of ontogenetic changes and/or post‐mortem deformation. The recent discoveries of multiple new South African proterosuchid specimens provide an impetus to revisit their taxonomy. Based upon a comprehensive re‐examination of all known specimens, as well as examination of other proterosuchid taxa in collections worldwide, we conclude that the holotype of Proterosuchus fergusi is undiagnostic. As a result, we propose a neotype (RC 846) for the species. ‘Chasmatosaurus vanhoepeni’ and ‘Elaphrosuchus rubidgei’ are considered subjective junior synonyms of P. fergusi. ‘Chasmatosaurus’ alexanderi is considered a valid species, for which we propose the new combination P. alexanderi comb. nov. A third species, P. goweri sp. nov., is erected on the basis of a single specimen (NMQR 880). All three species recognized here are taxonomically distinct from a previously described archosauriform maxilla from the lower Lystrosaurus AZ. As a result, we recognize a minimum of four archosauriform species following the Permo‐Triassic mass extinction in South Africa. Our results suggest a greater species richness of earliest Triassic archosauriforms than previously appreciated, but that archosauriform morphological disparity remained low and did not expand until the late Early Triassic – early Mid‐Triassic.     

Diversity starts early: notharctid primates from the Sandcouleean (Early Eocene) of the Powder River Basin,Wyoming, USA

Abstract

Abundant specimens, mostly isolated teeth, of the Primate family Notharctidae occur in the Early Eocene rocks of the Powder River Basin of northeastern Wyoming, USA. Very early in the North American history of the family, the notharctid species diversified and this diversity may have been widespread, and not restricted to more southerly areas in the Rocky Mountains. The diversity is shown by detailed analysis of the molar dentition. Two new genera are established: Megaceralemur with Megaceralemur trigonodus as its type and Megaceralemur matthewi sp. nov. as a Sandcouleean species and Pinolophus, with Pinolophus meikei sp. nov. as its type, for a form with an entoconid notch on lower molar 1. Megaceralemur has a prominent nannopithex-fold which dominates the posterior cingulum of upper molars 1–2 and a cristid obliqua on lower molar 1 which attaches to the metaconid, not the metalophid as it does in Cantius and other genera. A small species, Cantius lohseorum sp. nov., is named for a derived lineage the size of Cantius torresi.

urn:lsid:zoobank.org:pub:066DC515-A2DD-40AF-AD8A-3834E2AFD0FB     

Early Triassic bivalves from the Feixianguan Formation in Xingyi,Guizhou and the Ximatang Formation in Qiubei,Yunnan (southern China)

Based on newly collected materials from the Lower Triassic Feixianguan Formation of Xiongwu section in Xingyi, Guizhou and the Ximatang Formation of Ximatang section in Qiubei, Yunnan, southern China, nine species belonging to seven genera are described. Two bivalve assemblages are recognized and regionally correlated in South China. The bivalve assemblage from the Feixianguan Formation of Xiongwu exhibits a higher diversity including seven species belonging to seven genera: Claraia griesbachi, Leptochondria virgalensis, Entolium (Entolium) microtis, Towapteria scythicum, Bakevillia exporrecta, Bositra sp., and Unionites? fassaensis. In contrast, the bivalve assemblage from the Ximatang Formation of Ximatang has a much lower diversity, consisting of only two species, i.e., Claraia griesbachi and Claraia radialis. Additionally, C. griesbachi and C. radialis, as the most common species of Claraia in the Early Triassic, are revised.     

Discovery of the Jehol Biota from the Celaomiao region and discussion of the Lower Cretaceous of the Bayingebi Basin,northwestern China

Some typical components of the Jehol Biota, including conchostracans Eosestheria sp., the mayfly Ephemeropsis trisetalis Eichwald, 1864, the aquatic beetle Coptoclava longipoda Ping, 1928, and a fragmentary dragonfly, are reported for the first time from the Bayingebi Formation in the Celaomiao region, western Inner Mongolia, China. This discovery indicates that the middle Upper Member of Bayingebi Formation can be correlated with the upper Yixian and the lower Jiufotang formations in western Liaoning Province. Combining it with the radio-isotopic dating result, we further believed that the Upper Member of Bayingebi Formation could be roughly correlated with the Yixian, Jiufotang, and Shahai formations, and the overlying Suhongtu Formation with the Fuxin Formation in western Liaoning Province.In the major Bayingebi Basin, palaeontological and radio-isotopic dating evidence shows that the Bayingebi Formation has a long depositional history of over 30 Ma: its Upper Member bearing the Jehol Biota and the early Fuxin Biota is probably coeval to the Yixian, Jiufotang and Shahai formations and has a Barremian–early Albian age; its Lower Member may be Berriasian–Hauterivian in age and could be correlated with the upper Tuchengzi, Zhangjiakou, and Dabeigou formations in northern Hebei Province. This suggests that the Bayingebi Formation should be promoted to the stratigraphic rank of group and subdivided into several secondary units (formations). Unlike the previous result, the Yingen Formation is considered across the Lower Cretaceous–Upper Cretaceous boundary and being late Albian–early Turonian in age.     

An unusually diverse mollusc fauna from the earliest Triassic of South China and its implications for benthic recovery after the end-Permian biotic crisis

A single carbonate coquinoid lens from the Griesbachian (Early Triassic) of Shanggan, South China, yielded 11 bivalve species described in this study in addition to four gastropod and one ammonoid species reported elsewhere. This makes the Shanggan fauna one of the richest mollusc faunas from the early post-extinction interval after the end-Permian mass extinction event. Four of the present genera are long-term survivors, five are holdovers that went extinct at the end of the Griesbachian or later in the Early Triassic, and seven first appear in the Griesbachian. Three new bivalve species are described: Myalinella newelli nov. sp., Scythentolium scutigerulus nov. sp., and Eumorphotis shajingengi nov. sp. The genus Astartella, previously assumed to have vanished at the end of the Permian, is reported for the first time from the Early Triassic, which also removes Astartidae from Early Triassic Lazarus taxa. The small growth size of the Astartella specimens supports an earlier hypothesis that many of the Early Triassic Lazarus taxa did not survive in unknown refuges but were simply overlooked due to the scarcity of easily observable large-sized specimens. Ecologically, a comparatively high proportion of infaunal bivalve species (4/11) is remarkable for the early post-extinction interval, supporting the impression of a relatively advanced recovery state. Moreover, abundance-data of the bivalve-gastropod community reveal a remarkably low dominance index (D = 0.17) that is suggestive for advanced recovery and stable environmental conditions. It is proposed that the Shanggan fauna represents a late Griesbachian benthic recovery event that coincided with the appearance of similarly diverse benthic faunas in Oman and Primorye. A high proportion of genera that have previously not been reported from the Early Triassic indicate that the prevalence of poor preservation conditions is a major obstacle in identifying early phases of recovery from the greatest crisis in the history of metazoan life. The early recovery of benthic faunas reported in this study questions previous claims of a prolonged lag phase as a consequence of the extraordinary extinction magnitude or the persistence of adverse environmental conditions.     

An early cretaceous section in the Kircaova area (Berdiga Limestone,NE-Turkey) and its correlation with platform carbonates in W-Slovenia

Summary In the Kale (Gümüshane) area in the North Eastern Turkey, platform carbonates of the Berdiga Limestone were deposited during Late Jurassic-Early Cretaceous time in environments varying from intertidal to fore reef. The sequence shows extensive lateral and vertical alterations and interfingering of different facies types. In the upper part of the Berdiga Limestone in the Kircaova area a bituminous thin-bedded to platy limestone and shale 5 to 6 m thick occurs at the Early/Late Aptian boundary. It is underlain by limestones rich in silica nodules of up to 10 cm size. A facies analysis of a section about 70 m thick including the bituminous interval was carried out in 1994/95 at the SW border of the Kircaova area close to the road from L?rikas to Kale. The limestones consist mainly of packstones and grainstones locally rich in calcareaous algae and forminifera. Fragments of molluscs and echinoids as well as some ostracods and calcispheres occur. Some sponges, corals, and beds rich in molluscs occur in minor amounts in the middle part of the section which is characterized by intertidal to shallow subtidal facies. Algae and foraminifera indicate a Barremian-Early Aptian age of the lower part and Late Aptian age of the upper part of the section (e.g.Salpingoporellamuehlbergii, Salpingoporella aff.melitae, Clypeina solkani, Novalesia producta), divided by the bituminous limestones. In West Slovenia (close to the Italian border) a complete Cretaceous section occurs at Sabotin mountain containing Aptian beds with comparable faunal composition. In contrast to the Berdiga Limestone, in Slovenia at the rim of the dinaric platform a patch reef about 50 m in thickness is developed which is also covered by a bituminous limestones (black shale) marking the Early/Late Aptian boundary. Faunal elements in Slovenia arePalorbitolina lenticularis, Cuneolina laurentii, Orbitolina (Mesorbitolina) texana andSalpingopoprella dinarica. The bituminous limestone appears to be a marker horizon. At both locations it is locally rich in characeans probably indicating a regressive maximum before another transgression began in the Late Aptian/Albian as world-wide drowning event. Possibly the occurrence of the bituminous limestone (black shale) is associated with volcanic activity during the Aptian. If so it could be used as a chronostratigraphic marker horizon in both areas analyzed.     

Differentiation of tetrapod communities and some aspects of biotic events in the early triassic of Eastern Europe

The patterns of spatial differentiation of the Early Mesozoic terrestrial biota in Eastern Europe and Australia-Tasmania demonstrate that the tetrapod faunal recovery following the Permian extinction was characterized by both global and regional heterogeneity. Local distinctions observed in the development of Early Triassic tetrapod assemblages of European Russia allow the recognition of the following realms: (1) the central and northern regions of the East European Platform (Moscow-Mezen Syncline) and the Timan-North Ural Region; (2) the southern Fore-Urals, including the Obshchii Syrt Plateau; and (3) the southern regions of the East European Platform (the slope of the Voronezh Anticline). Climatic conditions at the initial stage of the development of local communities were characterized by an increase in aridity and seasonal contrasts of climate. Therefore, terrestrial assemblages mostly concentrated in the aquatic and coastal biotopes. Accordingly, vertebrate assemblages of the region were dominated everywhere by aquatic amphibians and semiaquatic reptiles, while the accompanying palynomorph assemblages show the predominance of hygrophilous vegetation indicative of swampy mangrove setting. With respect to amphibians, a peak of local biogeographic differentiation falls on the onset of the Early Triassic and, in the case of reptiles, on the end of this time span. This change conforms to the increasing role of reptiles in the overall taxonomic diversity with time. Among the three main biogeographic units of the region, the Southern Fore-Ural Realm is distinguished by the maintenance of distinct faunal links with Gondwanan regions. The Southern Realm shows a connection with the Germanic Basin and more western Euramerican areas, which is documented for the Late Olenekian and occurred under influence of coastal marine conditions.     

Neogene Fallout Tuffs from the Yellowstone Hotspot in the Columbia Plateau Region,Oregon, Washington and Idaho,USA

Sedimentary sequences in the Columbia Plateau region of the Pacific Northwest ranging in age from 16–4 Ma contain fallout tuffs whose origins lie in volcanic centers of the Yellowstone hotspot in northwestern Nevada, eastern Oregon and the Snake River Plain in Idaho. Silicic volcanism began in the region contemporaneously with early eruptions of the Columbia River Basalt Group (CRBG), and the abundance of widespread fallout tuffs provides the opportunity to establish a tephrostratigrahic framework for the region. Sedimentary basins with volcaniclastic deposits also contain diverse assemblages of fauna and flora that were preserved during the Mid-Miocene Climatic Optimum, including Sucker Creek, Mascall, Latah, Virgin Valley and Trout Creek. Correlation of ashfall units establish that the lower Bully Creek Formation in eastern Oregon is contemporaneous with the Virgin Valley Formation, the Sucker Creek Formation, Oregon and Idaho, Trout Creek Formation, Oregon, and the Latah Formation in the Clearwater Embayment in Washington and Idaho. In addition, it can be established that the Trout Creek flora are younger than the Mascall and Latah flora. A tentative correlation of a fallout tuff from the Clarkia fossil beds, Idaho, with a pumice bed in the Bully Creek Formation places the remarkably well preserved Clarkia flora assemblage between the Mascall and Trout Creek flora. Large-volume supereruptions that originated between 11.8 and 10.1 Ma from the Bruneau-Jarbidge and Twin Falls volcanic centers of the Yellowstone hotspot in the central Snake River Plain deposited voluminous fallout tuffs in the Ellensberg Formation which forms sedimentary interbeds in the CRBG. These occurrences extend the known distribution of these fallout tuffs 500 km to the northwest of their source in the Snake River Plain. Heretofore, the distal products of these large eruptions had only been recognized to the east of their sources in the High Plains of Nebraska and Kansas.     

江西玉山上奥陶统凯迪阶三衢山组的丛花海绵(Corymbospongia)*

串管海绵在中–晚奥陶世经历了的首次辐射演化事件, 在北美、新南威尔士、哈萨克斯坦、西伯利亚和中国西北等地的上奥陶统地层中皆有报道, 但研究程度较低。本文系华南奥陶系串管海绵首次系统古生物学的报道, 详细描述江西玉山上奥陶统凯迪阶三衢山组的Corymbospongia (丛花海绵属)化石, 并基于C. amplia Rigby, Karl, Blodgett & Baichtal, 2005和C. mica Rigby & Potter, 1986的标本展示该属化石外壁的微孔等特征性结构, 这2个种具有跨板块的生物地理分布。综合串管海绵产出层的碳酸盐岩微相以及伴生钙藻和珊瑚化石等群落分子的指相参照, 识别C. amplia和C. mica均具有明显的生态专属性: C. amplia为造礁生物, 在小型微生物岩中出现; C. mica则代表适应于更浅水生境的平地群落代表。本研究将为从底栖生物群落角度开展扬子区生物地层学及古地理重建提供进一步的依据。     

Middle-late Asselian (Early Permian) fusulinid fauna from the post-Variscan cover in NW Anatolia (Turkey): Biostratigraphy and geological implications

The earliest autochthonous cover of the Variscan basement of the Sakarya Composite Terrane (SCT) in NW Anatolia is represented by basal conglomerates and limestones. The microfacies types of the limestones in ascending order are: (1) bioclastic grainstone/packstone, (2) fusulinid grainstone/packstone, (3) smaller foraminiferal grainstone/packstone, (4) Anthracoporella (dasycladale) grainstone/packstone, and (5) wackestones. Twenty-three species assignable to 15 genera of fusulinids were recovered from the studied materials of the Kadirler section; Quasifusulinaguvenci nov. sp. and Pseudoschwagerinabeedeimagna nov. subsp. are created. Rugosofusulinids, sphaeroschwagerinids, pseudoschwagerinids, occidentoschwagerinids, pseudochusenellids, quasifusulinids, rugosochusenellids and paraschwagerinids are the main faunal elements of the succession, which shows two distinct faunal intervals. Eoschubertella, Schubertella, Biwaella?, Rugosofusulinastabilis group, and Pseudochusenella correspond to the first interval at the base; the second interval is characterized by the species of Sphaeroschwagerina, Pseudoschwagerina,Occidentoschwagerina, the Rugosofusulinalatispiralis group, and diverse quasifusulinids. A biostratigraphic correlation shows that the Kadirler section in the SCT in NW Anatolia shares many common species with Central Asia in the East but especially with the Carnic Alps and Karavanke Mountains in the West. The new data suggest that the close faunal relationship in the Late Carboniferous between eastern Alps, Ural Mountains, NW Turkey and Central Asia also continued during the Asselian.     

Evolutionary stasis,ecophenotypy and environmental controls on ammonite morphology in the Late Cretaceous (Maastrichtian) Western Interior Seaway,USA

We test for the presence of evolutionary stasis in a species of Late Cretaceous ammonoid cephalopod, Hoploscaphites nicolletii, from the North American Western Interior Seaway. A comprehensive dataset of morphological traits was compiled across the entire spatial and temporal range of this species. These were analysed in conjunction with sedimentologically and geochemically derived palaeoenvironmental conditions hypothesized to apply selective pressures. All changes in shell shape were observed to be ephemeral and reversable, that is, no unidirectional trend could be observed in any of the morphological traits analysed. Correlations between palaeoenvironmental conditions and morphological traits suggests ecophenotypic processes were at play; however, either environmental changes were too minor and/or provided no isolating mechanism to drive speciation. These data support mechanisms of stasis such as homogenizing gene flow or stabilizing selection under a fluctuating optimum (probably reflecting spatiotemporally heterogeneous palaeoenvironmental conditions). Finally, changes in shell size were not significantly associated with changes in shell-specific δ¹⁸O, despite a correlation between shell size and δ¹⁸O averaged across horizons. This suggests a mismatch in scales of geochemical sampling that supports caution when making broad interpretations based on averaged geochemical data.