Vyazniki biotic assemblage of the terminal Permian

A new unique and diverse biotic assemblage of the terminal Permian has recently been discovered in the town of Vyazniki (Central Russia). The Vyazniki terrestrial community is transitional between Permian and Triassic ones and represents the last, so far unknown stage of the global ecological crisis of the continental biota at the Permian-Triassic boundary. The successive development of land biotic crisis in the Late Permian, which was followed by mass extinction at the Permian-Triassic boundary, and long, successive postcrisis development and specialization of new Triassic groups as well as rearrangement and diversification of the biotic assemblage composition and community structure suggest predominance of intrinsic, biotic causes of this crisis, realized in destabilization, alteration, and new stabilization of continental communities and ecosystems.     

Sequence of Permian Tetrapod Faunas of Eastern Europe and the Permian–Triassic Ecological Crisis

Eastern Europe shows the most complete in the world continuous sequence of continental Permian and Triassic deposits, which allows the development of tetrapod faunas over more than 17 successive stages to be traced. The newly obtained data on transitional Vyazniki and Sundyr tetrapod faunas provide more complete characteristics of the Severodvinian (Late Guadalupian, pre-Lopingian) and Permian-Triassic ecological crises and the ways of replacement of the dominant vertebrate groups of Eastern Europe.     

The Permian–Triassic transition and the onset of Mesozoic sedimentation at the northwestern peri-Tethyan domain scale: Palaeogeographic maps and geodynamic implications

The main aim of this paper is to review Middle Permian through Middle Triassic continental successions in European. Secondly, areas of Middle–Late Permian sedimentation, the Permian–Triassic Boundary (PTB) and the onset of Triassic sedimentation at the scale of the westernmost peri-Tethyan domain are defined in order to construct palaeogeographic maps of the area and to discuss the impact of tectonics, climate and sediment supply on the preservation of continental sediment.At the scale of the western European peri-Tethyan basins, the Upper Permian is characterised by a general progradational pattern from playa-lake or floodplain to fluvial environments. In the northern Variscan Belt domain, areas of sedimentation were either isolated or connected to the large basin, which was occupied by the Zechstein Sea. In the southern Variscan Belt, during the Late Permian, either isolated endoreic basins occurred, with palaeocurrent directions indicating local sources, or basins underwent erosion and/or there was no deposition. These basins were not connected with the Tethys Ocean, which could be explained by a high border formed by Corsica–Sardinia palaeorelief and even parts of the Kabilia microplate. The palaeoflora and sedimentary environments suggest warm and semi-arid climatic conditions.At the scale of the whole study area, an unconformity (more or less angular) is observed almost everywhere between deposits of the Upper Permian and Triassic, except in the central part of the Germanic Basin. The sedimentation gap is more developed in the southern area where, in some basins, Upper Permian sediment does not occur. The large sedimentary supply, erosion and/or lack of deposition during the Late Permian, as well as the variable palaeocurrent direction pattern between the Middle–Late Permian and the Early Triassic indicate a period of relief rejuvenation during the Late Permian. During the Induan, all the intra-belt basins were under erosion and sediment was only preserved in the extra-belt domains (the northern and extreme southern domains). In the northern domain (the central part of the Germanic Basin), sediment was preserved under the same climatic conditions as during the latest Permian, whereas in the extreme southern domain, it was probably preserved in the Tethys Ocean, implying a large amount of detrital components entering the marine waters. Mesozoic sedimentation began in the early Olenekian; the ephemeral fluvial systems indicate arid climatic conditions during this period. Three distinct areas of sedimentation occur: a northern and southern domain, separated by an intra-belt domain. The latter accumulated sediments during the Early–Middle Permian and experienced erosion and/or no-deposition conditions between the Middle–Late Permian and the beginning of Mesozoic sedimentation, dated as Anisian to Hettangian. At the top of the Lower Triassic, another tectonically induced, more or less angular unconformity is observed: the Hardegsen unconformity, which is dated as intra-Spathian and is especially found in the North European basins. This tectonic activity created new source areas and a new fluvial style, with marine influences at the distal part of the systems. During the Anisian and Ladinian, continental sedimentation was characterised by a retrogradational trend. In other words, the fluvial system evolved into fluvio-marine environments, attesting to a direct influence of the Tethys Ocean in the southern and northern domains. Both at the end of the Olenekian (Spathian) and during the Anisian, the presence of palaeosols, micro- and macrofloras indicate less arid conditions throughout this domain.     

New tanystropheids (Reptilia: Archosauromorpha) from the Triassic of Europe

A new prolacertilian species and genus, Augustaburiania vatagini gen. et sp. nov. (Reptilia: Archosauromorpha), from the Lower Triassic of the Don River Basin is described. It is the first representative of the Tanystropheidae in the Eastern Europe and the world oldest member of this family. Another new genus (Protanystropheus gen. nov.) from Central and Western Europe is also established. The diversity, systematics, phylogeny, evolution, and stratigraphic and geographical distribution of prolacertilians are discussed. The ecological role of prolacertilians in Early Triassic communities and adaptation to marine environments are analyzed.     

CALIBRATED DIVERSITY,TREE TOPOLOGY AND THE MOTHER OF MASS EXTINCTIONS: THE LESSON OF TEMNOSPONDYLS

Abstract: Three family‐level cladistic analyses of temnospondyl amphibians are used to evaluate the impact of taxonomic rank, tree topology, and sample size on diversity profiles, origination and extinction rates, and faunal turnover. Temnospondyls are used as a case study for investigating replacement of families across the Permo‐Triassic boundary and modality of recovery in the aftermath of the end‐Permian mass extinction. Both observed and inferred (i.e. tree topology‐dependent) values of family diversity have a negligible effect on the shape of the diversity curve. However, inferred values produce both a flattening of the curve throughout the Cisuralian and a less pronounced increase in family diversity from Tatarian through to Induan than do observed values. Diversity curves based upon counts of genera and species display a clearer distinction between peaks and troughs. We use rarefaction techniques (specifically, rarefaction of the number of genera and species within families) to evaluate the effect of sampling size on the curve of estimated family‐level diversity during five time bins (Carboniferous; Cisuralian; Guadalupian–Lopingian; Early Triassic; Middle Triassic–Cretaceous). After applying rarefaction, we note that Cisuralian and Early Triassic diversity values are closer to one another than they are when the observed number of families is used; both values are also slightly higher than the Carboniferous estimated diversity. The Guadalupian–Lopingian value is lower than raw data indicate, reflecting in part the depauperate land vertebrate diversity from the late Cisuralian to the middle Guadalupian (Olson’s gap). The time‐calibrated origination and extinction rate trajectories plot out close to one another and show a peak in the Induan, regardless of the tree used to construct them. Origination and extinction trajectories are disjunct in at least some Palaeozoic intervals, and background extinctions exert a significant role in shaping temnospondyl diversity in the lowermost Triassic. Finally, species‐, genus‐, and family trajectories consistently reveal a rapid increase in temnospondyl diversity from latest Permian to earliest Triassic as well as a decline near the end of the Cisuralian. However, during the rest of the Cisuralian family diversity increases slightly and there is no evidence for a steady decline, contrary to previous reports.     

A new scanilepiform from the Lower Triassic of northern Gansu Province,China, and phylogenetic relationships of non‐teleostean Actinopterygii

A new scanilepiform, Beishanichthys brevicaudalis gen. et sp. nov. , is named and described based on fossils from the Lower Triassic lake deposits exposed in Beishan area, Gansu Province, China. The discovery documents a new record of this group, which is significantly older than other known scanilepiforms from China, and is slightly younger than Evenkia from the Lowest Triassic of Central Siberia. Although the Beishan beds were previously interpreted as Late Permian in age, based on megaplant fossils, this new discovery supports the reinterpretation of the deposits as Early Triassic in age, based on vertebrate fossils from the same locality and horizon. Phylogenetic analysis was conducted to resolve the relationships of Scanilepiformes with other actinopterygian clades, and the inter‐relationships within Scanilepiformes. Contrary to previous thought that scanilepiforms are closely related to the Amiidae, the phylogenetic results of this study recognize the Scanilepiformes as stem‐group neopterygians. Relationships of the Scanilepiformes and Australosomus with other neopterygians remain unresolved. With a characteristic long‐based dorsal fin, scanilepiforms represent a small group that emerged in Early Triassic freshwater environments, inhabited Eurasia and North America during the Middle–Late Triassic, briefly invaded the marine environment by the Late Triassic in Europe, and became extinct at the end of Triassic. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 595–612.     

Late Carboniferous-Early Permian Tetrapod Ichnofauna from the Khenifra Basin, Central Morocco

In terms of cumulative thickness and areal extent, the Khenifra Basin is one of the most important outcrops of Late Palaeozoic red-beds in central Morocco. Macro- and microfloral remains near the centre of the 1800 m-thick succession of interbedded conglomerates, sandstones, and mudstones are considered to be of middle to late Early Permian age. Here we give the first comprehensive analysis of the vertebrate ichnofossil record from the study area, based on 17 specimens of isolated footprints and incomplete step cycles collected at three localities that are lithostratigraphically equivalent to the plant-bearing horizons. The tetrapod ichnofauna comprises tracks of the plexus Batrachichnus Woodworth - Limnopus Marsh, Ichniotherium sphaerodactylum (Pabst), Dimetropus Romer and Price, and Dromopus Marsh which can be referred to temnospondyl, diadectomorph, synapsid (“pelycosaurian”) and early sauropsid trackmakers. This clearly Euramerican footprint assemblage, including the first occurrences of Ichniotherium and Dimetropus from outside Europe and North America, indicates a Late Carboniferous to Early Permian age of the fossiliferous strata. Judging from the relatively diverse ichnofauna and flora, the Khenifra Basin must have represented a well-established terrestrial ecosystem during that period. Its habitat could be specially important for the understanding of the phylogeny and dispersal of early tetrapods, inasmuch as we are able to report on an extremely rare type of diadectomorph footprint hitherto known only from the Early Permian of central Germany.     

Middle and Late Triassic radiolarians from northern Tibet: Implications for the Bayan Har Basin evolution

During the Triassic, the Bayan Har Basin is a huge triangular basin surrounded by the North China Platform, South China Platform and Qingtang Terrane. It is filled by a Triassic turbidite sequence, the Bayan Har Group. For a long time, the series of Bayan Har Group in the eastern part of the basin were considered to be a Lower to Upper Triassic sequence, and in the western part, was attributed to the Upper Triassic. A well-preserved diversified radiolarian fauna was recovered from radiolarian chert and tuffite interbeds of the Bayan Har Group turbidites and adjacent stratigraphic units in the Hoh Xil area, northern Tibet. Sixty-seven species are identified and subdivided into two assemblages: late Anisian and early Carnian. Combined with the discovery of the Late Permian and Early Triassic turbidite in the Bayan Har Group in this area by Huang et al., it proves that all the Triassic is also present in the Bayan Har Group sequence in the western part. The evolution of the Bayan Har Basin may be traced back to the Late Permian. The massive sequence of the Bayan Har Group and its provenance indicate that the Kunlun and Qinling orogenic belts rapidly rise during the Middle-Late Triassic. The basin extended to the end of the Triassic, possibly locally to the Jurassic.     

Permian–Triassic Osteichthyes (bony fishes): diversity dynamics and body size evolution

The Permian and Triassic were key time intervals in the history of life on Earth. Both periods are marked by a series of biotic crises including the most catastrophic of such events, the end‐Permian mass extinction, which eventually led to a major turnover from typical Palaeozoic faunas and floras to those that are emblematic for the Mesozoic and Cenozoic. Here we review patterns in Permian–Triassic bony fishes, a group whose evolutionary dynamics are understudied. Based on data from primary literature, we analyse changes in their taxonomic diversity and body size (as a proxy for trophic position) and explore their response to Permian–Triassic events. Diversity and body size are investigated separately for different groups of Osteichthyes (Dipnoi, Actinistia, ‘Palaeopterygii’, ‘Subholostei’, Holostei, Teleosteomorpha), within the marine and freshwater realms and on a global scale (total diversity) as well as across palaeolatitudinal belts. Diversity is also measured for different palaeogeographical provinces. Our results suggest a general trend from low osteichthyan diversity in the Permian to higher levels in the Triassic. Diversity dynamics in the Permian are marked by a decline in freshwater taxa during the Cisuralian. An extinction event during the end‐Guadalupian crisis is not evident from our data, but ‘palaeopterygians’ experienced a significant body size increase across the Guadalupian–Lopingian boundary and these fishes upheld their position as large, top predators from the Late Permian to the Late Triassic. Elevated turnover rates are documented at the Permian–Triassic boundary, and two distinct diversification events are noted in the wake of this biotic crisis, a first one during the Early Triassic (dipnoans, actinistians, ‘palaeopterygians’, ‘subholosteans’) and a second one during the Middle Triassic (‘subholosteans’, neopterygians). The origination of new, small taxa predominantly among these groups during the Middle Triassic event caused a significant reduction in osteichthyan body size. Neopterygii, the clade that encompasses the vast majority of extant fishes, underwent another diversification phase in the Late Triassic. The Triassic radiation of Osteichthyes, predominantly of Actinopterygii, which only occurred after severe extinctions among Chondrichthyes during the Middle–Late Permian, resulted in a profound change within global fish communities, from chondrichthyan‐rich faunas of the Permo‐Carboniferous to typical Mesozoic and Cenozoic associations dominated by actinopterygians. This turnover was not sudden but followed a stepwise pattern, with leaps during extinction events.     

A second varanopseid skull from the Upper Permian of South Africa: implications for Late Permian 'pelycosaur' evolution

Late Permian terrestrial faunas of South Africa and Russia are dominated taxonomically and ecologically by therapsid synapsids. On the basis of a single specimen from the Upper Permian of South Africa, the varanopseid Elliotsmithia longiceps is the sole basal synapsid ('pelycosaur') known from Gondwana. Recent fieldwork in the Upper Permian of South Africa has produced a second varanopseid specimen that is referrable to Elliotsmithia . Data from both this specimen and the holotype suggest that Elliotsmithia forms a clade with Mycterosaurus from the Lower Permian of North America and Mesenosaurus from the Upper Permian of Eastern Europe. That postulate is supported by the three most parsimonious trees discovered in a new analysis of varanopseid phylogeny. However, the available data cannot resolve the interrelationships of these three genera. The new phylogenetic results contrast with earlier work identifying Elliotsmithia as the basal member of a clade that includes the North American taxa Aerosaurus , Varanops , and Varanodon . The new trees reduce the stratigraphic debt required by the latter scenario, and the one with the least stratigraphic debt identifies Elliotsmithia and Mesenosaurus as sister taxa. Two new taxa are erected, Mycterosaurinae and Varanodontinae, for the two varanopseid subclades.     

The oldest stegocephalian from the Iberian peninsula: evidence that temnospondyls were euryhaline.

The previous fossil record of limbed vertebrates of the Iberian peninsula started in the Triassic (245 Ma). The discovery of a new temnospondyl from the Late Carboniferous (Stephanian C, 290 Ma) extends the fossil record of stegocephalians in this region by at least 45 Ma. Early stegocephalians are usually thought to have been unable to live in salt water, but the new temnospondyl described below appears to have lived in a coastal region, presumably in salt water.     

Growth patterns of fossil vertebrates as deduced from bone microstructure: case studies from India

Bone microstructure is affected by ontogeny, phylogeny, biomechanics and environments. These aspects of life history of an extinct animal, especially its growth patterns, may be assessed as fossil bone generally maintains its histological integrity. Recent studies on the bone histology of fossil vertebrates from India encompass different types of temnospondyls and dicynodonts from different Permian and Triassic horizons. The examined taxa show that they had distinct bone histology and varied growth patterns. The Early Triassic trematosaurids had an overall fast growth, which contrasts with that of the Middle and Late Triassic temnospondyl taxa examined. The dicynodonts on the other hand, were characterized by an overall fast growth with periodic interruptions, variable growth rates dependent on ontogeny and indeterminate growth strategy. A comparative study encompassing several neotherapsid genera including the dicynodonts shows significant evolutionary trends towards determinate growth strategy and reduced developmental plasticity.     

Refinements in the Upper Permian to Lower Jurassic stratigraphy of Karakorum, Pakistan

New sampling on critical intervals of the uppermost Permian and Triassic successions of the Northern Karakorum Terrain in the Karakorum Range (Pakistan) has refined the stratigraphy. Two types of successions may be distinguished in the Karakorum Range: a carbonate platform succession, spanning the whole interval from Upper Permian to Upper Triassic, possibly with several gaps; and a basinal succession, deposited from the Middle Permian to Early Carnian (Late Triassic), when the carbonate platform prograded into the basin. With the approaching and later docking of the Karakorum Block against the Asian margin closing the Paleo-Tethys, a portion of Karakorum emerged while another part subsided as a fore-deep, receiving clastics from the emerging Cimmerian Range. Molassic sediments filled the basin, whilst shallow-water carbonates transgressed over the emerged carbonate platform sometime between the latest Triassic and the Pliensbachian (Early Jurassic), with Cimmerian deformation occurring to the north. The age control is provided by conodonts, with assemblages of late Wuchiapingian, Changhsingian, Induan (Griesbachian and Dienerian), late Olenekian, early Anisian, late Ladinian, and early Carnian ages, respectively. Some information on the section around the P/T boundary is provided by palynology and isotopic C¹³ values. The dating of the Norian/Rhaetian platform is provided by foraminifers.     

The Earliest Case of Neoplastic Bone Lesion in Tetrapods

The results of analysis of a bone tissue neoplasm on the mandible of an Early Mesozoic temnospondyl amphibian Benthosuchus korobkovi Ivachnenko from the Tikhvinskoe locality (upper reaches of the Volga River, Yaroslavl oblast (Region); Lower Triassic, Lower Olenekian substage) are presented. The use of multispiral computed tomography enabled a rather well justified conclusion of the neoplastic (tumor) character of this pathological formation. Non-odontogenic osteoma is the most likely diagnosis, but hemangioma and fibrotic dysplasia cannot be ruled out either.     

New beetles (Insecta,Coleoptera) from the Lower Triassic of European Russia

Fossil remains of beetles are described from two Lower Triassic localities: Entala (Induan) and Tikhvinskoe (Olenekian). Only one beetle fossil was previously known from the Lower Triassic of Tikhvinskoe. The fossils are rather few and poorly preserved, but they are worth describing as finds rare for the Lower Triassic. Five fossils from Entala most probably belong to beetles of the same species of the formal genus Pseudochrysomelites. Beetles of this genus are especially abundant in deposits close to the Permian–Triassic boundary and can be considered “disaster taxa.” There are no known cases, either in the Permian or in the Middle–Upper Triassic, of a random sample of five specimens belonging to a single species. This suggests that in the Entala oryctocenosis the species diversity of beetles is extremely low. All three beetle fossils found in Tikhvinskoe belong to beetles of different species, showing that diversity had already started to increase. However, it remained low, and all fossils belong to the formal family Schizocoleidae, and two of the three belong to the same genus, Pseudochrysomelites. The Khei-Yaga locality, which immediately follows Tikhvinskoe in time (topmost Olenekian or early Anisian), already contains beetles of the families Asiocoleidae and Permosynidae. In the Lower Anisian of the Buntsandstein, such typical Mesozoic beetles as Cupedidae and Coptoclavidae have been recorded. The appearance of such advanced beetles as early as the Lower Anisian suggests that the famous Permian–Triassic crisis was not as deep as it is usually believed, and many beetles survived it, disappearing, however, from the fossil record in the Early Triassic.     

Trophic network models explain instability of Early Triassic terrestrial communities

Studies of the end-Permian mass extinction have emphasized potential abiotic causes and their direct biotic effects. Less attention has been devoted to secondary extinctions resulting from ecological crises and the effect of community structure on such extinctions. Here we use a trophic network model that combines topological and dynamic approaches to simulate disruptions of primary productivity in palaeocommunities. We apply the model to Permian and Triassic communities of the Karoo Basin, South Africa, and show that while Permian communities bear no evidence of being especially susceptible to extinction, Early Triassic communities appear to have been inherently less stable. Much of the instability results from the faster post-extinction diversification of amphibian guilds relative to amniotes. The resulting communities differed fundamentally in structure from their Permian predecessors. Additionally, our results imply that changing community structures over time may explain long-term trends like declining rates of Phanerozoic background extinction.     

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.