Carbon Isotope Disturbances Across the Smithian/Spathian Triassic Boundary in Vietnam

Carbon isotopic excursions and detailed ammonoid and conodont biostratigraphies around Smithian–Spathian boundary in the Bac Thuy Formation, Vietnam

Authors:

Komatsu et al

Abstract:

The Smithian–Spathian boundary is indicated by the first occurrence of the ammonoid Tirolites cf. cassianus in the Olenekian Bac Thuy Formation, northeastern Vietnam. The boundary is intercalated within organic-rich dark gray mudstone that accumulated under anoxic to dysoxic conditions in the An Chau and Nanpanjiang Basins on the South China Block. In Lang Son area, three conodont zones, Novispathodus ex gr. waageni, Novispathodus ex gr. pingdingshanensis, and Icriospathodus collinsoni, are recognized in the formation. The Smithian–Spathian boundary is intercalated within N. ex gr. pingdingshanensis conodont Zone. The positive excursion inδ13C with values increasing from around − 2.3‰ to + 5.7‰ was recorded in the uppermost Smithian Xenoceltites variocostatus ammonoid beds and N. ex gr. pingdingshanensis conodont Zone. The δ13C values decrease across the Smithian–Spathian boundary. These δ13C isotopic patterns are correlated with well-known positive excursions around the Smithian–Spathian boundary globally.

The Implications of a Stromatolite From the Olenekian (Spathian) Triassic of China

Upper Lower Triassic stromatolite from Anhui, South China: Geobiologic features and paleoenvironmental implications

Authors:

Luo et al

Abstract:

Widespread stromatolites and other microbialite deposits characterize Lower Triassic marine successions worldwide. This study documents a stromatolite deposit, 1.1 m thick, from the upper Spathian (Lower Triassic) of the Susong area, South China. The stromatolite comprises distinct laminated domes in the basal part and columns at the upper part. Dark laminae are loosely spaced and interlayered with thicker light colored laminae. Diffusive dark colored laminae are composed of peloidal micrite that grade locally into microclotted structures, and yield copies of bacteria clump-like and coccoid-like spheroid aggregates. The former are characterized by cloudy, micrite nuclei rimmed by coarse-grained, euhedral sparry calcite crystals, while the latter are comprised of solid calcite crystal nuclei coated with rather thin micrite envelopes. The cloudy, micrite nuclei resemble bacteria clump-like structures observed in present-day travertine. Both the coccoid-like spheroids and bacteria clump-like structures are surrounded by coarse-grained euhedral calcite crystals, suggesting a similar accretion mechanism. Both spherical structures therefore could be crucial in the accretion of the Susong stromatolite. The laminated/microclotted structures are interpreted as the result of variation in timing of lithification relative to the timing of the decay of microbes. Micro-analysis also unravels the common occurrence of authigenic micro-quartz crystals in association with Fe-bearing illite clay minerals in the stromatolite columns. Their coalescing nature with each other, together with the associated pyrite grains, strongly support the formation of micro-quartz crystals from microbial reduction of an Fe-bearing smectite precursor by sulfate reducing bacteria. A comparison of the Susong stromatolite with its counterparts from the upper Lower Triassic strata in Dajiang, South China reveals many similarities in stromatolite microstructures, suggesting that a harsh, euxinic–anoxic environment resulting in the bloom of sulfate reducing bacteria most likely extended into the latest Spathian in South China.

Teyujagua paradoxa: a new sister Taxon to Archosauriformes From Olenekian Triassic Brazil

An exceptional fossil skull from South America and the origins of the archosauriform radiation

Authors:

Pinheiro et al

Abstract:

Birds, dinosaurs, crocodilians, pterosaurs and their close relatives form the highly diverse clade Archosauriformes. Archosauriforms have a deep evolutionary history, originating in the late Permian, prior to the end-Permian mass extinction, and radiating in the Triassic to dominate Mesozoic ecosystems. However, the origins of this clade and its extraordinarily successful body plan remain obscure. Here, we describe an exceptionally preserved fossil skull from the Lower Triassic of Brazil, representing a new species, Teyujagua paradoxa, transitional in morphology between archosauriforms and more primitive reptiles. This skull reveals for the first time the mosaic assembly of key features of the archosauriform skull, including the antorbital and mandibular fenestrae, serrated teeth, and closed lower temporal bar. Phylogenetic analysis recovers Teyujagua as the sister taxon to Archosauriformes, and is congruent with a two-phase model of early archosauriform evolution, in response to two mass extinctions occurring at the end of the Guadalupian and the Permian.

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The Paleoenvironments of the Catalan Pyrenees From the Middle Permian Through the Olenekian Triassic

Constraining the Permian/Triassic transition in continental environments: Stratigraphic and paleontological record from the Catalan Pyrenees (NE Iberian Peninsula)

Authors:

Mujal et al

Abstract:

The continental Permian-Triassic transition in southern Europe presents little paleontological evidence of the Permian mass extinction and the subsequent faunal recovery during the early stages of the Triassic. New stratigraphic, sedimentological and paleontological analyses from Middle-Upper Permian to Lower-Middle Triassic deposits of the Catalan Pyrenees (NE Iberian Peninsula) allow to better constrain the Permian-Triassic succession in the Western Tethys basins, and provide new (bio-) chronologic data. For the first time, a large vertebra attributed to a caseid synapsid from the ?Middle Permian is reported from the Iberian Peninsula - one of the few reported from western Europe. Osteological and ichnological records from the Triassic Buntsandstein facies reveal a great tetrapod ichnodiversity, dominated by small to medium archosauromorphs and lepidosauromorphs (Rhynchosauroides cf. schochardti, R. isp. 1 and 2, Prorotodactylus-Rotodactylus, an undetermined Morphotype A and to a lesser degree large archosaurians (chirotheriids), overall suggesting a late Early Triassic-early Middle Triassic age. This is in agreement with recent palynological analyses in the Buntsandstein basal beds that identify different lycopod spores and other bisaccate and taeniate pollen types of late Olenekian age (Early Triassic). The Permian caseid vertebra was found in a playa-lake setting with a low influence of fluvial water channels and related to the distal parts of alluvial fans. In contrast, the Triassic Buntsandstein facies correspond to complex alluvial fan systems, dominated by high-energy channels and crevasse splay deposits, hence a faunal and environmental turnover is observed. The Pyrenean biostratigraphical data show similarities with those of the nearby Western Tethys basins, and can be tentatively correlated with North African and European basins. The Triassic Pyrenean fossil remains might rank among the continental oldest records of the Western Tethys, providing new keys to decipher the Triassic faunal biogeography and recovery.

Mesozoic Marine Revolution Started Very Quickly After Permian Triassic Extinction

Coprolites of marine vertebrate predators from the Lower Triassic of southern Poland

Authors:

Brachaniec et al

Abstract:

Numerous coprolites are described for the first time herein from the Lower Triassic (Olenekian) shallow marine sedimentary rocks in southern Poland. X-ray Diffraction and geochemical analyses show that they are preserved as calcium phosphate with small admixtures of quartz and calcite. Additionally, SEM and thin section studies revealed that they contain highly fragmented faunal remains (crinoids, molluscs and vertebrates). The size, shape, geochemistry, biostratigraphic distribution and co-occurrence with vertebrate skeletal remains imply that the coprolites at hand were likely produced by nothosaurids, the durophagous sauropterygian reptiles and actinopterygian (ray-finned) fish. The large number of recorded coprolites implies that durophagous predation has been intense during the Early Triassic and suggests that the so-called Mesozoic Marine Revolution probably started soon after the end-Permian extinction. Furthermore, discovery of sinusoidal trails attributable to nematodes in some coprolites implies that the intestinal parasitic associations with these predators had already evolved by at least the Early Triassic.

Eretmorhipis carrolldongi: an Excellent Fossil of a Mysterious Spathian Olenekian Triassic Hupehsuchian

A New Specimen of Carroll’s Mystery Hupehsuchian from the Lower Triassic of China

Authors:

Chen et al

Abstract:

A new specimen of an enigmatic hupehsuchian genus is reported. The genus was first recognized by Robert L. Carroll and Zhi-ming Dong in 1991, who refrained from naming it because of the poor quality of the only specimen known at the time. After more than two decades, we finally report a second specimen of this genus, which remained unprepared until recently. The new specimen preserves most of the skeleton except the skull, allowing us to erect a new genus and species, Eretmorhipis carrolldongi. The new species shares many characters with Parahupehsuchus longus, including the strange axial skeleton that forms a bony body tube. However, the body tube is short in the new species, being limited to the pectoral region. The vertebral count and limb morphology considerably differ between the new species and P. longus. The forelimb of E. carrolldongi is markedly larger than its hind limb as in Hupehsuchus nanchangensis but unlike in P. longus. The new species is unique among hupehsuchians in a list of features. It has manual and pedal digits that spread radially, forming manus and pes that are almost as wide as long. The third-layer elements of the dermal armor are unusually large, spanning four vertebral segments, yet there are substantial gaps among them. With the addition of the unique paddle, it is now clear that Hupehsuchia had diverse forelimb morphologies spanning from paddles to flippers, unlike ichthyopterygians that were taxonomically more diverse yet only had flippers.

Panthalassa Ocean was Suboxic/Hypoxic, not Anoxic Across the Spathian Olenekian/Anisian Triassic

Redox conditions in the end-Early Triassic Panthalassa

Authors:

Takahashi et al

Abstract:

This study focuses on an upper Lower Triassic (Spathian) to lowermost Middle Triassic (Anisian) section representing the central Panthalassic deep sea. Analysed organic carbon isotope ratio (δ13Corg) records from the section demonstrate that lower values in the Spathian increase by up to 6‰ at the Spathian–Anisian transition. This trend accords with the carbonate carbon isotope (δ13Ccarb) record from shallow-water carbonate sections. Most horizons during late Spathian–early Anisian show features of redox conditions of not fully oxic but dysoxic conditions, inferred from low Mn, U, V, Mo and euhedral pyrite-dominated occurrences. Conversely, in the end-Spathian black-coloured beds and underlying siliceous claystone beds, relatively higher concentrations of redox-sensitive elements such as U, V, Mo and abundant pyrite framboids are detected. As enrichment factors of redox-sensitive elements are not much higher than the typical anoxic–sulphidic trend and large pyrite framboids are found, these trends suggest suboxic rather than strong anoxic conditions. These oxygen-poor conditions coincide with carbon isotope minimum values at the late Spathian. At the same time, reducing seawater conditions have been also reported in from continental sections. These coincidences imply global environmental perturbations that may have been related to the delayed recovery of life after the end-Permian mass extinction.

Trace Fossils From Smithian/Spathian Triassic South China Suggest Gradual Biotic Recovery From PT Extinction

Early Triassic trace fossils from the Three Gorges area of South China: Implications for the recovery of benthic ecosystems following the Permian–Triassic extinction

Authors:

Zhao et al

Abstract:

The Lower Triassic Daye and Jialingjiang formations of the Three Gorges area (South China) record the recovery interval of benthic tracemaking invertebrates following the P–Tr mass extinction. A total of 17 ichnospecies in 14 ichnogenera are documented from Smithian and Spathian strata. Our trace fossil data, in combination with previously published studies, show that ichnodiversity in the Middle Yangtze region increased markedly in the early Spathian. Trace fossils in the Smithian are dominated by simple, small, horizontal burrows, including Didymaulichnus and Planolites, whereas Spathian trace fossils are diverse and abundant with moderate–high bioturbation levels and complex burrow networks, such as Thalassinoides. Both burrow sizes and penetration depths increased gradually from the early Spathian to the middle–late Spathian, implying a gradual recovery pattern for benthic ecosystems. Early Triassic ichnofossils are characterised by aspects of opportunistic behaviour (e.g., low-to-moderate ichnodiversity, low-to-moderate bioturbation, small burrow widths, and shallow tiering), suggesting stressed environmental conditions. The recovery tempo and pattern of ichnocoenoses in South China is likely structured by temporal and spatial changes of the refuge zone in the Early Triassic.

Evidence of the Smithian/Spathian Triassic Extinction From South China

High amplitude redox changes in the late Early Triassic of South China and the Smithian–Spathian extinction

Authors:

Sun et al

Abstract:

The Early Triassic was a time of remarkably high temperatures, large carbon cycle perturbations and episodes of widespread ocean anoxia. The sediments in the Nanpanjiang Basin of South China provide superb opportunities to examine the sedimentary response to these extreme conditions especially during the crisis interval at the Smithian–Spathian (S-S) boundary. We have investigated a deep water section at Jiarong and a shallower water section at Mingtang. These contain a range of facies including black shales, micritic limestone units and rudaceous carbonate event beds that include flat pebble conglomerates and breccia debrites that bear similarities to the hybrid event beds seen in clastic turbidite successions.

Redox proxies (pyrite framboids and trace metals) reveal that widespread anoxia in the late Smithian persisted into the Novispathodus pingdingshanensis Zone of the early Spathian before a sharp transition to highly oxygenated “griotte facies” (red marine strata) in the Icriospathodus collinsoni Zone that records an “oxic rebound”. Benthic faunas are locally common but of low diversity and dominated by thin-shelled bivalves and ostracodes with small foraminifers and exceptionally rare fish remains. Bioturbation was intense only in the early–middle Spathian (I. collinsoni conodont zone) Griotte facies. Anoxia and extremely high temperatures probably played a role in severely restricting the abundance of fish and the small sizes of marine invertebrates at this time. The presence of ooids and seafloor fan cements in our study sections indicates highly saturated conditions rather than acidification at the end of the Smithian.

Cranial Ontogeny of the Early Triassic Cynodont Thrinaxodon liorhinus

Ontogeny of the Early Triassic Cynodont Thrinaxodon liorhinus (Therapsida): Cranial Morphology

Authors:

Jasinoski et al

Abstract:

The cranial morphology of 68 Thrinaxodon liorhinus specimens, ranging in size from 30 – 96mm in basal skull length, is investigated using both qualitative and quantitative analyses. From this comprehensive survey, we determined that nine cranial features, including five in the temporal region, separated the sample into four ontogenetic stages. A bivariate analysis of 60 specimens indicated that the skull generally increased in size isometrically, with the exception of four regions. The orbit had negative allometry, a result consistent with other ontogenetic studies of tetrapods, whereas the length of the snout, palate, and temporal region showed positive allometry. The last trend had strong positive allometry indicating that during ontogeny the length of the sagittal crest increased at a much faster rate than the rest of the skull. The large number of changes in the temporal region of the skull of Thrinaxodon may indicate a greater development of the posterior fibres of the temporalis musculature from an early ontogenetic stage. For example, the posterior sagittal crest developed much earlier in ontogeny than the anterior crest that formed in adults, and bone was deposited dorsally creating a unified posterior sagittal crest rather than having a suture that spanned the entire depth of the skull roof. In combination with the isometric height of the zygomatic arch and the almost complete absence of the zygomatic arch angulation, these ontogenetic changes suggest that there was greater development of the temporalis relative to the masseter muscles, indicating a strong posterodorsal movement of the mandible in Thrinaxodon.

Spathian Triassic ichthyopterygian Chaohusaurus chaoxianensis is a Valid Taxon

Status of Chaohusaurus chaoxianensis (Chen, 1985)

Authors:

Motani et al

Abstract:

The Early Triassic ichthyopterygian Chaohusaurus chaoxianensis was previously known from juvenile specimens only. It was considered to represent immature forms of C. geishanensis, which was based on a single adult specimen, because allometric regression lines of the forelimb skeletons suggested that the two name groups fitted along a single growth trajectory. The sample size for the analysis, however, was small (n = 5). We collected new specimens of Chaohusaurus from Majiashan, Chaohu City, Anhui Province, China, through field excavations that started in 2010. New specimens included an immature individual whose forelimb resembled that of mature C. geishanensis, as well as a large adult individual whose forelimb retained the characteristics of immature C. chaoxianensis. Therefore, C. chaoxianensis is not the juvenile of C. geishanensis. With the addition of the new specimens, two growth trajectories are now clearly detected on allometric regression plots (n = 15). The two species are unambiguously distinguished from each other based on a suite of discrete characters that are diagnostic to each species, as well as statistical analyses of forelimb measurements. It is unlikely that the two forms represent the genders of a single species given that C. geishanensis is vastly outnumbered by C. chaoxianensis and completely lacking in major fossiliferous rock layers. Therefore, C. chaoxianensis should be resurrected as a valid species.

Chaohusaurus is Oldest Known Ichthyopterygian

Ammonoid age control of the Early Triassic marine reptiles from Chaohu (South China)

Authors:

Ji et al

Abstract:

Here we described a series of ammonoid specimens from the Early Triassic of Chaohu, South China and recognized the occurrence of Procolumbites for the first time in this area. The Procolumbites layer is about one meter above the first appearance of Chaohusaurus, indicating that the oldest Chaohusaurus is within the Procolumbites Zone of middle Spathian age. This new age constrain is significantly older than the previously suggested Subcolumbites Zone assignment (early late Spathian). To date, Chaohusaurus is the oldest known ichthyopterygian.

Eohupehsuchus brevicollis: a new Hupehsuchian Marine Reptile From Spathian Olenekian Triassic China

A Small Short-Necked Hupehsuchian from the Lower Triassic of Hubei Province, China

Authors:

Chen et al

Abstract:

Hupehsuchia is a group of enigmatic Triassic marine reptiles that is known exclusively from two counties in Hubei Province, China. One of the common features of the group was a modestly long neck with nine to ten cervical vertebrae. We report a new species of Hupehsuchia, Eohupehsuchus brevicollis gen. et sp. nov., which for the first time shows a short neck in this group, with six cervicals. The configuration of the skull roof in Eohupehsuchus is also unique among Hupehsuchia, with narrow frontals and posteriorly shifted parietals, warranting recognition of a new species. The taxon superficially resembles Nanchangosaurus in retaining hupehsuchian plesiomorphies, such as low neural spines and small body size. However, its limbs are well-developed, unlike in Nanchangosaurus, although the latter genus is marginally larger in body length. Thus, the individual is unlikely to be immature. Also, Eohupehsuchus shares a suite of synapomorphies with Hupehsuchus, including the second and third layers of dermal ossicles above the dorsal neural spines. A phylogenetic analysis suggests that the new species is not the most basal hupehsuchian despite its short neck, and instead forms the sister taxon of Hupehsuchidae. Until recently, Hupehsuchia contained only two monotypic genera. Now there are at least four genera among Hupehsuchia, and the undescribed diversity is even higher. The left forelimb of the only specimen is incomplete, ending with broken phalanges distally. The breakage could only have occurred pre-burial. The individual may have been attacked by a predator and escaped, given that scavenging is unlikely.

Garjainia madiba: a new Species of Erythrosuchid Archosauriform From Olenekian Triassic South Africa

A New Species of Garjainia Ochev, 1958 (Diapsida: Archosauriformes: Erythrosuchidae) from the Early Triassic of South Africa

Authors:

Gower et al

Abstract:

A new species of the erythrosuchid archosauriform reptile Garjainia Ochev, 1958 is described on the basis of disarticulated but abundant and well-preserved cranial and postcranial material from the late Early Triassic (late Olenekian) Subzone A of the Cynognathus Assemblage Zone of the Burgersdorp Formation (Beaufort Group) of the Karoo Basin of South Africa. The new species, G. madiba, differs from its unique congener, G. prima from the late Olenekian of European Russia, most notably in having large bony bosses on the lateral surfaces of the jugals and postorbitals. The new species also has more teeth and a proportionately longer postacetabular process of the ilium than G. prima. Analysis of G. madiba bone histology reveals thick compact cortices comprised of highly vascularized, rapidly forming fibro-lamellar bone tissue, similar to Erythrosuchus africanus from Subzone B of the Cynognathus Assemblage Zone. The most notable differences between the two taxa are the predominance of a radiating vascular network and presence of annuli in the limb bones of G. madiba. These features indicate rapid growth rates, consistent with data for many other Triassic archosauriforms, but also a high degree of developmental plasticity as growth remained flexible. The diagnoses of Garjainia and of Erythrosuchidae are addressed and revised. Garjainia madiba is the geologically oldest erythrosuchid known from the Southern Hemisphere, and demonstrates that erythrosuchids achieved a cosmopolitan biogeographical distribution by the end of the Early Triassic, within five million years of the end-Permian mass extinction event. It provides new insights into the diversity of the Subzone A vertebrate assemblage, which partially fills a major gap between classic ‘faunal’ assemblages from the older Lystrosaurus Assemblage Zone (earliest Triassic) and the younger Subzone B of the Cynognathus Assemblage Zone (early Middle Triassic).

Basal, Amphibious Ichthyosaur Relative Found in Spathian Olenekian Triassic China

A basal ichthyosauriform with a short snout from the Lower Triassic of China

Authors:

Motani et al

Abstract:

The incompleteness of the fossil record obscures the origin of many of the more derived clades of vertebrates. One such group is the Ichthyopterygia, a clade of obligatory marine reptiles that appeared in the Early Triassic epoch, without any known intermediates. Here we describe a basal ichthyosauriform from the upper Lower Triassic (about 248 million years ago) of China, whose primitive skeleton indicates possible amphibious habits. It is smaller than ichthyopterygians and had unusually large flippers that probably allowed limited terrestrial locomotion. It also retained characteristics of terrestrial diapsid reptiles, including a short snout and body trunk. Unlike more-derived ichthyosauriforms, it was probably a suction feeder. The new species supports the sister-group relationships between ichthyosauriforms and Hupehsuchia, the two forming the Ichthyosauromorpha. Basal ichthyosauromorphs are known exclusively from south China, suggesting that the clade originated in the region, which formed a warm and humid tropical archipelago in the Early Triassic. The oldest unequivocal record of a sauropterygian is also from the same stratigraphic unit of the region.

Marine–terrestrial Kockatea Biota From Smithian Olenekian Triassic Australia

Early Triassic (early Olenekian) life in the interior of East Gondwana: mixed marine–terrestrial biota from the Kockatea Shale, Western Australia

Authors:

Haig et al

Abstract:

A new terrestrial–marine assemblage from the lower beds of a thin outcrop section of the Kockatea Shale in the northern Perth Basin, Western Australia, contains a range of fossil groups, most of which are rare or poorly known from the Lower Triassic of the region. To date, the collection includes spinose acritarchs, organic-cemented agglutinated foraminifera, lingulids, minute bivalves and gastropods, ammonoids, spinicaudatans, insects, austriocaridid crustaceans, actinopterygians, a temnospondyl-like mandible, plant remains, and spores and pollen. Of these groups, the insects, crustaceans and macroplant remains are recorded for the first time from this unit.

Palynomorphs permit correlation to nearby sections where conodonts indicate an early Olenekian (Smithian) age. The locality likely represents the margin of an Early Triassic shallow interior sea with variable estuarine-like water conditions, at the southwestern end of an elongate embayment within the East Gondwana interior rift–sag system preserved along the Western Australian margin. Monospecific spinose acritarch assemblages intertwined with amorphous organic matter may represent phytoplankton blooms that accumulated as mats, and suggest potentially eutrophic surface waters. The assemblage represents a mixure of marine and terrestrial taxa, suggesting variations in water conditions or that fresh/brackish-water and terrestrial organisms were transported from adjacent biotopes. Some of the lower dark shaly beds are dominated by spinicaudatans, likely indicating periods when the depositional water body was ephemeral, isolated, or subjected to other difficult environmental conditions.

The biota of the Kockatea Shale is insufficiently known to estimate biotic diversity and relationships of individual taxa to their Permian progenitors and Triassic successors, but provides a glimpse into a coastal-zone from the interior of eastern Gondwana. Specialist collecting is needed to clarify the taxonomy of many groups, and comparisons to other Lower Triassic sites are required to provide insights into the pattern of biotic decline and recovery at the end-Permian crisis.

Induan/Olenekian Triassic South African Proterosuchid Archosauriforms Revised

Figure 11. Skull and lower jaw reconstructions of Proterosuchus species from the Lystrosaurus AZ of South Africa. A, juvenile of Proterosuchus fergusi (based on RC 59 and BP/1/4016); B, adult of Proterosuchus fergusi (based on BSPG 1934 VIII 514, GHG 231, RC 846); C, Proterosuchus alexanderi; and D, Proterosuchus goweri in left lateral views. Abbreviations: a1, a2, a4, diagnostic characters 1, 2 and 4 of Proterosuchus alexanderi; P1–3, diagnostic characters 1–3 of Proterosuchus; g1–7, diagnostic characters 1–7 of Proterosuchus goweri; f1–6, diagnostic characters 1–6 of Proterosuchus fergusi. Characters with asterisks indicate autapomorphies. All scale bars represent 20 mm.

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

Authors:

Ezcurra et al

Abstract:

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.

A Large Cymatosaurian Eusauropterygian From Olenekian/Anisian (?) Triassic Netherlands

Skeletal material from larger Eusauropterygia (Reptilia: Eosauropterygia) with nothosaurian and cymatosaurian affinities from the Lower Muschelkalk of Winterswijk, The Netherlands

Authors:

Voeten et al

Abstract:

Eusauropterygian elements from the Lower Muschelkalk (Vossenveld Formation) of Winterswijk, The Netherlands, comprising three mandibles and a selection of postcranial material, are described. The new mandibles correspond to crania larger than eusauropterygian cranial material previously known from this locality. The postcranial material represents a selection of isolated and associated material of comparably large size. Two of the mandibles conform to the morphology commonly recognized in Nothosaurus from the Lower Muschelkalk, but the third mandible accommodates five fangs per ramus in the symphyseal domain and exhibits a symphyseal ratio of 1.04, a condition not yet described for Eusauropterygia from the Vossenveld Formation. Body length for the animals represented by the finds was estimated through dimensional comparison with MB.R.27, a nearly complete skeleton from the lower Middle Muschelkalk locality of Rüdersdorf (Germany) assigned to Nothosaurus marchicus. Body length estimates for the individuals represented by the largest mandible and by a selection of associated postcranial material exceed 1,500 mm; approximately 50 % larger than the eusauropterygian taxa from Winterswijk described so far. Furthermore, certain morphological characters identified in one mandible and in the postcranial elements suggest a cymatosaurian affinity over a nothosaurian affinity. The present study indicates eusauropterygian diversity during the Lower Muschelkalk was greater than traditionally believed. This challenges the concept of a slow paced, gradual biotic response to the origination and expansion of the Muschelkalk Sea, which commenced only 5 million years after the Permian–Triassic mass extinction event.

Two New Bystrowianid Chroniosuchians From Olenekian Triassic Russia

New bystrowianid chroniosuchians (Amphibia, Anthracosauromorpha) from the Triassic of Russia and diversification of Bystrowianidae

Authors:

Shishkin et al

Abstract:

The first bystrowianids recorded in the Gamskian Horizon of the East European Platform, Vyushkoviana operta gen. et sp. nov. and Dromotectum abditum sp. nov. (Amphibia, Chroniosuchia), are described based on specimens from the Malaya Northern Dvina and Don river basins. The patterns of the dermal scute evolution observed in bystrowianids warrant the subdivision of the group into the subfamilies Bystrowianinae Vjuschkov 1957, Dromotectinae subfam. nov. and Axitectinae subfam. nov. The second and third show progressive reduction of the external (paraxial) zone of the interosteoderm articulation. New data supporting close proximity or phyletic succession of the chroniosuchid and bystrowianid types of the osteoderm design are revealed. The concept of the Chroniosuchidae as a paraphyletic group is rejected. Evolutionary significance of the key features distinguishing the bystrowianid subfamilies is analyzed.

Majiashanosaurus discocoracoidis: An new Eosauropterygian From Olenekian (Spathian) Triassic China

The Early Triassic eosauropterygian Majiashanosaurus discocoracoidis, gen. et sp. nov. (Reptilia, Sauropterygia), from Chaohu, Anhui Province, People’s Republic of China

Authors:

Jiang et al

Abstract:

Records of Early Triassic marine reptiles, when they first emerged after the end Permian mass extinction, are rare. During an excavation at Majiashan, Chaohu, Anhui Province, a new sauropterygian specimen was found co-occurring with the ichthyopterygian Chaohusaurus from the Upper Member of the Nanlinghu Formation, of Olenekian (Spathian, Early Triassic) age, for which a new taxon, Majiashanosaurus discocoracoidis, gen. et sp. nov., is erected. This skeleton is exposed in ventral view, with the last three cervical vertebrae together with 19 dorsal, three sacral, and more than 18 caudal vertebrae preserved. The cervical centra are keeled ventrally, and cervical ribs are double-headed, carrying a free anterior process. The transverse processes of the dorsal vertebrae are not distinctively elongated. The dorsal ribs are single-headed, and the clavicles articulate on the anteromedial aspect of the scapula. The humerus is curved. These features allow assignment to a new sauropterygian taxon. The interclavicle has no posterior process, and the scapula is of typical eosauropterygian shape, with a broad and ventrally expanded glenoidal portion that is separated from a narrow posterodorsal blade by a distinct constriction. The coracoid is round and plate-like without a waist. This feature is different from that of all other known eosauropterygians, but resembles that of placodonts.