8:30am - 8:45amTopics: 3.11 Triassic Revolution
Prevailing deteriorated palaeoenvironments related to the hyperthermal Permian-Triassic mass extinction
1School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK; 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China; 3State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing 210023, China; 4British Geological Survey, Maclean Building, Wallingford OX10 8BB, UK
The Permian-Triassic mass extinction, one of the most severe biotic crises in Earth's history, has been attributed to sharp heating (nearly 15°C in low-latitude areas) initially triggered by massive volcanic eruptions of the Siberian Traps in the latest Permian. Drastic environmental changes have been identified worldwide, both in the sea and on land. However, the connections of global palaeoclimate changes, particularly their detection in complex terrestrial systems, remain debatable. Here, based on sedimentological and geochemical data and state-of-the-art modelling from North China, we emphasise the drastically deteriorated palaeoenvironments (e.g. unstable, drought and intermittent heavy precipitation) under a regime of sharp heating, mass wasting and acid rain on land may be significant causes of the mass killing events near the end-Permian and the subsequent Early Triassic long-lasting stressed terrestrial palaeoclimate that delayed the recovery of life. Understanding the Permian-Triassic hyperthermal crisis may also provide critical insight into similar events of different magnitudes in Earth's history, and could inform our near future, in the context of anthropogenic warming and our rapidly changing planet.
8:45am - 9:00amTopics: 3.11 Triassic Revolution
From the field to the synchrotron, investigating the early Triassic recovery fauna from Driefontein, South Africa
1European Synchrotron and Radiation Facility, France; 2Evolutionary Studies Institute, University of Witwatersrand, Johannesburg; 3Department of Geological and Environmental Sciences, Appalachian State University
The Karoo Supergroup of South Africa contains extremely rich palaeontological record, including evidence of the largest mass extinction in history, the end-Permian extinction (±251.9 Ma). The recovery of terrestrial ecosystems from this mass extinction is an active area of research and one of South Africa’s most important contributions to the field of palaeontology. The farm Driefontein 11 in the Free State Province preserves an Early Triassic (upper Olenekian) fossil lagerstattë in the Burgersdorp Formation of the Karoo’s Beaufort Group . Driefontein yields tens of thousands of body and trace fossils. These fossils range in size from sub-mm scale teeth and invertebrates to bones of large temnospondyls and archosauromorphs. Despite the importance of these fossils, the fauna of Driefontein remains incompletely known – reflecting the sheer numbers of specimens (+- 30 000 coprolites alone) as well as the fragmentary and/or fragile nature and microscopic size of many of the remains. Here, we use a multiresolution (42µm to 1.14µm) approach with propagation phase contrast X-ray synchrotron micro computed tomography on the newly installed beamline, BM18, at the European Synchrotron and Radiation Facility, to investigate all trophic levels of Driefontein. We use this large dataset of high-resolution scans to investigate various aspects of organismal biology, including growth history, functional morphology, and comparative anatomy. This study contributes to our knowledge of the recovery of terrestrial ecosystems after the largest mass extinction in history, the end-Permian extinction, and highlights the importance of Driefontein 11 as a site for future research in the field of palaeontology
9:00am - 9:15amTopics: 3.11 Triassic Revolution
TETRAPODS FROM THE GERMAN BUNTSANDSTEIN (TRIASSIC: OLENEKIAN-ANISIAN): EVIDENCE ON TETRAPOD DIVERSIFICATION IN LAURASIA FOLLOWING THE END-PERMIAN EXTINCTION
Staatlichse Museum fur Naturkunde Stuttgart, Germany
Following the end-Permian biotic crisis, reptiles rapidly diversified and dispersed across the globe at the beginning of the Triassic Period. Non-mammalian synapsids became much less abundant and had massive losses in diversity during the end-Permian event. To date, the fossil record of continental tetrapods has largely been restricted to the Karoo of South Africa and European Russia. In the Central European Basin, Early and early Middle Triassic continental red beds are collectively referred to as the Buntsandstein Group. Whereas the strata of the Lower Buntsandstein are largely unfossiliferous, those of the Middle and Upper Buntsandstein have yielded many tracks and trackways representing a great diversity of tetrapods and occasionally skeletal remains of tetrapods. Temnospondyl stem-amphibians were common with a variety of ecomorphs. A sandstone quarry at Rotfelden in the Black Forest region (Germany) exposed a 6-to-8-m-thick section within the top of the Röt 4 Subformation. Tetrapod remains have been recovered from several horizons in this section. Previously, Amotosaurus rotfeldensis, a tanystropheid archosauromorph and the temnospondyl Eocyclotosaurus lehmani have been reported from this locality. New discoveries include a new Euparkeria-grade archosauriform and a rhynchosaur. The latter is documented by a group of three juvenile skeletons. The absence of unambiguous records of non-mammalian synapsids in the Buntsandstein is possibly related to environmental factors. The growing number of tetrapod taxa from the Buntsandstein suggests that assemblages of continental tetrapods had already recovered to a considerable extent 6-7 million years after the end-Permian extinction.
9:15am - 9:30amTopics: 3.11 Triassic Revolution
In a while it will be a crocodile: the early evolution of Crocodylomorpha in Europe
Naturkunde Museum Stuttgart, Germany
Crocodylomorpha, the crocodylian stem-lineage, is the only pseudosuchian clade that survived into the Jurassic. Its earliest members, the non-crocodyliform crocodylomorphs or ‘sphenosuchians’, were terrestrial and mostly small-bodied (<2 m long). A redescription of both known European ‘sphenosuchian’ taxa is provided, Terrestrisuchus gracilis from the Late Triassic (Norian-Rhaetian?) of southern Wales, and Saltoposuchus connectens from the Norian of southwestern Germany. Terrestrisuchus and Saltoposuchus can clearly be distinguished based on many character states, contrary to some previous hypotheses. A new phylogenetic analysis finds that both taxa form a clade of gracile, long-legged crocodylomorphs, identified as Saltoposuchidae, together with Litargosuchus leptorhynchus. Analysis of a µCT-scan provides a virtually complete threedimensional reconstruction of the Terrestrisuchus braincase. The quadrate only forms a small, unfused contact with the prootic, contrary to later crocodylomorphs in which the braincase is heavily fused to surrounding cranial elements. The posterior skull region is extensively pneumatised by, among others, large pre- and postcarotid recesses on the parabasisphenoid and a large pneumatic cavity within the articular of the mandible, revealing extensive braincase pneumatisation occurred early within Crocodylomorpha. Terrestrisuchus preserves an ossified basihyal and scleral ring, the latter representing the first occurrence among non-bird-line archosaurs. Based on phylogenetic flexible discriminant analysis (pFDA) of the relative dimensions of the sclerotic ring and orbit, Terrestrisuchus was likely active in a range of light levels. Histological long bone sections of both Terrestrisuchus and Saltoposuchus reveal highly vascularized fibrolamellar tissue, indicating sustained high growth rates and thus high resting metabolic rates and active lifestyles for saltoposuchids.
9:30am - 9:45amTopics: 3.11 Triassic Revolution
A new pachypleurosaur (Reptilia: Sauropterygia) from the Middle Triassic of southwestern China and its phylogenetic and biogeographic implications
1School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China; 2Institute of Geosciences, University of Bonn, Bonn 53115, Germany
After the devastating Permo-Triassic Mass Extinction, several new groups of large predators invaded the sea in the early part of the Triassic, including sauropterygians, ichthyosauromorphs and thalattosaurs. Among these predators, sauropterygians are the most abundant group in terms of the generic/species diversity. Here we report a new species of Pachypleurosauria (Sauropterygia: Eosauropterygia) from a recently discovered Lagerstätten in the Upper Member of Anisian Guanling Formation. The only known specimen of the new species was collected from Muta village, Luxi County, Yunnan Province, South China. Our new phylogenetic analysis based on a novel data matrix recovered the new taxon as a sister group to Dianmeisaurus. The new phylogenetic analysis also collapsed the monophyly of traditionally recgonized Eusauropterygia. Pistosauridea, Majiashanosaurus, and Hanosaurus comprise the consecutive sister groups to a new clade including Pachypleurosauria and Nothosauroidea. A monophyletic Pachypleurosauria, of which the clade consisting of Dianmeisaurus and Panzhousaurus occupy the basal-most position, is recovered by this study. The clade consisting of Dawazisaurus and Dianopachysaurus forms the sister group to remaining pachypleurosaurs included in this study. Since Dianmeisaurus, Panzhousaurus, Dawazisaurus and Dianopachysaurus are all exclusively known from South China, we suggest that pachypleurosaurs had a paleobiogeographic origin in the eastern Tethys.
9:45am - 10:00amTopics: 3.11 Triassic Revolution
The Triassic Revolution on land
University of Bristol, United Kingdom
The evolution of terrestrial life was as profoundly affected by the end-Permian mass extinction as life in the sea. The recovery of life in the Triassic represented much more than simply a return to pre-extinction conditions, but in fact an entirely new world was ushered in. The generalized replacement of synapsids by archosauromorph reptiles had long been recognized, together with the rise of the dinosaurs to ecological dominance and origins of many modern groups including lissamphibians, turtles, lizards, crocodilomorphs, and mammals. In addition, all the new larger tetrapods had switched from a sprawling posture before the crisis to an erect posture and parasagittal gait afterwards, and this hints at higher activity levels. This is confirmed by the more recent discovery that many of the Triassic archosauromorphs had indicators of endothermy (warm-bloodedness) in their bone histology, and that these Triassic tetrapods also had insulating dermal structures: hair in synapsids and feathers in dinosaurs, pterosaurs and their ancestors. All these indications of endothermy are debated and yet to be confirmed by further study, but they suggest an overall increase of energy in ecosystems, a general speeding up of life as competition and predation increased. Also, it means that these tetrapods were consuming more energy than their Permian forebears. In many ways, these discoveries suggest a macroevolutionary model equivalent to the Mesozoic Marine Revolution, in which Mesozoic marine life was more active and more meaty than much if Palaeozoic marine life.