Conference Agenda

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Session Overview
3.11-3 Triassic Revolution
Tuesday, 05/Sept/2023:
10:00am - 11:15am

Session Chair: Stephan N.F. Spiekman, Naturkunde Museum Stuttgart
Location: Wiwi 104a


10:00am - 10:15am
Topics: 3.11 Triassic Revolution

The Carnian Pluvial Episode in Tethys Realm: Insights from multiproxy paleoclimate data

Mina Mazaheri-Johari1, Jacopo Dal Corso2, Guido Roghi3, Evelyn Kustatscher4,5, Tamsin Mather6, Piero Gianolla1

1Department of Physics and Earth Sciences, University of Ferrara, Via G. Saragat 1, Block B, Ferrara 44100, Italy; 2State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China; 3Institute of Geosciences and Earth Resources - CNR, Via Gradenigo 6, Padova 35131, Italy; 4Department of Earth and Environmental Sciences, Paleontology & Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner-Straße 10, 80333 München, Germany; 5SNSB-Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, 80333 München, Germany; 6Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, UK

The Carnian Pluvial Episode (CPE, 234–232 Ma) was a major climate change event in the Triassic. The CPE brought substantial changes in ecological community structure and the appearance of many key groups dominating modern marine and terrestrial ecosystems. Here we present an interdisciplinary study of Upper Triassic strata in the Tethys realm to reconstruct the vegetation history and infer environmental changes during the Carnian. Furthermore, we applied Mercury (Hg) concentrations and Total Organic Carbon (TOC) to unwrap the role of volcanic activity as a major driver of this episode of climate warming and environmental perturbations. Palynological and paleobotanical data collected from the Northern Tethys (Kope-Dagh basin, NE Iran) show a shift towards hygrophytic elements reflecting the expansion of wet habitats on the continent during the latest early Carnian to late Carnian. The sedimentological and palynological patterns and plant fossil assemblages in the Northern Tethys closely resemble those observed in Western Tethys during CPE. This record represents the only clear record of the CPE in the Iranian plateau. Our geochemical data from Carnian marine sedimentary sequences of the Western Tethys demonstrate discrete spikes in Hg/TOC ratios during the CPE. The results suggest a direct link between the CPE and repeated pulses of the Wrangellia submarine Large Igneous Province that could have played a major role in the evolution of biota and the environment at that time. However, despite progress in understanding the CPE, significant uncertainty remains in addressing how the volcanic eruptions influenced different ecosystems/biotic communities, which deserves further studies.

10:15am - 10:30am
Topics: 3.11 Triassic Revolution

The Lower Keuper (Erfurt Formation, Middle Triassic) fossillagerstätten from SW Germany: flourishing tetrapod ecosystems

Eudald Mujal1,3, Raphael Moreno1,2, Rainer R. Schoch1,2

1Staatliches Museum für Naturkunde Stuttgart, Germany; 2Universität Hohenheim, Germany; 3Institut Català de Paleontologia Miquel Crusafont, Spain

Even if the knowledge of Triassic tetrapod communities and their role in terrestrial ecosystems has increased in the recent decades, the paucity of fossil sites from this time interval has hindered their complete understanding. In order to shed light on how the Triassic tetrapod communities were, evolved and interacted in their habitats, we are carrying out a series of multidisciplinary studies on the Ladinian Lower Keuper successions (Erfurt Formation) of southwestern Germany. These facies were deposited in a vast epicontinental platform of the Central European Basin, influenced by the Tethys Sea. The Lower Keuper in the study areas consists of a 20–25 m thick succession of alternating siliciclastic and carbonate deposits, mostly grey to green mudstones and marlstones, and yellowish to blueish dolostones, as well as occasional sandstones. The succession is divided in more discrete units, some of which forming exceptional fossillagerstätten with thousands of tetrapod remains recovered and tens of new tetrapod taxa (including basal members of different lineages) described to date. Sedimentological, taphonomic and palaeoecological data show that ecosystems were complex, with several levels within the trophic chain and including at least two top predators: a pseudosuchian archosaur and a giant capitosaur temnospondyl. Of note, fish diversity is particularly high, with at least 14 taxa so far known. The occurrence of the same vertebrate taxa, but in different proportions and from different ontogenetic stages throughout the stratigraphic succession and in different localities corresponding to slightly different environmental settings, indicates stability of the ecosystems.

10:30am - 10:45am
Topics: 3.11 Triassic Revolution

Reappraisal of the environmental setting and taphonomy of the Trossingen Plateosaurus bonebeds

Joep Schaeffer1, Eudald Mujal1,2, Rainer R. Schoch1,3

1Staatliches Museum für Naturkunde Stuttgart, Germany; 2Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain; 3Universität Hohenheim, Stuttgart, Germany

The Norian Trossingen Plateosaurus bonebeds have piqued the interest of many researchers over the past 100 years. Several investigations took place in the 1910’s to 1930’s excavating over 80 skeletons, but was then left to rest until 2007. In 2007, 2008 and 2010 small excavations took place, resulting in one and a half skeleton of Plateosaurus trossingensis. The depositional environment of the site has had a controversial history with several theories, ranging from a sandy desert to a catastrophic mudflow, to a watering hole with a muddy bottom. In the summer of 2022 an exploratory investigation was performed at the Trossingen site to prepare for large scale excavation in 2023, which will incorporate stratigraphical, sedimentological and taphonomic investigations to further dive into the evolution of the environment and its relation to the fossil remains. Here we present the first results of both the 2022 and 2023 field campaigns with a revised depositional history. The preliminary investigations in 2022 already showed the section is not as homogenous as previously thought and uncovered several structures, most of which not previously recognised, such as: (1) several small channel–like deposits likely of fluvial origin and (2) a carbonate layer with a possible lacustrine origin in the lower beds, (3) large pedogenetic carbonate nodules in the middle beds, and (4) large mudcracks in the upper beds. All these features, together with preliminary taphonomic data from the bones, suggest a potential upwards aridification trend across the entire section.

10:45am - 11:00am
Topics: 3.11 Triassic Revolution

A taxonomic Gordian Knot - the sauropodomorph diversity in the Germanic Basin during the Late Triassic

Omar Rafael Regalado Fernández

Eberhard-Karls Universität Tübingen, Germany

The sauropodomorph-bearing localities from the Norian-Rhaetian of Europe have been traditionally interpreted as monospecific, attributing the morphological disparity in Plateosaurus to intraspecific variability. The Norian and Rhaetian stages are currently not chronostratigraphically defined, making comparisons between the different deposition environments cumbersome. However, from the base of the Norian to the Rhaetian, the sizes of sauropodomorphs increase, with small to medium-sized sauropodomorphs found in the oldest layers of the Löwenstein Formation, to larger and more robust-sized sauropodomorphs from the Tübingen Sandstone (Rhaetian). This contribution presents the results of a basin analysis to reconstruct the environmental changes in the Germanic Basin during the Late Triassic, integrating stratigraphy, fossil record and structural geology. The results of this are that during the Carnian, the opening of Meliata, Pindos and Maliac Oceans in Western Pangaea created rift zones on the carbonate platforms. Towards the Norian, the sea-spreading ceased as these southern oceans started to close just before the new rifting of the Neothetys began. The complex fault systems generated an epicontinental sea that separated portions of Europe as an archipelago that fully developed when the Rhaetian Sea occupied the Germanic Basin. Independently, several iterations of specimen-level phylogenetics of sauropodomorphs found that the three specimens that have been traditionally referred to as Plateosaurus are placed at the base of a comb-like arrangement that includes robust forms, such as Schleitheimia and Tuebingosaurus—two sauropodomorphs that have been previously nested within sauropodiformes. The phylogenetic patterns in a comb-like arrangement suggest a combination of vicariance and migration in the archipelago.

11:00am - 11:15am
Topics: 3.11 Triassic Revolution

Climatic controls on the ecological ascendancy of dinosaurs

Emma Dunne1, Lisa Schnetz2, Alexander Farnsworth3, Richard Butler2, Roger Benson4, Pedro Godoy5, Sarah Greene2, Paul Valdes3, Daniel Lunt3

1Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany; 2University of Birmingham, Birmingham, UK; 3University of Bristol, Bristol, UK; 4University of Oxford, UK; 5Universidade de Sao Paulo, Sao Paulo, Brazil

The rise of dinosaurs during the Late Triassic was a pivotal event in the history of life on Earth, which led to them becoming dominant members of terrestrial ecosystems throughout the remainder of the Mesozoic. However, the drivers of this geographic expansion and explosion in biodiversity have been poorly understood. Early studies have hypothesized that the extinction of co-occurring vertebrate groups such as aetosaurs, rauisuchians, and therapsids at the end-Triassic mass extinction, provided early dinosaurs with the opportunity to diversify into new niches. However, this pattern could instead be a response to climatic changes during this interval, especially given the increasing evidence that climate played a key role in constraining Triassic dinosaur distributions. Our work is the first to quantitatively explore the opportunistic expansion model by examining changes in dinosaur and tetrapod ‘‘climatic niche space’’ across the Triassic-Jurassic boundary. We found that Late Triassic sauropodomorph dinosaurs occupied more restricted climatic niche spaces than other dinosaurs, and were excluded from the hottest climate zones at low latitudes. The geographic expansion of sauropodomorphs after the mass extinction is linked to the expansion of their preferred climatic conditions. Evolutionary model-fitting analyses provide evidence for an important evolutionary shift from cooler to warmer climatic niches during the origin of Sauropoda, the clade that later in the Mesozoic became the iconic long-necked forms. Together, our results provide support for the key role of climate in the ascendancy of dinosaurs.