The Palaeontological Association

51st Annual Meeting

16th–19th December 2007

Uppsala University, Sweden

______

PROGRAMME WITH ABSTRACTS ______

edited by

Graham E. Budd, Michael Streng, Allison C. Daley and Sebastian Willman

Uppsala, 2007 51st Palaeontological Association Annual Meeting Uppsala 2007

Biomarker analysis: a tool for investigating the diet and digestive biochemistry of ancient animals

Fiona Gill1, Ian Bull1, Richard Pancost1, Remmert Schouten2 and Tim Ewin3 1OGU, Bristol Biogeochemistry Research Centre, University of Bristol, UK 2School of Earth Sciences, University of Bristol, UK 3Bristol City Museum, UK

Biomarkers are biogenic molecules linked to particular taxa or biochemical processes, on the basis of their chemical structure. Biomarkers have been used extensively to investigate microbial communities in modern and ancient environments. We present evidence that the biomarker approach can be extended to the fossil record on the scale of individual macro- organisms, to elucidate diet and digestive biochemistry, including relationships with symbiotic gut micro-organisms. We used established organic geochemical techniques to extract biomarkers from faecal samples from a variety of modern animals, to test the hypothesis that there is a correlation between diet, digestive processes and biomarkers present in faeces. The organic geochemical content of faecal material comprised biomarkers derived from dietary materials, as expected, but also biomarkers from gut microbes, including the archaeal biomarker “archaeol”, which is attributed to methanogenic archaea, and various bacterial fatty acids. Based on these results, we applied the biomarker approach to a variety of coprolites, including one from the Pleistocene ground sloth Nothrotherium shastaensis. The sloth coprolite biomarker assemblage was dominated by a plant-derived sapogenin, providing evidence for the diet of the animal. We also analysed the preserved gullet contents of a well-preserved scelidosaur specimen, to determine diet and taphonomy. The preservation of diagnostic microbial and plant biomarkers in ancient coprolites and related materials indicates that this approach, together with traditional palaeontological methods, can provide critical complementary evidence for the diet of ancient animals and their digestive processes.

Dinosaur tectonics – structural geology as a tool to interpret theropod walking dynamics

Ole Graversen1, Jesper Milàn1 and David B. Loope2 1Department of Geography and Geology, University of Copenhagen, Denmark 2Department of Geosciences, University of Nebraska, Lincoln, NE, USA

A dinosaur trackway in the Middle Jurassic eolian Entrada Sandstone of southern Utah, USA, exposes three undertracks that we have modeled as isolated tectonic regimes showing the development of fold-thrust ramp systems induced by the dinosaur’s feet. The faulted and folded sequence is comparable to crustal scale tectonics associated with plate tectonics and foreland fold-thrust belts. A structural analysis of the dinosaur tracks shows the timing and direction of the forces exercised on the substrate by the animal’s foot during the stride. Based on the structural analysis, we establish a scenario for foot movements and weight distribution in the feet. During the end of the weight-bearing phase of the stride, the weight of the animal was transferred to the front of the digits, creating a rotated disc below the foot that was bounded by an extensional fault at the front and a thrust ramp toward the back. As the body accelerated, the foot was forced backward. The rotated disc was forced backward along a detachment fault that was bounded by lateral ramps. The interramp segment matches the 27 51st Palaeontological Association Annual Meeting Uppsala 2007 width of the dinosaur’s foot which created an imbricate fan thrust system that extended to the far end of the undertrack. The total length of the tectonic disturbance created by the dinosaur is up to three times that of the original footprint. Early, near-surface cementation gave the substrate the rheological properties necessary for development of the observed structures.

Late Ediacaran Avalon-type biota of Siberia

Dima Grazhdankin1, Uwe Balthasar2, Konstantin Nagovitsin1 and Boris Kochnev1 1Institute of Petroleum Geology and Geophysics, Novosibirsk, Russia 2Department of Earth Sciences, Palaeobiology, Uppsala University, Sweden

The earliest known communities of macroscopic organisms are represented by the extinct Avalon, Ediacaran and Nama biotas. The Avalon biota is typified by rangeomorphs (fusiform, frondose and plumose organisms characterized by the diagnostic fractal quilting) and frondose organisms distributed in low-energy shelf habitats. It has generally been regarded as the oldest (575-560 Ma) assemblage of Ediacara-type fossils and endemic to the Avalon Terrane. However, a diverse, abundant, and exceptionally well-preserved assemblage of Avalon-type macrofossils occurs in the much younger (<544 Ma) late Neoproterozoic Khatyspyt Formation cropped out along the Khorbusuonka River on the Olenëk Uplift, which is located at the northeastern margin of the Siberian Craton. The assemblage includes an assortment of holdfast structures (Mawsonites, Inaria, Protodipleurosoma, Aspidella), a frondose erect organism Khatyspytia, a rangeomorph Charnia, serially and radially chambered structures (Eoporpita and Palaeopascichus), problematic Hiemalora, as well as microbial colonies (Cyclomedusa, Ediacaria, Paliella, Nimbia). The Avalon-type biota of Siberia inhabited low- energy carbonate ramp environment in a foreland basin setting and is closely associated with a peculiar assemblage of carbonaceous compression fossils. The Khatyspyt fossil assemblage significantly extends both the stratigraphic and biogeographic ranges of the Avalon biota. If the Khatyspyt fossil assemblage is considered together with older low-energy shelf assemblages, a pattern emerges from the stratigraphic distribution of the Avalon-type fossils, with a gradual shift in dominance from rangeomorphs to frondose organisms. But it this an evolutionary succession?

The ocean chemistry at Cambrian deposits with exceptional preservation and the influence of sulfate on soft-tissue decay

Emma Hammarlund1, Donald E. Canfield1 and Stefan Bengtson2 1Nordic Center for Earth Evolution, University of Southern Denmark, Denmark 2Department of Palaeozoology, Swedish Museum of Natural History, Stockholm, Sweden

Cambrian deposits with exceptional fossil preservation have been investigated to promote understanding of the marine environment and taphonomy in the early Phanerozoic. Water- column anoxia, commonly correlated to these sites, was evaluated via contents of highly reactive iron, and no clear correlation between preservation and anoxia was found. Low pyrite contents reveal that periods of anoxia were iron-rich and non-sulfidic. Furthermore, the isotopic composition of the pyrite demonstrates low fractionations (4-17‰) from Cambrian seawater sulfate. This is indicative of low concentrations of seawater sulfate, arguably around 1 mM, and is one factor, apart from low levels of bioturbation, that these deposits have in common. The influence of sulfate on soft-tissue decay was tested. Decay rate and visual