Constraining the origins of the Metazoa: Insights from ichnology, palaeoecology and taphonomy

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Life on Earth has experienced a remarkable history, in which it has endured climatic catastrophes, developed incredible biological innovations, and survived cycles of extinction and radiation as organisms have continually adapted to their changing environment. One of the most dramatic intervals of Earth history is the late Neoproterozoic Era some 700-541 million years ago (Ma), which witnessed amongst other things the biological recovery from the great Snowball Earth global glaciations, and the evolution and radiation of the first animals. Characterizing and explaining the evolution of animals is currently one of the most topical areas in palaeontology. It not only excites philosophical interest, but also provides a wealth of scientific information that can advance our understanding of evolutionary processes and the interactions between life and the planet at times of major environmental change. Traditionally, scientists considered animals to have evolved suddenly and rapidly at the base of the Cambrian period, 541 Ma. That view was challenged in the 1940s and 1950s by the discoveries of complex fossilized impressions in rocks of Precambrian age - a suite of large, multi-cellular organisms that have become known as the Ediacaran biota. Their discovery prompted a paradigm shift from a rapid "Cambrian Explosion" model of animal evolution at the base of the Cambrian, to an "Ediacaran-to-Cambrian transition" whereby animal evolution extended over tens of millions of years.Ediacaran (635-541 Ma) fossils are currently known from over 50 localities worldwide and include more than 100 different species, but they remain some of the most enigmatic and controversial fossils in the geological record. Since they are preserved as impressions of soft-bodied organisms rather than as shells, bones, or teeth, and the shapes and structures of the fossils differ from those of any living organisms, there has been much disagreement amongst scientists about what the fossils might have originally been. An emerging view, however, is that the Ediacaran biota may include the remains of some of the first true animals.My research explores the initial evolution of animals, examining the causes for their emergence, and the consequences of their appearance for other organisms in marine habitats. In this project I aim to resolve the relationships between Ediacaran organisms and modern animals alive today, and investigate the ways in which Ediacaran fossils are preserved around the world, in order to improve our understanding of the timing and progression of animal evolution. By combining detailed study of Ediacaran fossils, sediments, and environments with experimental work to recreate the pathways through which organisms were fossilized 580 million years ago, I hope to constrain models for fossil preservation, and provide new insights into the tissues the organisms were originally composed of. I will also investigate the fossil record of animal movement in the Ediacaran period, since in recent years this has become a key piece of evidence for the presence of animals. Results I obtain will be fed into molecular studies, which will allow better prediction of how and when the major animal groups diverged and evolved at this critical point in Earth history.Taken together, the proposed project will rigorously address the questions of when and why animals evolved by improving our understanding of Ediacaran organisms and environments. It will reveal new information about Ediacaran marine ecosystems, and, most importantly, will provide us with a clearer picture of the steps involved in early animal evolution.