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

地球上的生命经历了一段非凡的历史，在这段历史中，它们忍受了气候灾难，发展出令人难以置信的生物创新，并在生物不断适应不断变化的环境的过程中，在灭绝和辐射的循环中幸存下来。地球历史上最引人注目的时期之一是新元古代晚期，大约7亿到5.41亿年前（Ma），这段时期见证了生物从巨大的雪球地球全球冰期中恢复过来，以及第一批动物的进化和辐射。描述和解释动物的进化是目前古生物学中最热门的领域之一。它不仅激发了哲学的兴趣，而且还提供了丰富的科学信息，可以促进我们对进化过程的理解，以及在重大环境变化时期生命与地球之间的相互作用。传统上，科学家们认为动物是在541年前的寒武纪底部突然而迅速地进化的。这种观点在20世纪40年代和50年代受到了挑战，因为在前寒武纪的岩石中发现了复杂的化石印记——一套大型的多细胞生物，被称为埃迪卡拉生物群。他们的发现推动了一种范式的转变，从寒武纪基础上的动物进化的快速“寒武纪大爆发”模式，到动物进化延续了数千万年的“埃迪卡拉-寒武纪过渡”模式。埃迪卡拉纪（635-541 Ma）化石目前在全球50多个地方被发现，包括100多个不同的物种，但它们仍然是地质记录中最神秘和最有争议的化石。由于这些化石是作为软体生物的印记而不是作为壳、骨头或牙齿保存下来的，而且它们的形状和结构与任何活的生物都不同，因此科学家们对这些化石最初可能是什么存在很大的分歧。然而，一种新兴的观点认为，埃迪卡拉动物群可能包括一些最早的真正动物的遗骸。我的研究探索了动物的最初进化，研究了它们出现的原因，以及它们的出现对海洋栖息地中其他生物的影响。在这个项目中，我的目标是解决埃迪卡拉生物和今天活着的现代动物之间的关系，并调查埃迪卡拉化石在世界各地的保存方式，以提高我们对动物进化的时间和进程的理解。通过对埃迪卡拉纪化石、沉积物和环境的详细研究与实验工作相结合，重新创造了5.8亿年前生物成为化石的途径，我希望能够限制化石保存的模型，并为生物最初组成的组织提供新的见解。我还将研究埃迪卡拉纪时期动物运动的化石记录，因为近年来这已经成为动物存在的关键证据。我所获得的结果将用于分子研究，这将有助于更好地预测在地球历史的这个关键时刻，主要动物群体是如何以及何时分化和进化的。总的来说，这个计划将通过提高我们对埃迪卡拉纪生物和环境的理解，严格地解决动物何时以及为什么进化的问题。它将揭示关于埃迪卡拉纪海洋生态系统的新信息，最重要的是，它将为我们提供早期动物进化步骤的更清晰图景。

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.