The Rise of Animal LIfe (Cambrian-Ordovician) - organization and tempo: evidence from exceptionally preserved biotas – RALI

Our project concentrates on one of the most important periods in the history of the biosphere, the Cambrian-Ordovician interval (ca. 542-443 Ma) during which animal Life arrives on the scene with unprecedently complex anatomies and functionalities and rapidly modifies the functioning of the global marine ecosystem. This ca. 100 million year time frame is crucial in that it lays the basic functioning principles that still prevail in present-day ecosystems. Although two major events are supposed to have taken place during this period, the so-called « Cambrian Explosion » and the « Great Biodiversification Event (GOBE) », it is still impossible to comprehend the chronology, the processes and the environmental triggers through which early animal Life organized and colonized the marine ecospace during its Early Palaeozoic history. The principal obstacles are 1) major discreapancies in the quality and completeness of the fossil record throughout the first 100 million years of animal evolution and 2) a lack of detailed information concerning the structure and functioning of the early Palaeozoic ecosystems, typically the way animals interact within the food chain and occupy the marine ecospace. Our project brings solution to overcome these obstacles by stuying exceptionally preserved biotas in the Early Cambrian of Australia, the Upper Cambrian of China and the Ordovician of Morocco. These three sites fill the gap of information concerning the biodiversity and organization of marine Life in the Early Palaeozoic, both in time and space. The second objective is to obtain new evidence for the organization of the Cambrian-Ordovician food chain through novel approaches such as the detailed analysis of the gut contents of fossil organisms and the reassessement of feeding types and strategies based on comparisons with modern analogues. The third objective is to build up a new database encompassing morphological, ecological and environmental information concerning all Cambrian and Ordovician exceptionally preserved biotas and to to apply a newly developed methods to quantify the evolution of biodiversity and occupation of ecospace within this time interval in a standardized fashion. Eventually, we expect to resolve fundamental issues concerning the early steps of animal evolution 1) How and how fast did the biodiversity of marine communities evolve through space and time ? 2) Are the current models of two separate evolutionary events («Cambrian radiation» and «GOBE») or replacing « Evolutionary Faunas » sensu Sepkoski correct or artefactual ? 3) How did the build-up process of trophic web and ecospace unfold through the first 100 million years of animal evolution ? 4) What are the essential ecological innovations that led to modern-style ecosystems ?