ANCIENT LIFE IN MOVING FLUIDS: HYDRODYNAMICS OF THE EDIACARAN-CAMBRIAN TRANSITION (Invited Presentation)

The Ediacaran–Cambrian transition (~571–539 Ma) represents one of the most dramatic geobiological revolutions in Earth history, recording the emergence of complex macroscopic ecosystems (the ‘Ediacara biota’), the onset of metazoan ecosystem engineering, and multiple waves of evolutionary innovation and extinction. Despite a wealth of recent and focused research on this interval there remain fundamental questions surrounding both the biology and affinities of Ediacaran organisms themselves, and their role in the emergence of modern marine ecosystems. Outstanding questions include: what were the Ediacara biota? How did they feed? How were their communities structured? And, how do changes in community composition reflect shifts in the character and availability of ecological resources? One technique that is increasingly being used to tackle these questions is computational fluid dynamics (CFD) modeling, which is enabling us to test hypotheses about how these enigmatic organisms fed, moved, and reproduced, and in turn highlighting dramatic changes in community structure and function in the lead-up to the Cambrian. Here, we summarize recent work from our group on the hydrodynamics of the Ediacaran–Cambrian transition, including insights into the paleobiology of enigmatic taxa, methodological advances (including simulating flow through whole communities), and larger-scale questions in evolutionary ecology that can be tackled with these models. Finally, we summarize emerging evidence for a late Ediacaran rise in suspension feeding, potentially representing a strengthening link between pelagic and benthic ecosystems, and which is coeval with clock estimates for the origination of a broad swathe of animal groups. In this fashion, we suggest the rise of suspension feeding may have helped fuel the Cambrian explosion.