RECONSTRUCTING PALEOECOLOGY AND FEEDING STRATEGY IN THE THE YOUNGEST EDIACARAN MACROFOSSILS

The latest Neoproterozoic Ediacara biota (571–541 Ma) is an enigmatic group of fossils that represents the first radiation of complex life; however, the paleobiology and -ecology of many of these organisms is poorly understood. Establishing how various Ediacaran taxa fed is critical to understanding their roles in Ediacaran benthic ecosystems, and may be key to placing them on the metazoan phylogenetic tree. Here, we use a virtual modeling technique – computational fluid dynamics (CFD) – to test between hypothesized feeding modes for the semi-infaunal and sack-like organism Ernietta. We use COMSOL, multiphysics analysis software, to simulate water flow over a block-model Ernietta. Simulations were carried at three different inlet velocities (0.1, 0.2, and 0.5 m/s) and with the Ernietta model at three different burial depths (midway below suture, at the suture, and midway above the suture). Initial simulations show the development of small-scale recirculation within the central cavity of the organism, supporting inference of a gravity-driven suspension feeding habit for this taxon. Furthermore, the simulations illustrate that recirculation vortices appear directly down-current from the model. This inference of suspension feeding in Ernietta provides a good match for observations made in the field illustrating that in-situ individuals apparently lived gregariously. Accumulations of Ernietta may therefore have formed the earliest eukaryotic and soft-bodied bioherms yet discovered in the fossil record.