HYDRODYNAMICS OF THE RANGEOMORPH EDIACARAN ORGANISM PECTINIFRONS ABYSSALIS

The late Ediacaran fossil surfaces at Mistaken Point (~574-564 Ma) preserve some of the oldest complex macroscopic communities, and which are dominated by ‘fractal’ rangeomorph organisms whose relationships to extant animal groups are unknown. Among the least well-understood of these is Pectinifrons abyssalis - a fence-like organism consisting of a curved basal pedicle rod and two upright rows of rangeomorph fronds. Like other rangeomorphs Pectinifrons is widely believed to have been a sessile osmotroph – feeding via the direct absorption of dissolved organic compounds – however this model has yet to be objectively tested. In this project I use computational fluid dynamics (‘CFD’) modeling to examine simulated flow patterns around Pectinifrons under a range of realistic paleoenvironmental conditions. I compare these patterns both with those computed for other Ediacaran organisms, as well as a range of potential modern analogues. These data allow me to critically assess the paleobiology of Pectinifrons, including the establishment of likely feeding mode, as well as examine a range of potential interactions with co-occurring rangeomorph organisms. Ultimately this work sheds new light on a little-studied Ediacaran organism, and tests the hypothesis that Pectinifrons formed part of a unique biocoenosis that disappeared prior to the base of the Cambrian.