FLUID-STRUCTURE INTERACTION (‘FSI’) ANALYSIS OF THE EARLIEST BIOMINERALIZING ANIMALS

The late Ediacaran Period (~571–539 Ma) was a pivotal time in geologic history that witnessed the first appearance of macroscopic animal biomineralization. A key taxon in this regard is the iconic and globally-distributed tubular fossil Cloudina, which is a potential index fossil of the terminal Ediacaran stage. The degree of Cloudina biomineralization has been debated despite abundant fossil evidence, partially due to their frequent preservation as fragments within a range of lithologies. Here we combine computational fluid dynamics (CFD) and structural mechanics to perform a series of fluid-structure interaction (FSI) analyses on idealized Cloudina models. Our results demonstrate large stresses near the sediment-water interface and assumed attachment location – providing an intuitive mechanism for their frequent breakage and preservation style. In addition, our simulations suggest fluid flow patterns around the living organism that would have brought food particles to the presumed location of feeding appendages, and which have been well-documented among modern dipteran (blackfly) larvae. This result thus suggests the convergent evolution of sophisticated feeding ecologies in organisms separated by over half a billion years of evolutionary history, and establishes new quantitative approaches for reconstructing Ediacaran paleobiology using multiphysics modeling.