A STUDY OF DIPLOPORAN ECHINODERM FEEDING AND RESPIRATION USING COMPUTATIONAL FLUID DYNAMICS

Diploporans were a diverse and enigmatic grouping of Paleozoic stemmed echinoderms; many details of their biological function and paleoecological interactions are still unknown, which is primarily due to their lack of extant analogs. This paucity is further compounded by the sparse fossil record of diploporans, which consists almost entirely of incomplete specimens, with complete specimens being rare. While some features are more commonly preserved, such as the thecal body, key characters like the brachioles (i.e., the ‘arms’) and the attachment structures (i.e., stems or holdfasts) are rarely found fossilized. To gain better insight into how diploporans may have interacted with their fluid environments to feed and respire, we created 3D models of select taxa which display exceptional preservation using a NextEngine 3D scanner. Completed 3D scans were then imported to GeoMagic Wrap for cleaning, alignment, reconstruction of arms, and creation of NURBS surface. Due to the incomplete preservation of specimens, arms were reconstructed based on exceptionally preserved fossils belonging to a closely related taxon. Models were imported into the computational fluid dynamics software Ansys Fluent, where the models were subjected to various simulated current velocities. The results provide insight into the functional relationships between the body morphology and arm positions, as they pertain to feeding, as well as to the performance of the diploporan double-pore respiratory structures. Further, we test hypotheses proposed previously that the number, location, and orientation of diploporan respiratory structures on the theca could be indicative of zones of greater efficiency, due to fluid turbulence induced by the morphology of the animal.