BRINGING BLASTOIDS (ECHINODERMATA) BACK TO LIFE: CFD SIMULATIONS OF VIRTUAL 3D MODELS

Virtual reconstruction of fossils is an important component of 21^st century paleontology enabled by the combination of detailed imaging modalities, high speed computing capabilities and sophisticated software to generate 3D models. The production of a detailed 3D model is the primary goal of many investigations with the model then being used to describe the morphology of the reconstructed fossil for taxonomic, phylogenetic, or functional studies. In the case of marine fossils, 3D models can also be used as input into computational fluid dynamics (CFD) simulations allowing investigators to delineate functional differences in the observed morphologies. Blastoids belong to an extinct class of Paleozoic echinoderms whose inferred functional morphology is modeled on modern stemmed crinoids. Although blastoids are rarely preserved as complete specimens, we can construct 3D models with theca (including internal, mostly soft tissue, organ systems), stem, and brachioles. These models can be input into CFD simulations to analyze the dynamics of water flow through the internal respiratory organs (hydrospires) and over various thecal and brachiolar filtration fan morphologies. The results suggest that blastoids formed a parabolic filtration fan with the theca more of less horizontal and stem bent in an arc in currents flowing aborally to orally at velocites of > 0.5 cm/s to 10 cm/s. At current velocities of 25 cm/s and 50 cm/s (the highest velocity modeled) hydrodynamic drag and adoral zones of turbulence were reduced suggesting that feeding efficiency of the filtration fan was compromised. We have produced a CFD simulation of a model of Monoschizoblastus visualizing water flow internally through the hydrospires and externally around the theca through the brachiolar filtration fan. This simulation functionally brings the blastoid back to life by modeling respiration, feeding and reproduction simultaneously. The simulation produced unexpected water flow interactions not seen in independent models of internal and external water flow, and provides the foundation for new interpretations of functionality in the respiratory and reproductive systems. These new interpretations will provide additional characters for phylogenetic synthesis of the Blastoidea, a task that has proven somewhat elusive to date.