Archaeocyathan (stem Group Porifera) Three-Dimensional Preservation, Reconstruction and Functional Analysis

Archaeocyaths are an extinct group of hypercalcified almost exclusively early Cambrian organisms. Despite their high diversity and fair well preservation in carbonates, a poor record of these fossils allowing their full extraction from rocks, still leaves a window of opportunity for other systematic interpretations. Finds of finely preserved phosphatized archaeocyathan cups in the Three Gorges area of the Hubei Province, Meitan county of Guizhou Province, South China and Orogol Gorge of Mongolia, let a possibility of three-dimensional reconstruction of complete skeletons with subsequent 3D-printing of their plastic copies. In this study, computational fluid dynamics (CFD) was employed to explore the function of the different archaeocyaths. Experiments conducted in flume tanks under flow revealed a suitability of sophisticated archaeocyathan skeletal structures for passive flow entrainment by the outer wall pores with its redirection to the central cavity through inner wall openings and, then, outside the cup. Remarkably, that models with additional outer wall elements (bracts and tumuli) show a better filtration ability when those with a simple wall. Morphological functional analysis confirms a filter-feeding nature of archaeocyaths similars to that of other sponges.