Microstructure and functional morphology of the Early Cambrian problematical fossil Rhombocorniculum

摘要

Rhombocorniculum cancellatum from the Lower Cambrian of southern Shaanxi Province (South China) is represented by the dextral and sinistral tooth-like sclerite.s (both in nearly equal numbers), indicating that, the body plan of the organism with these sclerites probably was bilaterian. The main feature of the microstructure of the sclerites is the presence of longitudinally arranged, mutually contiguous hollow tubules, the shared walls consisting of microcrstalline apatite. In transverse cross sections, the sclerite wall mainly exhibits a spongy structure, with pore size decreasing adapically. Functional morphological analysis indicates that the sclerites erve as a defensive rather than a grasping function.