Scleritome construction, biofacies, biostratigraphy and systematics of the tommotiid Eccentrotheca helenia sp. nov. from the Early Cambrian of South Australia

摘要: Large collections of Eccentrotheca helenia sp. nov. from the lower Cambrian Wilkawillina and Ajax limestones in Arrowie Basin, South Australia, contain abundant low, cap-shaped high, laterally compressed isolated sclerites addition to partially articulated tubular specimens. The scleritome is fully described for first time shown be formed by ontogenetic fusion into successively stacked sclerite rings, forming a larger, structure. apical termination tube highly variable, but primarily constructed characterised central aperture variable inclination. adapical portion predominantly sclerites, individual rings can both along with intermediate morphology. presumably housed organic structures attachment hard substrate, also occasionally preserves small lateral perforations between fused which may have served stabilise providing additional points anchorage. In E. found association archaeocyath-microbial-spongiomorph-dominated bioherms most likely inhabited pendant or cryptic habitats within these bioherms. Eccentrotheca-like form an integral part scleritomes many tommotiids confuse taxonomic analysis. Sclerites previously assigned 'E.' guano, consistently occur together Kulparina rostrata stratigraphic intervals older than strata hosting helenia. Rare specimens indicate that K. guano belong same scleritome.