TAPHONOMY AND PALEOECOLOGY OF AN OPHIUROID-STYLOPHORAN OBRUTION DEPOSIT FROM THE LOWER DEVONIAN BOKKEVELD GROUP, SOUTH AFRICA

Abstract

The taphonomy of a well preserved ophiuroid-stylophoran assemblage from the Bokkeveld Group, Lower Devonian of South Africa is described using micro-CT scanning techniques. This assemblage provides a taphonomic window into the structure of Early Devonian, echinoderm-dominated communities within the Malvinokaffric Realm of SW Gondwana. Micro-CT scanning and 3D modeling of a portion of an obrution bed revealed an assemblage of over 700 ophiuroids observed of the newly described Gamiroaster tempestatisReid 2019 associated with two species of stylophorans of two species, the mitrates Paranacystis cf. petriiCaster 1954 and Placocystella africana (Reed 1925). The 3D model permitted detailed sedimentologic and taphonomic analysis of the bed including determination of the degree of fossil articulation, orientation, and faunal counts. The results indicate that deposition took place in a storm-influenced, shallow marine environment smothering both attached and vagrant taxa of the benthic community during a high-energy storm event. Micro-CT scanning is a powerful taphonomic tool for the non-destructive analysis of delicate echinoderm assemblages that would otherwise be difficult to study.