New sea urchins (Echinodermata: Echinoidea) from the Famennian of Velbert (W Germany): Evidence for echinoid faunal turnover in the Late Devonian

Abstract

Despite the presumably lower diversity of Palaeozoic echinoids compared to their post-Palaeozoic relatives, a radiation during the Mississippian marked a first brief "golden age" of sea urchins. Carboniferous echinoid faunas feature distinct and specialised groups compared to those of the Devonian, suggesting important evolutionary changes during the Late Devonian, although the role of biotic crises like the Kellwasser and Hangenberg Events in these changes remains poorly known. This study describes an exceptionally well-preserved echinoid fauna from the middle to upper Famennian of Velbert near Düsseldorf, Germany. Description of six new species belonging to the lepidocentrid, hyattechinid, proterocidarid and archaeocidarid lineages along with a seventh species based on isolated remains greatly add to the knowledge of Late Devonian echinoids. The newly described genera Thielechinus gen. nov. and Velbertechinus gen. nov. represent the most derived proterocidarids and archaeocidarids known from the pre-Carboniferous. Moreover, the fossils offer new insights into phylogeny, ontogeny, and palaeobiology of several stem-group echinoid lineages. The fauna resembles Carboniferous echinoid faunas much more than earlier Devonian faunas, thus providing evidence that crucial developments had occurred from the Frasnian to the Famennian, possibly linked to global changes associated with the catastrophic Kellwasser Event. These developments include the appearance of several specialised lineages that would become important in the Late Palaeozoic as well as evolutionary innovations leading up to the establishment of the crown-group echinoid body plan.