A new Silurian ophiuroid from the west of Ireland.

Abstract

Silurian echinoderms from Ireland are poorly known; hitherto, only three nominal species have been described, all crinoids and all from the Telychian (Upper Llandovery, Lower Silurian) Kilbride Formation in County Galway. A new species from this formation, Crepidosoma doylei, is the first recorded Irish Silurian ophiuroid (brittle star). The new species is described from five articulated specimens; all are mouldic and none retains a counterpart. The disc and immediately adjacent arm lateral ossicles of the new species differ in shape from those of the type species in that these ossicles are comparatively flat rather than angular or ridged, and the series is marked by a well-defined channelway that appears to have extended from within the disc for the full length of the free arm. Ambital framework ossicles are smooth, and not S- or Z-shaped and ridged as in the type species. The new specimens of C. doylei were recovered from distal storm deposits that are thought to be deep-water equivalents of Benthic Assemblage Zone 5 (Clorinda Community).