Abstract

An echinoderm fauna from the Lower Devonian (Lochkovian) Cravatt Member of the Bois d'Arc Formation near Clarita, Oklahoma, has yielded specimens of recumbent, essentially bilaterally symmetrical taxa which are similar to Ordovician genera but absent or sparsely represented in Silurian strata. Claritacarpus smithi n. gen. and sp., is a dendrocystitid homoiostele with morphology similar to the Late Ordovician DendrocystoidesJaekel, 1918; the anomalocystitid stylophoran Victoriacystis aff. holmesorum Ruta and Jell, 1999 shows strong affinities to Victoriacystis holmesorum Ruta and Jell, 1999, Humevale Formation, of Victoria, Australia; and the pleurocystitid rhombiferan, Turgidacystis graffhami n. gen. and sp., has close affinities to the Middle Ordovician CoopericystisParsley, 1970 of West Virginia and HenicocystisJell, 1983 of Victoria, Australia. Claritacarpus and Turgidacystis are North American range extensions for homoiosteles and pleurocystitids, respectively, being previously unknown from rocks younger than Upper Ordovician. Globally, Silurian homoiosteles and pleurocystitids are unknown although both occur in the Lower Devonian of Germany and Australia; additionally, Early Devonian pleurocystitids are known from Great Britain and Bohemia. These genera illustrate a pseudoextinction pattern suggesting a significant unsampled Silurian “homalozoan” and pleurocystitid history.

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