Two Late Ordovician asteroids (Echinodermata) with characters suggestive of early ophiuroids

Abstract

Jugiaster n. gen. is based on the Upper Ordovician asteroid (Echinodermata) Petraster speciosus; in addition, a second Upper Ordovician occurrence, Phyrtosaster casteri, new gen. and sp., is described. Both species exhibit mouth frame characters suggestive of those long considered typical of early ophiuroids, thereby demonstrating the adaptive versatility and complexity of asterozoan diversification. Jugiaster specimens also exhibit delicate ambulacral column articulation. The new fossils indicate the need for much further study before early asterozoan history will be well understood.