Primary Interadials and the Centrodorsal Plate
he domed central disc of Stauranderasterids has a crown formed from six expanded ossicles. These vary in form from bulbous, to horn-like. The central ossicle is the centrodorsal plate, which is surrounded by a ring of five primary interadials (situated between the arms). The madreporite slots into the base of a primary interadial.
1). Very well preserved Stauranderasterids; (A) Stauranderaster squamatus (© Booth Museum, by kind permission of John Cooper); (B) Manfredaster bulbiferus (© HCCMS (Hampshire County Council Museum's Service) by kind permission of Dave Kemp, Gosport Museum).
2). Primary interadials; (A) Manfredaster bulbiferus, bulbous; (B) Stauranderaster pistilliferus, conical; (C) Manfredaster cf. bulbiferus, the madreporite slots into the primary interadial (© Booth Museum, by kind permission of John Cooper).