Edrioasteroidea Billings, 1858

Zamora, Samuel, Sumrall, Colin D. & Vizcaïno, Daniel, 2013, Morphology and ontogeny of the Cambrian edrioasteroid echinoderm Cambraster cannati from western Gondwana, Acta Palaeontologica Polonica 58 (3), pp. 545-559 : 547

Class Edrioasteroidea Billings, 1858 Order Stromatocystitida Bell, 1980

Emended diagnosis.—Edrioasteroid−grade echinoderms bearing interradial oral frame plates forming the mouth frame, ambulacra bearing biserial floor plates with sutural pores, cover plates arranged into multitiered series, interambulacral plates bearing epispires, aboral surface fully plated and bearing attachment disk with radially arranged elements.

Discussion.— Smith (1985) placed Cambraster within Isorophida , and Guensburg and Sprinkle (1994) left it in open nomenclature. Our restudy indicates that Cambraster is a stromatocystitid based on several features it shares with Stromatocystites including the interambulacral plating of the oral surface bearing epispires and the construction of the ambulacral system. Furthermore, both taxa have a fully plated aboral surface with a similarly arranged aboral disk. The primary differences between these taxa are the marginal ring and discoidal thecal construction in Cambraster vs. the more globular thecal shape and lack of marginal ring in Stromatocystites . Although these taxa live in very different environments, we do not interpret their differences as the result from ecophenotypic variation. The only substantial differences in individual edrioasteroid morphology noted result from ontogeny and teratology ( Bell 1976b; Bell and Sprinkle 1978; Smith and Arbizu 1987; Sumrall and Wray 2007; Zhao et al. 2010; McKinney and Sumrall 2011).