Protorophus, Zamora & Smith, 2010

Zamora, Samuel & Smith, Andrew B., 2010, The oldest isorophid edrioasteroid (Echinodermata) and the evolution of attachment strategies in Cambrian edrioasteroids, Acta Palaeontologica Polonica 55 (3), pp. 487-494 : 491

Genus Protorophus nov.

Etymology: A combination of the greek proto —the first or earliest and Isorophida .

Type species: Protorophus hispanicus sp. nov., see below.

Diagnosis.—Edrioasteroid with a discoidal theca with a wide and clearly differentiated peripheral rim composed of imbricate plates. Central area dominated by oral plates, six or seven in number. Ambulacra floored by a single large U−shaped plate. Aboral surface uncalcified.

Discussion.—With only one small specimen it is likely that many of the features of Protorophus are juvenile. However, the highly distinctive U−shaped terminal flooring plates of this genus are unique and seen in no isorophids whose ontogeny has been described ( Bell 1976a, b). The well−developed peripheral rim, lack of aboral plating and the uniserial nature of the ambulacral terminal flooring plates all suggest affinities with Isorophida rather than any of the other Cambrian non−isorophid edrioasteroid groups.

Geographic and stratigraphic range.—Iberian Chains (North Spain), middle Cambrian (Cambrian Series 3).