Genus Jurapecten Gale, 2011

Jurapecten Gale, 2011a: 84, pl. 19.

Type species

Jurapecten hessi Gale, 2011, by original designation.

Diagnosis

Benthopectinids which possess strongly rugose marginals; rugosities conjoined by thin radiating strips of imperforate stereom; ambulacrals lack abactinal ridges and inferomarginal articulation.

Assigned species

In addition to the type species, J. infrajurensis sp. nov. and J. dhondtae sp. nov., both described below.

Remarks

Jurassic–Cretaceous benthopectinids are locally common among isolated ossicles in washed residues. All share the same distinctive sculpture type of prominent imperforate rugosities, conjoined by radiating strips of stereom (e.g., Figs 6N–O, 7G, I–J), absent on extant genera. In the extant genera Pontaster and Cheiraster, the rugosities on the superomarginals are smaller and more widely spaced (e.g., Fig. 4J–M, Q), although the inferomarginal sculpture is similar to that seen in Jurapecten (Fig. 6C–E). Jurapecten also lacks a number of characters seen in all extant taxa, including an abactinal ridge on the ambulacrals (compare Fig. 7N–O with Fig. 5I, K–L, Q), and there is no ambulacral articulation surface with the inferomarginal (compare Fig. 7N–O with Fig. 5I, K, Q). Additionally, the ambulacral heads are more elongated in Jurapecten (e.g., Figs 6J, L, 8Q–U). The absence of the abactinal ridge, to which the longitudinal arm muscles attach in all living genera (Clark 1981), is a plesiomorphic feature of Jurapecten .