Pascahinnites Dijkstra & Raines, 1999

Dijkstra, Henk H. & Beu, Alan G., 2018, Living Scallops of Australia and Adjacent Waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae), Records of the Australian Museum (Rec. Aust. Mus.) 70 (2), pp. 113-330 : 251

Pascahinnites Dijkstra & Raines, 1999

Pascahinnites Dijkstra & Raines, 1999: 200 . Type species (by original designation): Pecten (Chalmys) [sic] pasca Dall, 1908 ; living, Easter Island .

Diagnosis. Small subcircular chlamydoid shells up to c. 20 mm high. Some species (including the type species) byssate in juvenile stage, cemented to hard substrates after a height of c. 9–11 and growing irregularly thereafter; others living byssally attached to hard substrates throughout life, without cementation. External prismatic layer lacking from early right dissoconch; antimarginal microsculpture in early pre-radial stage; shagreen microsculpture and radial macrosculpture present throughout; commarginal sculpture lacking. Byssal notch and functional ctenolium prominent in juvenile stage, absent in cemented adults.

Distribution. Pleistocene ( Oliver, 1911: 527; 1915: 554; Deyrell Islet, Kermadec Islands ; Waller, 1972a: 234; Midway I., Hawaii; Taylor, 1978; Aldabra) and Recent. Tropical and temperate Indo-West Pacific; Kermadec Islands and Easter Island, at sublittoral depths.

Remarks. For several years the following species has been included in Semipallium , but Paulay (2003), following advice from T. R. Waller, included it in Pascahinnites . The similarity of “ Pecten (Chlamys) ” pasca Dall to “ Chlamys ” coruscans has been commented on previously by Rehder (1980: 109, pl. 13, figs 3–6) (again, following advice from T. R. Waller) and Bernard (1986: 71). The style of radial sculpture, with each pair of high, narrowly rounded costae separated by a single relatively wide secondary costa, the presence of shagreen microsculpture, the lack of a pre-radial external prismatic calcite layer in the right valve, and the relatively wide, acline shape confirm that Pecten coruscans Hinds, 1845 is related phylogenetically to Pascahinnites pasca (Dall) rather than to the dorsoventrally elongate, prosocline species included in Semipallium . See also Dijkstra & Marshall (2008: 51).