Hyalopecten Verrill, 1897

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 : 165

Hyalopecten Verrill, 1897

Hyalopecten Verrill, 1897: 63 , 71, pl. 18, fig. 5. Type species (by original designation): Hyalopecten undatus Verrill & S. Smith in Verrill, 1885 (junior secondary homonym of Pecten undatus Defrance, 1825 ) = Hyalopecten dilectus Verrill & Bush in Verrill, 1897; see also North (1951a: 234); living, off Chesapeake Bay, Maryland, USA, 37°38'40"N 73°16'30"W, 2603 m.

Diagnosis. Shell inequivalve, hyaline; valves with commarginal undulations or corrugations and sculptured with fine radial lirae on one or both valves; lacking antimarginal microsculpture; auricles unequal; byssal notch well-developed, ctenolium present on most species.

Distribution. Miocene–Recent. Cosmopolitan, 800–7000 m ( Knudsen, 1970).

Remarks. Grau (1959: 55) treated Hyalopecten as a subgenus of Cyclopecten (a propeamussiid), which was followed by Knudsen (1970: 97) and Rombouts (1991: 79). Hertlein (1969: N354) considered Hyalopecten to be a subgenus of Palliolum (a pectinid), placed in the Eburneopecten group, and Vaught (1989: 119) placed Hyalopecten in the tribe Eburneopectinini . Hyalopecten was considered to be a valid Recent genus of Pectinidae by other authors (Bernard, 1983; Schein-Fatton, 1988; Schein, 1989; Dell, 1990; Dijkstra, 1991; Dijkstra & Goud, 2002).

In the opinions of Coan et al. (2000: 228), Palazzi & Villari (1996: 270) and T. R. Waller (USNM, pers. comm. 23 Jun 2017), Hyalopecten is a junior synonym of Ciclopecten Seguenza, 1877 . Microscopic examination by the first author of specimens of Ciclopecten peloritanus Seguenza, 1877 (Pliocene, Italy; type species of Ciclopecten ) revealed obvious antimarginal microsculpture, prominent on the right valve and weaker on the left. Palazzi & Villari (1996: figs 121, 122, 145, 146) illustrated specimens of C. peloritanus apparently not displaying antimarginal microsculpture, but in our opinion this is due merely to the low magnification of the illustrations. Antimarginal microsculpture is lacking in Hyalopecten , and we feel it is unwise to synonymize these names at this time, without further study.

Waller & Marincovich (1992: 219) considered Hyalopecten to be related to a radially sculptured ancestor, Praechlamys Allasinaz, 1972 from the Triassic. The position of Hyalopecten in the phylogeny of Waller (1991, 2006a) remains uncertain.