Similipecten Winckworth, 1932

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 : 152-154

Similipecten Winckworth, 1932

Similipecten Winckworth, 1932: 241 , 250 (proposed as a subgenus of Chlamys ). Type species (by original designation): Pecten similis Laskey, 1811 ; Recent, Firth of Forth, Scotland.

Arctinula Thiele, 1934: 806 (proposed as a section of Palliolum ). Type species (by original designation): Pecten greenlandicus G. B. Sowerby II, 1842 ; Recent, Greenland.

Diagnosis. A byssally attached or free-living, small to medium-sized, flattened propeamussiid; shell (sub)circular, opaque or translucent, smooth or sculptured with minute commarginal growth lines or fine striae; auricles almost equal in size, anterior auricle of right valve demarcated from shell disc, other auricles less clearly demarcated; byssal gape moderately deep; ctenolium absent; hinge dentition rather broad.

Distribution. Early Oligocene–Recent (pers. comm. D. Jablonski, 2017). Arctic to tropical Atlantic, NW Indian Ocean eastwards to southwestern Pacific, littoral (Arctic and boreal region) to bathyal depths.

Discussion. Similipecten was proposed by Winckworth (1932: 241) as a subgenus of Chlamys . Hertlein (1969:

Figure 19. A–D, Cyclopecten reticulatus sp. nov., holotype, pair, AM C.165220, ORV Franklin stn 14, Coral Sea, 11°35.61'S 145°29.42'E, 1770–1863 m; rv anterior auricle exterior (A), lv anterior auricle exterior (B), rv exterior (C), lv exterior (D). E–I, Similipecten colmani sp. nov., holotype,AM C.165504 (G, I) and 2 paratypes, AM C.209771 (E, F, H), MV San Pedro Sound stn P69-1140, c. 45 miles N of Croker Island, Arafura Sea, NT, 10°17'S 132°38'E, 65 m; rv exterior (E), lv interior (F), lv exterior (G), rv anterior auricle exterior (H), lv anterior auricle exterior (I). Scale bars represent 1 mm (A, B), 5 mm (C, D), 2 mm (E–G), 0.5 mm (H, I).

N354), however, placed Similipecten in the Eburneopecten group as a synonym of Palliolum (Delectopecten) Stewart, 1930 . Similipecten is now assigned to the Propeamussiidae ( Waller, 1984: 213; Dijkstra, 1991: 23; Dijkstra, 2002: 42) or to Propeamussiinae ( Schein, 1989: 95) . The morphological characters of Arctinula and Similipecten are identical (shell very fragile and subcircular, laterally flattened, hyaline to opaque, generally smooth, lacking internal riblets, byssal notch moderately developed, lacking a ctenolium) and we consider them to be synonyms.

Representative species of Similipecten are: S. similis ( Laskey, 1811) from the Arctic to the tropical eastern Atlantic, S. greenlandicus (G. B. Sowerby II, 1842) from the Arctic and the boreal western Atlantic, S. oskarssoni Dijkstra, Warén & Gudmundsson, 2009 from the boreal to tropical eastern Atlantic, S. nanus (Verrill & Bush in Verrill, 1897) from the tropical western Atlantic, S. eous (Melvill in Melvill & Standen, 1907) from the Red Sea and Arabean Sea, and S. colmani sp. nov. from Indonesia (probably) and northern Australia.