Catillopecten Iredale, 1939

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 : 155

Catillopecten Iredale, 1939

Catillopecten Iredale, 1939: 347 , 370. Type species (by original designation): Pecten murrayi E. A. Smith, 1885 ; Recent, N QLD, E of Cape York, Coral Sea, 12°08'S 145°10'E, 1400 fathoms [2561 m].

Bathypecten Schein-Fatton, 1985: 491 . Type species (by original designation): Bathypecten vulcani Schein-Fatton, 1985 ; Recent, eastern Pacific, 12°48'80"N 103°56'60"W, 2620 m.

Diagnosis. Propeamussiidae with a (sub)circular shape, shell hyaline or opaque, fragile, inequivalve, flattened, left valve slightly convex, right valve flat; exterior surface of disc weakly undulated or smooth, sculptured with commarginal lamellae and minute radial threads in some species.Auricles unequal, anterior auricle of right valve prominent and distinct, other auricles not delimited. Byssal notch deep, ctenolium absent. Shell microstructure of prismatic calcite layer on right valve and foliated calcite layer on left valve. Thin crossed-lamellar aragonite layer on interior shell surface near adductor scar.

Distribution. Oligocene–Recent (Oligocene Lincoln Creek Formation, cold-seep carbonate in Washington State, USA; Kiel, 2006: fig. 15.1–3).Atlantic Ocean, Indian Ocean, western and eastern Pacific, living in bathyal and abyssal depths.

Discussion. Schein-Fatton (1988) and Schein (1989, 2006) distinguished Catillopecten Iredale and Bathypecten Schein- Fatton by a few morphological characters. Catillopecten has commarginal sculpture, which is absent from Bathypecten . Bathypecten is slightly undulated in early ontogeny, whereas Catillopecten has a smoother shell disc. However, both morphological characters are very weak and highly variable, based on observed material (NHMUK, MNHN, ZMA, ZMUC). Both genera have a deep byssal notch throughout ontogeny ( Waller, 1984: 214) and their prismatic microstructure throughout ontogeny on the right valve is identical. We consider them to be synonyms.

Included living species are Catillopecten eucymatus (Dall, 1898) from the Atlantic Ocean (1057–4829 m) ( Schein, 1989: 101), C. translucens (Dautzenberg & Bavay, 1912) from Indonesia (1301 m), C. murrayi (E. A. Smith, 1885) from the northwestern Coral Sea (2561 m), C. knudseni (Bernard, 1978) from the northeastern Pacific (220–2900 m), C. squamiformis (Bernard, 1978) also from the northeastern Pacific (2030–2884), C. graui ( Knudsen, 1970) from the tropical eastern Pacific (3270–3670 m), C. vulcani (Schein- Fatton, 1985) also from the tropical eastern Pacifc (2620 m), and C. tasmani Dijkstra & Marshall, 2008 from the Tasman Sea (1097 m). Recently also from the northwestern Pacific (see Kamenev, 2018).