Delectopecten musorstomi Poutiers, 1981

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 : 169-170

Delectopecten musorstomi Poutiers, 1981

Figs 24, 25F,H–J

Delectopecten musorstomi Poutiers, 1981: 331 , pl. 1, figs 2–3; Dijkstra, 1991: 26; Dijkstra, 1995b: 53, figs 69–70; Dijkstra & Marshall, 1997: 88, pl. 8, figs 1–6; Dijkstra & Knudsen, 1998: 51, pl. 7, figs 31–32; Dijkstra, 2001: 91; Dijkstra & Kilburn, 2001: 269, figs 1–2; Raines & Poppe, 2006: 58–59, lower figs; pl. 2, fig. 1; Dijkstra & Maestrati, 2008: 105; Dijkstra & Maestrati, 2009: 44, pl. 4, figs 29–31; Dijkstra & Maestrati, 2010: 344; Dijkstra, 2013: 25, pl. 5, figs 2a–d; Dijkstra & Janssen, 2013: 202, figs 56–57.

Type data. Holotype (pr) MNHN Moll 21162. Type locality: Philippine Islands , N of Lubang, 13°57'N 120°16.5'E, alive, 150–159 m (MUSORSTOM I stn 18).

Additional material examined. — AUSTRALIA: QUEENSLAND: 18.5 ml E of North Reef , 23°11.5'S 152°14.5'E, dead, 188 m (1 v, C.165518 [in part]); Barwon Bank, 26°32'S 153°32'E, alive, 37 m (1 pr, C.165233). TASMAN SEA: Lord Howe Shelf, 31°44'S 159°04'E, dead, 117.5 m (1 v, C.461385 [in part]) .

Description. Shell small, up to 6.1 mm high (Dijkstra & Kilburn, 2001), circular, hyaline or opaque, equivalve, equilateral, anterior auricle somewhat larger than posterior, umbonal angle c. 120°. Prodissoconch c. 200 µm in height. Whitish with a few white spots; external sculpture visible from interior.

Left valve with microscopic antimarginal striae and 14–20 delicate, unevenly spaced, scaly radial lirae commencing at c. 1 mm shell height, enlarging progressively. Commarginal growth lines fine, evenly spaced, somewhat crenulated. Scales broken on many specimens. Auricles continuous with disc and similarly sculptured. Dorsal margin straight.

Right valve sculpture similar to that of left valve, with slightly more prominent microscopic commarginal lirae on early disc, commencing at about 1.5 mm shell height. Anterior auricle with 4–5 antimarginal ridges and commarginal lamellae, the latter strongly developed at dorsal margin, separated from disc by distinct suture. Byssal fasciole and notch well-developed. Functional ctenolium with 2–3 teeth. Resilifer triangular.

Habitat. Living on the continental shelf and in the bathyal zone, attached amongst sponge or coral rubble on mud or sand.

Distribution. Red Sea, 121–350 m, dead (Dijkstra & Knudsen, 1998); South Africa, 70–305 m (Dijkstra & Kilburn, 2001); Taiwan, 234 m, dead (Dijkstra & Maestrati, 2009: 45); Philippine Islands , 150–159 m ( Poutiers, 1981); Indonesia, 175–185 m (Dijkstra, 1991); New Caledonia, 250 m (Dijkstra, 1995b); Norfolk Island, 210 m, dead (Dijkstra & Marshall, 1997); Solomon Islands , 302–396 m, dead (Dijkstra & Maestrati, 2008); Austral Islands , 176–340 m, dead (Dijkstra & Maestrati, 2010). Now also from Australia. Maximum depth range of live-taken specimens 37– 305 m. Present specimen from Queensland taken alive at 37 m.

Remarks. Delectopecten musorstomi is significantly smaller (up to 5 mm in height) than D. alcocki (up to 19 mm in height) and D. fosterianus (up to 20 mm in height). Its sculpture differs mainly in having numerous prominent scaly radial riblets, which are lacking in Delectopecten alcocki and D. fosterianus .

Delectopecten musorstomi is a new record for Australia.