Mirapecten mirificus (Reeve, 1853)

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 : 201

Mirapecten mirificus (Reeve, 1853)

Pecten mirificus Reeve, 1853 : sp. 104, pl. 26, fig. 104.

Mirapecten thaanumi Dall, Bartsch & Rehder, 1938: 84 , pl. 21, figs 7–8.

Chlamys (Mirapecten) mirifica (Reeve) .–Springsteen & Leobrera, 1986: 329, pl. 93, fig. 17; Rombouts, 1991: 31, pl. 12, figs 3–3a.

Mirapecten mirificus (Reeve) .– Kay, 1979: 526, figs 158B, 169A–B; Dijkstra, 1991: 48; Dijkstra, (1983–1994) 1994: 8, figs 1–4; Dijkstra, Drivas & Jay, 1998: 7, fig. 12; Hayami, 2000: 903, pl. 449, fig. 28 (rv only, lv is M. rastellum ); Raines & Poppe, 2006: 130–131, upper figs; pl. 77, figs 1–7; pl. 78, figs 1–7; pl. 79, figs 1–7; Dijkstra & Maestrati, 2010: 354, figs 5G–H; Huber, 2010: 199; Raines, 2010: 610, pl. 996, figs 1–8; Dijkstra, 2013: 47, pl. 12, figs 1a–d, pl. 13, figs 3a–b.

Type data. Pecten mirificus Reeve : holotype (pr) NHMUK 1950.11.14.46.Type locality:“Amboyna” [ Ambon, Indonesia]. Mirapecten thaanumi Dall, Bartsch & Rehder : holotype (lv) USNM173195. Type locality: Hawaiian Islands , off the south coast of Molokai, 21°08'N 157°0'W, 70–99 fathoms [128–181 m] (Albatross stn 3819).

Extralimital material examined. — THAILAND: Phuket Island, Kho Raya Noi , alive, 30–40 m (1 pr, ZMA Moll. 145489) . — JAPAN: Okinawa, Horseshoe , alive, 40 m (1 pr, ZMA Moll. 140201); off Zampa, alive, 46 m (2 pr, ZMA Moll. 142606) . — PHILIPPINE ISLANDS : Cebu,off Punta Engano , alive, 60–80 m (1 pr, ZMA Moll. 140288) ; Bohol,off Panglao,alive, 100–150 m (3 pr, ZMA Moll. 145848); Mindanao, Balut Island , alive, 128–146 m (2 pr, ZMA Moll. 140800) .— MALAYSIA: N Sabah, off Balahac Strait , alive, 145 m (1 pr, ZMA Moll. 142598) . — INDONESIA: off N Sulawesi,alive, 101–110 m (1 pr, ZMA Moll.141280).CORAL SEA: Chesterfield Island, alive, 52 m (1 pr, ZMA Moll.142609); Lansdowne-Fairway Banks, alive, 60 m (2 pr, ZMA Moll.139786). HAWAIIAN ISLANDS : Oahu, Sand Island , alive, 76 m (1 pr, ZMA Moll. 144043) . — SOLOMON ISLANDS : Guadalcanal, Bonegi , alive, 30 m (9 pr, ZMA Moll. 142603) .— FIJI ISLANDS : Viti Levu, Yanuca Island , dead, 34 m (1 v, ZMA Moll. 143982) .

Description. Shell up to 40 mm high, most specimens to c. 30 mm; rather thin, somewhat posteriorly oblique and roundly triangular, strongly inequivalve, inequilateral, left valve almost flat, right valve inflated, auricles somewhat unequal in shape and size, umbonal angle c. 90°; internal rib carinae present around ventral margin; colour highly variable, cream, yellow, red, purple, brownish to almost black, some specimens mottled; interior porcelanous, somewhat paler than exterior; resilial teeth weak or lacking, dorsal teeth prominent.

Left valve sculptured with 4–5 distinct primary radial plicae, one secondary costa intercalated in each interspace on most specimens, very weak or lacking on some. Primary plicae bearing widely spaced, thorn-like, curled scales, variable in prominence; lacking on secondary costae. Plicae and costae unevenly spaced. Very closely spaced, fine commarginal microsculpture throughout. Posterior auricle somewhat larger than anterior, with one scaly radial costa; costa weaker on anterior auricle. Dorsal margin straight.

Right valve with 7–9 unevenly spaced radial plicae (4 main plicae more or less bifurcated); secondary costae lacking. Anterior auricle with 4–6 radial costae, lacking or very weak on posterior; dorsal margin scaly. Byssal notch moderately deep, byssal fasciole broad. Functional ctenolium with 4–6 well-developed teeth.

Habitat. Living byssally attached to hard substrates or amongst coral rubble on sandy bottoms, in the sublittoral zone and on the continental shelf.

Distribution. Tropical Indo-West Pacific and Hawaiian Islands , from southern Japan to Indonesia and the Coral Sea (not recorded from Australia), westward to Thailand and eastward to the Fiji Islands and Austral Islands (partly MNHN and NBC, unpublished records; Raines & Poppe, 2006: 130); East Africa to the Hawaii Islands , 5–181 m (Huber, 2010: 199); Philippines, 62–90 m (unpublished data, HHD); Indonesia, 70 m, dead (Dijkstra, 1991: 48); Papua New Guinea, 25–57 m, dead (Dijkstra, 1998a: 23–24); Vanuatu, 1–92 m, dead (Dijkstra & Maestrati, 2012: 406). Maximum depth range of live-taken specimens is 30– 150 m.

Remarks. For comparison with congeneric species see Dijkstra & Kilburn (2001: 285).

Mirapecten mirificus is not recorded from the continental shelf or slope of Australia, but records are known from the Coral Sea (MNHN, HD). It is quite possible that this species also occurs on the Great Barrier Reef, because Mirapecten rastellum ( Lamarck, 1819) , which lives in a similar habitat to the present species, was recently found there.