Glorichlamys elegantissima (Deshayes, 1863)

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 : 193

Glorichlamys elegantissima (Deshayes in Maillard, 1863)

Figs 36G–I, 38G,I, 39

Pecten elegantissimus Deshayes in Maillard, 1863: 32, pl. 4, figs 11–12.

Pecten (Chlamys) elegantissimus Deshayes. –Bavay, 1903: 403, pl. 8, figs 5–7.

Pecten cooperi E. A. Smith, 1903: 621 , pl. 36, figs 15–18.

“ Chlamys ” elegantissima (Deshayes) .–Dijkstra, (1983– 1989) 1989: 12, figs; Carless, 1998: 7, figs.

Chlamys s.l. elegantissima (Deshayes) .–Dijkstra, Drivas & Jay, 1998: 6, fig. 4.

Chlamys (Chlamys) elegantissima (Deshayes) .– Rombouts, 1991: 11, pl. 24, fig. 1; Lamprell & Healy, 1998: 238, fig. 710.

Glorichlamys elegantissima (Deshayes) .–Dijkstra, 1991: 45, fig. 91; Dijkstra, (1983–1994) 1992: 6, 22, figs; Dijkstra, 1998a: 20, pl. 2, figs 5–6; Dijkstra & Kilburn, 2001: 279; Raines & Poppe, 2006: 116–117, upper figs; pl. 68, figs 1–3, 6–7; Dijkstra & Maestrati, 2010: 353, fig. 5E; Huber, 2010: 199, central fig.; Raines, 2010: 606, pl. 994, figs 5–6; Dijkstra, 2013: 39, pl. 10, figs 1a–d, 4a–b, pl. 26, figs 3a–b; Dijkstra & Maestrati, 2013a: 372.

Type data. Pecten elegantissimus Deshayes : repository of type material unknown; not in MNHN (P. Bouchet, pers. comm.) or in Université Lyon-1, where most of Deshayes’s collection is located. Type locality: Réunion. The specimen in ZMA (now in NBC) from Cap la Houssaie , Réunion, alive, 46 m ( ZMA Moll.142222) is here designated the neotype of Pecten elegantissimus Deshayes, 1863 .

Pecten cooperi Smith: Holotype (pr) NHMUK1903.9 . 17.47. Type locality: Maldives, Felidu Atoll , 1–35 fathoms [2–64 m].

Additional material examined. — AUSTRALIA: QUEENSLAND: No. 9 Ribbon Reef, SW end, 14°57'S 145°42.5'E, dead, 11 m (1 v, C.165154); No. 5 Ribbon Reef, 15°21'S 145°46' E, dead, 6 m (1 v, C.165155); Moreton Island, N of Cape Moreton, off NE side of Flinders Reef, 27°01'S 153°43' E, alive, 12–15 m (1 pr, NTM P054288). WESTERN AUSTRALIA: Serangapatam, NE corner, 13°38'S 122°05' E, dead, 20–25 m (1 v, ZMA Moll.146224); Serangapatam, NE corner, outside of reef, 13°37'S 122°05'E, dead, 16 m (1 v, ZMA Moll.146225). — MADAGASCAR:Tuléar, taphocoenose, alive, 26 m (1 pr, ZMA Moll.143631). — REUNION:Cap la Houssaie, alive, 46 m (1 pr, ZMA Moll.142222). — THAILAND: S of Phuket Island, Kho Raya Ya, alive, 26–40 m (9 pr, ZMA Moll.143692); Phuket Island,off Rawai,alive, 28–30 m (2 pr, ZMA Moll.139655). — JAPAN: Okinawa, Seragaki, alive, 45–60 m (2 pr, ZMA Moll.141482). — NEW CALEDONIA: Koumac, alive, 82–120 m (1 pr, 2 v, ZMA Moll.139676). — FIJI ISLANDS :Viti Levu, Mbengga Island, alive, 36 m (1 pr, ZMA Moll.143970).—LINE ISLANDS : Christmas Island, Cook Isle, alive, 12 m (1 pr, 1 v, ZMA Moll.142224). —SOCIETY ISLANDS : Tahiti, Tiarei, outside of lagoon, alive, 20 m (1 pr, ZMA Moll.144605).—TUAMOTU ISLANDS :Mataiva Island,outside of reef, alive, 24 m (1 pr, ZMA Moll.144616).

Description. Shell up to c. 20 mm high, most specimens moderately flattened, some specimens more inflated, with curved ventral margin, almost circular to oblong, inequivalve (ribbing of valves discrepant), inequilateral, auricles very unequal in shape and size, umbonal angle c. 90°; cream with pink or brown maculations, right valve paler.

Left valve with 9–13 prominent radial plicae and 1–3 intercalated secondary riblets, one of which is dominant, in each radial interspace. Plicae bearing irregular lamellae, slightly noduliferous on some specimens. Interspaces bearing commarginal lamellae. Anterior auricle much larger than posterior (c. 3:1), sculptured with 4–6 lamellate, noduliferous radial costae; posterior auricle almost smooth.

Right valve with 9–13 prominent radial plicae, subdivided into 3–4 lamellate secondary costae, interspaces each narrower than one costa, commarginally lamellate.Anterior auricle with 5–7 noduliferous and/or lamellate radial riblets, less prominent than on left valve. Posterior auricle nodulous. Dorsal margin straight. Byssal notch relatively deep, byssal fasciole broad. Functional ctenolium with 3–5 teeth. Resilifer narrowly triangular, somewhat oblique. Very short, weak, internal rib carinae around ventral margin of some specimens.

Dimensions. Illustrated specimen: QLD, Moreton Island, N of Cape Moreton , off NE side of Flinders Reef , 27°01'S 153°43'E, 12–15 m (NTM P054288): H 16.8, L 14.7, D 5.6 mm .

Habitat. Living in the intertidal zone to on the continental shelf, byssally attached to undersides of coral slabs amongst live coral or amongst coral rubble on sand, most specimens covered with sponges, which match the sponges under the slabs.

Distribution. Throughout the tropical Indo-West Pacific, from the Ryukyu Islands , southern Japan, to northern Australia, westwards into the Indian Ocean to South Africa and Mozambique, and eastwards across the central Pacific to the Tuamotu Archipelago and the Austral Islands (Raines & Poppe, 2006: 116). South Africa, 8-250 m, dead; Mozambique, beach, dead; Réunion, 8–17 m, alive (Dijkstra & Kilburn, 2001: 279). Philippines, 12–19 m, 30–50 m (alive), 5–410 m (dead) ( Raines, 2010: 606; Dijkstra, 2013: 39, 41); Indonesia, Borneo (Huber, 2010: 199), Flores Sea, 130–155 m, dead (Dijkstra, 1991: 45). Papua New Guinea, 30–35 m, dead (Dijkstra, 1998a: 21); New Caledonia, littoral to sublittoral (Dijkstra, 1992c: 7, 22); Vanuatu, 4–7 m (Dijkstra & Maestrati, 2012: 405); Tuamotu Archipelago, 285–890 m, dead (Dijkstra & Maestrati, 2013a: 373); Austral Islands , 212–470, dead (Dijkstra & Maestrati, 2010: 353). Maximum depth range of live-taken specimens is 4–120 m (unpublished data, HHD). Present specimens from Australia alive at 12– 15 m.

Remarks. The present material closely resembles topotype specimens from Réunion (MNHN, HD), although the sculpture is more delicate (typical material has c. 10 prominent primary radial costae, present material 13) with more divided secondary radial riblets. Examined material from the Indo-West Pacific is strongly variable and intermediate variations are observed (MNHN, HD).

Smith (1903: 621) described the new species Pecten cooperi from the Maldives, but it is indistinguishable from Glorichlamys elegantissima . He probably overlooked Deshayes’s description of the right valve and Bavay’s subsequent description of the left valve, some time before his description of Pecten cooperi .

The following species, Glorichlamys quadrilirata ( Lischke, 1870) , is closely similar, with a similar distribution. It differs from Glorichlamys elegantissima in its quadri- or tripartite radial costae and more delicate commarginal sculpture.