Juxtamusium maldivense (E.A. Smith, 1903 )

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 : 200

Juxtamusium maldivense (E.A. Smith, 1903)

Figs 40J, 42, 43D

Pecten maldivensis E.A. Smith, 1903: 622 , pl. 36, figs 19–20; Melvill & Standen, 1907: 809; Hedley, 1909: 423; Melvill, 1909: 126; Waller, 1972a: 250, pl. 7, figs 111–112 [lectotype].

Amussium scrobiculatum Schepman, 1908: 201 , pl. 13, figs 4–4a [syn. nov.]

Chlamys maldivensis (Smith) .– Lamy, 1935: 311; Viader, 1937: 61; Oliver, 1982: 10.

Juxtamusium maldivense (Smith) .– Iredale, 1939: 368; Waller, 1972a: 250, pl. 7, figs 111–127, pl. 8, fig. 134; Thayer, 1975: 447–449, 3 figs; Abbott & Dance, 1982: 315, fig; Dijkstra, (1983–1989) 1984: 8, figs; Sharabati, 1984: pl. 44, figs 4–4a; Waller, 1984: 211; Dijkstra, 1990: 4, figs; Dijkstra, (1983–1994) 1992: 24, figs; Dijkstra, 1998a: 23, pl. 3, figs 1–3; Dijkstra, Drivas & Jay, 1998: 7, fig. 11; Dijkstra & Knudsen, 1998: 64, pl. 5, fig. 22; Hayami, 2000: 901, pl. 447, fig. 17; Dijkstra & Kilburn, 2001: 281, figs 14–15; Raines & Poppe, 2006: 127–128, pl. 74, figs 1, 3; pl. 75, figs 1–7; Huber, 2010: 200; Raines, 2010: 608, pl. 995, figs 6–11, 13; Dijkstra, 2013: 46, pl. 11, figs 2a–d, pl. 13, figs 2a–b, pl. 27, figs 3a–b.

Chlamys (Juxtamusium) maldivensis (Smith) .– Oliver, 1992: 71, 76, pl. 12, figs 5a–b, text-figs 10a–b.

Type data. Pecten maldivensis Smith: lectotype [secondlargest pr] NHMUK 1903.9.17.49, designated and refigured by Waller (1972a: 250, pl. 7, figs 111–112), 4 paralectotypes (pr) NHMUK 1903.9.17.50–53. Type locality: Indian Ocean , Maldive Islands , 1–44 fathoms [2–80 m] .

Amussium scrobiculatum Schepman : holotype (lv) RGM107619 . Type locality: Indonesia, Sulawesi, Manado, Kaju Ragi (Pleistocene).

Comments on type data. Although Smith (1903: 622) recorded three localities for Juxtamusium maldivense , viz. II. Suvadiva Atoll (5–44 fathoms), IV. Kolumadulu Atoll (1–40 fathoms), and VI. Mulaku Atoll (1–40 fathoms) of the Maldive Islands , the types have not been segregated into these separate localities.

Additional material examined. — AUSTRALIA: QUEENSLAND:

GBR, Fraser Island, off S end, 25°48'S 153°46'E, dead, 73 m (1 v, C.165160).

WESTERN AUSTRALIA: Cartier Island , N side, alive, 50–70 m (1 pr, 1 v, ZMA

Moll.146422); Timor Sea, Sahul Banks , 11°50'S 125°50'E, dead, 27 m (1 v, C.161001; 1 v, C.161002; 1 v, C.161003) .— RED SEA: Gulf of Aqaba,off Eilat ,alive, 6–10 m (2

pr, ZMA Moll.141484);off Wadi Murach,alive, 73–82 m (3 pr, ZMA Moll.142619).—

REUNION: S Chaude,dead, 58 m (3 v, ZMA Moll.142610) .— THAILAND: Andaman Sea,off Phuket Island,alive, 24 m (1 pr, ZMA Moll.143689) .— PHILIPPINE ISLANDS :

Cebu, Punta Engano , alive, 140–160 m (1 pr, ZMA Moll.140957) ; Bohol, off Panglao

Island,alive, 80–200 m (1 pr, ZMA Moll.144212);Bohol,Balicasag Island,alive, 80–180 m (1 pr, ZMA Moll.146105);Calituban Island,alive, 15–20 m (2 pr, ZMA Moll.146229).

For other locality data see Waller (1972a: 254).

Description. Shell small, up to 35 mm high (Hayami, 2000; Huber, 2010), most specimens c. 15 mm; flattened (left valve almost flat, right valve weakly inflated), thin, circular to ovate, slightly higher than wide, inequivalve, almost equilateral, auricles unequal in shape and size, umbonal angle c. 85–90°; cream to pink, with shades of red or brown, and paler and darker blotches, interior purple or reddish, right valve paler.

Both valves sculptured with numerous fine, unevenly spaced radial riblets of angular section (with narrow crests), increasing by bifurcation and/or intercalation, and very closely spaced, microscopic commarginal lamellae. Posterior auricle larger than anterior, with c. 3–7 radial riblets, riblets very weak on some specimens. Byssal notch and fasciole weak to almost lacking. Functional left and right ctenolia with a few teeth, lacking from some specimens. Resilifer oblong, oblique. Internal expressions of external radial riblets with sharply raised edges, but not carinate. Hinge teeth weak.

Dimensions. Illustrated specimen: QLD, off S end Fraser Island, 73 m, rv only (AM C.165160): H 11.4, L 10.7 mm.

Habitat. Living byssally attached to coral branches, under rocks or amongst coral rubble on sandy bottoms at littoral to uppermost bathyal depths.

Distribution. Throughout the tropical Indo-West Pacific, from southern Japan to northern Australia, westwards to South Africa and the Red Sea, eastwards to Wallis and Futuna Islands (MNHN, unpublished records; Raines & Poppe, 2006: 126); South Africa, 50–65 m (Dijkstra & Kilburn, 2001: 282); Red Sea, 6–82 m (Dijkstra & Knudsen, 1998: 66); Maldive Islands , 39 m, dead; Marshall Islands , 5–60 m (Waller, 1972: 254); Philippines, 20–90 m ( Raines, 2010: 608; Dijkstra, 2013: 46); Indonesia, 34–305 m, dead (Dijkstra, 1991: 47); Papua New Guinea, 25–30 m (Dijkstra, 1998a: 23); Vanuatu, 6–114 m, dead (Dijkstra & Maestrati, 2012: 406). Maximum depth range of live-taken specimens is 5– 200 m. Present specimens fromAustralia alive at 50– 70 m.

Remarks. The present specimens are indistinguishable from the type material and Juxtamusium maldivense is a new record for Australia.