Semipallium dianae (Crandall, 1979)

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 : 263

Semipallium dianae (Crandall, 1979)

Figs 78H, 79, 80D

Chlamys dianae Crandall, 1979: 114 , figs 3–8; Matsukuma et al., 1991: 137, 185, pl. 135, fig. 9; Lan, 1993: 161, 219, fig.

Semipallium dianae (Crandall) .–Dijkstra, 1991: 38; Rombouts, 1991: 59, pl. 5, figs 3–3b; Dijkstra & Kastoro, 1997: 270, figs 135–137; Dijkstra, 1998a: 36, pl. 6, figs 5–8; Hayami, 2000: 901, pl. 448, fig. 19; Raines & Poppe, 2006: 238–239, lower figs; pl. 188, figs 1–6; Huber, 2010: 206; Raines, 2010: 632, pl. 1007, figs 1–6; Dijkstra, 2013: 80, pl. 21, figs 2a–d, pl. 25, figs 5a–b, pl. 30, figs 2a–b.

Type data. Holotype (pr) National Taiwan Museum, Taipei, TM7911, 3 paratypes (pr): PRC collection, 2 TCL collection. Type locality: Japan, Ryukyu Islands , alive, c. 30 m.

Additional material examined. — AUSTRALIA: QUEENSLAND: N side No. 8 Sandy Cay , 13°21' S 143°57'E, dead, 4–21 m (1 v, C.138324) . WESTERN AUSTRALIA: Rowley Shoals, Clerke Reef ,off N end of reef, approx. 17°10'S 119°20'E, outer reef slope,dead, 9–18 m (1 v, WAM1615.82 ) ; Scott Reef , approx. 14°0'S 121°45'E, dead, 34 m (2 v, WAM) ; Scott Reef , N of North Entrance, approx. 14°0' S 121°45'E,dead, 42 m (5 v, WAM) ; Scott Reef ,NE side, approx. 14°0'S 121°45'E,dead, 18 m (1 v, WAM) ; Seringapatam Reef , 13°40'S 122°05'E,dead (1 v, WAM) ; Cartier Island , 12°32'S 123°33' E, dead, 10–20 m (2 v, WAM) ; Ashmore Reef , NE corner, 12°17'S 123°02'E, dead, 20–25 m (1 v, WAM) ; Ashmore Reef , NE corner, 12°17' S 123°02'E, dead, 20 m (1 v, WAM) ; Hibernia Reef , approx. 11°58'S 123°19'E, dead, 15–18 m (1 v, WAM) ; Hibernia Reef , approx. 11°58'S 123°19'E, in lagoon, dead, 3 m (1 v, WAM) . — JAPAN: Kagoshima, Amami Islands , Uke Islet ,alive, 20–24 m (5 pr, ZMA Moll. 146226) ; Okinawa, Seragaki , alive, 35 m (5 pr, ZMA Moll. 141057) .— PHILIPPINE ISLANDS : Cebu, Punta Engano , alive, 80–180 m (4 pr, ZMA Moll. 144551) ; Cebu,off Sogod ,alive, 120–180 m (1 pr, ZMA Moll. 144553) . — PAPUA NEW GUINEA: Port Moresby, Quayles Reef , alive, 6 m (1 pr, ZMA Moll. 141103) .— SOLOMON ISLANDS : Guadalcanal, Bonegi ,alive, 30 m (2 pr, 3 v, ZMA Moll. 141936) ; Russell Islands , alive, 18 m (2 pr, 1 v, ZMA Moll. 142218) .

Description. Shell up to 70 mm high (Huber, 2010), most specimens under 35 mm; elongate, weakly inflated, left valve slightly more convex than right, equivalve, subequilateral, auricles very unequal in size, umbonal angle 80–90°; colour highly variable, brown, orange, red, purple or yellow, many specimens creamy-yellowish with brown and milky white dots and streaks.

Both valves with 8–10 (most specimens with 9) evenly spaced radial plicae, covered with shagreen microsculpture. Delicate radial riblets develop on plicae and in interspaces near ventral margin, more prominent on right valve.Anterior auricle with 5–6 radial riblets, posterior with 2–4. Dorsal margin straight on anterior, somewhat declined on posterior auricle. Inner surface plicate, striated near ventral margin of some specimens. Resilifer narrowly triangular. Byssal notch relatively deep, byssal fasciole broad. Functional ctenolium well-developed, with 5–7 teeth. Internal plicae with carinate edges around ventral margin. Hinge with weak resilial and dorsal teeth.

Dimensions. Illustrated specimen: QLD, GBR, No. 8 Sand Cay, 4–21 m (AM C.331999), single lv: H 41.5, L 35.4 mm.

Habitat. Living in the littoral zone to the uppermost bathyal zone, byssally attached to the undersides of coral or amongst coral rubble on sandy bottoms.

Distribution. Western and southwestern Pacific, from southern Japan southwards to the Philippines, Indonesia and northwestern Australia, and eastwards to the Solomon Islands (Raines & Poppe, 2006: 238); Japan, Okinawa to Indonesia, 10–150 m (Huber, 2010: 206); Philippines, 20–200 m, dead; 80–120 m, alive ( Raines, 2010: 632; Dijkstra, 2013: 80); Papua New Guinea (Dijkstra, 1998a: 36). Maximum depth range of live-taken specimens is 10– 200 m. Present specimens from Australia dead at 3– 34 m. Semipallium dianae is a new record for Australia.

Remarks. The present specimens are indistinguishable in all characters from the type material. The most closely similar congeneric species is Semipallium crouchi ( Smith, 1892) , known from the western Indian Ocean. Semipallium crouchi differs from S. dianae in having narrower, more prominent radial plicae and in its colour (brownish-purplish maculated, S. dianae brightly polychrome).