Bractechlamys vexillum (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 : 184

Bractechlamys vexillum (Reeve, 1853)

Figs 32B,F,H, 33, 34E –F

Pecten distans Lamarck, 1819 .–G. B. Sowerby II, 1842: 61, pl. 13, fig. 46; pl. 18, fig. 182; Reeve, 1853: sp. 49, pl. 13, fig. 49 (misidentification).

Pecten digitatus Hinds, 1845: 61 , pl. 27, fig. 2 (junior primary homonym of Pecten digitatum [sic] Perry, 1811).

Pecten vexillum Reeve, 1853 : sp. 114, pl. 27, figs 114a–b.

Pecten janus Montrouzier in Fischer, 1858: 340 (replacement name for Pecten distans Lamarck as figured by Reeve (1853: pl. 13, fig. 49); junior primary homonym of Pecten janus Münster in Goldfuss, 1833); Küster & Kobelt, 1888: 186, pl. 51, figs 3–4.

Pecten (Chlamys) zeteki Hertlein, 1935: 306 , pl. 19, fig. 9 (replacement name for Pecten digitatus Hinds, 1845 ).

Bractechlamys evecta Iredale, 1939: 367 , pl. 5, figs 20–20a; Lamprell & Whitehead, 1992: [30].

Semipallium zeteki (Hertlein) .–Grau, 1959: 122, pl. 41, figs 1–2.

Comptopallium vexillum (Reeve) .– Waller, 1972a: 243, pl. 4, figs 64–75, pl. 5, figs 76–83, 86; Abbott & Dance, 1982: 307, fig.; Dijkstra, (1983–1994) 1985: 7, figs.

Semipallium vexillum (Reeve) .– Rombouts, 1991: 60, pl. 22, figs 2–2a; Xu & Zhang, 2008: 89, fig. 248.

Bractechlamys vexillum (Reeve) .–Springsteen & Leobrera, 1986: 328, pl. 93, fig. 12; Dijkstra, 1991: 44; Dijkstra, 1998a: 16, pl. 2, fig. 4; Raines & Poppe, 2006: 104, 105, upper figs; pl. 39, figs 1–7; pl. 40, figs 1–7; pl. 41, figs 1–8; pl. 42, figs 1–7; pl. 47, fig. 6; pl. 297, fig. 2; Huber, 2010: 198; Raines, 2010: 600, pl. 991, figs 3–8.

Type data. Pecten digitatus Hinds : holotype (pr) NHMUK 1879.2 .26.190, refigured by Waller (1972a: 243, figs 76–79, 81, 82). Type locality: “ Bay of Guayaquil ” [erroneous], mud, 23 fathoms [42 m].

Pecten vexillum Reeve : lectotype (pr) NHMUK197010, figured by Reeve (1853: pl. 27, fig. 114a), designated and refigured by Waller (1972a: 243, figs 64–68, 71). Type locality not mentioned in original description, although on labels of type lot “Australian Seas”.

Bractechlamys evecta Iredale : holotype (rv) AM C.075283 (Fig. 32B). Type locality: Great Barrier Reef Exped. stn XIV, Australia, Great Barrier Reef , 0.5 ml SE of Lizard Island, 19 fathoms [35 m].

Comments on type data. The type locality “Bay of Guayaquil” [ Ecuador] of Pecten digitatus Hinds, 1845 is incorrect. Species of Bractechlamys do not occur in the eastern Pacific. See also Grau (1959: 122, pl. 41 figs 1–2).

Additional material examined. — AUSTRALIA: QUEENSLAND: GBR,0.5 ml NW of Howick Isle, 14°29' S 144°57'E,dead, 18 m (1 v,C.075244); Lizard Island, Rocky Point, 14°40'S 145°26'E, alive, 6–9 m (1 pr, C.105244); Lizard Island, off Rocky Point, 14°40'S 145°26'E,dead, 15 m (1 v,C.363917); Lizard Island , Watsons Bay , 14°40'S 145°27'E, alive, 10.5–23 m (4 pr + 6 v, C.104440; 1 pr, C.105836; 1 pr, C.106274; 2 pr, C.131837; 3 pr + 3 v, C.363916; 5 pr, C.364030; 1 pr, C.364034; 1 pr, C.364037);GBR,0.5 ml N of Eagle Isle, 14°41'S 145°22'E,alive, 18 m (1 pr,C.119718); GBR, 0.5 ml SE of Lizard Island, 14°41'S 145°29' E, dead, 35 m (1 v, C.075283; 3 v, C.119716); GBR, 0.25 ml N of North Direction Isle, 14°44' S 145°31'E, dead, 34.5 m (11 v,C.119717);0.5 ml W of North Direction Isle, 14°45'S 145°30'E,alive, 36.5 m (11 v, C.119719); Low Isles, 16°23'S 145°34'E, alive (1 pr, C.097432); Michaelmas Cay, 16°36'S 145°59'E, alive, 20 m (2 pr, C.053721; 9 v, C.119720); Green Island , 16°46'S 145°58'E, dead (1 pr, C.009982); Swain Reefs, 3 km NE of W side of Bylund (Gillett) Cay, 21°42'S 152°26'E, dead, 64–73 m (3 v, C.363918); Swain Reefs, Bylund (Gillett) Cay, W shore, 21°43'S 152°25'E, intertidal, dead (1 pr, C.363919) . — PHILIPPINE ISLANDS : Cebu Sea, alive, 20–40 m (4 pr, ZMA Moll.140612); Sulu Sea, Laminusa Island, alive, 5 m (3 pr, ZMA Moll.141353); Mindanao, Davao Gulf, Talikud Island , alive, 20–28 m (1pr, ZMA Moll. 144472) . — MALAYSIA: Singapore, off Sentosa , alive, 15–20 m (1 pr, ZMA Moll. 140282) . — SOLOMON ISLANDS : Ontong Java , alive, 38 m (2 pr, ZMA Moll. 143053) . — NEW CALEDONIA: Poum Bay, Daomboui, 20°09'S 163°59'E, alive, 0–3 m (2 pr, C.364038); Poindimié , 20°56'S 165°20'E, alive (1 pr,C.105836); Noumea, Anse Vata, 22°19' S 166°27'E,alive, 1–3 m (3 pr,C.364039) . VANUATU: Efate Island, Port Vila , 17°44'S 168°18'E, dead (4 v, C.131843) .

Description. Shell up to 74 mm high (Huber, 2010), most specimens 30–40 mm; solid, inflated, almost equally convex, oblong, almost equivalve and equilateral, auricles slightly unequal in shape and size, umbonal angle about 90°; left valve brightly coloured, highly variable, uniformly cream, yellow, orange, red, mauve, maroon or dark brown with whitish dots or streaks; right valve of most specimens paler, interior of most white with dark brown hinge plate.

Both valves sculptured with 9–11 prominent radial plicae, most specimens with 9, covered throughout with very closely spaced commarginal lamellae. Secondary radial riblets on plicae and interspaces in late growth stage, near ventral margin. Interspaces almost the same width as plicae.Anterior auricle of right valve with 3–4 radial costae, other auricles very weakly ribbed or almost smooth. Dorsal margin of right valve with low tubercles. Dorsal margin of left valve straight, of right valve slightly raised. Byssal notch shallow, byssal fasciole rather wide, functional ctenolium lacking in mature specimens. Resilifer narrowly triangular. Intermediate and dorsal teeth well-developed, prominent. Internal rib carinae present near ventral margin.

Dimensions. Illustrated specimen: QLD, GBR, 0.8 km N of Eagle Isle, 18 m ( AM C.119718): rv: H 38.0, L 34.8 mm; lv: H 37.2, L 34.6 mm; D 17.5 mm. Iredale (1939: 367) stated the dimensions of the holotype of Bractechlamys evecta as H 35, L 30 mm .

Habitat. Juveniles living byssally attached to substrates, adults free amongst marine grasses or coral rubble on soft sediment (sand or mud), in the intertidal to sublittoral zones.

Distribution. Tropical Indo-West Pacific from the Philippines southwards to northern Australia, westwards to Andaman, and eastwards to Vanuatu. Philippines, Irian Jaya ( Indonesia), Solomon Islands , New Caledonia, Palau Islands , and Marshall Islands , intertidal to 55 m ( Waller, 1972a: 246); Andaman to China, 1-67 m (Huber, 2010: 198); Philippines, 40 m ( Raines, 2010: 600). Maximum depth range of livetaken specimens is of the intertidal zone to 80 m (HHD, unpublished data). Present material from Australia alive at intertidal to 40 m.

Remarks. Lamprell & Whitehead (1992: [30]) did not record this species from Australia due to lack of material at that time. Bractechlamys vexillum is now recorded alive from Queensland and is morphologically identical to the type specimens. The Philippines morph is slightly different from the type specimens in having one or two more primary radial plicae. Other characters are identical. The specific epithet vexillum is an indeclinable noun (Latin, a flag or standard).