Minnivola pyxidata (Born, 1778)

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 : 295-296

Minnivola pyxidata (Born, 1778)

Figs 53F,H, 55A,C,F,I, 97

Ostrea pyxidata Born, 1778: 93 ; Born, 1780: 108, pl. 6, figs 5–6; Dijkstra, 2009: 113, figs 47–50 [figured syntype NHMW14110].

Ostrea sulcata Gmelin, 1791: 3325 (junior primary homonym of O. sulcata of Müller, 1776, and of Born, 1778).

Pecten pyxidatus (Born) .–G. B. Sowerby II, 1842: 49, pl. 12, figs 24–25; Chenu, 1843: 3, pl. 9, figs 6–6d [1844, as P. pixidatus Sowerby ]; Reeve, 1853: sp. 96, pl. 24, figs 96a–b; Küster & Kobelt, 1888: 57, pl. 15, figs 5–6; pl. 35, figs 1–2; Crosse & Fischer, 1892: 75; Lynge, 1909: 153; Dautzenberg & Bavay, 1912: 3; Abbott & Dance, 1982: 304, fig.; Bernard et al., 1993: 52; Wang, 2002: 236, pl. 3, fig. 2; Xu & Zhang, 2008: 91, fig. 258.

Pecten crebricostatus Philippi, 1845: 100 , pl. 1, fig. 2.

Pecten (Vola) crebricostatus (Philippi) .–Küster & Kobelt, 1888: 264, pl. 70, figs 1–2.

Pecten (Pecten) pyxidatus (Born) .– Oostingh, 1935: 150.

Minnivola isomeres Iredale, 1939: 364 ; Lamprell & Whitehead, 1992: [32], pl. 14, fig. 84; Raines & Poppe, 2006: 172, 173, upper figs; pl. 120, figs 2–3.

Pecten isomeres (Iredale) .–Coleman, 1982: 223, pl. 628.

Pecten (Minnivola) pyxidatus (Born) .–Springsteen & Leobrera, 1986: 326, pl. 93, fig. 2; Wang, 1989: 180, figs 5.1–2; Dijkstra, 1990: 9, 12; Rombouts, 1991: 53, pl. 20, fig. 2; Dharma, 2005: 250, pl. 100, figs 14a–c.

Pecten pyxidata [sic] (Born).–Dharma, 1992:84, pl.20, fig. 17.

Minnivola pyxidata (Born) .–Lamprell & Whitehead, 1992: [32], pl. 14, fig. 85; Dijkstra, 1998a: 26; Hayami, 2000: 909, pl. 452, fig. 54; Subba Rao & Dey, 2000: 228; Swennen et al., 2001: 74, fig. 073; Raines & Poppe, 2006, p. 172–173, lower figs; pl. 120, figs 1, 4–7; pl. 121, figs 1–7; Huber, 2010: 195; Raines, 2010: 616, pl.999, figs 1–3.

Minnivola pyxidatus [sic] (Born).– Morton, 1996: 735–760, pl. 1, figs 1–22.

Comments on synonymy. Gmelin’s (1791) description of Ostrea sulcata is based upon Born’s (1780) reference to Ostrea pyxidata : “v. Born mus. Caes. Vind. test. t. 6, f. 5, 6” and is therefore an objective junior synonym of the present species.

Philippi (1845) described a new pectinid species from China, Pecten crebricostatus , which is identical to M. pyxidata in all characters and we regard it as a subjective junior synonym.

Iredale (1939) introduced a new pectinid species, Minnivola isomeres , from Queensland and placed it in the new genus Minnivola . However, this species is only a local morph (see remarks) and we regard it as another subjective junior synonym of M. pyxidata .

Type material. Ostrea pyxidata Born : syntype (pr) NHMW14110, figured in Born (1780: pl. 6 figs 5–6), refigured in Dijkstra (2009: 107, figs 47–50). Type locality: Not indicated (Born, 1778), “Patria ignota” (Born, 1780). Unknown .

Ostrea sulcata Gmelin : lectotype (pr) NHMW14106, probably figured by Born (1780, pl. 6, figs 5–6), also figured by Dijkstra (2009: 102, figs 5–8), designated by Dijkstra (2009: 104). Type locality: Not indicated (Born, 1778), “Patria ignota” (Born, 1780). Unknown .

Figure 97. Distribution of Minnivola pyxidata (Born) .

Pecten crebricostatus Philippi : type material not seen, probably in National Museum of Natural History , Santiago de Chile (G. Pastorino, National Museum of Natural History, Buenos Aires, pers. comm.), not available for examination at present. Type locality: China.

Minnivola isomeres Iredale : holotype (pr) AM C.047392 (Fig. 55C, I). Type locality: QLD, GBR, Bunker Group , Lady Elliot Island, 24°07'S 152°42'E, alive.

Additional material examined. — AUSTRALIA: QUEENSLAND: Gulf of Carpentaria,alive (4 pr, QM MO33656); SW Gulf of Carpentaria, 15°18'S 136°39'E, dead, 21 m (1 v,C.375430); Gulf of Carpentaria,S of Sweers Island, 17°06'S 139°37'E, dead, 9–22 m (10 v, C.375428);Gulf of Carpentaria,28 ml S of Sweers Island, 17°06'S 139°37'E, alive (5 v, C.375429); Gulf of Carpentaria, 10 ml SW of Mapoon, 12°05'S 141°40'E, dead, 18 m (4 v, C.014077); Cape York Peninsula,Albany Passage, 10°45'S 142°37' E,alive, 7–26 m (9 v,C.036132);Torres Strait, Gannet Passage, NNE of Booby Island, 10°36' S 141°55'E, dead, 11 m (1 v, C.375426); GBR, off Cape Tribulation, 16°10'S 145°28' E, dead, 0–15 m (1 v, C.375423); Low Isles, 16°23'S 145°34'E, dead, 16–22 m (3 v, C.336919); off Cairns, 16°51.6' – 16°51' S 146°01.2'– 146°04' E, dead, 33–35 m (1 v, C.375420); Townsville, off Horseshoe Bay, Magnetic Island, 19°07'S 146°51'E, dead, 5.5–9 m (1 v, C.375422); off Bowen, 19°44' S 148°14'E, dead, 40 m (1 v, C.375418); GBR, E of Bowen, 19°45.7' S 148°19'E, dead, 46 m (1 v, C.375419); W of Hayman Island, 20°03'S 148°50'E, dead, 33 m (many v, C.375416); Whitsunday Passage, 20°13.5'S 148°47.5'E,dead, 24 m (11 v,C.375417);GBR,Whitsunday Passage, Lindeman Island, 20°27'S 149°02' E, alive (9 v, C.058938); Whitsunday Passage, 20°32.3'S 149°01.4' E, dead, 27 m (many v, C.375413); GBR, E of Mackay, 20°52'S 149°29'E, dead, 35 m (1 v, C.375415);Seaforth, N of Mackay, 20°54' S 148°58' E, dead (4 v, C.375414); GBR, E of Sarina, 21°27.5' S 150°08'E, alive, 42 m (4 pr + many v, C.119594);GBR, E of Sarina, 21°28'S 150°08.5'E,dead, 40 m (many v,C.375411);GBR, SE of Sarina, 21°47'S 150°34' E,alive, 59 m (10 v,C.375410); GBR, E of Broad Sound, 21°58.5' S 150°45'E, dead, 57 m (many v, C.375406); GBR, off Broad Sound, 22°06'S 150°49' E,dead, 53 m (10 v,C.375407);off Yeppoon, 22°40'S 151°16'E,dead, 58 m (1 v, C.375408);Keppel Bay,W of North Keppel Island, 23°04'S 150°53'E,dead, 3.5 m (1 v, C.375405);Keppel Bay,Yeppoon, 23°08' S 150°44' E,dead (6 v,C.130054);Keppel Bay, 23°25' S 150°55'E, dead (2 v, C.075254; 9 v, C.130053; 2 v, C.132207; 5 v, C.375465); Port Curtis, Rat Island, 23°46'S 151°19'E, dead (1 v, C.021828); Tannum Sands, S of Gladstone, 23°57'S 151°22'E, dead (1 v, C.375464); GBR, Bunker Group, Lady Elliot Island, 24°07'S 152°42'E,alive (holotype of M. isomeres , C.047392);off Burnett Heads, 24°46' S 152°25' E,alive, 30 m (1 pr,C.097547);Bargara, 24°49' S 152°28' E,dead(many v, C.130055); Hervey Bay, 25°06' S 152°49'E, alive (2 pr, C.102337); Hervey Bay, off Picnic Point, 25°06'S 152°49'E, alive, 9–12 m (4 pr, C.102329); off Frazer Island, 25°09.6'S 153°34' E, dead, 48 m (1 v, C.375461); Hervey Bay, Point Vernon, 25°15'S 152°49' E,dead (1 v, C.132208);Hervey Bay, near Urangan, 25°17'S 152°54'E, alive (2 pr,C.130056); Hervey Bay, Dundowran, 25°18'S 152°46'E, alive (2 pr, C.375402; 1 v, C.375463); Hervey Bay, Dundowran Beach, 25°18'S 152°46' E, alive (2 pr, C.097548; 5 v, C.375462); Hervey Bay, S of Woody Island, 25°18.5'S 152°56' E, alive, 9 m (6 pr, C.097546);Moreton Bay, off Redcliffe Beach, 27°14'S 153°07'E,dead (1 pr,C.303796); Moreton Bay, Green Island, 27°26'S 153°14'E, dead (2 v, C.375459); Moreton Bay, off Peel Island, 27°30'S 153°21'E, dead, 9–11 m (19 v, C.375460); Moreton Bay, off Dunwich,Stradbroke Island, 27°30' S 153°24'E,dead, 5–7 m (10 v,C.375458);Moreton Bay, Peel Island, off SW side, 27°31'S 153°21'E, dead (1 pr, C.068420). WESTERN AUSTRALIA: SE corner of Cassini Island, 13°57' S 125°38' E, 40–45 m, dredged alive (1 pr, HM). NORTHERN TERRITORY: 8 km N of Cape Ford, Anson Bay, SW of Darwin, 13°19.14'S 129°56.28' E, dead, 29 m (1 pr, NTM P003278); 7 n. mls NE of Cape Ford,Anson Bay, SW of Darwin, 13°22.08'S 129°58.98' E, dead, 23 m (2 pr, NTM P003232); 12 km W of Daley River mouth, Anson Bay, SW of Darwin, 12°19.14'S 129°59.16' E, alive, 31 m (1 pr, NTM P003289); Bathurst Island, 12°01'S 130°08'E, alive, 51 m (1 pr, WAM 446); Darwin, 36 km off Point Charles, 12°10'S 130°22'E, dead, 27–37 m (10 v, C.375466); Darwin, 32 km off Point Charles, 12°10'S 130°22'E, dead (4 v, C.375467); Buchanan Island, S side of Melville Island, 11°49'S 130°39'E, dead (1 v,C.375468);W of Gunn Point, N of Darwin Harbour, 12°10.02'S 130°49.86'E, dead, 27 m (2 v, NTM P005396 [in part]); N of Lee Point, WSW of Gunn Point, NNE of Darwin Harbour, 12°13.02'S 130°50.04'E, dead, 22 m (2 v, NTM P004715); Shoal Bay, N of Lee Point, NNE of Darwin Harbour, 12°13.02'S 130°52.92'E, dead, 19 m (2 v, NTM P004774); Casuarina Beach, Darwin , adjacent to outlet of Sandy Creek, 12°21'S 130°53.3'E, on mid- and high-tidal drift lines, dead (1 v, NTM P011454); E of Darwin, Gunn Point Public Beach, 12°11.0'S 131°0'E, beach drift, dead (2 v, NTM P000132;1 v, NTM P000440; 1 v, NTM P010150);Arafura Sea, c. 95 ml N of Cobourg Peninsula, 9°45'S 132°04'E, dead, 108 m (1 v, C.375470); Eastern Arnhem Land, Gove Harbour,off Drimmie Head, 12°13.746'S 136°41.317'E, dead, 14.5 m (1 v, NTM P012235); Gove Peninsula, Nhulunbuy town beach, 12°18.3'S 136°78.3' E, alive (1 pr, C.375471);Arafura Sea, 67 km NE of Croker Island, 10°36'S 132°56.5'E,dead, 62 m (2 v,C.375469).— CHINA:Kwangtung, alive, 24 m (3 pr, ZMA Moll.144257). TAIWAN: off SW coast, alive, 73 m (4 pr, ZMA Moll.140567). — PHILIPPINE ISLANDS : Sulu Sea, Siasi, off Laminusa, alive, 25–40 m (5 pr, ZMA Moll.144189); off Cebu, alive, 30–40 m (1 pr, ZMA Moll.146564).— MALAYSIA: Malacca Strait,alive, 46 m (10 pr, ZMA Moll.141278).— INDONESIA:N Sumatra, N of Tanjung Balai,alive, 36 m (4 pr, ZMA Moll.143733).— THAILAND:Siam Gulf,alive, 16 m (1 pr, ZMA Moll.143679); Andaman Sea, off Phuket Island, alive, 10–35 m (1 pr, ZMA Moll.142729); Kantang, Khor Libong, alive, 10–20 m (8 pr, ZMA Moll.143672). BURMA: Bay of Bengal, off Sandoway,alive, 35 m (1 pr, ZMA Moll.145585). INDIA:off Madras (Chennai),alive, 25–40 m (5 pr, ZMA Moll.140986).

Description. Shell up to c. 50 mm high, subcircular, rather thin, inequivalve, almost equilateral, left valve weakly concave, right valve strongly inflated, auricles almost equal in size, unequal in shape, umbonal angle c. 115°. Left valve of most specimens brownish with radially arranged pale dots of different sizes, right valve paler or whitish (see also Morton, 1996: 737, pl. 1).

Both valves sculptured with c. 20–30 weak radial plicae, each plica narrower than one interspace on left valve, each plica wider than one interspace on right valve. Left valve with reticulate (squamiformous) “pseudo-shagreen” microsculpture in radial interspaces early in ontogeny, interstitial sculpture commarginal late in ontogeny; interstitial sculpture weak or lacking on right valve. Auricles each with 4–8 delicate radial riblets. Interior weakly furrowed to almost smooth, internal rib carinae prominent in narrow zone around ventral margin. Hinge teeth weak. Byssal notch deep, functional ctenolium well-developed in adults.

Dimensions. Illustrated specimens: QLD, Hervey Bay, S of Woody Island, 9 m ( AM C.097546): rv: H 32.1, L 34.5 mm; lv: H 30.9, L 33.8 mm; D 10.8 mm. Iredale (1939: 364) stated the dimensions of the holotype of Minnivola isomeres as H 29, L 32, D 10 mm .

Habitat. Living free, shallowly recessing (not byssally attached to substrate) from the littoral zone to 100 m on the continental shelf, on soft sediment (sand and/or mud). In this genus, the deep byssal notch and functional ctenolium of adults evidently reflects Miocene evolution from a Mimachlamys -like ancestor and retention of ancestral characters.

Distribution. Sumatra, offshore (Dharma, 1992: 84); Indian Ocean, Philippine Islands , South China Sea, Hong Kong, Hainan, Taiwan and Fujian, 5–100 m (Bernard et al., 1993: 52); Gulf of Thailand, 12–20 m ( Swennen et al., 2001: 74); Queensland and New South Wales, to 10 m (Lamprell & Whitehead, 1992: 32; as Minnivola isomeres ). Maximum depth range of live-taken specimens is c. 5–100 m, occurs generally in shallow waters. Although Lamprell & Whitehead (1992) recorded New South Wales as the southern limit of distribution, we have not seen material from this area. Now also known from the Northern Territory. Present material from Australia alive at 7– 59 m.

Remarks. The Queensland morph ( Minnivola isomeres ) differs somewhat from typical specimens in having a smaller and more fragile shell, and is generally uniform in colour (brownish, purplish, whitish or cream). However, typical colour variations are also observed in Queensland. Radial macrosculpture and intercostal microsculpture are highly variable in both typical and local morphs.

For biology and functional morphology see Morton (1996: 735–760).