Zygochlamys delicatula (Hutton, 1873)

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 : 273-274

Zygochlamys delicatula (Hutton, 1873)

Figs 82F, 87

Pecten delicatula [sic] Hutton, 1873: 30.

Chlamys asperrimus (Lamarck) .–Hedley & May, 1908: 113 (misidentification).

Chlamys antiaustralis (Tate) .–Hedley, 1911: 96 (Cape Pillar record only); May, 1912: 44; May, 1923: pl. 3, fig. 8 (misidentification).

Pecten (Patinopecten) delicatulus Hutton. – Suter, 1914: 42, pl. 9, fig. 4.

Chlamys subantarctica Hedley, 1916b: 23 , pl. 2, figs 14–15; Tomlin, 1948: 230.

Pecten delicatulus Hutton. – Thomson, 1919: 282.

Chlamys campbellicus [sic] Odhner, 1924: 61, pl. 2, fig. 36.

Chlamys instar Iredale, 1925: 251 , pl. 41, figs 5–7.

Chlamys delicatula (Hutton) .– Marwick, 1928: 453; King, 1933: 353; Fleming, 1944: 210; Boreham, 1963: 3–25; Beu, 1977: 199–203; Fleming, 1979: 72, figs 72a–d; Fleming, 1980: 20, fig. 5.

Chlamys titirangiensis Marwick, 1928: 458 , fig. 28.

Chlamys campbellicus [sic] Odhner.– Powell, 1939: 222, pl. 50, figs 10–14.

Chlamys campbellica Odhner. –Fleming, 1944: 209.

Chlamys (Zygochlamys) delicatula (Hutton) .– Powell, 1950: 76; Powell, 1955: 25; Dell, 1956: 19; Fleming, 1957: fig. 1E; Fleming & Boreham in Pantin, 1957: 788, figs 1–2; Powell, 1960: 175; Pantin, 1963: 507, figs 1, 3–4; Dell, 1964: 180; Boreham, 1965: 22, pl. 5, figs 8–10; Beu et al., 1977: 217–234, figs 3-6; Powell, 1979: 379, pl. 68, fig. 3; Beu et al., 1981: 127–132.

Mimachlamys instar (Iredale) .– Kershaw, 1955: 294.

Chlamys (Zygochlamys) instar Iredale. –Dell, 1964: 180.

Chlamys patagonica delicatula (Hutton) .–Beu, 1985: 4, pl. 1, figs 5–9; pl. 2, figs 1–5; Beu & Maxwell, 1990: 308, pl. 38j.

Zygochlamys delicatula (Hutton) .– Waller, 1991: 28, pl. 2, figs 15–16, pl. 3, fig. 4; Beu, 1995: 15, figs 3a–d, 23b–c, e; Beu, 1999: 534, figs 4–7; Beu & Darragh, 2001: 118,

Figure 87. Distribution of Zygochlamys delicatula (Hutton) (circles) and Haumea rehderi (Grau) (stars).

figs 41A–G; Dijkstra & Marshall, 2008: 63, figs 53A–F, 54A–F, 55A–B, D–E, 56; Spencer et al., 2009: 198; Huber, 2010: 205.

Psychrochlamys delicatula subantarctica (Hedley) .– Jonkers, 2003: 48, pl. 1, fig. b; pl. 9, figs a–d; pl. 11, figs d–g.

Psychrochlamys delicatula delicatula (Hutton) .– Jonkers, 2003: 49, pl. 10, figs e–g.

Psychrochlamys delicatula instar (Iredale) .– Jonkers, 2003: 51, pl. 11, figs a–c.

Psychrochlamys delicatula (Hutton) .–Raines & Poppe, 2006: 224, 227, upper figs; pl. 172, figs 1–4.

Type data. Pecten delicatula Hutton : lectotype GNS TM2835, designated by Boreham (1965: 22, pl. 5, fig. 9). Type locality: Castlepoint, eastern Wairarapa, Castlepoint Formation (early Nukumaruan) (early Pleistocene, 2.4 Ma).

Chlamys subantarctica Hedley : holotype AM C.047411 (Hedley 1916b: pl. 2, fig. 14). Type locality: Macquarie Island, Lusitania Bay , 25 m.

Chlamys campbellicus Odhner : lectotype ZMUC, designated by Beu (1995: 17), 9 paralectotypes ZMUC ( Odhner 1924: pl. 2, figs 36–39). Type locality: Campbell Island, Perseverance Harbour, 20 fathoms [37 m].

Chlamys instar Iredale : holotype AM C.029103, 9 paratypes C.029103 (holotype: Iredale, 1925: pl. 41, figs 5–6). Type locality: SE Tasmania, 11 km east of Cape Pillar , c. 180 m (late Pleistocene fossils).

Chlamys titirangiensis Marwick : holotype GNS TM4207, 2 paratypes GNS GS1178, CH /f04 ( Marwick 1928: fig. 28). Type locality: Chatham Island , Titirangi Point, Titirangi Sand (early Nukumaruan) (early Pleistocene, 2.4 Ma).

Comments on type data. For additional information see Beu (1995: 17).

Additional material examined. — AUSTRALIA: NEW SOUTH WALES: E of Eden ,36°56'– 36°58'S 150°20'E,dead, 274 m (1 v,C.122923) ; SE of Eden , 37°04' – 37°13'S 150°21'– 150°20'E,dead, 269–282 m (1 v, C.346882) ; off Green Cape, 37°22'– 37°14'S 150°18'– 150°19' E, dead, 154–157 m (1 v, C.346879) . VICTORIA: E of Gabo Island , 37°35' – 37°41'S 150°11'– 150°14'E, dead, 220 m (4 v, C.110804) ; E of Gabo Island , 37°38' – 37°46'S 150°13'– 150°08' E, dead, 208–223 m (11 v, C.346889) ; SE of Gabo Island , 37°43'– 37°46'S 150°08'– 150°10' E, dead, 220 m (1 v, C.108843) . TASMANIA: NE of Cape Pillar , 43°10'S 148°12'E, dead, 172 m (3 v, C.115202) ; off Cape Pillar , 43°13'S 148°05'E, dead, 183 m (7 v, C.029103; 1 v, C.053769; 1 v, C.105646; 4 v, C.346892) ; 2.5 ml E of Tasman Island , 43°15'S 148°03' E, dead, 183 m (1 v, C.098623) ; off Cape Raoul , 43°31'S 147°48'E, dead, 140 m (1 v, C.097427) . MAQUARIE ISLAND: The Nuggets , 54°31'S 158°57' E, alive, 22 m (1 pr,C.155794) ; Lusitania Bay, 54°41' S 158°54'E, dead, 26 m (1 v, C.047411).

Description. Shell up to 110 mm high, most specimens smaller, to c. 70 mm; thin to more solid ( Macquarie Island morph), adults almost circular, moderately inflated, left valve of most specimens a little more convex than right, equivalve, equilateral, anterior auricles larger and longer than posterior ones, umbonal angle of juveniles c. 85–90°, of adults c. 115–120°; most specimens white or yellowish, others orange, red or cream.

Both valves sculptured with c. 20 moderately prominent radial plicae; with narrow plicae with broader, evenly concave interspaces on left valve, wider plicae with narrower interspaces on right valve, subdivided and flanked by lamellose secondary and tertiary radial riblets. Antimarginal microsculpture in pre-radial stage and intercostally (Beu & Darragh, 2001: figs 41C, E; Dijkstra & Marshall, 2008: figs 53C, 54C). Auricles with 10–16 squamous radial riblets, except 4–5 riblets on anterior auricle of right valve. Byssal notch moderately deep, byssal fasciole broad, both decreasing in prominence with age. Functional ctenolium well-developed in juveniles, with 4–5 teeth, decreasing in number with age. Internal radial furrows present, edges not carinate. Hinge with moderately weak resilial and dorsal teeth.

Dimensions. Illustrated specimen: VIC, E of Gabo I, 208–223 m (AM C.346889), large single lv: H 89.6, L 90.5 mm.

Habitat. Living in the sublittoral to bathyal zones, many specimens encrusted with sponges. However, not known living around Australia.

Distribution. Cook Strait to the southern region of the South Island, New Zealand, southwards to the Bounty, Antipodes, Auckland, Campbell and Macquarie Islands ; dead specimens on the Chatham Rise, off W Auckland and N of the Three Kings Islands , New Zealand (Beu, 1999; Dijkstra & Marshall, 2008: fig. 56), westwards to southernmost New South Wales, eastern Victoria and eastern Tasmania. Present specimens dead at 140– 282 m.

Remarks. The present specimens from Australia are Last Glacial Maximum fossils and no living records are known from Australia (see also Beu & Darragh, 2001: 121). Specimens from southeasternAustralia have been incorrectly identified in the past as “ Mimachlamys asperrima ” or “ Mimachlamys antiaustralis ” by Hedley & May (1908), Hedley (1911) and May (1921) (Beu, 1985).

For information on biostratigraphy see Beu (1995: 16).