Elliptiolucina neozelandica, Amano & Little & Campbell, 2018

Amano, Kazutaka, Little, Crispin T. S. & Campbell, Kathleen A., 2018, Lucinid bivalves from Miocene hydrocarbon seep sites of eastern North Island, New Zealand, with comments on Miocene New Zealand seep faunas, Acta Palaeontologica Polonica 63 (2), pp. 371-382 : 375-377

Elliptiolucina neozelandica sp. nov.

Fig. 4 .

Etymology: Named for New Zealand, the country of the type locality. Type material: Holotype, UOA L4771( Fig. 4A ) from locality Y16/ 1174 (Moonlight North), collection AU19923. Paratypes: UOA L4783

Fig. 4B ); UOA L4775 ( Fig. 4C ); UOA L4774 ( Fig. 4D ); from locality Y16/f1059 (Moonlight North), collection AU 19982. One silicone rubber cast of the internal shell features made from UOA L4775.

Type locality: Moonlight North seep site, North Island, New Zealand .

Type horizon: Bexhaven Limestone, middle Miocene.

Dimensions.—See Table 2.

Diagnosis.—Small and compressed Elliptiolucina having a thin shell without a sulcus. Antero-dorsal margin gently sloping to subtruncated anterior margin. Lunule narrow and escutcheon deeply sunken, demarcated by sharp ridge.Hinge of right valve shallowly sunken and edentulous with nymph.

Description.—Shell size rather small for genus, up 34.9 mm in length; rather thin-shelled, elongate ovate (H/L = 0.75), compressed, equivalve and inequilateral. Antero-dorsal margin gently sloping, making right angle with subtruncated anterior margin; ventral margin broadly arched and subparallel with dorsal margin; postero-dorsal margin nearly straight, leading into subtruncated posterior margin. Distinct but shallow sulcus present from beak to antero-ventral corner; shallow depression from beak running in postero-ventral direction. Surface largely smooth, sculptured by growth lines and about four very low and dense commarginal threads between growth lines. These growth lines turning into lamellated ribs near anterior and posterior dorsal margins. Umbo not prominent, prosogyrate and located at anterior one-third of shell length in one small entire specimen. Lunule narrow, lanceolate, shallowly sunken. Escutcheon lanceolate, deeply sunken and demarcated by sharp ridge. Hinge of right valve shallowly excavated and edentulous with nymph. Pallial line entire. Anterior adductor muscle scar elongate, long and slightly detached from pallial line; posterior adductor muscle scar large, subquadrate and rather deeply depressed on dorsal side.

Remarks. —The outlines, hinge characters, and shape of the posterior adductor scar show that the specimens belong to the genus Elliptiolucina , except for having rather thin shells. This is the first record of fossil Elliptiolucina in New Zealand.

Elliptiolucina neozelandica sp. nov. is most similar to the Recent Philippines Sea species, E. labeyriei Cosel and Bouchet, 2008 in having a relatively small, rather thin shell, a narrow lunule and a similar outline. However, E. labeyriei has a distinct and wide sulcus from the beak to the postero-ventral corner, which is not seen in E. neozelandica sp. nov.

Elliptiolucina williamsae Glover and Taylor, 2016 from the central Philippines lives in rather shallow water (280– 679 m depth) compared to other species in the genus. This species also has a small, thin shell (up to 44.1 mm), as in E. neozelandica sp. nov. However, the Recent species has a well-rounded ventral margin with a cardinal tooth and an anterior lateral tooth.

Elliptiolucina washingtonia Kiel, 2013 from the upper Oligocene Lincoln Creek Formation in Washington State (Kiel 2013) is up to 140 mm long, larger than any of the extant species, and larger than E. neozelandica sp. nov.

Elliptiolucina hetzeli ( Martin, 1933) from the upper Miocene formation of Buton Island, Indonesia, redescribed by Kiel (2013), can be separated from E. neozelandica sp. nov. by its larger shell (more than 48 mm) and acutely rounded posterior margin.

Another Indonesian species, the living E. virginiae Cosel and Bouchet, 2008 , can be easily separated from E. neozelandica sp. nov. by its larger size (up to 78 mm long), truncated posterior margin and narrow hinge plate.

The Recent species, Elliptiolucina ingens ( Okutani, 2011) from off Amami-Oshima, southwestern Japan, differs from E. neozelandica sp. nov. in having a larger (up to 98.4 mm in length; Kuhara et al. 2014) and thick shell with a rounded posterior margin.

Stratigraphic and geographic range. —Moonlight North seep site; middle Miocene Bexhaven Limestone, North Island, New Zealand.

Figures

Fig. 4. Lucinid bivalve Elliptiolucina neozelandica sp. nov. from the middle Miocene Bexhaven Limestone at Moonlight North (A, Y16/f1174; B–D, Y16/1059), North Island, New Zealand. A. UOA L4771 (holotype), dorsal view (A1), right (A2) and left (A3) valves. B. UOA L4783 (paratype), dorsal view (B1), right valve (B2), internal mould of left valve (B3), enlargement of anterior adductor muscle scar in B2 (B4). C. UOA L4775 (paratype), edentulous hinge plate of right valve (C1), left valve (C2). D. UOA L4774 (paratype), dorsal view (D1), right (D2) and left (D3) valves. Scale bars 10 mm.