Solemyidae

Saether, Kristian P., Jingeng, Sha, Little, Crispin T. S. & Campbell, Kathleen A., 2016, New records and a new species of bivalve (Mollusca: Bivalvia) from Miocene hydrocarbon seep deposits, North Island, New Zealand, Zootaxa 4154 (1), pp. 1-26 : 5

Solemyidae gen. indet.

( Fig. 3 B)

Material. Three specimens from Moonlight North (Y16/f0694), two medium sized, L4647, L4648, one larger, L4649 ( Fig. 3 B), UOA.

Description. Shell small (H up to ca. 12 mm, L up to ca. 21 mm), inequilateral, elongate oval; faint radial striae in anteroventral area, absent in other areas; posterior margin narrowly rounded; anterior margin more broadly rounded; dorsal and ventral margins gently convex; umbones prominent, angulated, situated ca. 20% along shell length from anterior margin; anterior portion of pallial line subparallel to ventral margin, adjoining anterior adductor scar directly medioventrally; anterior adductor scar rather large, situated with centre just in dorsal half of shell close to anterior margin.

Remarks. New Zealand Miocene seep solemyids are known from only three poorly preserved internal moulds. A tenuous pallial line and anterior adductor scar were observed faintly in one of the three specimens. Critically, the posterodorsal region is never well enough preserved to show the presence or absence of an external ligament. Therefore, from the appearance of the shells and quality of preservation it is not possible to categorically place the specimens within any particular solemyid genus. Not only does the preservation of the New Zealand seep specimens hinder identification, but solemyid taxonomy is complex (e.g. Taylor et al. 2008; Kamenev 2009; Oliver et al. 2011) and external shell morphology in this group is conservative (e.g. Taviani et al. 2011; Hryniewicz et al. 2014). The Moonlight North locality is inferred as a bathyal deposit ( Saether et al. 2010), and of those solemyid genera found in the New Zealand fossil record and at modern New Zealand seeps, Acharax is a deep-water genus. Solemya is found predominantly in shallower waters of the continental shelf and upper slope ( Neulinger et al. 2006; Oliver et al. 2011), although Solemya has been recorded from bathyal depths ( Kamenev 2009; Rodrigues et al. 2011; Sato et al. 2013).

Figures

FIGURE 3. Bivalves of uncertain sub-familial identity. A. Small (? juvenile) protobranch bivalve from Bexhaven. Specimen L 4646. Internal mould showing taxodont dentition typical of this group. Scale bar is 0.5 mm. B. Solemyidae gen. indet. Specimen L 4649 from Moonlight North. Scale bar is 5 mm. B 1. Lateral view of right valve. B 2. Lateral view of right valve, faint radial striations highlighted. B 3. Lateral view of left valve. B 4. Dorsal view.