Solemyidae Gray, 1840

Hryniewicz, Krzysztof, Little, Crispin T. S. & Nakrem, Hans Arne, 2014, Bivalves from the latest Jurassic-earliest Cretaceous hydrocarbon seep carbonates from central Spitsbergen, Svalbard, Zootaxa 3859 (1), pp. 1-66 : 7-8

Family Solemyidae Gray, 1840

Genus Solemya Lamarck, 1818

Type species. Solemya mediterranea ( Lamarck, 1818) = Tellina togata Poli, 1795 (by subsequent designation, Children, 1823).

Remarks. Our species is included in Solemya Lamarck, 1818 , because of its internal ligament ( Taylor et al. 2008; Kamenev 2009; Oliver et al. 2011). It is not a member of the genus Acharax Dall, 1908 , because this taxon has an external ligament positioned above the thickened shell margin, developed probably as a support for the ligament nymphs ( Amano & Ando 2011; Oliver et al. 2011; Taviani et al. 2011). Solemya has an internal ligament with a distinct resilium supported on a chondrophore.

Fossil solemyids are morphologically very conservative, having a cylindrical shape with inequilaterally positioned beaks and an elongated shell anterior (e.g. Logan 1967; Duff 1978; Liljedahl 1984; Cope 1996; Kiel et al. 2008a; Bailey 2011). This conservatism (e.g. Taylor & Glover 2010) is maintained not only at the genus, but also at the species level, as testified by the presence of cryptic modern species of Acharax ( Neulinger et al. 2006) . Thus, the taxonomy of solemyids is difficult, and there are few characters useful for species discrimination.

Subgenus Petrasma Dall, 1908

Type species. Solemya borealis Totten, 1834

Remarks. We have included our species in the subgenus Petrasma Dall, 1908 , because of the presence of a chondrophore supporting an oblique buttress adjoining the anterior side of the posterior adductor muscle scar, and small ligament demipads elongated along the dorsal margin and developed in front of the chondrophore. A buttress in front of the posterior adductor muscle scar is also present in the subgenera Solemyarina Iredale, 1931 , Zesolemya Iredale, 1939 , and Austrosolemya Taylor, Glover & Williams 2008 , all of which have large ligament demipads perpendicular to the dorsal margin in front of the chondrophore (e.g. Kamenev 2009, fig. 4–6). For more detailed discussion of subgeneric differences in the genus Solemya see Taylor et al. (2008), Kamenev (2009) and Oliver et al. (2011).