Syssitomya, Oliver, 2012

Oliver, P. Graham, 2012, Taxonomy of some Galeommatoidea (Mollusca, Bivalvia) associated with deep-sea echinoids: A reassessment of the bivalve genera Axinodon Verrill & Bush, 1898 and Kelliola Dall, 1899 with descriptions of new genera Syssitomya gen. nov. and Ptilomyax gen. nov., European Journal of Taxonomy 12, pp. 1-24 : 13-14

Genus Syssitomya gen. nov.

Type species

Syssitomya pourtalesiana sp. nov. (here designated).

Diagnosis

Shell small, thin. Equivalve. Inflated. Inequilateral, beaks behind the midline. Outline roundly subovate, distinctly expanded anteriorly, lunule depression distinct. Hinge with an anterior cardinal peg in the right valve, an anterior marginal flange in the left valve, posterior teeth lacking; ligament internal on a recessed resilifer beneath and posterior of the beaks. Sculpture weak primarily of commarginal lines. Ctenidium of single partly reflected demibranchs; filaments laminar ( Fig. 4E ), extended abfrontally, abfrontal surfaces lined with bacteriocyte cells densely packed with symbiotic bacteria. A detailed scanning electron and transmission electron microscopy study of the ctenidium is in preparation and is beyond inclusion in this taxonomic paper (Oliver, Southward & Dando in press).

Etymology

From the Greek, syssitos a messmate and mya a clam, referring to the commensal habit and bacterial symbiosis.

Figures

Fig. 4. Scanning electron micrographs of anatomy. A. K. symmetros (Jeffreys, 1876) from Biscay. B. Syssitomya pourtalesiana sp. nov. from Norwegian Sea. C. Montacuta substriata (Montagu, 1808) from North Sea. D. Excised ctenidium of M. substriata. E. Excised piece of ctenidium from S. pourtalesiana sp. nov.