Falsolucinoma, Cosel, 2006

Cosel, Rudo von, 2006, Taxonomy of tropical West African bivalves. VI. Remarks on Lucinidae (Mollusca, Bivalvia), with description of six new genera and eight new species, Zoosystema 28 (4), pp. 805-851 : 815-817

Genus Falsolucinoma n. gen.

TYPE AND ONLY SPECIES. — Lucina leloeuffi Cosel, 1989 .

ETYMOLOGY. — In spite of the differences, at a first glance and external view, the valves resemble a Lucinoma , and this is expressed in the name (falsus, Latin = false).

DISTRIBUTION. — Northern Gulf of Guinea, tropical West Africa.

DIAGNOSIS. — Shells large, subcircular-triangular, compressed, with short and conspicuously rostrate anterior part and broad and longer posterior part.

Anterior and posterior area well demarcated. Surface with 10-15 conspicuous, thin, raised and widely spaced commarginal lamellae and smooth interspaces. Lunule very small and short, slightly asymmetric, escutcheon long and deeply sunken, delimited by a keel and almost entirely filled by ligament. Hinge plate narrow, left valve with two cardinal teeth, a strong anterior lateral and a smaller, narrower knob above it, and a narrow posterior lateral; right valve with two cardinals, two anterior laterals and two posterior laterals. Ligament short. Adductor scars small for the shell size, diverging part of anterior adductor scar very short and rather narrow, tapering; pallial line meeting the scar about in its middle. Inner margins smooth, but radial wavy sculpture on the zone between pallial line and margin and occasionally a few vestiges of irregular crenulations.

REMARKS

This genus is characterized by the strong anterior and posterior laterals in both valves, the small anterior adductor scar with the short and narrow diverging part and the short and rostrate anterior part of the shell. Externally it reminds a Lucinoma , with which it has in common the toothed hinge and the lamellose exterior with well separated anterior and posterior areas. There are also Lucinoma species with rostrate anterior margins (e.g., in this paper), but to a lesser extent. Moreover, the very much forward placed umbones, the more conspicuously rostrate anterior margin and the very small diverging part of the anterior adductor scar clearly distinguish Falsolucinoma n. gen. The highly asymmetric lunule and the short anterior adductor scar place the genus closer to the Myrtea group; however, species of Myrtea are smaller and often more tumid with their characteristicelly raised escutcheonal keel, often with tiny and dense spines. Their outline is more regular with the umbones placed less forward.

There is only one other genus known which has a similarly short and rostrate anterior part and a very short diverging part of the anterior adductor scar. It occurs in the Indo-West Pacific and will be published elsewhere (Cosel & Bouchet unpubl. data). Species of that genus, however, are more elongate, they have very densely spaced commarginal lamellae, the diverging lower part of the anterior adductor scar is much broader, and their hinge plate is narrower and almost toothless.

The genus most similar to Falsolucinoma n. gen. is Lamellolucina Taylor & Glover, 2002 , which is predominantly Indo-West Pacific, but one species, L. reyrei (Nicklès, 1955) occurs in West Africa. It is also characterized by prominent and more or less widely spaced commarginal lamellae, a similar hinge dentition with strong laterals and a generally rather short extension of the anterior adductor scar. Falsolucinoma n. gen. differs in the absence of a regularly crenulate margin, the more foreward placed umbones, the less asymmetric lunule and the much larger size.