Taxonomic review of the elongated cockles: genera Trachycardium, Vasticardium and Acrosterigma (Mollusca, Cardiidae)

The cardiids of the subfamily Trachycardiinae Stewart, 1930 (sensu Keen, 1969, genus Papyridea excluded), are reviewed, with special attention given to the genera Trachycardium, Acrosterigma, and Vasticardium. No change is proposed here to the relatively well-defined taxonomy of Trachycardium, considered to be exclusively American, with six subgenera, nor to the American Acrosterigma. In contrast, the generic taxonomy of the Indo-Pacific Trachycardiinae, quasi-randomly distributed by authors among the three genera cited above, was not clear and is reevaluated. All of the species are regrouped here into two genera Vasticardium and Acrosterigma which receive clear and usable definitions. The American genus Trachycardium differs widely from them in both hinge and rib morphology. The two genera Vasticardium and Acrosterigma are distinguished mainly by rib morphology. These three genera are now grouped in the subfamily Cardiinae. In several previous articles, I have analyzed in detail the genus Vasticardium, including fifteen Recent species. The results are summarized here. The genus Acrosterigma is represented in America by several fossil species and two Recent species; in the Indo-Pacific, where no general study has previously been undertaken, it is represented by several fossil species (one new) and twenty five Recent species, of which nine are new; these species are divided into six species-groups. Neotypes are proposed for Cardium magnum Linné, 1758 and Cardium biradiatum Bruguière, 1789 and lectotypes for Cardium laevigatum Linné, 1758, Cardium serratum Linné, 1758, and Cardium marmoreum Lamark, 1819.