Description of four new species of Neolepton Monterosato, 1875 (Mollusca: Bivalvia: Neoleptonidae), with comments on the genus and on its affinity with the Veneracea

Abstract

The type species of Neolepton Monterosato, 1875, Lepton sulcatulum Jeffreys, 1859, is redescribed using SEM of shells, critical-point dried soft parts, and semi-thin sections. Four new species (N. guanche from the Canary Is., N. cancellatum from the Azores, N. benguelensis from Angola, N. caledonicum from New Caledonia) are described; for the latter species is presented data on living animals and anatomy. Notolepton Finlay, 1927 and Neodavisia Chavan in Moore, 1969 are confirmed as synonyms of Neolepton, and the shells of their type species are figured. Kellya atlantica Smith, 1890 (with Rochefortia milda Bartsch, 1915 as a new synonym) from St Helena and South Africa, and Halodakra subtrigona (Carpenter, 1857) from California, are newly assigned to Neolepton. Notolepton atlanticum Soot-Ryen, 1960 from Tristan da Cunha is renamed Neolepton sootryeni n. nov.

The hinges of postlarval Veneridae, Gouldia minima (Montagu, 1803) and Chamelen striatula (da Costa, 1778) were found to share essential traits with the hinge of adult Neolepton. The morphology of the mantle edge in Neolepton sulcatulum was found to fit the descriptions given for the Veneridae. The two short siphonal apertures are also similar to those found in shallow infaunal venerids (e.g. Gouldia) and similarly have a delicate siphonal membrane inside the exhalant siphon. These observations are given as arguments to consider the Neoleptonidae as paedomorphic Veneracea, instead of Leptonacea or Cyamiacea as stated in the literature. It is further suggested that all Cyamiacea should be reevaluated for their systematic position with respect to Veneracea.

Key words:

• Neoleptonidae
• Veneracea
• Cyamiacea
• Taxonomy
• Paedomorphy.