Interactive 3D anatomy and affinities of Bathysciadiidae (Gastropoda, Cocculinoidea): Deep-sea limpets feeding on decaying cephalopod beaks.

The anatomy of five bathysciadiid limpets, the type species Bathysciadium costulatum (Locard, 1898), Bathysciadium sp. B (off New Zealand), Bathypelta pacifica (Dall, 1908), Bathypelta sp. A (off New Zealand), and Bathyaltum wareni n.g., n.sp. (deep East Atlantic Ocean Basins), which all feed on decaying cephalopod beaks, has been investigated by means of semithin serial sectioning and interactive, computer-aided 3D reconstructions. Bathyaltum wareni is described as a species new to science based on additional SEM photos of shell and radula. Differences between species are found in conditions of shell, protoconch, mantle papilla, copulatory organ, receptaculum openings, oral lappets, and rectal histology. The Bathysciadiidae share several synapomorphies with the Cocculinidae (s. str.), namely the pseudoplicatid gill, a single, left kidney, the hermaphroditic gonad with the single, glandular gonoduct, and the statocysts with single statoliths. Therefore, these families are united in a clade Cocculinoidea, which is considered to be highly modified offshoot of early gastropods independent of the likewise "cocculiniform" Lepetelloidea, which should be classified among the Vetigastropoda.