A New Species of Dianadema (Bivalvia: Pholadomyida: Clavagelloidea) from Japan

Abstract

A new species of Dianadema (Clavagellidae), Dianadema ikebei n. sp., is described from Japan and comparisons are made with the other three known Indo-West Pacific species of the genus. Dianadema ikebei n. sp. has been collected from two localities in waters of between 50–100 metres depth off central to southern Japan (Honshû). The species occurs cemented to the walls of borings made by other bivalves, such as pholadids and lithophagines, in weakly consolidated sedimentary rocks composed of sand and mud. It may also cement itself to dead conspecifics and other nestling bivalves, which are secondary occupants of such borings. This is the first record of the genus in Japan and the Northwest Pacific.