Lobatoradarea, a new genus of the family Calliopiidae Sars, 1895 (Crustacea: Amphipoda) from Japan, with descriptions of ten new species.

Ten new species of calliopiid amphipods were collected from Japanese waters between 0694 m deep. All specimens commonly exhibit (1) 1-articulate accessory flagellum, (2) developed inner lobes of lower lip, (3) elongate carpus and propodus of gnathopod 2 in both sexes, and (4) entire telson. Among these characters 1, 3 and 4 are shared with the genus Oradarea, but the character 2 is quite different from Oradarea; therefore, Lobatoradarea gen. nov. is established herein to house these species. The ten new species are described in detail, including Lobatoradarea angulata sp. nov., L. anko sp. nov., L. coccina sp. nov., L. inermis sp. nov., L. kagoshimensis sp. nov., L. lignorum sp. nov., L. littoralis sp. nov., L. obliquua sp. nov., L. subinermis sp. nov., and L. thermicola sp. nov. These species can be distinguished from one another mainly by the presence or absence of the posterodorsal projections on pereonite 7 and pleonites 1, 2, and the shapes of the anteroventral corner of head, the dactyli of pereopods 37, the ventral margin of coxa 4, the posteroventral corner of epimeral plate 2, and the telson. A key to these species of Lobatoradarea gen. nov. is provided and the diagnosis of Oradarea is emended.