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Abstract
Four species including one new species of the genus Stephonyx are described from Japan: Stephonyx perexcavatus sp. nov., Stephonyx biscayensis (Chevreux, Citation1908), Stephonyx laqueus (Barnard, Citation1967) and Stephonyx mytilus (Barnard and Ingram, Citation1990). Stephonyx perexcavatus sp. nov. is distinguished from the congeners by the combination of the following features: dorsal margin of body smooth, posteroventral corner of epimeral plate 1 not pointed, lateral cephalic lobe rounded, article 1 of mandibular palp shorter than 0.5 times article 2, length of carpus of gnathopod 1 longer than 0.75 times propodus, and palm of gnathopod 2 deeply concave. This is the first record of S. biscayensis and S. mytilus from Japan. A key to the species of Stephonyx is provided.
Acknowledgements
We express sincere gratitude to Dr Keiichi Kakui (Hokkaido University), Dr Katsuhiko Tanaka (Global Oceanographic Data Centre), Mr Hiroshi Yamasaki (Hokkaido University), Mr Masanori Okanishi (Tokyo University), Mr Atsushi Kaneko (Okinawa Churaumi Aquarium) and Ms Hiroko Takaoka (Okinawa Churaumi Aquarium) for providing specimens. Thanks are also due to the crew of R/V Soyo-maru of National Research Institute of Fisheries Science for their cooperation during the field survey. We are deeply indebted to Dr Shunji Takeshita (Hiroshima University) for his valuable comments on this study. Thanks are also extended to Ms Mika Tokizawa, Ayane Maga, Kazune Makise, Mr Daisuke Saiga, Ken Ito, Masaya Nakanishi, Kengo Tokuno and Takeshi Matsumoto (Hiroshima University) for their support of our study. This study was partly supported by a grant from the Nihon Kyoiku Koumuin Kousaikai to KT.