Champsodon Günther, 1895 is composed of 13 valid species known from the Indo-West Pacific, which are divided into the “C. atridorsalis species group” (five spp.) and the “C. vorax species group” (eight spp.) by the shape of their anterior haemal spines, nasal rosette, and premaxillary. Among the four species of Champsodon found in Japan, C. guentheri, C. longipinnis, and C. pantolepis are included in the former group and C. snyderi in the latter, respectively. Four specimens (48.3–88.7 mm standard length) collected from the Okinawa Trough, Amami-oshima Island, Hyuga-nada Sea, and Tosa Bay, southern Japan, were identified as Champsodon sagittus Nemeth, 1994. They are characterized by having normal haemal spines and premaxillary notch (“C. vorax species group”) and the following features: first spine on ventral lachrymal reaching below premaxillary; a row of six pairs of sensory papillae paralleled on dorsal surface of head from snout to interorbital; papillae on nape between posterior of orbits not arranged in an arc; pupil indented ventrally; posterior end of maxillary not beyond a vertical below posterior rim of orbit; 2 + 12–13 gill rakers on first arch; area behind chin naked or with small patch; breast scaled; abdomen and the area between pectoral- and pelvic-fin bases naked; first dorsal fin pale; and body scales sparse around transverse lateral lines. Although C. sagittus has been recorded from India, Andaman Sea, Philippines, Indonesia, and Australia, it has not been reported from Japanese waters. Thus, the present specimens represent not only the first record from Japan but also the northernmost record of the species. The new standard Japanese name, “Yajiri-wanigisu”, is proposed for C. sagittus, in referring to its characteristic body shape.
