Redescription of Bassozetus compressus (Günther 1878), a senior synonym of Bassozetus elongatus Smith and Radcliffe 1913 (Ophidiiformes: Ophidiidae)

Abstract

Re-examination of two deep-sea ophidiid species, Bassozetus compressus (Gunther 1878) and Bassozetus elongatus Smith and Radcliffe in Radcliffe 1913, based on specimens from the West Pacific, Atlantic and Indian Oceans, disclosed no morphologically significant differences amongst those from the West Pacific, including the lectotype of B. compressus and holotype of B. elongatus. Two characters considered to distinguish between the species [pelvic-fin length to standard length (SL) ratio and position of a small process on the sagittal otolith] were found to be invalid, leading to the conclusion that B. compressus is a senior synonym of B. elongatus. The remaining specimens from the Atlantic and Indian Oceans, previously reported as B. compressus or B. elongatus, represented one or more as-yet undescribed species. A detailed redescription of B. compressus is provided on the basis of the West Pacific specimens, the species being distinguishable from all other congeners by the following combination of characters: dorsal-fin rays 118–127; pectoral-fin rays 22–26; oblique scales ca. 18–20; vertebrae 11–13 + 54–58 = 66–69; distance between base of pelvic fin to origin of anal fin 15.8–20.5 % SL; eye diameter 2.0–2.7 times in snout length; a median basibranchial tooth patch; anterior margin of sagittal otolith with a small process, dorsal margin smooth. Two specimens of B. compressus, collected from off Uotsurijima Island, Senkaku Islands and Kumejima Island, Okinawa Islands, represent the first record of this species from Japanese waters.