A new species of deep-water tonguefish (Pleuronectiformes: Cynoglossidae: Symphurus) from the western North Pacific Ocean.

A new species of symphurine tonguefish, Symphurus oxyrhynchus sp. nov., is described from two specimens captured in deep waters (718-852 m) off Taiwan and Japan. This new species is distinguished from congeners by the following combination of characters: predominant 1-2-2-1-2 pattern of interdigitation of dorsal pterygiophores and neural spines, 14 caudal-fin rays, 93 dorsal-fin rays, 80-81 anal-fin rays, 9 abdominal and 52 total vertebrae, 5 hypurals, small eye (7.5-8.0 % HL) with relatively large pupil (78-85% ED), moderately large scales (87-89 scales in longitudinal series, 31 scales in transverse row), snout square and projecting anteriorly, ocular side uniformly yellow to dark brown with intense pigmentation on body areas overlying dorsal- and anal-fin pterygiophores, outer surface of opercle on both sides bluish black, general background coloration shared the same coloration in blind side, including more intense on body areas overlying dorsal and anal pterygiophores. Symphurus oxyrhynchus sp. nov. is a rare species, only two specimens were retrieved by research vessels. This study provides formal description of this unique new species based on these two specimens. Further investigations and expeditions are necessary for better understanding of the biodiversity of tonguefishes in the western Pacific.