Abstract
We assessed the taxonomic relationships of an endangered Japanese small salamander, Hynobius hidamontanus Matsui, 1987, and its close relative H. tenuis Nambu, 1991 electrophoretically and found that they were not clearly distinguished from each other. This result, together with available morphological and ecological information, strongly indicates that H. tenuis Nambu, 1991 is a subjective junior synonym of H. hidamontanus Matsui, 1987. By this conclusion, the total distribution range of H. hidamontanus is greatly expanded, but its endangered status and the necessity of its conservation is not be changed since the habitats of this species are fragmented and not continuous. The distribution pattern of this species is interesting from the viewpoint of biogeography.
