eng Science and Education Publishing American Journal of Zoological Research 2373-6771 2023-10-24 8 1 6 26 10.12691/ajzr-8-1-2 AJZR2023812 article Hirotaka Sugawara 1 Takayuki Iwata 2 Jun-ichi Naito 3 Masaru Yamada 4 Kazuto Onomura 5 Masahiro Nagano masanagano@oita-u.ac.jp 6 Faculty of Science and Technology, Kochi University, Akebonocho 2-5-1, Kochi City, Kochi Prefecture, 780-8520, Japan Yasugi City Hall, Yasugicho 878-2, Yasugi City, Shimane Prefecture, 692-8686, Japan Wildlife Conservation Promotor of Hiroshima Prefecture, Motomachi 10-52, Naka Ward, Hiroshima City, Hiroshima Prefecture, 730-8511, Japan Nature Conservation Promotor of Okayama Prefecture, Daiku 1-2-3, Kita Ward, Okayama City, Okayama Prefecture, 700-8554, Japan Independent Researcher, Ato-kanekami 3441-1, Yamaguchi City, Yamaguchi Prefecture, 759-1601, Japan Faculty of Science and Technology, Oita University, Dannoharu 700, Oita City, Oita Prefecture, 870-1192, Japan Four new species of Hynobius are described from the Chugoku Mountains, Japan. The complex of Hynobius utsunomiyaorum, including Hynobius hidamontanus, was divided into six groups based on morphological and molecular analyses. The Mt. Sanbe and Kitahiroshima, Mt. Mengame, northern central Okayama, and northeastern Okayama groups of H. utsunomiyaorum were described as Hynobius pseudoutsunomiyaorum sp. nov., Hynobius mengamemontanus sp. nov., Hynobius sakuhokumontanus sp. nov., and Hynobius ushiromontanus sp. nov., respectively. Molecular analyses of samples from across the entire distribution range of H. utsunomiyaorum revealed that H. utsunomiyaorum (including H. hidamontanus) has six genetic groups. Morphological analyses suggested that males of the four new species are morphologically different from H. utsunomiyaorum according to specific characters. The distribution of the new species, as well as those of H. utsunomiyaorum and H. hidamontanus, were determined and compared to indicate the isolation among the species. Although further sampling from the northern part of Okayama Prefecture is needed to determine the distribution ranges of H. utsunomiyaorum and H. sakuhokumontanus sp. nov., our results suggest that the distribution area of true H. utsunomiyaorum is mainly limited to the central area of the Chugoku Mountains. http://pubs.sciepub.com/ajzr/8/1/2/ajzr-8-1-2.pdf Chugoku Mountains conservation cryptic species geographic isolation Hokuriku District mitochondrial DNA