A new deep-sea shark of the genus Scymnodalatias (Squaliformes, Somniosidae), S. kazenobon sp. nov., is described from the middle Miocene Yatsuo Group in Central Japan. This is the first fossil record of the genus Scymnodalatias from the Miocene strata and its first occurrence in the Pacific region. This discovery seems to indicate that major distributional changes occurred in the Pacific region sometime during the late Cenozoic era.