Abstract
Two isolated teeth belonging to the subfamily Halitheriinae (Carus, 1868) are described from the Late Miocene Aoso Formation of Sendai Prefecture, northern Japan. One of the teeth, the left upper third molar, is relatively large in size and has a centrally located hypoconule that is coalesced with a reduced hypocone. These characters are typical of somewhat derived halitheriine dugongids so far known in the eastern Pacific and Atlantic realm. This record is the first occurrence of the subfamily Halitheriinae from the western Pacific region and provides evidence that the halitheriine had been distributed in the Late Miocene age western Pacific Ocean before the hydrodamalines migrated from the eastern to the western North Pacific. It indicates a more complicated migratory and evolutionary history of the Pacific dugongids than previously known in the Pacific Ocean.
