Ocadia nipponica, a new species of aquatic turtle (Testudines: Testudinoidea: Geoemydidae) from the Middle Pleistocene of Chiba Prefecture, central Japan

A new species of the genus Ocadia (Testudines; Testudinoidea; Geoemydidae), O. nipponica, is described on the basis of a nearly complete skeleton from the Middle Pleistocene Kiyokawa Formation of the Shimosa Group at Sodegaura City, Chiba Prefecture, central Japan. O. nipponica is distinguished from O. sinensis (Gray) by its more extensive secondary palate, smoother shell surface, narrower second and third vertebral scutes, and larger size (carapace up to 33 cm long). Considering that the living species O. sinensis is distributed in the coastal area of eastern to southeastern Asia in subtropical to tropical climates, the new fossil species may have been thrived in warmer paleoclimatic conditions for the Japanese Islands in the Pleistocene age than hitherto have been estimated on the basis of floral evidences.