The partially preserved left humerus of the Desmostylia (Mammalia) has been collected from the riverbed in Obara, Misaki-cho, Okayama Prefecture in the western Japan. This specimen can be classified to the genus Paleoparadoxia by the following features: the absence of the supratrochlear foramen; the curved disto-lateral border of the shaft in the antero-posterior view; the medio-laterally expanded flat trochlea of
humerus. Moreover, this specimen can be referred to cf. P. media on the basis of its middle-sized dimensions. This is the second occurrence of Palaeoparadoxia from Okayama Prefecture.