Bulletin of the Mizunami Fossil Museum

Bulletin of the Mizunami Fossil Museum Vol. 50, No. 3 Research reports of the “Paleoparadoxiid Mizunami-Kamado specimen”

Identification of a nearly complete skeleton of a paleoparadoxiid (Mammalia: Desmostylia) from the Lower to Middle Miocene Shukunohora Formation, Mizunami Group in Kamado Town, Mizunami City, central Japan

Naoki Kohno

Published: 2024/3/29   Page: 43–50

A nearly complete paleoparadoxiid skeleton, i.e., MFM 18130, from the Lower to Middle Miocene Shukunohora Formation, Kamado Town, Mizunami City, Gifu Prefecture, Japan, is identified based on the cranial, mandibular and postcranial characters. MFM 18130 has such unique characters as pres-ence of the postzygomatic foramen on the skull, collumnar cusps on the molars, paired sterna, strongly twisted tibia and astragalus, and therefore, belongs in the family Paleoparadoxiidae of the Desmostylia. In addition, MFM 18130 has some derived characters that are possessed in the genera Archaeopara-doxia and Neoparadoxia such as dorsally high suprraoccipital process and shortened zygomatic pro-cess. On the contrally, the conditions of these characters are opposite in the monospecific Paleopara-doxia. In addition, the presence of the hypoconulid on M/3 is different from that of the monospecific Archaeoparadoxia, and the body size is much smaller than any species of Neoparadoxia. Accordingly, MFM 18130 is provisionally identified as Paleoparadoxiidae genus and specis undetermined.