Abstract
Abstract. Inioidea, which consists of Iniidae and Pontoporiidae, includes only four extant species, all of which occur in South America. Inioids were, however, more diversified and widely distributed in the past, starting from the late middle Miocene, as recorded from the eastern Pacific, North and South Atlantic, North Sea and the riverine systems of South America. In this paper, the author describes a new extinct inioid, Awadelphis hirayamai gen. et sp. nov. (WU SILS G 408), from the uppermost Miocene Senhata Formation (6.3–5.7 Ma) of Chiba, central Japan. Morphological cladistic analysis supports placement of this new taxon within the Inioidea. The new species is characterized by a right premaxillary eminence with a pronounced overhang on the right maxilla and a short zygomatic process of the squamosal. This is the first fossil record of an inioid not only from Japan but also from the North Pacific. The discovery of this new taxon considerably extends the paleobiogeographic range of inioids, and indica...
Published Version
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