Middle Miocene ostracods from the Fujina Formation, Shimane Prefecture, Southwest Japan and their paleoenvironmental significance

Thirty-five ostracod species belonging to 18 genera are recognized from the Middle Miocene Fujina Formation (ca. 14-12 Ma), 3km southwest of Matsue City, Shimane Prefecture, Japan. Most of these species are part of the recent Japan Sea proper water fauna; they are also classified into 4 categories, circumpolar, cryophilic, endemic cool-temperate and temperate species. These ostracod assemblages indicate that the Fujina Formation was deposited under a cold-water environment. Ten new species, Ambtonia shimanensis, A. takayasui, Acanthocythereis fujinaensis, A. izumoensis, Cluthia tamayuensis, C. subjaponica, Kotoracythere tsukagoshii, Laperousecythere ikeyai, Palmoconcha irizukii, and Robertsonites yatsukanus are described.