Geohistorical succession of the Japanese Cenozoic shallow-water benthic faunas and their relation to the Late Shallow-Tethys fauna

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The Japanese Cenozoic shallow-water faunas have been considered to a representative of the Indo-West Pacific element which was originated in the shallow Tethys regions. However, recent studies suggested that there are some East-Pacific element in the Japanese Cenozoic. The present study is a trial to consider the geohistorical proccess of birth of the Japanese Cenozoic shallow-water faunas from a zoogeographic oint of view. The following outlines are summerized mainly based on comparative studies on shallow-water elements between the Japanese and Tethys regions;1. Related genera and species between the two regions are recognizable during the Mesozoic2. There are some elements in common between the two at the Paleogene although data is insufficient3. At the early Middle Miocene, there are some common warm-water elements in the area from Java, Philippines through Southwest Japan to southern Hokkaido4. After the early Middle Miocene, there is no element in common between the two5. At the early Middle Miocene, there are some. characteristic elements restricted in the Taiwan-Yaeyama regionThese tentative conclusions from paleozoogeographic point of view are examined from the paleogeographic, paleoceanographic and paleoclimatic studies. Consequently, it can be said that the proto-Kuroshio Current first appeared at the early Miocene corresponding to form a zoogeographic barrier between the Indian and Westerm Pacific oceans. Such paleogeographic and paleoceanographic backgrounds maight be permitted a wide invasion of Miocene warm-water elements to the North, Succeed this event, faunal endemism of the Late Miocene Japanese shallow-water fauna maight be progressed corresponding to cooling event of about 5 ゜C mean temparature decrease which is estimated by paleobotanical studies.