| Project/Area Number |
11640464
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Kagoshima University |
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Principal Investigator |
OTSUKA Hiroyuki Department of Earth & Enviromental Sciences, Faculty of Science, Kagoshima University, Professor, 理学部, 教授 (50041223)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Toshio Dating and Material Research Center, Nagoya University, Professor, 年代測定資料研究センター, 教授 (10135387)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Nansei islands / vertebrate fossils / Pleistocene / adaptive radiation / endemics / speciation / extinction / Watase line / シカ類化石 |
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| Research Abstract |
Results of the studies on the stratigraphic levels and the paleontological analysis of terrestrial vertebrates fossil in the Ryukyu islands furnish valuable clues and considerations as to the history and age of animal migration from the continent to its neighboring islands. To date, five diagnos-tically different stratigraphic levels containing Late Miocene to latest Pleistocene vertebrate fossils have been delineated in the islands. Geological and paleontological data suggest that the area of the Ryukyu Islands has been repeatedly connected to the Asiatic Continent and each land connection has been followed by migration of characteristic terrestrial vertebrates from the continent. Among the fossil assemblages found in these five different stratigraphic levels, those from Level 2 (Early Pleistocene) are known to occur in shallow marine deposits underlying the Early to Middle Pleistocene Ryukyu Group. They are named Imadomari-Akagimata assemblage and are considered to be immigrants from
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neither the latest Pliocene Renzidong fauna in Anhui Province nor the Wushan hominid fauna in Sichuan Province, both located in Central China, during the second land connection. This assemblage may be regarded as the oldest post-Miocene fauna and might include the ancestors of the Pleistocene fossil and living endemic terrestrial vertebrate faunas of the Ryukyu islands. Among the vertebrates in the Imadomari-Akagimata assemblage, the archetypal deer (= Cervus (Metacervulus) flourished in the islands during the Pleistocene, together with other immigrants of the third land connection such as Dicrocerus? sp. and large tortoise (=Manouria Sp.).
Another important species of fossil assemblage of terrestrial vertebrates in the islands is closely associated with the latest Pleistocene fissure and cave deposits developed within the Ryukyu Group or coeval terrace deposits (Level 4). These assemblages are considered to be mixed faunas that migrated from the Asiatn mainland to the islands during different periods of land connection in the past. Terrestrial vertebrate fossils from this level include large mammal (deer) and giant land tortoises that became extinct at the end of the latest Pleistocene. However, decendants of other animals including mammals, amphibians and reptiles, are still living in the islands forming characteristic insular endemic fauna. Less
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