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Studies on the origin og the fossil vertebrate faunas in the Ryukyu islands ant its international correlation

琉球群岛脊椎动物群化石起源及其国际关联研究

基本信息

批准号：
16540427
负责人：
OTSUKA Hiroyuki
金额：
$ 1.98万
依托单位：
Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16540427/
关键词：
Ryukyu Islands terrestrial vertebrate fossil Pleistocene geographic isolation endemic species relics 移住

项目摘要

Result of study on the paleontological analysis of terrestrial vertebrate fossils 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. 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. So long as result of excavations done in post five years in the Ryukyu islands, five diagnostically different stratigraphic levels containing Late Miocene to latest Pleistocene vertebrate fossils have been delinated in the islands. 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 the latst Okiocene Renzidong fauna in Anhui Province 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 derr (=Cervus (Metacervulus) new species A) arrived to the islands from the continent as a progenitor and its descendants were dflourished in the islands during the Pleistocene together with another cervid and large terrestrial tortoise (=Manouria). These taxa became complately extinct at the end of Pleistocene (ca. 15,000 years B.P.), after the formation of many morphotypes. It can be said that other animal in this assemblage may serve as the progenitors of the present mammals, reptiles, and amphibians living in the Ryukyu Islands.

通过对琉球群岛陆生脊椎动物化石的古生物学分析，对动物从大陆向邻近岛屿迁徙的历史和年代提供了有价值的线索和思考。地质学和古生物学数据表明，琉球群岛的区域已经多次与亚洲大陆相连，每次陆地连接之后，都有来自大陆的特有陆生脊椎动物迁移。经过5年的发掘，琉球群岛划分出5个不同的地层级别，其中包括晚中新世至更新世的脊椎动物化石。在这五个不同的地层级别中发现的化石组合中，第二层（早更新世）的化石组合已知出现在早更新世至中更新世琉球群下面的浅海沉积物中。它们被命名为Imadomari-Akagimata组合，被认为是在第二次陆地连接过程中从安徽省晚中新世人字洞动物群迁移而来的。该组合可能是中新世以后最古老的动物群，可能包括琉球群岛更新世特有陆生脊椎动物群的祖先化石和现存动物群。在今岛-赤俣组合的脊椎动物中，原型鹿（=Cervus（Metacervulus）新种A）作为祖先从大陆来到群岛，其后代在更新世与另一种鹿类和大型陆栖龟（=Manouria）一起在群岛上繁衍。这些分类群在更新世末（约1000年）完全灭绝。15，000年B. P.），在许多形态类型形成之后。可以说，这一组合中的其他动物可能是生活在琉球群岛的哺乳动物、爬行动物和两栖动物的祖先。