Study on the adaptive radiation and extinction of Quaternary terrestrial vertebrates of the Nansei Islands.

琉球群岛陆生脊椎动物化石的地层研究和古生物学分析结果，为琉球大陆动物向邻近岛屿迁徙的历史和时代提供了有价值的线索和参考。迄今为止，在这些岛屿上已经圈定了五个诊断上不同的地层水平，其中包含晚中新世至晚更新世的脊椎动物化石。地质和古生物学资料表明，琉球群岛地区曾多次与亚洲大陆相连，每次陆地连接都伴随着大陆特征的陆生脊椎动物的迁徙。在这5个不同地层中发现的化石组合中，已知2级（早更新世）化石组合出现在早更新世至中更新世琉球群下的浅海沉积中。它们被命名为Imadomari-Akagimata组合，被认为是在第二次陆地连接期间从中国中部地区的安徽上新世人子洞动物群和四川巫山人科动物群迁移而来的。这个组合可能被认为是最古老的后中新世动物群，可能包括更新世化石和琉球群岛现存的特有陆生脊椎动物动物群的祖先。在imadomori - akagimata组合的脊椎动物中，原型鹿（= Cervus (Metacervulus)）在更新世期间与其他第三陆地连接的移民(如Dicrocerus？和大龟（=Manouria Sp.）。岛上另一重要的陆生脊椎动物化石组合与琉球群内最新更新世裂缝和洞穴沉积或同世阶地沉积密切相关（4级）。这些组合被认为是在过去不同的陆地连接时期从亚洲大陆迁移到岛屿的混合动物群。来自这一层的陆生脊椎动物化石包括大型哺乳动物（鹿）和大型陆龟，它们在最新更新世末期灭绝。然而，包括哺乳动物、两栖动物和爬行动物在内的其他动物的后代仍然生活在这些岛屿上，形成了特有的岛屿特有动物群。少

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 … More 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