日本九州西部赤崎组和中甑组始新世哺乳动物：初步结果及其与亚洲陆相哺乳动物分期的对比(英文)

EOCENE MAMMALS FROM THE AKASAKI AND NAKAKOSHIKI FORMATIONS,WESTERN KYUSHU,JAPAN:PRELIMINARY WORK AND CORRELATION WITH ASIAN LAND MAMMAL AGES

日本已知时代最早的古近纪哺乳动物化石产自九州西部熊本县天草(Amakusa)地区始新世地层赤崎(Akasaki)组以及鹿儿岛县甑岛(Koshiki Islands)相当层位的中甑(Nakakoshiki)组。初步研究显示这两个组产出的哺乳动物分异度较高,包括9个目的至少18种动物。赤崎动物群有3种trogosine裂齿类、2种冠齿兽科全齿类、1种等脊貘科奇蹄类、2种dichobunoid偶蹄类、1种下齿兽科踝节类、1种西瓦兔猴科灵长类、1种未定食虫类以及2种可能的梳趾鼠类。中甑动物群包括1种冠齿兽科全齿类、2种小型雷兽科奇蹄类、1种高冠的下齿兽科踝节类、2种啮齿类和1种细齿兽科食肉类。这两个日本哺乳动物组合很接近早-中始新世界线。由于出现了trogosine裂齿类和雷兽,它们的时代要晚于伯姆巴动物群,极有可能与亚洲大陆阿山头期哺乳动物群相当。这两个动物群还包含了在亚洲大陆没有发现过的几个新种,并具有独特的哺乳动物组合。

The earliest known Paleogene mammals from Japan are reported from the Eocene Akasaki Formation,Amakusa area,Kumamoto Prefecture and from the stratigraphically equivalent Nakakoshiki Formation,Koshiki Islands,Kagoshima Prefecture,western Kyushu.Preliminary work has revealed a high diversity of mammals from these formations,including at least 18 different species from nine orders.The Akasaki fauna is represented by three trogosine tillodonts,two coryphodontid pantodonts,an isectolophid perissodactyl,two dichobunoid artiodactyls,a hyopsodontid condylarth,a sivaladapid primate,an unidentified insectivoran,and two possible ctenodactyloid rodents.The mammal fauna from the Nakakoshiki Formation includes a coryphodontid pantodont,two small brontotheriid perissodactyls,a hypsodont hyopsodontid condylarth,two rodents,and a miacid carnivoran.These Japanese mammal assemblages are from near the Early/Middle Eocene boundary,which is previously poorly known in Asia.Given the occurrences of trogosine tillodonts and brontotheriid perissodactyls,the Akasaki and Nakakoshiki faunas are younger than Bumbanian faunas and are most likely correlated with Arshantan faunas on the Asian mainland.The Japanese faunas contain several new taxa unknown from the Asian mainland,and there are unique faunal combinations in the mammal assemblages.