2.5 Ma B.P.真马快速扩散事件在中国的表现

Expression of the rapid dispersal event of the horse Equus at 2. 5 Ma B. P. in China

通过对甘肃庆阳巴家嘴第四系底部地层中发现的２种真马化石研究得出，其地质年龄为２．５Ｍａ Ｂ．Ｐ，是欧亚大陆发现最早真马化石的地点之一。认为：第四纪初真马从北美向欧亚大陆快速扩散的背景，是全球冰期气候的出现；中国与整个欧亚大陆一样，在一系列年龄为 ２． ５ Ｍａ Ｂ．Ｐ．的地点发现了最早的真马；这些化石显示出种级单元丰富的多样性，即在同一生态区域内常常同时有２种真马共同生活，还有三趾马共生；这是在气候突变条件下动物快速扩散事件产生的适应辐射，为区域叠覆成种理论提供了大型动物成种的证据。

Two fossil species of Equus are discovered from the bottom of the Quaternary strata at Bajiazui in Qingyang, Gansu. Their geological age was 2. 5 Ma B. P. It is one of the earliest localities of Equus in Eurasia. The background of the rapid dispersal of Equus from North America to Eurasia at the Quaternary beginning was the advent of the glacial climate. As in the whole Eurasia, the earliest species of Equus were discovered from a lot of localities at 2. 5 Ma B. P. in China. These fossils showed various diversity of peeles. In the same ecological regions, two species of Equus usually lived togther as well as Hipparion lived in the regions at the same time, which was the adaptive radiation caused by the rapid dispersal event under the sudden climatic change and provided the evidence of large animals for the theory of sympatric speciation.