1. 1 Key Laboratory of Zoological Systematics and Evolution Institute of Zoology, Chinese Academy of Sciences Beichen West Road, Chaoyang District Beijing 100101 China
2. 2 Department of Anthropology The Field Museum Chicago, Illinois 60605 USA
3. 3 Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences Beijing 100044 China
4. 4 Email: yangqs@ioz.ac.cn