1. Institute of Paleontology, Shenyang Normal University, Shenyang 110034, People's Republic of China
2. School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
3. Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, People's Republic of China
4. School of Geosciences, University of Edinburgh, Edinburgh EH9 3JW, UK
5. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, People's Republic of China
6. Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9