1. Department of Vertebrate Paleontology, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles CA 90007, USA;
2. Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, PR China;
3. School of Dentistry, University of California, Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA;
4. Beijing Natural History Museum, 126 Tian Qiao Nan Street, Dongcheng District, Beijing, 100050, PR China