1. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, and Center for Excellence in Life and Paleoenvironment Chinese Academy of Sciences Nanjing 210008 China
2. Department of Geological Science University of Saskatchewan Saskatoon Saskatchewan S7N 5E2 Canada
3. Department of Earth and Environmental Sciences University of Ottawa Ottawa Ontario K1N 6N5 Canada
4. Paleontology and Stratigraphy, School of Earth and Space Sciences Peking University Beijing 100871 China
5. University of Chinese Academy of Sciences Beijing 100049 China