1. State Key Laboratory of Palaeobiology and Stratigraphy; Nanjing Institute of Geology and Palaeontology; Chinese Academy of Sciences; Nanjing 210008 China
2. Department of Earth Sciences; Durham University; Durham DH1 3LE UK
3. Department of Earth Sciences; University of Western Ontario; London Ontario N6A 5B7 Canada
4. Institute of Paleontology and Paleoenvironment; School of Earth and Space Sciences; Peking University; Beijing 100871 China
5. Department of Geography and Geology; University of Copenhagen; Øster Voldgade 10 DK-1350 Copenhagen K Denmark
6. Natural History Museum of Denmark (Geological Museum); University of Copenhagen; Øster Voldgade 5-7 DK-1350 Copenhagen K Denmark