1. Key Laboratory for Evolution of Past Life and Environment in Northeast Asia, Ministry of Education, Changchun 130026, Jilin, China
2. Research Center of Palaeontology and Stratigraphy, Jilin University, Changchun 130026, Jilin, China
3. Departments of Geology and Biology, Indiana University, Bloomington, Indiana 47405, USA
4. Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA