1. Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
2. Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
3. Nanoscale Characterization and Fabrication Laboratory, Institute for Critical Technology and Applied Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
4. State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 210008, China.