1 Biology and Paleo Environment, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964.
2 School of Geosciences, University of the Witwatersrand, Johannesburg 2017, South Africa.
3 Department of Geosciences, Princeton University, Princeton, NJ 08544.
4 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Nanjing 210008, China.
5 Earth and Planetary Sciences Rutgers University, Piscataway, NJ 08854.
6 Department of Paleoichthyology and Paleoherpetology, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China.