1. Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, USA.
2. Department of Geological Sciences, Michigan State University, East Lansing, MI 48824, USA.
3. Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA.
4. Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA.
5. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.