1. Division of Geological and Planetary Sciences California Institute of Technology Pasadena CA 91125 USA
2. Department of Geoscience University of Wisconsin Madison Madison WI 53706 USA
3. Department of Geological Sciences University of Colorado Boulder CO 80309 USA
4. Department of Earth and Planetary Sciences Johns Hopkins University Baltimore MD 21218 USA
5. Department of Integrative Biology and Museum of Paleontology University of California Berkeley CA 94720 USA
6. Department of Earth, Atmospheric and Planetary Sciences Massachusetts Institute of Technology Cambridge MA 02139 USA
7. Department of Earth Sciences Dartmouth College Hanover NH 03755 USA
8. Department of Organismic and Evolutionary Biology Harvard University Cambridge MA 02138 USA