1. Department of Geosciences, Pennsylvania State University University Park Pennsylvania 16802 USA
2. Department of Biology University of Washington Seattle Washington 98105 USA
3. Department of Paleobotany and Paleoecology Cleveland Museum of Natural History Cleveland Ohio 44106 USA
4. Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography University of California San Diego La Jolla California 92093 USA