1. Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA
2. Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California 94709, USA
3. Department of Integrative Biology, University of California, Berkeley, California 94720, USA
4. Museum of Paleontology, University of California, Berkeley, California 94720, USA
5. Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, Washington 98195, USA