1. Burke Museum and Department of Biology, University of Washington, Seattle, Washington 98195, U.S.A.,
2. Department of Paleobiology, National Museum of Natural History, NHB MRC 121, Washington DC, 20013, U.S.A.
3. Negaunee Integrative Research Center, Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, Illinois 60605, U.S.A.