1. Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, MRC 121, P.O. Box 37012, Washington, D.C. 20013-7012, U.S.A.,
2. Department of Geoscience, University of Wisconsin–Madison, 1215 W. Dayton Street, Madison, Wisconsin 53706, U.S.A.,
3. School of Liberal Arts and Sciences, Columbia College Chicago, 600 S. Michigan Avenue, Chicago, Illinois 60605, U.S.A.,