1. Department of Paleobiology, NMNH Smithsonian Institution, Washington, DC 20560, USA
2. Kentucky Geological Survey, University of Kentucky, Lexington, Kentucky 40506, USA
3. Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104, USA
4. Illinois State Geological Survey, University of Illinois, 615 E. Peabody Drive, Champaign, IL 61820, USA
5. New Mexico Museum of Natural History and Science, 1801 Mountain Road NW, Albuquerque, NM 87104, USA