1. R. W. Graham, M. A. Graham, E. K. Schroeder, and R. S. Toomey III are at Research and Collections Center, Illinois State Museum, 1011 East Ash, Springfield, IL 62703, USA.
2. E. L. Lundelius Jr., Department of Geological Sciences, University of Texas, Austin, TX 78712, USA.
3. E. Anderson, Denver Museum of Natural History, Denver, CO 80205, USA.
4. A. D. Barnosky, Mountain Research Center, Montana State University, Bozeman, MT 59715, USA.
5. J. A. Burns, Provincial Museum of Alberta, Edmonton, Alberta, Canada T5N 0M6.
6. C. S. Churcher, Department of Zoology, University of Toronto, Toronto, Ontario, Canada M5S 1A1.
7. D. K. Grayson, Department of Anthropology, University of Washington, Seattle, WA 98195, USA.
8. R. D. Guthrie, Department of Biology, University of Alaska, Fairbanks, AK 99701, USA.
9. C. R. Harington, Earth Sciences Section (Paleobiology), Canadian Museum of Nature, Ottawa, Ontario, Canada K1P 6P4.
10. G. T. Jefferson, Anza-Borrego Desert State Park, 200 Palm Canyon Drive, Borrego Springs, CA 92004, USA.
11. L. D. Martin, Museum of Natural History, University of Kansas, Lawrence, KS 66045, USA.
12. H. G. McDonald, Hagerman Fossil Beds National Monument, Post Office Box 570, Hagerman, ID 83332, USA.
13. R. E. Morlan, Canadian Museum of Civilization, Post Office Box 3100 Station B, Hull, Quebec, Canada J8X 4H2.
14. H. A. Semken Jr., Department of Geology, University of Iowa, Iowa City, IA 52242, USA.
15. S. D. Webb, Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA.
16. L. Werdelin, Department of Paleozoology, Swedish Museum, Box 50007, S-104 05 Stockholm, Sweden.
17. M. C. Wilson, Department of Archaeology, Simon Fraser University, Burnaby, BC, Canada V5A 1S6.