1. Dinosaur Institute, Natural History Museum of Los Angeles County, 900 Exposition Blvd., Los Angeles, California 90007, U.S.A.,
2. Department of Earth and Environmental Sciences, University of Minnesota, 116 Church Street SE, Minneapolis, Minnesota 55455, U.S.A.,
3. Department of Biology and Burke Museum, University of Washington, Seattle, Washington 98195, U.S.A.,
4. Department of Geology, Augustana College, 639 38th Street, Rock Island, Illinois 61201, U.S.A.,