Thanks to W.W. and D. Jones for their warm hospitality and enthusiastic support that allowed this project to be such a success. I wish to thank the Western Interior Paleontological Society, the Dallas Paleontological Society, the Graduate Student Assembly of Southern Methodist University, and the Institute for the Study of Earth and Man who helped provide funding for this research. I greatly appreciate the help of L. Ivy of the Denver Museum of Science and Nature, C. Mehling of the American Museum of Natural History, M. Carrano of the National Museum of Natural History, W. Simpson of the Field Museum, and W. Langston Jr. and T. Rowe of the Texas Memorial Museum for access to and assistance with comparative collections.
Additional thanks to L. Jacobs and D. Winkler for their guidance and helpful comments during the preparation of this manuscript. J.A. Wilson, M. Wedel, V. Tidwell, and J. Pittman provided helpful discussions, comments, and suggestions during the course of this research. Thank you to K. Newman for preparation of specimens and J. Diffily and the Fort Worth Museum of Science and History for their efforts with the Jones Ranch project.