This study comprises a portion of my doctoral dissertation in the Department of Geosciences, University of Nebraska. During the course of research, I received financial support from the Department of Geosciences, Department of Physics and Astronomy, the Center for Math, Science, and Computer Education, and the University of Nebraska State Museum at the University of Nebraska-Lincoln. Museum travel was partially supported by a Day Dissertation Travel Award from the College of Graduate Studies, University of Nebraska-Lincoln. I thank P. Holroyd (UCMP) for access to and loans of specimens and kind assistance. Special thanks to B. and I. Kraatz and S. Hopkins for hospitality during museum visits.
I thank M. Dawson, J. Storer, and B. Kraatz for fruitful discussions on the morphology of Hesperolagomys and other dentally archaic lagomorphs. I particularly thank an anonymous reviewer for thorough and detailed comments. Critical readings by M. Voorhies and R. Hunt substantially improved early versions of this manuscript.
Research personnel, specimens, and facilities at the University of Nebraska State Museum made this study possible. In particular, R.G. Corner, M. Voorhies, R. Hunt, and B. Bailey provided access to specimens and data in the collections of the Division of Vertebrate Paleontology. I thank T. Labedz and P. Freeman for access to comparative material in the collections of the Division of Zoology. F. Ocampo, M.L. Jameson, and B. Ratcliffe kindly allowed use of photographic facilities of the Division of Entomology, and A. Fox provided assistance and advice on figures. I am indebted to UNSM field crews, including members B. Bailey, G. Brown, R.G. Corner, and M. and J. Voorhies. Specimens needing stabilization and repair were kindly and expertly attended to by G. Brown. This study would not be possible without salvage collections made by the Highway Salvage Paleontology Program, a cooperative project between the Nebraska Department of Roads and the University of Nebraska State Museum.