SYSTEMATICS OF THE MIDDLE EOCENE (UINTAN-DUCHESNEAN) PROTOCERATID LEPTOREODON

The primitive hornless protoceratid Leptoreodon occurs widely in the Uintan (Utah, California, Saskatchewan, Texas, Wyoming, and Montana) and briefly in the Duchesnean (California and Texas). Large new collections of Leptoreodon have been made in the middle Eocene rocks of San Diego County, California, and allow for a re-examination of the systematics of the genus. Early Uintan localities (Friar’s and Devil’s Graveyard Formations, Uinta B) yield the type species, L. marshi, the largest species, L. major, and the diminutive species L. pusillus. Late Uintan localities (Mission Valley, upper Santiago, lower Sespe, Cypress Hills, Devil’s Graveyard, and Laredo Formations, Wind River and Sage Creek Basins, Uinta C) yield more of L. pusillus, L. marshi, and L. major, the somewhat rare L. edwardsi, the more common L. stocki, and a new small species, L. golzi, morphologically similar to L. leptolophus but distinctly smaller in size. Duchesnean localities (Laredo, lower Sespe, upper Santiago, Cypress Hills Formations) yield the somewhat rare species L. leptolophus and remnants of L. golzi, L. pusillus, and L. stocki. We attempted to combine several species, but statistical analysis did not support any of these hypotheses. Thus we must come to the conclusion that all seven species are valid. Although the sample size of good skulls is still small, there is slight sexual dimorphism in the upper canines. This is consistent with the pattern in many other hornless artiodactyls, such as tragulids and moschids.