Early Tertiary Vertebrate Faunas, Vieja Group and Buck Hill Froup, Trans-Pecos Texas: Photoceratidae, Camelidae, HyperTragulidae

Upper and lower dentitions of Leptoreodon marshi from the late Eocene are described. Leptoreodon is placed in the Protoceratidae and the family Leptomerycidae abandoned. A new genus of late Eocene protoceratid is described and believed to be ancestral to Heteromeryx. An associated upper and lower dentition of Heteromeryx is described for the first time. Pseudoprotoceras is synonymized with Poabromylus and a new species described. Oromeryx and Eotylopus are identified from the Chadronian. A new and primitive species of Poebrotherium shows closer relationship to Protylopus than Poebrodon. A new genus of camel id in the Chadronian thought to be related to Poebrodon is described. A new species of Leptomeryx is described and Leptomeryx is placed in the Hypertragulidae. Hypisodus is reported from west Texas for the first time. Full selenodonty in the upper molars appears earliest in the Protoceratidae and in a family of camelids which includes Poebrodon. Full selenodonty in Poebrotherium and Leptomeryx is not achieved until the late Chadronian.