Vertebrate faunas 49 to 36 million years ago and additions to the species of Leptoreodon (Mammalia: Artiodactyla) found in Texas

ABSTRACT A comparison of parts of the fossil mammalian faunas of southern California and western Texas with those of the northern Rocky Mountain states, combined with K/Ar dates, permits a division of the Duchesnean land-mammal age into early and late subages. The early Duchesnean fauna is more closely related to the Uintan and the late Duchesnean fauna is more closely related to that of the Chadronian. Leptoreodon major, L. pusillus, L. edwardsi, and L. leptolophus are recognized in late Eocene faunas of western Texas. A lower jaw fragment of L. leptolophus from the Laredo Formation, Claiborne Group, of the Texas Coastal Plain is described.