Eocene (Duchesnean and earliest Chadronian) brontotheres (Brontotheriidae), Protitanops curryi and cf. Parvicornus occidentalis, from west Texas and Mexico

Abstract

Large horned brontotheres (Brontotheriidae) are abundantly represented in Duchesnean and early Chadronian mammal faunas from the Big Bend Area of West Texas and nearby Mexico. The majority of this material, which until now has never been fully examined, is identified and described. The first brontothere to be named from this region, Menodus bakeri Stovall, 1948, is found to be a nomen dubium. The majority of the fossil material is referrable to Protitanops curryi Stock, 1936. P. curryi, previously only known from a single specimen from the Titus Valley Formation of Southern California, is now recognized in both the Duchesnean and Chadronian land mammal ages of Texas. It occurs in the late Duchesnean Porvenir Local Fauna from the lower part of the Chambers Tuff Formation and from the early Chadronian Little Egypt local fauna from the upper part of the Chambers Tuff Formation and the lower Chisos Formation in the Big Bend National Park Texas. A single specimen from the early Chadronian Rancho Gaitan local fauna of the Prietos Formation of Mexico is also identified as P. curryi. The extensive Protitanops curryi material from Texas and Mexico broadens the biostratigraphic and geographic ranges of this species and provides a more extensive understanding of its morphology and phylogenetic position. Duchesneodus uintensis (Peterson, 1931) has been previously identified with diagnostic material in the Blue Cliff horizon of the lower Chambers Tuff. Duchesneodus was previously identified in the early Duchesnean Skyline Channels of the Devil’s Graveyard Formation, but this material is better identified as cf. Parvicornus occidentalis Mihlbachler and Deméré, 2009. D. uintensis is therefore restricted to the late Duchesnean in Texas. Matthew C. Mihlbachler. Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York 11658, USA. mmihlbac@nyit.edu Donald R. Prothero, Department of Vertebrate Paleontology, Natural History Museum of L.A. County, 900 Exposition Blvd., Los Angeles, California 90007, USA. donaldprothero@att.net MIHLBACHLER & PROTHERO: TEXAS BRONTOTHERIIDAE 2