A latest Eocene (Chadronian) brontothere (Mammalia, Perissodactyla) from the Antero Formation, South Park, Colorado Journal Article uri icon



  • ABSTRACTLate Eocene brontotheres are documented most prevalently from formations in the Great Plains of North America. Here we describe UCM 109045, a mandible and lower dentition of a brontothere recovered from a latest Eocene (Chadronian) locality in the Antero Formation in South Park, Colorado. This is a high-altitude locality in which vertebrate fossils are rare. Lower incisor number and presence of a long postcanine diastema indicate that UCM 109045 does not belong to Megacerops coloradensisLeidy, 1870, by far the most abundant brontothere from the Chadronian North American Land Mammal Age. Instead, UCM 109045 is morphologically most similar to Protitanops curryiStock, 1936, from the early Chadronian of the southwestern United States, and nomen dubium Megacerops primitivusLambe, 1908, from the Chadronian of Saskatchewan, Canada. It is possible that Megacerops kuwagatarhinusMader and Alexander, 1995, is a junior synonym of M. primitivus. If UCM 109045 belongs to Megacerops primitivus (= M. kuwgatarhinus), it would support the hypothesis that only two species of brontothere—M. primitivus (= M. kuwgatarhinus) and M. coloradensis—survived into the latest Eocene. Regardless of its exact identification, the discovery of UCM 109045 in the Antero Formation provides insight into a poorly understood, high-altitude locality in North America from just before brontothere extinction at the Eocene–Oligocene boundary.

publication date

  • June 1, 2021

has restriction

  • closed

Date in CU Experts

  • January 30, 2022 10:58 AM

Full Author List

  • Sweedler RE; Eberle JJ; Mihlbachler MC

author count

  • 3

Other Profiles

International Standard Serial Number (ISSN)

  • 1555-7332

Electronic International Standard Serial Number (EISSN)

  • 1555-7340

Additional Document Info

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  • 37

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