Abstract
Abstract. We report on the first occurrence of an early horned brontothere in the Brennan Basin Member of the Duchesne River Formation in northeastern Utah. This is the first record of a brontothere from the Brennan Basin Member. Previously, brontotheres have been reported from the higher stratigraphic La Point Member (Duchesneodus uintensis) and the lower stratigraphic Uinta Formation (Sphenocoelus uintensis, Fossendorhinus diploconus, Metarhinus fluviatilis, Metarhinus abbotti, Sthenodectes incisivum, Metatelmatherium ultimum, Protitanotherium emarginatum, Pollyosbornia altidens, Diplacodon elatus). The recovered specimen consists of an upper third molar, which is comparable to the species Diplacodon elatus. The specimen supports the continued presence of brontotheres throughout the deposition of the Duchesne River Formation across the late Uintan to early Duchesnean North American Land Mammal Age. The previous lack of brontotheres within the lower beds of the Duchesne River Formation is likely a result of poor sampling and the relative rarity of fossils from this unit.
Highlights
IntroductionOne of the most characteristic large mammals of the Eocene of North America are brontotheres (order Perissodactyla, family Brontotheriidae), known as titanotheres
One of the most characteristic large mammals of the Eocene of North America are brontotheres, known as titanotheres
In this article we describe the first occurrence of an early horned brontothere in the lower portion of the Brennan Basin Member of the Duchesne River Formation in northeastern Utah
Summary
One of the most characteristic large mammals of the Eocene of North America are brontotheres (order Perissodactyla, family Brontotheriidae), known as titanotheres. Nowhere is the record of brontotheres as diverse as the fossil record obtained from the middle Eocene depositional basins located in northeastern Utah, southwestern Wyoming and northwestern Colorado (Lull, 1905; Cook, 1926; Douglass, 1909; Gregory, 1912; Gunnell and Yarborough, 2000; Hatcher, 1895; Lucas et al, 2004; Lucas and Holbrook, 2004; Lucas and Schoch, 1982; Mader, 2000, 2009a, b, Mihlbacher, 2008, 2011; Osborn, 1889, 1895, 1908, 1913, 1929; Peterson, 1914a, b, 1931, 1934; Riggs, 1912; Stucky et al, 1996) Workers, such as Osborn (1929), viewed the evolution of brontotheres as a stepwise progression, culminating in forms such as the large horned Megacerops. Mihlbachler et al (2004) advocated grouping late Eocene brontotheres from the Chadronian into two species of Megacerops, and a single species of Protitanops, but still left 18 genera of brontotheres in North America during the middle Eocene
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