Twin Buttes (Lower Bridger) (Eocene of the United States)
Where: Sweetwater County, Wyoming (41.7° N, 109.0° W: paleocoordinates 45.6° N, 95.1° W)
• coordinate based on political unit
When: lower Member (Bridger Formation), Bridgerian (50.3 - 46.2 Ma)
Environment/lithology: terrestrial
Primary reference: C. L. Gazin. 1976. Mammalian Faunal Zones of the Bridger Middle Eocene. Smithsonian Contributions to Paleobiology 26:1-25 [J. Alroy/J. Alroy/J. Marcot]more details
PaleoDB collection 16448: authorized by John Alroy, entered by John Alroy on 26.03.1995, edited by Jonathan Marcot
Creative Commons license: CC BY (attribution)
Taxonomic list
• Twin Buttes records of unclear status: "Notharctus robustior" Robinson 1957: supposedly upper Bridger, but probably lower Bridger based on Gazin's discussion of Smilodectes; could be N. pugnax or perhaps N. tenebrosus based on chart Patriofelis ferox Wortman 1894: "Twin Buttes" Limnocyon verus Thorpe 1923a: level not stated Orohippus progressus type if from an unknown level at Twin Buttes according to Gazin but from "Hor. C" according to Granger 1908; see also Kitts 1957b, who implies that O. progressus and O. sylvaticus are present in Bridger C sensu Gazin Palaeosyops robustus Osborn 1929: from "C or "D" Telmatherium cultridens Osborn 1929: "C or D" Mesatirhinus megarhinus Osborn 1929: level not stated "Homogalax bridgerensis" Troxell 1922b: type, level not stated and Isectolophus latidens ranges throughout section according to Gazin Hyrachyus eximius Wood 1934: "Twin Buttes... hence Bridger C or D" and "South Twin Buttes"; referred specimen of "H. princeps"; all are possibly from Bridger B based on revised stratigraphy of Gazin Hyrachyus modestus and type of "Ephyrachyus cristalophus" of Wood 1934: both from "Bridger C3" and based on Wood's map it is not clear whether this is above or below the Sage Creek White Layer "agreeing in size with" Homacodon sp. Sinclair 1914: Bridger "C1"; specimen not mentioned by West 1984, and probably from Bridger B based on stratigraphy of Gazin 1976 "Lophiohyus alticeps" type is from an unknown level; see also Sinclair 1914
Show authors, comments, and common names
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Palaearctonyx meadi n. sp.
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Machaeroides eothen2 Matthew 1909 creodont "low exposures, probably of Bridger 'C', immediately to the north of Twin Buttes" (Bridger B sensu Gazin 1976)
Patriofelis ulta Leidy 1870 creodont from Bridger B, not "very low in Bridger C" contra Gazin 1957; specimen from "Twin Buttes" also mentioned by Wortman 1894
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Helohyus plicodon4 Marsh 1872 even-toed ungulate Bridger B "North of Twin Buttes, near conical butte"
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Orohippus progressus n. sp.3
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Smilodectes gracilis Marsh 1871 primate specimens said by Robinson 1957 to be from the "upper Bridger"
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Uintatherium anceps5 Marsh 1871 uintathere includes type of "U. robustum" from "Bridger C on or near the northeast base of Twin Buttes"; referred specimen from "northeast flank of Twin Buttes, probably Bridger D"
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