Article · Wikipedia archive · Last revised Jun 6, 2026

Uintan

The Uintan North American Stage is the North American faunal stage, typically set from 46,3 to 40,1 million years before present. The Uintan Stage is a key part of the North American Land Mammal Age. In the Uinta Basin, a thriving subtropical ecosystem was formed at around 46.0 million years ago. It falls within the Eocene epoch, preceded by the Bridgerian and followed by the Duchesnean NALMA stages. The Uinta Formation is a key piece of this geologic stage. Mammalian sabretooths evolved and became dominant predators in the now-Western United States. These included Apataelurus, Diegoaelurus, and Machaeroides.

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Uintan
Chronology
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←
←
First Antarctic permanent ice-sheets1
←
Subdivision of the Paleogene according to the ICS, as of 2024.2
Vertical axis scale: Millions of years ago
Formerly part ofTertiary Period/System
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Upper boundary definition candidatesCalcareous nannofossil near LAD of the Haptophyte Reticulofenestra reticulata
Upper boundary GSSP candidate section(s)Contessa highway section, Gubbio, Central Apennines, Italy

The Uintan North American Stage is the North American faunal stage, typically set from 46,3 to 40,1 million years before present.3 The Uintan Stage is a key part of the North American Land Mammal Age. In the Uinta Basin, a thriving subtropical ecosystem was formed at around 46.0 million years ago. It falls within the Eocene epoch, preceded by the Bridgerian and followed by the Duchesnean NALMA stages.4 The Uinta Formation is a key piece of this geologic stage. Mammalian sabretooths evolved and became dominant predators in the now-Western United States. These included Apataelurus, Diegoaelurus, and Machaeroides.56

Substages

Uinta Formation, Uintah County, Utah, United States source ↗

The Uintan is considered to be contained within the Lutetian sharing the upper boundary and contains the following substages:

  • Late/Upper Uintan: Lower boundary source of the base of the Uintan (approximate).
  • Early/Lower Uintan: Upper boundary source of the base of the Duchesnean (approximate)
References

References

  1. Zachos, James C.; Kump, Lee R. (May 2005). "Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene". Global and Planetary Change. 47 (1): 51–66. Bibcode:2005GPC....47...51Z. doi:10.1016/j.gloplacha.2005.01.001. Retrieved October 2, 2025.
  2. "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. December 2024. Retrieved October 23, 2025.
  3. Hodnett, John-Paul M.; Welsh, Edward T.; Santucci, Vincent L.; Tweet, Justin S. (2022). "A Middle Eocene brontothere (Mammalia; Perissodactyla; Brontotheriidae) from Yellowstone National Park, Wyoming". FOSSIL RECORD 8. New Mexico Museum of Natural History and Science. p. 211.
  4. "GeoWhen Database - Uintan". timescalefoundation.org. Retrieved 2025-06-01.
  5. Zack, Shawn P. (2019-11-22). "The first North American Propterodon (Hyaenodonta: Hyaenodontidae), a new species from the late Uintan of Utah". PeerJ. 7 e8136. doi:10.7717/peerj.8136. hdl:10150/636415. ISSN 2167-8359. PMC 6876642.
  6. County~tom@tskelly.gardnerville.nv.us, Thomas S. Kelly~Natural History Museum of Los Angeles; History~pmurphey@sdnhm.org, Paul C. Murphey~San Diego Museum of Natural (2016-07-14). "Mammals from the earliest Uintan (middle Eocene) Turtle Bluff Member, Bridger Formation, southwestern Wyoming, Part 1: Primates and Rodentia". Palaeontologia Electronica. doi:10.26879/586. Retrieved 2025-06-01.