The Uintan North American Stage is the North American

faunal stage In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by conven ...

, typically set from 46,200,000 to 42,000,000 years before present lasting 4.2 million years. The Uintan Stage is a key part of the

North American Land Mammal Age The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals (or stages when ref ...

. In the

Uinta Basin The Uinta Basin (also known as the Uintah Basin) is a physiographic section of the larger Colorado Plateaus province, which in turn is part of the larger Intermontane Plateaus physiographic division. It is also a geologic structural basin in ...

, a thriving subtropical ecosystem was formed at around 46.0 million years ago. It falls within the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

epoch, preceded by the

Bridgerian The Bridgerian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 50,300,000 to 46,200,000 years BP lasting . It is usually c ...

and followed by the

Duchesnean The Duchesnean North American Stage on the geologic timescale is a North American Land Mammal Age (NALMA), with an age from 42 to 38 million years BP, representing . It falls within the Eocene epoch. The Duchesnean is preceded by the Uintan and f ...

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 ''Apataelurus'' ("false cat") is an extinct genus of saber-toothed placental mammals from the extinct family Oxyaenidae, that lived in North America and East Asia from the early to middle Eocene, 48-40 million years ago. This genus was defined b ...

'', ''

Diegoaelurus ''Diegoaelurus'' ("San Diego's cat") is an extinct genus of placental mammals from the extinct subfamily Machaeroidinae within extinct family Oxyaenidae. This genus contains only one species ''Diegoaelurus vanvalkenburghae'', which was found in ...

,'' and ''

Machaeroides ''Machaeroides'' ("dagger-like") is an extinct genus of sabre-toothed predatory placental mammals from extinct subfamily Machaeroidinae within extinct family Oxyaenidae, that lived in North America (Wyoming) from the early to middle Eocene. Des ...

''.

Substages

The Uintan is considered to be contained within the

Lutetian The Lutetian is, in the geologic timescale, a stage (stratigraphy), stage or age (geology), age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it ...

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

(approximate)

References

Eocene life Eocene animals of North America {{geochronology-stub