Florissant mammal bed (Eocene of the United States)

Where: Teller County, Colorado (38.9° N, 105.3° W: paleocoordinates 40.4° N, 97.0° W)

• coordinate based on political unit

When: Florissant Formation, Chadronian (37.2 - 33.9 Ma)

• said to be Chadronian

•there are four 40Ar/39Ar dates on sanidine from three levels higher in the section, with overlapping errors: the first one up is from the "top of the caprock conglomerate" and is 34.03 +/- 0.09 Ma, and the weighted mean average of all four is 34.07 +/- 0.10 Ma; the entire formation is of reversed polarity, and the dates match it with Chron C13r (Prothero and Sanchez 2004)

•"most of" the reported material comes from a single bed in the "lower mudstone unit" that is shown in a section diagram to be about 1 m thick and conglomeratic, and there is an unpublished micromammal fauna from somewhere in the same unit (Prothero and Sanchez 2004)

• bed-level stratigraphic resolution

Environment/lithology: fluvial; conglomerate

Size class: macrofossils

Primary reference: E. Evanoff and P. M. Detoledo. 1999. Fossil mammals and biting insects from the upper Eocene Florissant formation of Colorado. Journal of Vertebrate Paleontology 19(3):43A [J. Alroy/J. Alroy/J. Ju]more details

Purpose of describing collection: biostratigraphic analysis

PaleoDB collection 16968: authorized by John Alroy, entered by John Alroy on 13.10.1999

Creative Commons license: CC BY (attribution)

Taxonomic list

Mammalia
 Perissodactyla - Brontotheriidae
Brontotheriidae indet. Marsh 1873 brontothere
 Perissodactyla - Rhinocerotidae
Rhinocerotidae indet. Gray 1821 rhinoceros
 Perissodactyla - Equidae
Mesohippus sp. Marsh 1875 anchitheriine horse
 Ungulata - Merycoidodontidae
Merycoidodon sp. Leidy 1848 oreodont
 Ungulata - Leptomerycidae
? Leptomeryx sp. Leidy 1853 ruminant
 Theriiformes - Peradectidae
"Herpetotherium huntii" = Nanodelphys hunti
"Herpetotherium huntii" = Nanodelphys hunti Cope 1873 metatherian