Middle Park (Upper) (Miocene to of the United States)

Also known as USGS D520

Where: Grand County, Colorado (40.2° N, 106.1° W: paleocoordinates 40.9° N, 102.5° W)

• coordinate based on political unit

• small collection-level geographic resolution

When: upper Member (Troublesome Formation), Hemingfordian to Hemingfordian (20.4 - 13.6 Ma)

• JA: Hemingfordian to Barstovian based on AEO results

Environment/lithology: terrestrial; lithology not reported

Reposited in the USGS

Primary reference: G. E. Lewis. 1969. United States Geological Survey Professional Paper 650-B [J. Alroy/J. Alroy]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 18979: authorized by John Alroy, entered by John Alroy on 27.09.1993

Creative Commons license: CC BY (attribution)

Taxonomic list

• dated at 12.8 +/- 2.0 Ma FT zircon, 10.9 +/- 1.4 Ma FT glass: Izett 1975
additional dates of 13.3 +/- 0.6 Ma, 13.5 +/- 0.4 Ma (FT on zircon: avg = 13.4 Ma): Kelly and Lander 1988
apparently entirely from "loc. 4" of Izett 1975 and NOT from Granby (see); this is in SE 1/4 sec 24 T1N R80W and definitely includes USGS D520 of Izett and Lewis 1969
upper part of "orange-gray siltstone and sandstone unit"
Mammalia
 Rodentia - Mylagaulidae
Mylagaulidae indet. Cope 1881 rodent
"Mylagaulus laevis or M. vetus"
 Perissodactyla - Chalicotheriidae
Chalicotheriidae indet.1 Gill 1872 chalicothere
 Perissodactyla - Rhinocerotidae
Peraceras cf. profectum1 Matthew 1899 rhinoceros
 Perissodactyla - Equidae
Equidae indet.2 Gray 1821 horse
Equinae indet.1 Steinmann and Döderlein 1890 horse
Hypohippus sp.2 Leidy 1858 anchitheriine horse
 Ungulata - Merycoidodontidae
Brachycrus sp.3 Matthew 1901 oreodont
 Ungulata - Camelidae
Camelidae indet. Gray 1821 camel
two forms, said to be "Alticamelus-like" and "Oxydactylus-like"
Protolabis heterodontus1 Cope 1874 camel
 Ungulata - Antilocapridae
Paracosoryx sp. Janis and Manning 1998 pronghorn