Rancho El Ocote (Medial) (Neogene of Mexico)

Also known as Arroyo de la Carreta; White layer

Where: Guanajuato, Mexico (21.2° N, 100.7° W: paleocoordinates 21.5° N, 99.1° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Rancho Viejo Beds Formation, Late/Upper Hemphillian (10.3 - 4.9 Ma)

• level dated at 4.6 Ma FT on zircon; according to Kowallis et al. 1986, this is the youngest of three modes, the others being at 11.0 and 24.5 Ma

•this date is superseded by an Ar/Ar date of 4.74 +/- 0.14 Ma reported by Flynn et al. 2005 for an ash immediately overlying the fauna

•unit is "2-3 m thick, lies disconformably on the lower unit" (Carranza-Castañeda and Walton 1992)

• group of beds-level stratigraphic resolution

Environment/lithology: "channel"; tuffaceous, gray, white claystone and sandstone

• at GTO 2a the unit is "channeled, muddy clay" and at GTO 2c is is "incised by a sand-mud channel"
• "gray and white volcanic ash and clay. Crossbedded sand occurs in rare, poorly defined lenses" (Carranza-Castañeda and Walton 1992)

Size classes: macrofossils, mesofossils

Collected by O. Carranza-Castañeda, B. Slaughter, C. McKinney

Collection methods: bulk, sieve

• microfossils collected by "screenwashing" (Carranza-Castañeda and Walton 1992)

Primary reference: O. Carranza-Castaneda. 1989. Rinocerontes de la fauna local Rancho el Ocote, Mioceno Tardio (Hemfiliano tardio) de estado de Guanajuato. Universidad Nacional Autónoma de México, Instituto de Geológia, Revista, Publicación Especial 8(1):88-99 [J. Alroy/J. Alroy/M. Uhen]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 18738: authorized by John Alroy, entered by John Alroy on 26.03.1995

Creative Commons license: CC BY (attribution)

Taxonomic list

Mammalia
  - Mylodontidae
cf. Glossotherium sp. Owen 1840 edentate
possibly includes "Pampatherium" of Carranza et al. 2000 from "4.7 Ma" level
 Proboscidea - Gomphotheriidae
cf. Stegomastodon sp. Pohlig 1912 gomphothere
 Perissodactyla - Equidae
Dinohippus mexicanus Lance 1950 horse
Astrohippus stockii Lance 1950 horse
 Artiodactyla - Camelidae
Megatylopus sp., "Hemiauchenia vera" = Pleiolama vera2
Megatylopus sp. Matthew and Cook 1909 camel
"Hemiauchenia vera" = Pleiolama vera2 Matthew 1909 camel
probably includes "H. sp."; may also include "Palaeolama guanajuatensis," although this is much smaller
 Artiodactyla - Tayassuidae
Platygonus sp. Leconte 1848 peccary
 Rodentia - Sciuridae
Paenemarmota sp. Hibbard and Schultz 1948 squirrel
includes "P. mexicana" of Dalquest and Mooser 1980a
 Rodentia - Cricetidae
Cricetidae indet.1 Fischer von Waldheim 1817 mouse
section GTO 2a
Baiomys kolbi1 Hibbard 1952 pygmy mouse
sections GTO 2a and 2b
Calomys (Bensonomys) elachys1 Lindsay and Jacobs 1985 mouse
sections GTO 2a and 2b
Calomys (Bensonomys) baskini1 Lindsay and Jacobs 1985 mouse
Calomys (Bensonomys) winklerorum n. sp.1 Carranza-Castañeda and Walton 1992 mouse
sections GTO 2a and 2b
Prosigmodon ferrusquiai n. sp.1 Carranza-Castañeda and Walton 1992 mouse
Prosigmodon oroscoi1 Jacobs and Lindsay 1981 mouse
sections GTO 2a and 2b
Prosigmodon chihuahuensis1 Lindsay and Jacobs 1985 mouse
section GTO 2b
Neotoma (Paraneotoma) sp.1 Hibbard 1967 pack rat
possibly new: section GTO 2a
Neotoma (Paraneotoma) cf. sawrockensis1 Hibbard 1967 pack rat
sections GTO 2a and 2b
 Lagomorpha - Leporidae
Hypolagus cf. ringoldensis3 Gustafson 1978 rabbit
Notolagus velox4 Wilson 1937 rabbit