Rancho El Ocote (Basal) (Neogene of Mexico)

Also known as GTO-2; TMM 41685; Arroyo de la Carreta

Where: Guanajuato, Mexico (21.1° N, 100.7° W: paleocoordinates 21.4° 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)

• apparently includes the Rhino Layer of Flynn et al. 2005, and therefore also the underlying Proboscidean layer; they report a fission track date of 4.8 +/- 0.2 Ma beneath the Proboscidean layer, and the GMPTS chron C3n.4n/C3n.3r transition falls in between the two layers

•from the "lower unit, 2-4 m thick" (Carranza-Castañeda and Walton 1992)

• group of beds-level stratigraphic resolution

Environment/lithology: fluvial; green, conglomeratic claystone and coarse-grained sandstone

• Arellano (1951): "Bone-bed about 2m thick, of white to light green or yellowish silty sand with coarser detritus disseminated, or in pockets or lenses"

•Carranza-Castañeda and Walton 1992: "green swelling clay. Pockets of gravel lag consist of subangular to rounded rhyolite and basalt clasts of 3-6 cm (maximum 10 cm) diameter"; macrofossils at GTO 2b are from this "basal clay" and those at GTO 2c are from a "sand and gravel zone (probably a local channel)"

Size class: macrofossils

Collected by O. Carranza-Castañeda

Collection methods: quarrying

• collected by "trenching" (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 18737: authorized by John Alroy, entered by John Alroy on 26.03.1995, edited by Jonathan Marcot and Jill Wertheim

Creative Commons license: CC BY (attribution)

Taxonomic list

• Rancho El Ocote in general spans several meters and three faunal zones: list of Miller and Carranza 1984 is a composite, and that of Dalquest and Mooser 1980a appears to span the lower two zones

•following records are of uncertain provenance: ? Indarctos sp. Dalquest and Mooser 1980a Neohipparion gidleyi MacFadden 1984b: "N. otomii" in part

•not clear what "Nannippus hesperides" of Dalquest and Mooser 1980a is, but the holotype is clearly a large form of Nannippus: JA pers. obs. 12.1.93; looks more like a medium-sized Neohipparion, especially the referred lower tooth; JA 9.6.96

•Machairodus sp. - not described by Carranza and Miller 1996, and record probably pertains to either Arroyo Tepalcates or Rinconada (see); however, M. cf. coloradensis is implied to be present by Miller and Carranza 1998a

Mammalia
 Lagomorpha - Leporidae
Notolagus velox6 Wilson 1937 rabbit
 Perissodactyla - Rhinocerotidae
Teleoceras hicksi11 Cook 1927 rhinoceros
 Perissodactyla - Equidae
Nannippus aztecus1, "Neohipparion eurystyle" = Neohipparion eurystyle, "Neohipparion otomii n. sp." = Neohipparion eurystyle8, "Neohipparion monias n. sp." = Neohipparion eurystyle9, "Dinohippus mexicanus" = Dinohippus mexicanus, "Hippotigris ocotensis n. sp." = Dinohippus mexicanus7, "Protohippus muelleri n. sp." = Dinohippus mexicanus10, Astrohippus stockii
Nannippus aztecus1 Mooser 1968 hipparionine horse
"Neohipparion eurystyle" = Neohipparion eurystyle Cope 1893 hipparionine horse
includes "N. otomii" in part; "N. monias"
"Neohipparion otomii n. sp." = Neohipparion eurystyle8 Cope 1893 hipparionine horse
"Neohipparion monias n. sp." = Neohipparion eurystyle9 Cope 1893 hipparionine horse
"Dinohippus mexicanus" = Dinohippus mexicanus Lance 1950 horse
includes "D. ocotensis"
"Hippotigris ocotensis n. sp." = Dinohippus mexicanus7 Lance 1950 horse
"Protohippus muelleri n. sp." = Dinohippus mexicanus10 Lance 1950 horse
Astrohippus stockii Lance 1950 horse
includes "A. albidens"
 Carnivora - Ursidae
Agriotherium schneideri6 Sellards 1916 bear
 Carnivora - Canidae
Canis ferox n. sp.6 Miller and Carranza-Castaneda 1998 canine
Rancho San Martin, 2 km NE of Rancho Viejo, lower Rancho Viejo beds
Borophagus secundus6 VanderHoof 1931 bone-crushing dog
 Carnivora - Felidae
Pseudaelurus ? intrepidus2 Leidy 1858 cat
"Rancho El Ocote" - probably this level because Carranza 1989 lists "P. sp."
 Xenarthra - Megalonychidae
Megalonyx sp.4 Harlan 1825 edentate
 Xenarthra - Mylodontidae
Mylodontidae indet.3 Ameghino 1889 edentate
 Proboscidea - Gomphotheriidae
Rhynchotherium sp.4 Falconer 1868 gomphothere
 Ungulata - Tayassuidae
"Catagonus brachydontus" = Protherohyus brachydontus1
"Catagonus brachydontus" = Protherohyus brachydontus1 Dalquest and Mooser 1980 peccary
 Ungulata - Camelidae
Megatylopus cf. matthewi4, "Palaeolama guanajuatensis n. sp." = Hemiauchenia guanajuatensis5, "Hemiauchenia vera" = Pleiolama vera6, cf. Alforjas sp.
Megatylopus cf. matthewi4 Webb 1965 camel
concurs with Montellano 1989
"Palaeolama guanajuatensis n. sp." = Hemiauchenia guanajuatensis5 Dalquest and Mooser 1980 camel
"Hemiauchenia vera" = Pleiolama vera6 Matthew 1909 camel
cf. Alforjas sp. Harrison 1979 camel
see also Montellano 1989: presumably includes "Pliauchenia sp."
 Ungulata - Antilocapridae
Hexobelomeryx cf. fricki6 Furlong 1941 pronghorn