Also known as GTO-2; TMM 41685; Arroyo de la Carreta; Rhino layer
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
•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
•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
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"Agriotherium schneideri" = Huracan schneideri6
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"Canis ferox n. sp." = Eucyon ferox6 Miller and Carranza-Castaneda 1998 canine Rancho San Martin, 2 km NE of Rancho Viejo, lower Rancho Viejo beds
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Pseudaelurus ? intrepidus2 Leidy 1858 cat "Rancho El Ocote" - probably this level because Carranza 1989 lists "P. sp."
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"Neohipparion eurystyle" = Neohipparion eurystyle, "Neohipparion otomii n. sp." = Neohipparion eurystyle8, "Neohipparion monias n. sp." = Neohipparion eurystyle9, Nannippus aztecus1, Astrohippus stockii, "Dinohippus mexicanus" = Dinohippus mexicanus, "Protohippus muelleri n. sp." = Dinohippus mexicanus10, "Hippotigris ocotensis n. sp." = Dinohippus mexicanus7
"Neohipparion eurystyle" = Neohipparion eurystyle Cope 1893 hipparionine horse includes "N. otomii" in part; "N. monias"
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"Catagonus brachydontus" = Protherohyus brachydontus1
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cf. Alforjas sp., "Hemiauchenia vera" = Pleiolama vera6, "Palaeolama guanajuatensis n. sp." = Hemiauchenia guanajuatensis5, Megatylopus cf. matthewi4
cf. Alforjas sp. Harrison 1979 camel see also Montellano 1989: presumably includes "Pliauchenia sp."
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