Marfil (Eocene of Mexico)

Where: Guanajuato, Mexico (21.0° N, 101.3° W: paleocoordinates 24.2° N, 90.4° W)

• coordinate based on nearby landmark

When: lower Member (Guanjuato Red Conglomerate Formation), Bridgerian (50.3 - 46.2 Ma)

• bed-level stratigraphic resolution

Environment/lithology: terrestrial; lithology not reported

Size classes: macrofossils, mesofossils

Primary reference: I. Ferrusquia. 1989. A new rodent genus from central Mexico and its bearing on the origin of the Caviomorpha. In C. C. Black, M. R. Dawson (eds.), Los Angeles Museum of History, Science Series 33:91-118 [J. Alroy/J. Alroy/M. Uhen]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 16598: authorized by John Alroy, entered by John Alroy on 18.02.1993, edited by Jonathan Tennant

Creative Commons license: CC BY (attribution)

Taxonomic list

• earlier list of Ferrusquia 1984 based on Black and Stephens 1973
there is a date of 49.3 +/- 1.0 Ma (whole-rock K-Ar: Aranda-Gomez and McDowell 1998) for the lower mbr., but it is hundreds of meters thick and directly overlain by a much younger rhyolite, and it is not clear how the fossil locality relates to the dated horizon
originally regarded as late Eocene or early Oligocene, but new taxa indicate a Bridgerian or Uintan age
Mammalia
 Rodentia -
Marfilomys aewoodi Ferrusquia 1989 rodent
Floresomys guanajuatoensis n. sp. Fries et al. 1955 rodent
see Fries et al. 1955
 Rodentia - Sciuravidae
Guanajuatomys hibbardi Black and Stephens 1973 rodent
 Theriamorpha - Plesiosoricidae
? Plesiosoricidae indet. Winge 1917 placental
 Perissodactyla -
Tapiroidea indet. Gill 1872 odd-toed ungulate
 Theriamorpha - Viverravidae
? Viverravus sp. Marsh 1872 placental
 Condylarthra - Hyopsodontidae
Hyopsodontidae indet. Trouessart 1879 condylarth
"Apheliscus or Haplomylus"
Reptilia
 Squamata - Iguanidae
Paradipsosaurus mexicanus n. gen. n. sp. Fries 1955 squamates