DIVERSITY OF NATIVE UNGULATES IN THE LATE OLIGOCENE OF WEST-CENTRAL ARGENTINA

CERDEÑO, E

Mendoza

Congreso; 4TH INTERNATIONAL PALAEONTOLOGICAL CONGRESS; 2014

IPA

Knowledge of South American Cenozoic mammals has increased during the last several decades thanks to many extra-Patagonian local faunas. For the late Oligocene Deseadan Mammal Age in particular, Patagonian assemblages (Scarritt Pocket, Cabeza Blanca, Gran Barranca, La Flecha) are still the most abundant and diversified. Nevertheless, faunas from Uruguay (Fray Bentos Formation, which also crops out in Argentina), Bolivia (Salla, Lacayani), central Chile (Abanico Formation), Brazil (Tremembé Formation) and Peru (Moquegua Formation, Santa Rosa) have provided interesting taxa that have begun to fill in the picture of the South American late Oligocene. In this context, the faunal association from Quebrada Fiera, in Mendoza Province, west-central Argentina, is shedding additional light on that scenario by contributing to a better understanding of Deseadan mammal distributions and the role of this area in a paleobiogeographic context. Aside from a small lizard and some birds (a phorusrhacid and small birds), the long list of mammals from Quebrada Fiera includes three carnivorous metatherians, two rodents, nine xenarthrans (two Pilosa, seven Cingulata) and many native ungulates (Pyrotheria, Litopterna, and Notoungulata). The 13 notoungulate species comprise more than 80% of ungulate species and represent eight families of both suborders, Typotheria and Toxodontia. Within Typotheria, Archaeohyracidae, Hegetotheriidae and Interatheriidae are relatively abundant whereas Mesotheriidae are notably scarce. The archaeohyracid Archaeohyrax suniensis is shared with the Salla fauna, in which mesotheriids, by contrast, are very abundant. The high diversity of hegetotheriids resembles Patagonian faunas, mainly by the presence of pachyrukhines, but some hegetotheriines are shared with Salla and Fray Bentos Fm. The interatheriid Plagiarthrus clivus also has Patagonian affinities. Among Toxodontia, a new notohippid, Mendozahippus fierensis, has been recognized along with a second, poorly known taxon. A new genus and species of leontiniid is recognized, sharing features with both Salla and Patagonian genera. Two toxodontids, Proadinotherium sp. and Pronesodon sp., and a new species of the homalodotheriid Asmodeus are the first Deseadan extra-Patagonian records of these families and genera. The notoungulates and the mammal assemblage as a whole of Quebrada Fiera include typical Patagonian taxa (at generic and specific levels) and species present in Bolivia and Uruguay, together with many apparently endemic species (at least six new species of six families). Thus, this unusual fauna from Mendoza and its latitudinal position appear to represent a nexus between two paleobiogeographic regions, the higher latitudes of Patagonia and the lower latitudes of sites such as Salla.