José E. Ruiz-González

Quaternary Mammals, People, and Climate Change: A View from Southern North America

The Pleistocene and modern mammal faunas of southern North America strongly differ in taxonomic makeup, distribution, and physiognomy. The former faunal complexes are part of the ancient landscape in which early peoples may have interacted. Customarily, differences between the Pleistocene and modern faunas have been attributed to climate change or human-impact driven extinctions. Mexico’s Pleistocene mammal record is analyzed in time and space, emphasizing the study of the Rancholabrean Chronofauna, which is the most recent North American Land Mammal Age fauna. Palynological and paleosol records are reviewed as an independent check of the interpretation derived from mammals. The integration of the information provides the basis for a proposal regarding Late Pleistocene climate change trends across the country, and whether people were involved in the mammalian community response to climate change in terms of extinction or biogeographic shifting within and outside the country. This approach supports an explanation of the differences between southern North America’s Pleistocene and modern mammal faunas.

Depositional systems of the late Eocene Yolomécatl Formation, northwestern Oaxaca, southeastern Mexico: a first approach

RMCG | v. 35 | núm. 2 | www.rmcg.unam.mx | DOI: http://dx.doi.org/10.22201/cgeo.20072902e.2018.2.559 Ferrusquía-Villafranca, I., Torres-Hernández, J.R., Ruiz-González, J.E., Martínez-Hernández, E., 2018, Depositional systems of the late Eocene Yolomécatl Formation, northwestern Oaxaca, southeastern Mexico: a first approach: Revista Mexicana de Ciencias Geológicas, v. 35, núm. 2, p. 142-157. ABSTRACT

The diet of Leptomeryx sp. from the Late Eocene Yolomécatl Formation, NW Oaxaca, Sierra Madre del Sur Morphotectonic Province, SE México and its palaeoecological significance

The diet and habitat of Leptomeryx sp. from the Late Uintan Yolomecatl Formation of NW Oaxaca, SE Mexico were inferred using dental enamel carbon and oxygen isotopic relationships, and compared with those of congeneric species from temperate North America. Results show that Leptomeryx sp. fed on C3 plants and lived in open forest or forest/savanna ecotone. The palynoflora and co-occurrence of perissodactyls and artiodactyls that live in an environment like that of Leptomeryx support this interpretation. Further, both records disclose that in NW Oaxaca (southern North America) tropical conditions prevailed at that time, unlike that of temperate North America.