The Rise and Fall of South American Metatherians: Contexts, Adaptations, Radiations, and Extinctions

FRANCISCO J. GOIN; ANA NATALIA ZIMICZ; ANALÍA M. FORASIEPI; LAURA CHORNOGUBSKY; M. ALEJANDRA ABELLO

Origins and Evolution of Cenozoic South American Mammals

Springer

Año: 2010;

Major aspects of the evolution of South American metatherians are summarized, including their paleontological, phylogenetic, biogeographic, faunal, tectonic, paleoclimatic, and metabolic contexts. A brief overview of the evolution of each major South American lineage (“Ameridelphia”, Sparassodonta, Didelphimorphia, Paucituberculata, Microbiotheria, and Polydolopimorphia) is provided. It is argued that, due to physiological constraints, metatherian evolution closely followed the conditions imposed by global temperatures. We discuss the adaptive and taxonomic significance of the metatherian associations recorded from two distinct and geographically close Cenozoic Patagonian fossil localities: first, the Las Flores association (Itaboraian Age), which coincided with the climax of the last greenhouse World in the latest Paleocene-early Eocene. Second, the La Cancha and La Cantera associations (early Oligocene, pre-Deseadan Age), occurring successively after the earliest Oligocene “Big Chill” that signaled the beginning of the icehouse World. Both associations reflect the two main turnovers of metatherian evolution in South America. In general terms, during the Paleocene and the early Eocene multiple radiations of metatherian lineages occurred, with many adaptive types exploiting insectivorous, frugivorous, and omnivorous adaptive zones. In turn, a mixture of generalized and specialized types, the latter mainly exploiting carnivorous and granivorous-folivorous adaptive zones, characterized the second half of the Cenozoic. In both periods, climate was the critical driver of their radiation and turnovers.