This book summarizes major aspects of the evolution of South American
metatherians, including their epistemologic, 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. 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.