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...