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A multivariate analysis of the current South American Land-Mammal Ages is used to reanalyse the recognized “faunistic (mammal) units” or chronofaunae that appear related to radical environmental and climatic changes, which we characterize as Faunistic Cycles and Subcycles. The compositional changes recorded in the successive Faunistic Cycles reflect regional environmental and climatic variations, thus patterns of climatic change. Basically we used cheek teeth of ungulates — natives and immigrants — as an indicator of dietary preference. We then try to infer the structure of successive fossil ungulate communities to deduce the structure of their associated vegetation, and thus the prevailing climatic conditions. We also used other native mammals that followed similar dental modifications, e.g., some rodents and some marsupials, and various types of biological and/or geological evidence. These include …