List of South American mammals

This is a list of the native wild mammal species recorded in South America. South America's terrestrial mammals fall into three distinct groups. The marsupials and xenarthrans are 'old-timers', their ancestors having been present on the continent since at least the very early Cenozoic Era. During the early Cenozoic, South America's only land connection was to Antarctica, so it was effectively cut off from most of the world; as the fragments of Gondwana continued to separate, this connection was lost, leaving South America an island continent. Caviomorph rodents and monkeys arrived as 'waif dispersers' by rafting across the Atlantic from Africa in the Eocene epoch, 35 million or more years ago. All the remaining nonflying mammals of South America are recent arrivals, having migrated from North America via Central America during the past seven million years as part of the Great American Interchange; this invasion, which peaked around three million years ago, was made possible when the formation of the volcanic Isthmus of Panama bridged North and South America. The newcomers out-competed and drove to extinction many unique mammals that had evolved during South America's long period of isolation, as well as some species from other classes (e.g., terror birds).

South America suffered another major loss of mammal species in the Quaternary extinction event, which started around 12500 cal BP, at roughly the time of arrival of Paleoindians, and may have lasted up to several thousand years. At least 37 genera of mammals were eliminated, including most of the . While South America currently has no megaherbivore species weighing more than 1000 kg, prior to this event it had a menagerie of about 25 of them (consisting of gomphotheres, camelids, ground sloths, glyptodonts, and toxodontids – 75% of these being 'old-timers'), dwarfing Africa's present and recent total of 6.

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