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How did the rise of the Isthmus of Panama allow the Great American Interchange?
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Cenozoic Era
Principal Cenozoic faunal migration routes and barriers.
During most of the Paleogene and Neogene periods, the Isthmus of Panama remained submerged, which kept the faunas of North and South America evolutionarily isolated from one another.1
The Great American Interchange became possible when the isthmus was elevated during the Pliocene Epoch, specifically becoming reestablished as a land connection around 3.5 million years ago. This physical bridge provided a terrestrial corridor that allowed for the migration of animals between the two continents. As a result, various terrestrial mammals that had previously been isolated on the South American continent—such as ground sloths, glyptodonts, armadillos, opossums, and porcupines—began to appear in the North American fossil record.12