Great American Faun Exchange

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Animal forms that immigrated from South to North America during the exchange (olive), and those that immigrated from North to South America in reverse (blue)

The Great American Fauna Exchange is the name given to the exchange of numerous animal forms between North and South America, which took place after the formation of the Isthmus of Panama in the Pliocene about 2.8 to 2.7 million years ago. The ancestors of numerous mammals that are typical of South America today, such as camels, cats, dogs, peccaries , tapirs and small bears , immigrated from North America at that time. But some of today's North American mammal species, such as armadillos and opossums, as well as the later extinct giant sloths and glyptodons , made their way from South to North America during the exchange.

The isolated development of the South American fauna

About 100 million years ago, South America began to separate from the rest of the continents. The animal world developed over a very long period of time completely independent of other parts of the world. Only a few forms, such as rodents and primates , made it to the isolated continent as so-called island hoppers, which was otherwise populated by unique mammalian orders ( Sparassodonta , Notoungulata , Litopterna , Astrapotheria ).

The creation of the land bridge and the consequences

At the end of the Pliocene , on the threshold of the Quaternary , a stable land bridge to North America, the Isthmus of Panama, was formed 2.76 million years ago. Numerous animal species migrated across this land bridge from north to south, but also in the opposite direction. This large fauna exchange led to the disappearance of numerous native animal forms, especially in South America, which were replaced by other animal forms with similar ecological niches. Shrews, cats, dogs, bears, small bears, martens, deer, umbilical pigs, horses, tapirs, gomphotherias , hares, croissants and cricetides immigrated from North America to South America. Many of the native mammals disappeared because they were replaced by the newcomers. Among the survivors were the xenarthras , opossums, rodents and primates as well as the toxodonts and macrauchenia . The families that immigrated from South America to North and Central America include the giant sloths (Megatheriidae, Mylodontidae), the glyptodons, the armadillos, the anteaters , the capybaras , the tree spines , the opossums and the later extinct toxodons. The terror bird Titanis walleri also immigrated to North America, with finds in Florida, among others.

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