page_title: Great American Interchange
section_title: South America's endemic fauna
hierarchical_section_title: Great American Interchange / South America's endemic fauna
caption_attribution_description: Thylacosmilus.
context_page_description: The Great American Interchange was an important zoogeographic event about three million years ago. Land and freshwater fauna migrated between North America and South America.
  The migration happened during the Pliocene, 3.6–2.6 million years ago. The volcanic Isthmus of Panama rose from the seafloor and bridged the two continents.
  The land bridge in what is now Panama joined the Neotropic and Nearctic ecozones to form the Americas.
  The interchange is visible from both stratigraphy and nature. Its most dramatic effect is on the distribution of mammals, but weak-flying or flightless birds, reptiles, amphibians, arthropods and even freshwater fish also migrated.
  The differences in the fauna of North and South America had been known for some time. Both Humboldt and Darwin discussed it. The interchange as a concept was first fully laid out in 1876 by the "father of biogeography", Alfred Russel Wallace. Wallace had spent 1848–1852 exploring and collecting specimens in the Amazon Basin. Others who made significant contributions to understanding the event in the century that followed include Florentino Ameghino and George Gaylord Simpson.
context_section_description: After the late Mesozoic breakup of Gondwana, South America spent most of the Cainozoic era as an island continent.
  Its "splendid isolation" allowed the fauna to evolve into many forms found nowhere else on earth, most of which are now extinct.
caption: The sabertooth "marsupial" †Thylacosmilus
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