The Great American Interchange occurred 3 million years ago when the Isthmus of Panama was created, allowing the exchange of numerous mammal species between North and South America. North American fauna was better adapted to competition, but some South American species, like the Terror Bird, made it as far as Texas and Florida. Some animals that successfully exploited the interchange and survive to this day include the armadillo, Virginia Opossum, porcupine, bat vampire, puma, and king vulture.
The Great American Interchange may look like a highway, but it is actually a paleozoogeographic event that occurred in the Americas about 3 million years ago, during the Pliocene epoch. The Great American Exchange was caused when volcanic activity created the Isthmus of Panama, linking North and South America, which had been separated for 200 million years, by the dissolution of the supercontinent Pangaea. Numerous mammals, part of lineages that had been separated for eons, were traded between continents, which thereafter became part of the same general biogeographic region, the Americas.
The mammalian fauna of North America prior to the Great American Interchange was broadly boreoeutherian, a clade composed of sister taxa Laurasiatheria and Euarchontoglires, which includes New World primates, lagomorphs (pikas, rabbits, hares), rodents (rats and mice) , moles, shrews, rodents, ancient horses, deer, the now extinct American camel, skunks, bears, saber-toothed cats, wolves, foxes, cougars, American lion, and others. South American fauna was more unique than that continent, including marsupials (with some carnivorous variants), xenartrans (armadillos, anteaters, and sloths, including giant ground sloths), porcupines, vampire bats, dire wolves, “terror birds,” numerous native ungulates (hoofed animals) including the peculiar Macrauchenia, which is described as a camel without a hump, of short stature with a short trunk.
In general, if the Great American Interchange is seen as some kind of evolutionary competition, North America has won. The North American fauna, which lived on a somewhat harsher, colder and more climatically diverse continent, had adaptations better suited to competition than the South American fauna, much of which was highly rainforest adapted and did not reach over Central America. An exception are the notorious Terror Birds, which have made it as far as Texas and Florida, allegedly consuming millions of small mammals along the way with their huge, razor-sharp beaks. Yet this success was short-lived, as the Terror Birds became extinct within a million years of the journey.
Some examples of animals that have successfully exploited the Great American Interchange and survive to this day include the armadillo, found most often in Texas, the Virginia Opossum, the only marsupial found north of the Rio Grande, the porcupine, the bat vampire, found in Mexico, the puma and king vulture, which can be found throughout Central America.
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