<P> The Great American Interchange was an important late Cenozoic paleozoogeographic event in which land and freshwater fauna migrated from North America via Central America to South America and vice versa , as the volcanic Isthmus of Panama rose up from the sea floor and bridged the formerly separated continents . The migration peaked dramatically around three million years ( Ma ) ago during the Piacenzian age . It resulted in the joining of the Neotropic ( roughly South America ) and Nearctic ( roughly North America ) ecozones definitively to form the Americas . The interchange is visible from observation of both biostratigraphy and nature ( neontology ) . Its most dramatic effect is on the zoogeography of mammals but it also gave an opportunity for reptiles , amphibians , arthropods , weak - flying or flightless birds , and even freshwater fish to migrate . </P>
<P> The Great American Interchange was an important late Cenozoic paleozoogeographic event in which land and freshwater fauna migrated from North America via Central America to South America and vice versa , as the volcanic Isthmus of Panama rose up from the sea floor and bridged the formerly separated continents . The migration peaked dramatically around three million years ( Ma ) ago during the Piacenzian age . It resulted in the joining of the Neotropic ( roughly South America ) and Nearctic ( roughly North America ) ecozones definitively to form the Americas . The interchange is visible from observation of both biostratigraphy and nature ( neontology ) . Its most dramatic effect is on the zoogeography of mammals but it also gave an opportunity for reptiles , amphibians , arthropods , weak - flying or flightless birds , and even freshwater fish to migrate . </P>
when did south america and north america join
when did south america and north america join
around three million years ( Ma ) ago during the Piacenzian age
around three million years ( Ma ) ago during the Piacenzian age