Humans and animals migrated to South America

Horses, llamas, tapirs, cougars, saber-toothed cats, gomphotheres, and later humans also headed south across the land bridge. But what happened on land is only half the story. What had been one giant ocean was now two, creating differences in temperature and salinity for the two bodies of water.The isthmus also became a barrier for many marine organisms, like mollusks, crustaceans, foraminifera, bryozoans, and fish, and separated the populations of many marine species.