South America has had an interesting history. After it had broken away from the ancestral supercontinent of Pangaea it remained an island continent for most of its life. It connected only occasionally to the continent of North America in the north, as it is today. At the end of the Cretaceous period the hadrosaurs spread over most of the continents and established themselves as the principal large herbivores, replacing the great four-footed sauropods. The sauropods still exist, but mostly in places where the hadrosaurs never gained a foothold, such as the South American continent. Isolated from the influences of migration from other continents, the sauropods evolved in their own way.