These giant animals lumbered slowly across the landscape in large herds.With tiny brains the size of a golf ball,they were neither quick-witted nor fleet-footed. They didn't need to be.Sheer size was their defense.Only the youngest or the sickest were at risk from smaller predators.The reign of the long-necks lasted for 60 million years, and then they died out; no one knows why.By the end of the final age of dinosaurs, the Cretaceous Period, things were very different.A new and more vicious species of dinosaur arrived on the scene, the massive carnivorous tyrannosaurs.They were enormous creatures. Indee they were the biggest carnivores known.And for the next 25 million years, these huge meat-eaters preyed upon everything around them.These giant predators never met the long-necked herbivores.But there was a part of the world where the story of evolution took a different path... South America.Millions of years ago, when dinosaurs first appeared, all the land was connected in one huge super-continent, known as Pangea.
