An asteroid impact may have ended the reign of the dinosaurs here on Earth about 65 million years ago, but new evidence suggests many of the large, plant-eating dinosaurs were already dying out during the last 12 million years of the Cretaceous period.

Dinosaurs survived two mass extinctions and 50 million years before taking over the world and dominating ecosystems, according to new research published this week.

By the skin of their teeth 200 million years ago, dinosaurs defeated a fierce group of beasts competing for the right to rule the Earth, said scientists Tuesday.