National Geographic : 1978 Aug
specialized for shearing could chop them fine enough to swallow. Triceratops and other dinosaurs van ished about 65 million years ago. Final ex tinction may have taken several thousand or several million years. A cooling climate, sped by the effects of an exploding super nova, may have done them in. Long suppressed, mammals began to fill the ecological niches vacated by dinosaurs. But birds, their insulating feathers adapt ed for flight, survived.