Over 50 million years huge meat-eating, ground-dwelling dinosaurs shrunk and evolved into flying birds, according to scientists.
New research from University of Southampton and presented in the journal Science, says that the branch of theropod dinosaurs, which gave rise to modern birds, were the only dinosaurs that kept getting smaller.
Darren Naish, vertebrate palaeontologist, said: "These bird ancestors also evolved new adaptations, such as feathers, wishbones and wings, four times faster than other dinosaurs."
Associate professor Michael Lee, from the University of Adelaide, added: "Being smaller and lighter in the land of giants..provided these bird ancestors with new ecological opportunities, such as the ability to climb trees, glide and fly.
"Ultimately, this evolutionary flexibility helped birds survive the deadly meteorite impact which killed off all their dinosaurian cousins."