The crocodilians — crocodiles and their relatives, like the American Alligator — are the closest living relatives of birds. About 250 million years ago, the ancestors of all crocodiles split off from the dinosaur group that gave rise to modern birds. While crocs these days are mostly short-legged ambush predators, before mass extinction there were ocean-dwelling crocodilians and even species that ran around on two legs.More info and transcript at BirdNote.org. Want more BirdNote? Subscribe to our weekly newsletter. Sign up for BirdNote+ to get ad-free listening and other perks. BirdNote is a nonprofit. Your tax-deductible gift makes these shows possible.