Prehistoric Crocodilians

• Of all the reptiles alive today, crocodiles and alligators may be the least changed from their prehistoric ancestors of the late Cretaceous period, over 65 million years ago—although the even earlier crocodiles of the Triassic and Jurassic periods sported some distinctly un-crocodile-like features, such as bipedal postures and vegetarian diets
• Before the first true crocodiles emerged on the prehistoric scene, there were the phytosaurs (“plant lizards”): archosaurs that looked very much like crocodiles, except that their nostrils were positioned on the tops of their heads rather than the tips of their snouts. You might guess from their name that phytosaurs were vegetarians, but in fact they subsisted on fish and marine organisms in freshwater lakes and rivers worldwide
• By the start of the Jurassic period (about 200 million years ago), crocodiles had mostly abandoned their terrestrial lifestyles. This is when we begin to see the marine adaptations that characterize modern crocodiles and alligators: Long bodies, splayed limbs, and narrow, flat, tooth-studded snouts with powerful jaws (a necessary innovation, since crocodiles feasted on dinosaurs and other animals that ventured too close to the water)