Crocodilians, along with birds, are the only survivors of the once-prevalent Archosauria. During the Mesozoic (245-65 million years ago) this group, including dinosaurs and other reptiles, dominated life on all continents and in the oceans. Most or all of crocodilians' adaptations had already evolved by the late Triassic (about 200 million years ago). Crocodilians are the most advanced surviving reptiles; many of their features are more similar to mammals or birds than to other reptiles.

Crocodilians' eyes are immobile spheres covered by three eyelids: the third eyelid, the nictitating membrane, is transparent, but protects the eye from water.

http://animaldiversity.ummz.umich.ed...rocodilia.html