Tetrapods (Greek tetrapoda, Latin quadruped, "four-legged") are vertebrate animals having four feet, legs or leglike appendages. Amphibians, lizards, crocodiles, dinosaurs, birds, and mammals are all tetrapods, and even the limbless snakes are tetrapods by descent. The earliest tetrapods radiated from the Sarcopterygii, or "lobe-finned" fishes, into air-breathing "amphibians" in the Devonian period.