Eryops (pronounced AIR-ee-ops), meaning "drawn-out eyes" (from the Greek eryin, 'drawn out' and ops, 'face' or 'eyes') was a large amphibian dating to the Middle Permian period of North America and lived 10's of millions of years before the Dinosaurs. Eryops is an example of an animal that made successful adaptations in the movement from a water environment to a terrestrial one. It retained, and refined, most of the traits found in its fish ancestors. Sturdy limbs supported and transported its body while out of water. A thicker, stronger backbone prevented its body from sagging under its own weight. Also, by utilizing vestigial fish jaw bones, a rudimentary ear was developed, allowing Eryops to hear airborne sound. The type species of Eryops has been named Eryops megacephalus, due to its large skull.