Edaphosaurus was a plant eating pelycosaur. It was a lot gentler than it's cousin Dimetrodon. It was part of a group of mammal-like reptiles that would eventually evolve into today's mammals.
Popular Culture
Edaphosaurus appeared in Walking With Monsters where a herd of them were attacked by a Dimetrodon. In the animated television series Dink, the Little Dinosaur, a young Edaphosaurus named Shyler is one of the main characters.
Several appear during the Great Earthshake in The Land Before Time, running away.