Dimetrodon

Dimetrodon meaning "Two-measures Tooth" is a carnivore meat-eating pelycosaur mammal-like reptile, an ancestor of the mammals, that lives during the Permain Period, long before the dinosaurs evolved.

Physical Appearence
The Dimetrodon has a large sail-like flap of skin along its back, dense with blood vessels. The sail was supported by long, bony spines, each of grew out of a separate spinal vertebra. The sail may have been a thermoregulatory structure, used to absorb and release heat. The sail mayhave also been used for mating and dominance rituals, and/or for making it look much larger than it was to predators. Dimetrodon had sharp teeth and clawed feet.

Fantasia
In "The Rite of Spring", a pair Dimetrodons were seen, one was yawning and the other one was eating a Nothosaurus. Even though they were carnivores, they lived with herbivorous dinosaurs. One was seen when the Tyrannosaurus Rex arrived in the thunderstorm. One Dimetrodon was running away along with a Parasaurolophus, Triceratops, flying pterosaur, 2 lizards from the Tyrannosaurus Rex hunting and chasing them.

One Dimetrodon was seen after the Stegosaurus' death from been killed by the T-Rex along with a group of herbivorous dinosaurs (A Parasaurolophus, Triceratops, Corythosaurus and a Diplodocus) looking and watching. There were no Dimetrodons seen again at the end of the segment, But they most likely died in the drought of starvation, and dehydration.