Dimetrodon
Dimetrodon lived during the Permian Period 280 million years ago in what is now North America. Dimetrodon was a fierce carnivore. Dimetrodon's name means "two-measures of teeth", so named because it had a large skull with two different types of teeth. Shearing teeth and sharp canine teeth. Dimetrodon is one of the most popular, best known of the pelycosaurs or "sailbacks", reptiles with tall growths of skin supported by bony spines on their backs. This sail had a network of blood vessels running through it. It was useful in regulating the reptile's body temperature. Dimetrodon may have also used it in mating rituals, or to ward off other predators. Dimetrodon had a bulky body and moved on all four side-sprawling legs and had a large tail. Dimetrodon moved similarly as the modern komodo dragon.
Image courtesy of Raul Martin
Image courtesy of David Bonadonna