Dimetrodon

Dimetrodon - ancestor of the mammals belonged to the family called Pelycosaurs, which had both mammal and reptile characteristics. Dimetrodon preceded the earliest dinosaurs by more than 40 million years but physically it looked a lot like one. It is often referred to as mammal-like reptile, based on characteristics of the skull and dentition. Dimetrodon was a dominant carnivore, the largest one of the Permian period. It was a predacious reptile that was on the top of the food chain during the early Permian.
This pelycosaur possessed a spectacular sail on its back, supported by long, bony spines, each of which grew out of a separate spinal vertebra. The sail was probably an early experiment in controlling body temperature. It is believed that the sail absorbed the heat of the sun and warmed the blood and body. It warmed up early after sunrise and cooled off more efficiently during the heat of the day. It may have also been used for mating and dominance rituals and making it look much larger than it was to predators. Dimetrodon had a large skull with two types of teeth (sharp canines and shearing teeth). It was probably quite slow because it walked on four side-sprawling legs.
Dimetrodon is one of the more recognized of the early reptiles..
TIME - 280 - 260 MYA, Early Permian period.RANGE - Russia, E. Europe. USA Texas, Oklahoma.DIET - Smaller reptiles and other small vertebrates.SIZE - Up to 6ft (2m) long.