Probably the most familiar of the pelycosaurs, notably because of the spectacular sail, Dimetrodon predated the dinosaurs by 50 million years and belonged to a totally different line of reptile evolution. It was the biggest and fiercest terrestrial predator of the time.(Walking dinosaur costume)
Features:The significant feature, the sail, is formed from elongated spines that grow upwards from the vertebrae of the back. In life this would have been covered in skin. Turned to the sun in the early morning, the sail would have absorbed heat into the blood stream and made the animal active. If the temperatures became too hot in the day the sail would cool the blood in the wind, like a car radiator. Apart from that. Dimetrodon is very similar to Sphenacodon, from which it probably evolved.(dinosaur equipment)
PELYCOSAURS AND OTHER EARLY SYNAPSIDS
The pelycosaurs were not all fierce hunters. Some developed into berbivores, and as such became the first of the plant-eating reptiles. At the same time the early synapsids branched out into other specialized forms, but eventually settled into the evolutionary line that became the advanced mammal-like reptiles.