Dimetrodon grandis, Art Print 13" x 19"
Permian Period 280-260 million years ago.

Dimetrodon grandis - Permian period. Printed on premium glossy photo paper.
Original oil painting 24" x 18" by J. Moravec is in the art collection of Dinosaur Corporation.

Dimetrodon (/daɪˈmɛ.tɹəʊˌdɒn/) ("two measures of teeth"), was a predatory synapsid ('mammal-like reptile') genus that flourished during the Permian Period, living between 280 and 265 million years ago. It was more closely related to mammals than to true reptiles (Sauropsida), like dinosaurs, lizards and birds.
Dimetrodon was not a dinosaur, despite being popularly grouped with them. Rather, it is classified as a pelycosaur. It is surprisingly well-known to the general public and makes an appearance in the James Mason film Journey to the Center of the Earth, as well as in Yor, the Hunter from the Future. Fossils of Dimetrodon have been found in North America and Europe. The climate of Europe and North America in the Early Permian, was probably arid to continental, so Dimetrodon was probably adaptable.

Dimetrodon was an apex predator, among the largest of its day. It grew to up to 3 meters (9.8 feet) in length. The name Dimetrodon 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), unlike reptiles. Dentition showing this differentiation of teeth is called heterodonty. It walked on four side-sprawling legs and had a large tail. Dimetrodon may have moved in a manner similar to present-day lizards.
The most distinctive characteristic of Dimetrodon was the spectacular sail on its back (another pelycosaur, Edaphosaurus, also has this trait). The sail was probably used to regulate body temperature; the surface area would allow it to warm up or cool off more efficiently. This adaptation was important because it would give the animal more time to hunt prey. The sail may also have been used in mating rituals and to warn off other predators. The sail was supported by neural spines, each one sprouting from an individual vertebra. Bramwell and Fellgett (1973) calculate that a 200 kg Dimetrodon would heat up from 26° C to 32° C in 205 minutes without a sail and in only 80 minutes with a sail.