Contrary to what is sometimes thought, Dimetrodon, of the species Dimetrodon Grandis that we see here, is not a dinosaur but a reptile. This genus of reptile is close to the ancestors of mammals, mammalian reptiles.The Dimetrodon is best known for its huge dorsal sail which probably allowed it to regulate its body temperature by warming or cooling its body, depending on how it oriented with respect to the Sun. It disappeared tens of millions of years before the appearance of the first Triassic dinosaurs...until now.