Dimetrodon is often mistaken for a dinosaur or as a contemporary of dinosaurs in popular culture.
However, Dimetrodon became extinct some 40 million years before the first appearance of dinosaurs. Its most prominent feature is the large sail on its back formed by elongated spines extending from the vertebrae.
Means: Two measures of teeth
Size: 11.5 ft (3.5 m)
Where: North America (Texas, Oklahoma, Nova Scotia)