Dimetrodon grandis
Permian synapsid

Dimetrodon is often mistaken for a dinosaur, but it is actually much more closely related to mammals! It belongs to a group of animals called synapsids, which are distinguished from reptiles by their skull features. Today, mammals are the only living synapsids, but Dimetrodon was one of the earliest members of this group. Primitive synapsids were succeeded by a more advanced group called the therapsids, sometimes called “mammal-like reptiles.”

Dimetrodon lived during the Permian Period from 292-272 million years ago, about 30 million years before the first dinosaurs appeared. Reaching lengths of up to 15 feet, Dimetrodon was a top predator, and fed on other land animals as well as fish. The sail on its back is thought to have been used in courtship displays, or to help the animal regulate its body temperature. Most Dimetrodon fossils from the United States have been found in the Red Beds of Texas and Oklahoma.

Length: 20 inches