Though often thought of as a dinosaur the Dimetrodon was actually an ancestor of the mammals and belonged to the family called Pelycosaurs, which had both mammal and reptile characteristics. It lived during the Early Permian Period, between 280–265 million years ago and preceded the earliest dinosaurs by more than 40 million years but physically it looked a lot like one. It was about 3.5 metres/11.5 ft in length. It had legs splayed out to the side and is thought to have walked much like today’s komodo dragon.