Dimetrodon was a solar-powered reptile. It had a large sail on its back thought to be used for taking heat from the sun, in much the same way as a solar panel does today. As its body was warmer than that of most of the other reptiles of the time, the dimetrodon was far more active than some other species. It measured about 3 metres long and had large front teeth for attacking and killing its prey. Dimetrodon was a type of reptiles known as the mammal-like reptiles. Mammal-like reptiles were the reptile ancestors of the mammals.