The Dimetrodon, is an impressive creature with a huge sail on its back and a powerful jaw including teeth of different sizes. Resembling an enormous lizard, this animal had a sail held in place by bony spines which stood vertically above each vertebra. This enabled the Dimetrodon to regulate its body temperature by heating or cooling its body depending on the direction it was facing. A fearsome carnivore despite its short legs, it could reach impressive speeds when pursuing prey. It lived during the Permian period between 280 and 265 million years ago in what is today North America and Europe. It measured between 3.3 and 3.5 m.