The Dimetrodon is often referred to as a dinosaur. However, it is a primeval reptile, a so-called Pelycosaurus. The Dimetrodon is often referred to as a dinosaur. However, it is a primeval reptile, a so-called Pelycosaurus. The sail on its back was made of skin and bones, helping it to warm itself quicker in the sun. If it wanted to cool down, it positioned the sail parallel to the sun's rays. Fun fact The Dimetrodon was an excellent hunter with extremely sharp teeth. Functions With moveable lower jaw