Dimetrodon

Dimetrodon was a carnivorous mammal-like reptile, or a synapsid during the Permian era

Dimetrodon.jpg
Dimetrodon was a pelycasaur, a type of synapsid. It was a predator and ironically, It ate another creature that also had a sailback called Edaphosaurus.

Trivia

 * dimetrodon is often mistaken to be a dinosaur even though lived before them