As the reptiles multiplied they became more diverse. Among them were mammal-like reptiles called the synapsids. One of these, Dimetrodon, had a sail-like structure on its back. The sail may have helped control body temperature. By turning the sail to face the Sun these cold-blooded reptiles could absorb heat. Dimetrodon was a large, 3 m long predator with sabre-like teeth. Other mammal-like reptiles called dicynodonts are thought to have become warm-blooded to gradually evolve into the true mammals.
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