Dimetrodon (meaning "two measures of teeth") was a predatory "pelycosaur" synapsid (a relative of mammals) that lived during the Permian period, 280–265 million years ago.Dimetrodon was a Sphenacodontid synapsid. It was closely related to Sphenacodon.

Dimetrodon was one of the largest land animals and the apex predator of its time. It and other "pelycosaurs" ruled the Earth before the time of their relatives therapsids. Dimetrodon had two types of teeth, shearing teeth and sharp canine teeth.

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