Dimetrodon (meaning "two measures of teeth") was a predatory synapsid ("mammal-like reptile") genus that flourished during the Permian period, living between 280–265 million years ago (Artinskian to Capitanian stages). It was more closely related to mammals than to true reptiles such as lizards. It is classified as a pelycosaur. Fossils of Dimetrodon have been found in North America and Europe. Description Dimetrodon was an apex predator, among the largest of its day. It grew to up to in… (More on Dimetrodon)