It was the diapsid group of the reptiles that eventually produced the dinosaurs. The jaw muscles in these reptiles were attached to the two openings on each side of the skull, giving their jaws better leverage and strength. Sometime in the Permian period, the diapsid line branched into two groups: lepidosaurs and archosaurs. The lepidosaur group evolved into today’s lizards and snakes; the archosaurs eventually gave rise to the dinosaurs.