 Dimetrodon was a quadrupedal , sail @-@ backed synapsid . Most Dimetrodon species ranged in length from 1 @.@ 7 to 4 @.@ 6 metres ( 5 @.@ 6 to 15 @.@ 1 ft ) and are estimated to have weighed between 28 and 250 kilograms ( 62 and 551 lb ) . The largest known species of Dimetrodon is D. <unk> at 4 @.@ 6 metres ( 15 ft ) and the smallest is D. teutonis at 60 centimetres ( 24 in ) . The larger species of Dimetrodon were among the largest predators of the Early Permian , although the closely related <unk> , known from skeletal fragments in slightly younger rocks , may have been even larger at an estimated 18 feet ( 5 @.@ 5 m ) in total body length . 
