Dimetrodon << dy MEHT ruh don >> was an early prehistoric animal from what is now North America. It lived before the dinosaurs, about 290 million to 260 million years ago, during the Permian Period. The animal is an early member of a group called the synapsids, the ancestors of modern mammals.
Dimetrodon grew about 111/2 feet (3.5 meters) long. It walked on four legs, which sprawled out to its sides. The animal possessed a tall, saillike fin on its back. This fin measured 2 to 3 feet (60 to 90 centimeters) high and was supported by bony spines and covered with scaly skin. Scientists believe the creature used its sail to control body temperature and to signal other Dimetrodons.
Dimetrodon’s name means two sizes of teeth. Its powerful jaws had long, sharp teeth in front, probably for killing prey. Smaller, shorter teeth for chewing food grew on the sides of the jaws. Dimetrodon ranked as one of the largest meat-eaters of its time. Its diet probably included other synapsids.
The American scientist Edward Drinker Cope named Dimetrodon in the 1880’s. Scientists have found its remains in the southwestern United States.
