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Dinosaur Fact Sheets
Dimetrodon Fact Sheet
Dinosaur/Paleontology Dictionary
NAME: Meaning - Dimetrodon means "Two measures tooth"
Pronounced - di-MET-ro-DON
Named By - Edward Drinker Cope
When Named - 1884
DIET: Carnivore (meat-eater)
SIZE: Length - 11.5 feet (3.5 m) long
Height - about 3 ft (1 m) tall at the hips
Weight - 550 pounds (250 kg)
WHEN IT LIVED: Permian period, about 280-245 million years ago (long before the dinosaurs appeared).
WHERE IT LIVED: Fossils have been found in Texas and Oklahoma in the USA, North America. Trackways (fossilized footprints) of Dimetrodon have been found in Nova Scotia, Canada.
FOSSILS: Dimetrodon is known from many fossils and some footprints.
  • Kingdom Animalia (animals)
  • Phylum Chordata (having a hollow nerve chord ending in a brain)
  • Class Synapsida (synapsids) - these include the mammals, sphecodonts, basal therapsids, caseasaurs, and pelycosaurs. They are distinguished by having a skull with a low opening behind their eyes, whose only non-extinct members are the mammals.
  • Order Pelycosauria (pelycosaurs) - the earliest synapsids which evolved during the Carboniferous period, 300 million years ago. These included Archaeothyris, Ophiacodon, Varanosaurus, Casea, and Edaphosaurus.
  • Family Sphenacodontidae (sail-finned pelycosaurs)
  • Genus Dimetrodon
  • Species Many species - the largest is D. angelensis (Olson, 1962)
Dimetrodon had a large sail-like flap of skin along its back, dense with blood vessels. The sail was supported by long, bony spines, each of which grew out of a separate spinal vertebra (a bone in the back). The sail may have been a thermoregulatory structure, used to absorb and release heat. The sail may have also been used for mating and dominance rituals, and/or for making it look much larger to predators. Dimetrodon had sharp teeth and clawed feet.

Dimetrodon was not a dinosaur, but a pelycosaur, a so-called mammal-like reptile. The pelycosaurs led to the mammals; they are more closely related to us than to the dinosaurs.

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