Dimetrodon was a pelycosaur synapsid that lived in the Permian period. Being a synapsid it was a relative of mammals.

As a synapsid, it was more closely related to mammals than to true reptiles such as lizards and snakes. It is classified as a pelycosaur. Fossils of Dimetrodon have been found in North America and Europe.

Description and Paleobiology


Dimetrodon was a carnivore and had two types of teeth in its mouth, like a mammal, shearing teeth and sharp canine teeth. Its name, in fact, means "two-measures of teeth". This genus was one of the first with different-shaped teeth, and the teeth could for kill prey, then tear them to bits. It has a large skull with a temporal holes at the back of each eye on the side, a unique trait of synapsid skull. This made possible new attachment sites for jaw muscles, which could run fast and let the animal chew.[1][2]

In a 2001 study on the biomechanics of the dinosaur Albertosaurus's teeth, William L. Abler saw that examined Dimetrodon teeth had serrations so fine as to look like a crack in the tooth.[3] Though Albertosaurus had similar serrations, the base of each serration included a round void which would have functioned to distribute force over a larger surface area.[3] These voids would not let the "crack" formed by the serration to spread through the tooth.[3] Dimetrodon was found to lack adaptations to stop "crack" spreading.[3]


The strong legs of Dimetrodon were spread beside the body. Based on the construction of the legs, it was a fast and smoothly moving animal, especially compared to its solidly built, herbivorous relatives. The shape of the hip bones, the hind legs and the joints between the vertebrae can be seen.[4]


Dimetrodon's most recognizable feature was a sail on its back, not unlike that of Spinosaurus. It is thought to have been used to regulate it's body temperature. It would be able to pump blood into the sail and the sun would heat it. Then Dimetrodon's blood would go back into its body, warming the creature.

Dimetrodon in The Land Before Time

The Land Before Time Dimetrodon
Dimetrodon only appears in the original Land Before Time, when Littlefoot, Ducky, and Petrie hide from one crossing their path. As the Dimetrodon passes it flicks out it's tongue like a snake or monitor lizard and hisses. There are two inaccuracies in this encounter: One, is that Dimetrodon did not live at the same time as the dinosaurs. However, many dinosaurs from different times and places appear in The Land Before Time, which could excuse this. And two, is how it sticks its tongue out to taste the air like a snake. Since it was a relative of mammals and not monitor lizards and snakes, Dimetrodon would not have done this. Also, new discoveries seem to imply the sail's covering may not have been as extensive as previously imagined, and it is likely Dimetrodon could have been more mammalian in appereance.
Dimetro cel

The Dimetrodon.


  1. R & Demar Barghusen HR. (1972) "Mechanics and the Evolution of the synapsid jaw". Evolution, 26(4):622-637.
  2. HR Barghusen. (1973) "The adductor jaw musculature of Dimetrodon (Reptilia, Pelycosauria)". Journal of Paleontology, 47(5):823-834.
  3. 3.0 3.1 3.2 3.3 Alberto tooth abs 84
  4. The illustrated encyclopedia of dinosaurs and prehistoric animals. D & B Palmer Cox. Second Edition; Könemann, 2000, p. 184.

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