This is Dimetrodon, a vicious carnivore. The biggest reptile on Earth.
— Allen, about Dimetrodon

Dimetrodon (name meaning "Two Measured of Teeth") is a genus of pelycosaur synapsid, a species of carnivorous, non-therapsid mammal-like reptile, that originated during the Early Permian era in what is now Germany and North America. It was the apex predator of its time.

Dimetrodon is of the strange and iconic looking 'sailbacks', that are often incorrectly referred to as Dinosaurs. Fossils of them are known from North America and Europe. They were the largest predatory Pelycosaurs ever, at 3.5 meters long and weighing over 500 pounds. They were formidable carnivores in their day, preying on even their 'own kind', as in other Pelycosaurs such as Edaphosaurus

It is most likely they were even cannibals, not being above preying on newly hatched infants of their own species when given the chance to. Dimetrodon is also known for being one of the most famous prehistoric creatures in the world. 


Era & DiscoveryEdit

The top predator of its time and region, Dimetrodon lived in North America and Germany during the Early Permian era, around 280–260 million years ago. Dimetrodon was first described in 1878. Fossils of Dimetrodon have been found in North America and Europe, as well as the significant discovery of Dimetrodon footprints in southern New Mexico by Jerry MacDonald.

The name Dimetrodon means "Two Measures of Teeth", so named because it had a large skull with two different types of teeth (shearing teeth and sharp canine teeth), unlike reptiles. Since their discovery, Dimetrodon has also become one of the most well known prehistoric creatures in the world.

Physical AttributesEdit

Dimetrodon was a large, quadrupedal apex predator, among the largest of its day, notable for its very large spinal sail. It grew to up to 11 feet (3.4 m) in length and weighed 226 kilograms (550 lbs.), the size of an alligator or big cat. Additionally, when Edaphosaurus flushed blood into their sails to distract predators from their heads, Dimetrodon was somehow able to see through their disguise. It was green with a white underbelly. Its sail was green and orange and was decorated with striped and circular patterns. It walked on four side-sprawling legs like a crocodile and had a large tail.


Dimetrodon's teeth

As well as their utter power and size, Dimetrodon possessed a killer edge; as a protomammal, or mammal-like reptile, their blunt-snouted heads were equipped with very powerful jaws that had evolved large, specialized teeth, which gave it a bone-crushing bite force. Their incisors sheared of chunks of flesh, while their serrated canines cut and sliced the flesh. Although having inherited the same form of meat-eating teeth, humans today, however, have a smaller version. Dimetrodons also had a deadly amount of microbes and bacteria in their mouths, enough that even if a bitten animal were to get away alive, they would suffer massive infection which would be crippling and, in a human's case, slow but fatal.


The most distinctive characteristic of Dimetrodon was the large sail on its back (other pelycosaurs, such as Edaphosaurus, also have this trait). Dimetrodon was well adapted to life in the Permian, with their sails being used for thermo-regulation in an increasingly arid climate. Seasons would bring different conditions, and winter in the Permian may have brought ice and snow. The ability to absorb every bit of energy and heat from the sun upon the large surface area of their sails would have been a great advantage over other reptiles.

The sail, which was dense with blood vessels, was probably used to regulate body temperature; the surface area would allow it to warm up or cool off more efficiently. This adaption was important because it would give the animal more time to hunt prey. The sail may also have been used in mating rituals and to warn off other predators. The sail was supported by neural spines, each one sprouting from an individual vertebra. Bramwell and Fellget (1973) calculate that a 200 kg Dimetrodon would heat up from 26 °C to 32° 205 minutes without a sail and in only 80 minutes with a sail. However, some other studies indicate it made a poor heat loss object.

Behavior & TraitsEdit

Dimetrodon was a solitary hunter, only getting together in groups during mating season or scavenging off a kill. However, being cold-blooded creatures, Dimetrodons would have gathered in large numbers early during the day to bask and warm up under the sun, with their sails serving as heat regulators. In this state, they were slow, sluggish and disinterested.

Though Dimetrodon generally attacked adult Edaphosaurus, pregnant females nearly ready to lay their eggs preferred to steer clear of getting injured, and therefore attacked smaller and younger Edaphosaurus. Whenever they hunted animals, such as Edaphosaurus, Dimetrodon first started off with mock charges, tactics to disperse the group and expose the vulnerable youngsters. But when Dimetrodon took interest in prey and became active, they could give disturbing bursts of speed and agility.

Kills were crucial for pregnant female Dimetrodon. Before they could lay their eggs, they needed to eat enough food that would last them for seven months of their eggs incubation. And to increase their babies chances of survival, the females evolved a basic form of parental care: guarding their eggs. For example, when a female had already laid her eggs, she would defend them fiercely from anything, whether a thieving scavenger or even another female Dimetrodon.

Once the eggs hatched, the females' duty of guarding their eggs would be done and their goal achieved, but however, her maternal bond with them would then be severed. Unlike their mammalian descendants, female Dimetrodon would not and never nurtured their young. After they hatched, the females first and only instinct was to save themselves by searching for food.

Male Dimetrodon were highly aggressive and when it came to them scavenging for food, even females knew better than to defend their kill. While lions today consume 70% of a carcass, Dimetrodon ate 90%. By the time a group of Dimetrodon was finished eating, there would be nothing left but the bones of their food. However, they only ate intestines after shaking out the waste inside. Dung is one thing a Dimetrodon couldn't stomach.

Additionally, adult Dimetrodon were also observed to have apparently had loose social structure, easily fighting rivals in the pursuit of food and being quick to cannibalism, even going as far as to eat baby or even hatchling Dimetrodon, even if the adult Dimetrodon was the hatchlings mother. They would weed out weaker babies straight away, which helped the strong ones and her species as a whole survive. Whenever hatchling Dimetrodon hatched from their eggs, they would have to be ready to go it alone without their mothers' protection.

The hatchling Dimetrodon came out of the nest and made quick dashes for the safety of the trees. Whilst some were caught by adults, not all babies were helpless. Some already knew instinctively how to defend themselves. They rolled in dung, something adults can't stand, repelling their pressures long enough to get a head start. And hatchlings could also climb up trees.

Journal EntryEdit

The apex predators of the Permian age, Dimetrodon, "Two Measures of Teeth", were at the top of the food chain in their bay. Just as large as Edaphosaurus, these sail-back, mammal-like reptilian carnivores were the Edaphosaurs' greatest enemy. In addition to their sheer size and overall power, they also evolved specialized, meat-eating teeth; incisors shear off flesh whereas their serrated canines cut and slice. By the time a Dimetrodon were finished with their food, there would be but the bones of their food left.

While Male Dimetrodon were highly aggressive, the females were more solitary and they also evolved a form of care for their young, guarding them even from other desperate pregnant females. It appears that when pregnant females make a kill, they need enough food to last them for seven long months before their eggs are born. The moment the hatchling Dimetrodon are born, the females appear to not care for their young anymore and abandon them. It seems that the female Dimetrodon do not nurture their young and would even go as far as to eat them, hinting a form of cannibalism between these creatures.

— Allen, in his Journal, about Dimetrodon



  • Dimetrodon hatchlings are shown with their back sails fully erect, when in reality, they probably wouldn't have grown yet.
  • Dimetrodon is depicted as living in a desert-like enviornment, when in fact, Dimetrodon is known to have lived in a swamp-like enviornment.
  • The tops of some Dimetrodon's nureal spines may have been exposed bone rather than covered with a full sail, and some animals may have only had a sail halfway up the spines.
  • Dimetrodon had incisors that were longer than the rest of their teeth.
  • Dimetrodon is shown without mother instinct, but this animal had mammal glands, indicating that she took care of her babies, at leasts the first month.
  • The sound effects of Dimetrodon are that of crocodile hisses, Komodo dragon and Smilodon sounds as well as wolf growls and howls and sounds of a peacock.