An Ultimate Guide to Dimetrodon: The Two-Measured Tooth

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Name Meaning“Two Measures of Teeth”Height2 meters (7 feet)
PronunciationDie-met-ro-donLength3 to 4.5 meters (10 to 15 feet)
EraPaleozoicPermian PeriodWeight28 to 250 kg (62 to 551 pounds)
ClassificationSynapsida,‭ Pelycosauria & SphenacodontidaeLocationNorth America, Europe

Dimetrodon Pictures

Dimetrodon in a landscape | MR1805 via Getty Images

The Dimetrodon

Gage Beasley Prehistoric's Dimetrodon Concept
Gage Beasley Prehistoric’s Dimetrodon Concept

Most fierce-looking prehistoric animals are often mislabelled as dinosaurs

It often happens with flying reptiles (pterosaurs) and marine reptiles like the mosasaurs that lived during the Mesozoic Era alongside the dinosaurs. 

The Dimetrodon is another animal that is commonly misidentified as a dinosaur. 

That’s probably because the giant sail on its back is similar to that of some dinosaur species, such as the Spinosaurus.

Gage Beasley's Prehistoric Shirt Collection
Gage Beasley’s Prehistoric Shirt Collection
Gage Beasley's Prehistoric Plush Collection
Gage Beasley’s Prehistoric Plush Collection

But the Dimetrodon wasn’t really a dinosaur. 

It is a genus of prehistoric reptiles that can be more accurately described as a synapsid rather than a dinosaur. 

It is often called a mammal-like reptile because it is more closely related to modern mammals than reptiles.

Dimetrodon lived during the Permian Period from about 295 to 272 million years ago. 

Dimetrodon in a landscape | MR1805 via Getty Images

This was more than 40 million years before the first dinosaurs evolved.

It was the largest terrestrial animal in its ecosystem and the earliest known large predator. 

In this article, we’ll discuss the Dimetrodon and explore various aspects of this prehistoric reptile’s life. 

Physical Characteristics

Dimetrodon was more closely related to mammals than reptiles. 

Nevertheless, it was still very reptile-like in physiology and appearance. 

It had a sprawling lizard-like posture, with legs positioned at the sides of its body instead of under the boy. 

The legs were short and didn’t really elevate Dimetrodon’s body above the ground. 

It was a relatively large creature for its time.

Gage Beasley Prehistoric's Dimetrodon Concept
Gage Beasley Prehistoric’s Dimetrodon Size Comparison Chart

The average length for most species was between 1.7 and 4.6 meters (5.6–15.1 feet), and it weighed between 28 and 250 kg (62–551 pounds).

Size varied from one species to the other, but the largest species may have been as large as modern monitor lizards or crocodiles.

The most distinctive feature of the Dimetrodon was the sail-like structure on its back. 

The sail was formed by elongated bones, called neural spines, which projected vertically from the vertebrae.

The sail was probably covered with skin which gave it a broad and flat appearance. 

The tallest neural spine was in the middle of the sail, giving it a dumbbell shape. 

Restoration of Dimetrodon milleri | DiBgd via Wikipedia (CC BY 2.5)

In the largest Dimetrodon individual, the sail stood at a height of about five feet (1.5 meters) off the ground.

The purpose of this sail is still a subject of scientific debate, but the options that have been proposed include thermoregulation, species recognition, or sexual display.

It is not the only prehistoric reptile with this type of sail on its back. 

Another reptile called the Edaphosaurus also had a structure like this. 

However, it was smaller, lived on terrestrial plants, and was not related to the Dimetrodon

It had a tall, laterally-compressed skull. 

A skull of D. grandis | Daderot via Wikipedia

The front of the skull was curved, and the Dimetrodon’s massive jaws featured a set of teeth that were of different sizes.  

The name translates as “two measures of tooth.” 

This refers to the set of small and large teeth that lined this ancient reptile’s jaws. 

It also had a long tail with up to 50 caudal vertebrae. 

This takes up a large part of this reptile’s total length. 

Habitat and Distribution

Dimetrodon lived during the Permian Period in what is now North America and Europe.

These landmasses were part of the supercontinent known as Euramerica (Laurasia) at the time. 

The specific geographic range included parts of the present-day United States, Canada, Germany, and the Czech Republic

It lived in an environment characterized by swampy wetland-like conditions.

It was predominantly land-dwelling and could adapt to arid conditions in some places. 

Dimetrodon on arid landscapes | MR1805 via Getty Images

But there was also an abundance of coastal areas with inland seas that may have served as a home for this reptile. 

Dimetrodon would have preferred habitats near water sources, such as rivers, lakes, or coastal areas, where it could find a steady supply of both aquatic and terrestrial prey. 

The arid inland regions would have been more challenging for them due to the scarcity of resources. 

However, the reptile’s ability to regulate its body temperature using its sail may have provided an advantage in these hot and dry conditions.

Behavior and Diet

Dimetrodon | CoreyFord via Getty Images

Dimetrodon was an active and agile creature. 

Its sprawling limb posture suggests that its locomotion was similar to that of modern reptiles. 

Its sail may have limited its ability to make quick turns., but the Dimetrodon still had the capability to move swiftly. 

Generally, it is considered a predominantly solitary animal. 

There’s no direct evidence that they lived in large groups or herds. 

However, during mating seasons, the individuals may have engaged in social interactions and displays to attract mates.

Dimetrodon primitive predators stick together looking for prey during the Permian Period. | CoreyFord via Getty Images

As for its diet, Dimetrodon was a carnivorous predator, which means it primarily fed on other animals.

It is considered the oldest large predator ever found and was one of the largest predators of the Permian Period. 

Dimetrodon’s dentition was well-adapted to a meat-eating diet. 

It had a large head with sharp, elongated teeth at the front of its jaws. 

These teeth resembled the canines of big cats and were useful for seizing and puncturing prey. 

Maxilla of Dimetrodon borealis, the first Dimetrodon fossil to be described | Daderot via Wikipedia (CC0)

Towards the back of its jaws, it had smaller, serrated teeth for cutting and tearing flesh.

Its diet likely included early amphibians, reptiles, and possibly smaller synapsids. 

Since it wasn’t remarkably swift, the Dimetrodon likely relied on an ambush hunting strategy to catch prey. 

It probably concealed itself in vegetation or near water sources, waiting for terrestrial prey returning to the water for a drink or aquatic prey such as amphibians venturing onto land. 

Once a suitable opportunity arose, Dimetrodon would swiftly strike, using its sharp teeth to capture and subdue its prey.

Life Cycle

D. grandis skeleton, North American Museum of Ancient Life | Ninjatacoshell via Wikipedia (CC BY-SA 3.0)

Our knowledge of the life cycle of the Dimetrodon is limited because of how long ago they lived, the lack of fossil evidence, and their evolutionary position as mammal-like reptiles. 

It likely reproduced sexually, with male and female individuals coming together during the mating season to breed. 

Since they weren’t true mammals, they most likely laid eggs. 

However, there is no direct evidence of their nesting behavior.

It also isn’t clear if the Dimetrodon provided parental care for their young.

Antique illustration: Dinosaurs, Dimetrodon | ilbusca via Getty Images

But it is possible that females provided some form of protection for the developing embryos.

Dimetrodon juveniles hatched from eggs after a short incubation period. 

Like most reptiles, the early years of the juvenile were characterized by rapid growth. 

They were most likely on their own during this time, which means they were vulnerable to predation and faced other challenges as they developed.

Evolution and History

Dimetrodon | Elenarts108 via Getty Images

Dimetrodon is a synapsid, a group of prehistoric animals that includes mammals and their closest relatives. 

Modern mammals are the only members of the synapsid group that are still living. 

During the Carboniferous Period, about 310 million years ago, a new animal group known as the amniotes emerged. 

The amniotes were the first vertebrates capable of laying eggs with protective shells on land. 

Soon, the amniotes group split into two lineages: synapsids and true reptiles (also known as sauropsids). 

Two D. grandis skeletons, Royal Tyrrell Museum | Cherrysweetdeal via Flickr (CC BY 2.0)

Unlike other amniotes, the skull of the synapsids have an opening known as temporal fenestra, behind each eye orbit. 

The fenestra provides a site for the powerful muscles that control the movement of the jaw to attach.

The Dimetrodon’s lineage diverged from other synapsids early in the evolution of this group about 300 million years ago. 

Synapsids like the Dimetrodon were the first tetrapods to evolve a heterodont dentition

This type of dentition is characterized by teeth of varying sizes. 

Skeleton of D. limbatus, Staatliches Museum für Naturkunde Karlsruhe | H. Zell via Wikipedia (CC BY-SA 3.0)

Unlike the true reptiles that could not chew their food, synapsids like the Dimetrodon developed the ability to cut meat into smaller pieces, making their food easier to digest. 

Another distinctive feature of this large reptile was its sail-like structure.

This giant sail formed by their elongated neural spines most likely helped with thermoregulation, display, or attracting mates. 

The rise of more advanced reptilian species led to the decline of the synapsids, including Dimetrodon

This marked the end of their reign as the dominant predators of the Permian period. 

Interactions With Other Species

Restoration of D. grandis and the temnospondyl Eryops, both found in the Red Beds of Texas | Dmitry Bogdanov via Wikipedia (CC BY 3.0)

Dimetrodon was an apex predator in the Permian ecosystem. 

It was a formidable carnivore whose diet would have included a variety of small animals, including the early amphibians, reptiles, and smaller synapsids. 

Dimetrodon killed both near-shore aquatic animals as well as terrestrial prey.

Their prey likely included Xenacanthus, a type of prehistoric shark

They also fed on amphibians like the Diplocaulus and Trimerorhachis 

Terrestrial tetrapods like Seymouria and Trematops were on the menu as well. 

Restoration of Dimetrodon limbatus feeding on a synapsid | Dmitry Bogdanov via Wikipedia (CC BY 3.0)

Given their size, Dimetrodon didn’t have many natural enemies. 

Large prehistoric amphibians like the Eryops and Mastodonsaurus were present during the Permian Period. 

Although they occupied different niches as predators or scavengers, they may have crossed paths occasionally or competed for the same prey as the Dimetrodon

As the Permian Period progressed, more advanced reptiles, such as early relatives of dinosaurs and crocodile-like reptiles, began to emerge. 

These reptiles, including species like Protorosaurus and Erythrosuchus, competed with Dimetrodon for prey and territory. 

Their proliferation eventually contributed to their disappearance. 

Cultural Significance

Dimetrodon grandis in an upright posture based on Dimetropus tracks, with scaleless skin and scutes on its underside | Max Bellomio via Wikipedia (CC BY-SA 4.0)

Dimetrodon is one of the most recognizable and iconic prehistoric animals well-known to both scientists and the general public. 

The giant sail-like structure on the reptile’s back and fearsome appearance led to its misrepresentation as a dinosaur. 

But this has been proven to be inaccurate. 

Dimetrodon has been extensively studied by paleontologists seeking to gain insights into the evolution of the synapsids. 

It is an important fossil species with an evolutionary history that places it at a crossroads as animals transitioned from reptilian to mammalian traits. 

The unique anatomical features of this synapsid, especially the giant sail on its back, have been controversial since Dimetrodon’s discovery. 

Dimetrodon in Journey to the Centre of the Earth | Photo via California Herps

The most widely accepted theory is that the sail performed a thermoregulatory function. 

It was richly supplied with blood vessels and could easily absorb heat from the surroundings or dispense heat from Dimetrodon’s body as needed. 

It may have also served display purposes during mating or functioned as a fat storage site. 

Due to its distinctive appearance, the Dimetrodon is commonly featured in paleoart, museum reconstructions, books, documentaries, and other media about the prehistoric planet. 

It was featured in James Mason’s film titled “Journey to the Centre of the Earth.” 


Dimetrodon | Kitti Kahotong via Getty Images

Dimetrodon is an extinct synapsid genus that lived during the Permian Period. 

It is one of the most well-known prehistoric animals, commonly confused for a dinosaur. 

But despite the reptilian appearance of the Dimetrodon, it wasn’t a dinosaur or a close relative of the reptiles. 

It was more closely related to mammals. 

Dimetrodon is popular for its giant sail formed by elongated spines that extend vertically from its vertebrae. 

The purpose of the sail has remained controversial, with speculations ranging from temperature regulation to attracting mates. 

Dimetrodon also had a unique dentition that included two different types of teeth. 

It was one of the first animals to develop this adaptation seen in later mammal groups. 

This dentition favored the Dimetrodon’s carnivorous diet. 

It was adapted to feeding on various prey, including amphibians, reptiles, and other synapsids present in the Permian landscape. 


Are there any living descendants of Dimetrodon?

No, Dimetrodon and its relatives went extinct millions of years ago. 

However, their evolutionary legacy continues through their descendants, as the synapsid lineage eventually led to the emergence of mammals.

Is Dimetrodon related to humans?

Yes, the Dimetrodon is distantly related to humans and other mammals but isn’t a direct descendant. 

Did Dimetrodon have ears? 

No, Dimetrodon did not have visible ears. 

But they may have used their lower jaws to detect vibrations transmitted through the ground. 


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