The Dimetrodon was a prehistoric animal that was present on our planet during what we know as the Paleozoic, and within this classification, specifically in the Permian period (approximately 290 million years ago). It has been classified within the group of the pelicosauric synapsids.

This genus, as we have seen, would have inhabited the Permian, even before the existence of the dinosaurs. The most peculiar aspect of its appearance was undoubtedly the sail-shaped crest on its back. You can see it in the picture you see a little bit below.

The Dimetrodon was a rather angry, voracious and surprising animal. In fact, the BBC has dedicated a documentary almost exclusively to him. Because this prehistoric animal is a very important piece in the history of evolution.

If you’ve found this information about the Dimetrodon interesting, then you’re in luck. We have the most complete information about this peculiar prehistoric animal… Keep reading and discover everything about this Permian carnivore!

The family: pelicosaurus synapse

“But what did you say? What is that?”

It’s normal that you’ve never heard of the “synapsids” and the “pelicosaurs”. But do not worry, now I explain everything about these ancient beings 😀

A little lesson on the origin of dinosaurs

The first reptiles to appear on Earth were an evolution of the first amphibians. Please note that we have just summarized several hundred million years in one sentence, but we do not want to dwell on this point since we are interested in the synapses (Dimetrodon family).

These early reptiles are very important in the process of evolution. The reason is in the shape of an egg and is that these beings were the first ones prepared to be able to reproduce out of water. And all thanks to the amniotic egg.

The embryos, in order to develop, needed to be in a water environment; but as we have said, these reptiles already lived outside of it. The eggs had inside several membranes that allowed to reproduce the conditions of humidity that the embryo needed to be able to grow.

These beings were called amniotes. Be careful, we are talking about the great-great-grandparents of the Dimetrodon.

The amniotes were able to reproduce very quickly thanks to that special egg, which also caused their evolution in several groups.

The diypsids into archosaurs, lepidosaurs, ichthyosaurs and sauropterigians. The dinosaurs were derived from the Arcosaurus branch.

Wait, so these beings predate the dinosaurs?


In fact, they’re not at all close in time. The amniots appeared in the Paleozoic, Carboniferous period: over 360 million years ago. To talk about dinosaurs, we already have to change era and jump to the next one, the Mesozoic in the Jurassic period. There’s about 100 million years of difference between the two.

As you can see in the diagram, from the amniotes come the synapses (the Dimetrodon family).

What is so characteristic about these beings?

With the arrival of the synapsids an important step in the process of evolution is taken since the first mammals that step on the face of the earth appear: the Pelicosaurs (yes, the second surname of the Dimetrodon).

However, we must take into account that none of the mammals of that time managed to evolve: today’s mammals come from another line.

The main characteristic of these beings is the “fan” that runs along their back. In fact, they are usually known as the “sail dinosaurs” or “fin dinosaurs. However, we will talk about this “ridge” in more detail later on.

But notice one thing, we saw before that the amniots appeared well before the dinosaurs. The synapses, too, though somewhat less so. This branch of the amniots inhabited the earth in the Permian (Paleozoic Era) period about 280 million years ago.

You are realizing what I am getting at: was the Dimetrodon a dinosaur or not?

No, the Dimetrodon was not a dinosaur.

In fact, if you look again at the schematic above you will see that dinosaurs come from the Sauropod branch, not the Synapsid branch. So, although Dimetrodon has been commonly considered the dinosaur of the candle, it is not. Our friend was not a dinosaur.


  • KINGDOM Animalia
  • FILO Chordata
  • SINAPSIDE CLASS (if it had been a dinosaur, here would appear Archosauria)
  • ORDER Pelicosauria
  • SUBORDER Eupelycosauria
  • No rank: Sphenacodontia
  • FAMILY Sphenacodontidae
  • GENDER Dimetrodon

Dimetrodon species: a large family synapse

We must recognize this prehistoric being that has had abundant descent. Since 1978, some 20 species of this synapse have been catalogued.

However, with the passage of time it has been seen that many did not cease to be synonymous*.

The term synonym is used to mention when a species has been catalogued as different, when in fact it is the same as another.

Let’s look at the ones that are different species:

  • Dimetrodon limbatus: the first one is always important. Because this species was the first fossil to be found. Although from that one, in 1877, Edward Drinker Cope named it Clepsydrops limbatus. These remains were renamed D. limbatus in 1940 by Alfred Romer and Llewellyn Ivor Price.
  • Dimetrodon milleri: precisely, it was Romer who discovered this other species, the milleri. In this case, it is singular since it is the smallest species in size. Also, its sail is completely round (as if drawing a semicircle). The rest of the specimens had ripples in their sail.
  • Dimetrodon angelensis: its name derives from the fact that its fossils were found in the San Angelo Formation in Texas.
  • Dimetrodon booneorum: also discovered by Alfred Romer.
  • Dimetrodon dollovianus: like his brother D. limbatus, Cope named this specimen “Embolophorus dollovianus”. It would be in 1903 when Ermine Cowles Case would reassign it as Dimetrodon.
  • Dimetrodon giganhomogenes: this species was also classified by E.C. Case.
  • Dimetrodon grandis: in this case, Alfred Romer and Llewellyn Ivor Price would re-determine a classification originally set by E.C. Case. He had named it Theropleura grandis.
  • Dimetrodon loomisi: was also classified by Alfred Romer.
  • Dimetrodon macrospondylus: as in other specimens, Cope called it Clepsydrops macrospondylus. In 1907, Case renamed it again.
  • Dimetrodon natalis: together with D. milleri it was the smallest species. The largest was D. limbatus.
  • Dimetrodon occidentalis: its most special feature is that it does not come from Texas or Oklahoma like the rest. These fossils were found in New Mexico.
  • Dimetrodon teutonis: this species was discovered very recently and is also a very special find. It is the only specimen found outside North America (in Germany).

What does its name mean?

Its name, literally, means “two-sided tooth”. The reason is that this synapse had two canine teeth that protruded by length from all others. Whenever I see a picture of the Dimetrodon’s teeth I remember the teeth of a vampire.

Can you imagine a prehistoric vampire creature?

Who discovered this synapse?
In 1875, the paleontologist Edward Drinker Cope found the first remains of the Dimetrodon, although as we saw before he gave them another name. It was discovered in the Red Beds of Texas.

However, it would take many more years, particularly until 1978, for Cope himself to discover the most striking feature of this synapse: the sail. Fossils from this area had never been found in the previous remains. From that time, the paleontologist assimilated that more than a sail, it was a fin to be able to move faster in the sea.

Where and when did the Dimetrodon live

All the remains of this synapse were found in North America, with Texas and Oklahoma being the places where the greatest concentration of fossils have been found. However, it is curious to see that a few years ago a specimen was found in Germany.

The explanation for this phenomenon is due to the history of the earth itself.

In the Palaeozoic era, right in the Carboniferous period, the Pangaea (the union of all the contents) was formed having only one sea, the Panthalassa.

Therefore, everything was a single land mass, giving the option to the Dimetrodon to move and settle in other places.

How the Dimetrodon was: characteristics

This synapse is known as the “ridge dinosaur” although we already know that it is an amniotic being and not a dinosaur. Let’s see what this Dimetrodon looked like:

  • Name Dimetrodon
  • Length Between 1.5 and 3.2 metres on average
  • Height Measured 1 meter to the hip
  • Weight Between 25 and 250 kilos
  • Herbivore Diet
  • Paleozoic Era, Carboniferous Period (Lower Permian)
  • Years About 280 million years ago
  • Found in Texas, Oklahoma and Germany
  • The Dimetrodon was a quadruped whose main feature was the sail on its back. It’s as if it had a huge fan embedded in its back.

How big was the Dimetrodon

It wasn’t an animal as big as many of the dinosaurs we’ve seen. Note that the largest Dimetrodon ever found (of the Grandis species) was over 3 meters long. The smallest one (a Teutonis), on the other hand, was barely more than half a meter.

Within its body, the skull stands out. It was large, curved and triangular in shape (it narrowed at the muzzle). Its jaw was strong and powerful, this already indicates, although we will see it later, that it fed on large animals. In fact, it is considered one of the super predators of its time.

The shape of the Dimetrodon’s mouth draws an upward oscillation. That’s why, when it had its mouth closed (difficult considering that it loved to eat) it seemed to be smiling. Although no matter how much he smiles at you, if you run into him, it’s best to run away.

The Dimetrodon’s teeth: what a bite

Although the sail is the most spectacular thing about this synapse, its teeth are no less so. We’ve already seen that its name is derived from its two spectacular canines. These two teeth stood out a lot in size compared to the others.

It reminds a bit of a Sabretooth (Diego, in the Ice Age movies).

As if these two Dimetrodon incisors were not enough, the rest of the teeth were finished off with a serrated shape. Thus, they could tear the flesh better and do more damage to their opponents.

The tail that grew over time

When this synapse was discovered, its tail was thought to be very small. The reason was that no skeleton had been found that showed the entire tail. It would be quite a few years before a fossil was found with all the bones in its tail.

Since that day, it is known that the tail of the Dimetrodon was made up of about 50 vertebrae that became smaller as they reached the end of the tail.

The Dimetrodon’s fan, crest, fin or sail

Yes, we have just reached the most characteristic part of this synapse, so we are going to dedicate a whole section to it.

As we said, this crest or fin runs all the way down your back. It starts at the neck and goes all the way to the tail end. It is believed that the shape of the fin could be a sign of sexual dimorphism (body differences between the male and female). The female would have a smaller wing, while the male’s was larger.

The spines forming the crest came from the spine, the longest being those in the middle of the back (they could be up to one metre high).

What did the Dimetrodon use the candle for?

Thermoregulatory function

One of the great paleontological debates centres on whether dinosaurs were hot or cold-blooded. We could say without fear of confusion that something similar happens in relation to the function of the ridge in terms of giving body temperature.

There are many studies regarding how and how long it took for the ridge to provide heat to the Dimetrodon. Scientists (including Stephen C. Haack) say it is possible that this synapse put its candle to “sunbathe”.

You could say that they attributed to the fin the functioning of a battery. The Dimetrodon put the crest to the sun to keep as much heat as possible, so it could provide it little by little.

But as I said before, there was no conformity on this issue. For other palaeontologists, the fin was meant to eliminate the possible excess heat that the Dimetrodon suffered when sunbathing in the morning to warm up. It is even believed that at night it could cut off the flow of blood to the fin and thus keep the heat better.

Over time, there have been more voices claiming that the candle could not perform a thermoregulatory function. Their argument is based on the fact that the smaller species of Dimetrodon also had a crest.

The smaller Dimetrodon, only with the heat of the sun could they keep warm; therefore, the crest had to fulfill another function.

Sexual Selection

We have already said that the size of the ridge could indicate the gender of the Dimetrodon; however, there is also speculation as to whether it could be a sexual claim. A larger ridge size could be more appealing to the female when choosing who to mate with.

In fact, it is believed that the larger or more exaggerated the ridge, the more it attracted the female’s attention. Therefore, the evolution of this species was directed to develop bigger and bigger sails.

Other functions

There have been many hypotheses about what the fin was for. We’ll tell you some of them briefly:

  • One theory was that it could have been used to camouflage itself better among the reeds and thus stalk its prey.
  • Another proposal indicated that it was really a fin and that it served to allow the Dimetrodon to swim in an agile way.
  • The sail could also serve to stabilize the animal in its movements.
  • Intimidating function: the crest could make its enemies think that the Dimetrodon was bigger than it really was. It could then deter them from attacking it.

How far did the sail go?

We don’t mean how high it could get, as we mentioned before the longest spines were about a meter long.

We could say that the Dimetrodon’s candle was composed of two elements: the thorns and the fabric or hard skin that covered it. To understand me better, you only need to imagine the sail of a boat itself. The cloth is supported by the masts that make it spread.

It’s the same here.

A few years ago (in 2012) a study was published that made us think that the sail did not completely cover the thorns, and that therefore, the thorns would look loose. Almost as if they were spikes.

Although that vision of the Dimetrodon has been widely commented on, the reality is that the study was misinterpreted. That research was based on the fossils of a specimen that had suffered several fractures in the spines. These fractures meant that the ridge did not reach the tips of the spines; therefore, it was misunderstood that the spines were exposed.

Behavior of this synapse

One of the most peculiar things said about the Dimetrodon is that it was more about the night life than the day life. This statement comes from a study published in 2014 in “Proceedings of the Royal Society”.

This study explains that the eyes of the synapses (specifically, among other specimens, quotes the species Dimetrodon milleri) had special characteristics due to their diameter and sclerotic rings. Everything seems to indicate that they lived more at night than during the day.

In fact, this study explains that the life of vegetarian synapsids was more diurnal, while that of carnivores was nocturnal. This aspect of the Dimetrodon’s life would help to reaffirm that the candle did not have a thermoregulatory function. What use would it be at night?

What did the Dimetrodon eat

The Dimetrodon was a carnivore, and as we saw, it was a super predator. So we can say that it was very carnivorous.

Also, its huge incisor teeth and powerful jaw indicate that it could hunt animals of its own size. Possibly, other pelicosaurs. It also ate fish, reptiles and amphibians.

Dimetrodon vs Edaphosaurus

Both synapses are very similar, almost the same. They only have two differences, although one of them is fundamental. The Edaphosaurus was herbivorous (its teeth were blunt, not useful for tearing); on the other hand, the Dimetrodon liked meat, like the Edaphosaurus.In the video it is perfectly explained how these herbivorous synapsids are one of the favorite dishes of the Dimetrodon.

The other difference has to do with the shape of the candle. The Edaphosaurus’ was more arched.