The genus Acrocanthosaurus consists of a single species called Atokensis and belongs to a group of allosaurid theropod dinosaurs that lived in the Cretaceous Period.

The name of this dinosaur means “lizard with high spines” since the spines had a slightly longer apophysis.

As a whole, this greater extension of the apophysis gave the sensation of a small hump along the entire spine, which has been assumed to be a structure containing energetic substances as a reserve.

The Acrocanthosaurus was one of the largest theropods of the Cretaceous, but there were even larger ones like the Giganotosaurus.

But that’s not all there is to tell about this spectacular dinosaur. If you want to discover many more things about this prehistoric animal, below you will find complete information about the Acrocanthosaurus. Read on and find out everything about this carnivorous dinosaur from the Cretaceous!

Acrocanthosaurus Taxonomy

  • The kingdom of Acrocanthosaurus is that of Animalia.
  • The division to which Acrocanthosaurus belongs is Chordata.
  • The class of this dinosaur is Sauropsida.
  • The superorder of Acrocanthosaurus is Dinosauria.
  • The order that Acrocanthosaurus belongs to is Saurischia.
  • The suborder to which this dinosaur belongs is Theropoda.
  • The infra-order of Acrocanthosaurus is Carnosauria.
  • The superfamily of this dinosaur is Allosauroidea.
  • The family to which Acrocanthosaurus belongs is Carcharodontosauridae.

Controversies in the classification of Acrocanthosaurus

The Acrochanthosaurus presents characteristics typical of the superfamily to which it belongs, Allosauroidea, the most typical and peculiar features of which are the following:

The presence of two ridges that are inserted into the bone tissue from the nasal cavities.
The presence of lacrimal glands located in the muzzle, with a secretory function, on the other hand, inherent to any glandular tissue.

The presence of neural spines mainly located in the neck vertebrae.
However, a special detail about Acrocanthosaurus is that from the beginning it was only linked to the superfamily Allosauridea, together with the famous Allosaurus, however, while this decision was supported by recent research by some scientists, it also found detractors.

It was other careful researchers who finally classified Acrocanthosaurus within a family named Carcharodontosauridae, because they claim to have enough evidence to differentiate these two taxonomic groups.

When Acrocanthosaurus was first discovered (in addition to other large theropods), scientists realized that they only had a few remains to be able to investigate and analyze the past of this individual, which led these same researchers to a series of errors, since they did not have enough remains of

Acrocanthosaurus to make conclusive statements.

One of these errors resulted in the fact that this dinosaur changed its classification frequently, in fact scientists Wann Langston and Willis Stovall, initially put it inside the “Antrodemidae”, instead of classifying it as part of “Allosauridae”.

On the other hand, another famous researcher called Alfred Sherwood Romer, in 1956 decided to place this dinosaur inside the “Megalosauridae”.

Meanwhile, a numerous group of independent scientists assert that the characteristic long spines indicate that there is an intense and notorious kinship with the dreaded Spinosaurus.

This theory had a lot of resonance and authority until the year 1980, for that reason it was taken into account as a legitimate assumption on which many books and researches are based, evidently, this is another of the errors that are generated in this area due to the lack of contrastable information.

The life of Acrocanthosaurus

The Acrocanthosaurus could develop its existence in what we know today as North America, approximately 115 million years ago and specifically the territory it occupied is the one currently constituted by the states of Oklahoma and Texas, without forgetting to mention Maryland as one of the nests of this specimen.

It is believed that this dinosaur maintained its existence during the Cretaceous period, as it has been mentioned before, even though it didn’t live during the whole of it but during the lower Cretaceous. Scientists believe that this period took place more than 125 million years ago.

Obviously the Acrocanthosaurus had the opportunity to coexist with other dinosaurs that we will point out later with much more precision.

Its diet was clearly carnivorous and this has been determined thanks to the fossil remains found. This fact, together with its large size, made Acrocanthosaurus a great predator of the ecosystem existing at that time.

Although it did not possess great speed, it had diverse abilities as a hunter and as you can see below, its great size was a real ally in its hunt.

His discovery

In summary, the fossil remains and vestiges of Acrocanthosaurus were found in the current territory of the United States of America as we have previously specified.

The locations of the fossil remains were diverse, some came from Oklahoma, other vestiges were found in the state of Texas, and besides that we have dental pieces that were found within the current Maryland, a finding no less important in comparison with the others.

We also have a series of large fossilized footprints, which were also found within what we now know as the state of Texas, however, are not related to the skeleton found in the same state and although it is believed that they belong to the same genus of dinosaur, the truth is that even today there is no conclusive data.

Thanks to the recent discoveries, science has been able to advance in the analysis, study and research of Acrocanthosaurus, since these findings have made it possible to determine more specifically the classification of this dinosaur, a classification that from the beginning refused to be clear and conclusive, due to the fact that the opinions and studies of various scientists were opposed and had adequate grounds to raise this opposition.

Thanks to these recent investigations it was possible to obtain valuable information about the brain structure that the Acrocanthosaurus had, in addition, it was possible to find out for sure the true function that its interesting front extremities fulfilled.

In 1950, two renowned figures in Paleontology, Willis Stovall and the famous Wann Lagngston, had the idea of naming this dinosaur “Acracanthus atokaensis”, an idea that was contained within Wann Lagngston’s master’s thesis, which was presented in 1947. However, in the formal publication they decided to modify the name to Acrocanthosaurus.

As for the holotype and the para-type, we have no less than two incomplete individuals that were found in the state of Oklahoma at the beginning of 1940, although the study about them lasted a whole decade so they were not described until 1950.

Now we will talk about two other individuals that were described in 1990 and that are worth mentioning if we talk about the discovery and subsequent study of Acrocanthosaurus.

First individual (SMU 74646)

This finding has an incomplete skeleton, evidently, which not only “lost” most of its skull, but was also discovered within an enigmatic formation called Twin Mountain, in the state of Texas.

This individual is now in the famous collection of the Museum of Science and History, note that, you will be of great interest to fans of these fascinating prehistoric animals.

Second Individual (NCSM 14345)

This fossil was nicknamed with the humorous denomination of “Fran”, found within the very popular Antlers formation thanks to the action of a group of powerful collectors.

After some time this individual was successfully reconstructed by the professional team of the Black Hills Institute, which is located in South Dakota.

At present we can find the remains of this individual within the state of North Carolina, specifically in Raleigh, in the famous Museum of Natural Sciences.

The great importance of this second individual is its size, since it is the largest that has been discovered so far in comparison with all the other Acrocanthosaurus found, besides turning out to be the only one that has a totally intact skull and one of the arms in the same state.

What is interesting is that a tooth was also found right in the southern part of the state of Arizona, a tooth that was classified within this genus of dinosaur, and in addition to that, markings of this type of teeth have been discovered in numerous bones of another dinosaur in the same area, being more specific, in a sauropod, which makes the proper taxonomy of Acrocanthosaurus even more difficult.

On the other hand, we also have another set of teeth found in a formation called Arundel, within the state of Maryland, teeth that have been assigned to this dinosaur and that give us a very important fact: Acrocanthosaurus also lived in the extreme east of the current territory of the United States.

The debate on the evolution of this dinosaur continues to this day. A serious group of scientists maintains that it belongs to the allosaurs, while another sector of researchers categorically denies this information and states that it is in fact a carcarodontosaurid.

There are also numerous groups of teeth and also various bones that have been found in nearby geological formations or similar, but which actually belonged to other dinosaurs and not to the Acrocanthosaurus, and vice versa.

Physical Characteristics

All the fossil remains found led us to believe that this specimen turned out to be nothing more and nothing less than a great predator of a bipedal nature, and its great quality was the spinous apophysis, that is, a series of spines located at the same time as its vertebrae, which gave the sensation of being a hump located just above its neck and back.

This animal also turned out to be one of the largest theropod dinosaurs of its time, with an approximate length of 12 meters and a weight that could reach 6 tons once it reached adulthood.

Even though it was a little smaller than Giganotosaurus, it is still among the largest theropod dinosaurs that have ever existed.

The arms of this individual never had the function of regulating locomotion, for the simple reason that they never touched the ground, just like some other theropods, but they were of great importance when it came to hunting and getting food, especially when the prey resisted greatly.

After the first study of the arms, from the discovery of a fossil of the complete arm, much more was known about it, for that reason it was affirmed that the arms were a main tool to obtain food, remaining shrunk and inclined towards the body.

There is an important piece of information that we should take into account, when we say that his small arms were used for hunting I do not mean that they were used in the initial stage of the hunt, but that after having caught the victim, these arms served as a tool to imprison him and prevent him from escaping, only in the only case that he was still alive, since in reality they could not be used to initiate the attack, since it was almost impossible that they could open completely and attack with the claws.

For this reason it is strongly stated that the main weapon for attacking was the jawbone of the Acrocanthosaurus, which emanated quite a lot of strength and power, leaving its victims defenseless.

This great dinosaur has the quality of “big” for the simple reason that it turned out to be the largest theropod within its ecosystem, and there has even been talk of the great possibility of being the largest predator that fed on other huge sauropods, and even on ornithopods, which were not exactly small in size.

The Acrocanthosaurus and its resemblance to other dinosaurs

An important characteristic of the Acrocanthosaurus was its elongated and narrow skull, similar to the skull of other allosaurid dinosaurs, it also had an enigmatic hole that was located just in front of the developed eye socket, this hole is called “anteorbital fenestra”.

This complexly named structure had the simple function of reducing its weight, since it was a fairly wide opening, more than a quarter of the total length of the skull.

The dental area had a square shape, located just outside the front edge, just like the Giganotosaurus. Additionally, it was of a shallow nature, very different from the jaw, which turned out to be extremely deep in this dinosaur.

Another interesting quality of the Acrocanthosaurus was the group of neural spines, which we could find right in the neck vertebrae, distributed up to the end of its own tail, which led it to have more than twice the length of the vertebra itself.

In that sense, let’s remember that many other dinosaur specimens also had that kind of spines on their backs, even much bigger (or higher) than those of the Acrocanthosaurus, being this the case of the famous Spinosaurus, which could reach an average of about two meters high, but its spines reached a length 11 times higher than its own vertebrae.

However, the difference between the spines of the Spinosaurus and those of the Acrocanthosaurus was that the spines of the former presented a “sail” shape along with its own skin, whereas in the second case they did not.

Continuing with the subject of the spines and vertebrae, the function of these famous spines remains a mystery at present, whereas some researchers assert that they may have been useful for communication among the Acrocanthosaurus, other scientists assure that they served as fat storage, whereas a third group of paleontologists is certain that they worked as thermoregulators.

Another interesting detail about the vertebrae is that the dorsal and the cervical vertebrae presented wide depressions called pleuroceles, right on the side, a characteristic only presented by the allosaurs, until now.

Leaving aside the vertebrae, just for a moment, we can clearly observe that the Acrocanthosaurus had a skeleton quite similar to that of the allosaurs, it had a quite long tail and it also turned out to be very strong and useful when balancing its body, so it helped to keep its balance.

The arms of the Acrocanthosaurus were shorter than originally thought, although they were very strong and powerful, which also contained three fingers on each hand, using the claws for various purposes, remember that the arms of the Allosaurus were not so short or so robust.

Acrocanthosaurus and the differences with Giganotosaurus

The Acrocanthosaurus has marked differences with respect to the Giganotosaurus, one of them is located in the maxilla, precisely on the external surface, and touching what we know as the nasal bone, exactly in the upper lateral zone.

In this place we found that this dinosaur had a rough texture, which made it very similar to the Giganotosaurus; but the big difference is that these nasal bones turned out to be long, besides having quite short edges.

Another difference of great magnitude was the curved teeth that Acrocanthosaurus presented, besides that they had as main quality that of being sawed, located in the lateral ones of the superior jaw, in the inferior jaw we still do not have official information about it.

Additionally, the teeth of the specimen studied were much wider than the teeth of the Carcharodontosaurus, and these teeth did not have a rough texture either.

The Acrocanthosaurus has a quality that differentiates it greatly from the Allosaurus, this quality, as you may have noticed, is the protruding ridge that lies right in the tear duct, a bone that was located precisely in front of each of this specimen’s eyes.
In addition, we notice that these lacrimal bones, together with the postorbital bones, manage to form a kind of arch right in the upper area of the animal’s eye; this happens in a similar way in the abelisaurids.

An interesting fact is that several fossil footprints were found, or as scientists call it: ichnites.

These tracks were found inside the Glen Rose Formation, which is located precisely in the central part of the state of Texas, and other finger marks of some other theropods were discovered.

Of all these tracks, there is a very famous group of ichnites, which was found on the banks of a river called Paluxy, precisely in the renowned Dinosaur Valley National Park.

Besides, this group of ichnites is nowadays being exhibited in a very valuable museum for science: the Museum of Natural History (located inside the city of New York – United States of America).

An important detail that we must have very clear is that it is an impossible fact to know for sure to which animal the footprints belonged, however, there are great probabilities that these ichnites belong to the dinosaur that we are studying today.

On the other hand, we have a famous study in which the work of comparing Glen Rose’s footprints was carried out in 2001, however, in spite of that comparative research, it was not possible to determine whether these footprints belonged to any particular dinosaur.

The only way to determine or get closer to the truth is to study the size of the footprints, by which we can say that they probably belong to a large dinosaur like Acrocanthosaurus.

Taking into account this data and analyzing the place where it was discovered (near the Glen Rose Formation), an area where only one large dinosaur lived, we can say that in great probability it is Acrocanthosaurus.

Another interesting fact is that footprints of various theropod dinosaurs were found, and also ichnites of other dinosaurs called sauropods were found, some footprints above others.

This is a great indicator that at that time, group hunting was carried out on another group of dinosaurs. In this case, cooperative hunting was carried out by the Acrocanthosaurus, with the purpose of getting food from the flesh of the sauropods.

But this theory is not conclusive, like everything else in this science, since several explanations have also been given about the position of the footprints, explanations that base their foundations on the fact that these footprints were probably made at different times and not at the same time, this could collapse the theory explained in the previous paragraph.

However, other researchers claim that this is not the case, that is, they defend the first theory of cooperative hunting, due to the fact that some prints disappear just at the moment when the other print intercepts them, which makes the attack evident.

And you… What do you think about Acrocanthosaurus? We are very interested in your opinion about this enigmatic animal, which has caused a stir in the whole scientific world and especially in the world of Paleontology.