|Name Meaning||High-spined lizard||Height||4.8 meters (16 feet)|
|Pronunciation||Ah-kroh-kan-tho-sore-us||Length||11-11.5 meters (36-38 feet)|
|Era||Mesozoic – Early Cretaceous||Weight||4.4-6.6 metric tons (4.9-7.3 short tons)|
|Classification||Dinosauria, Saurischia & Theropoda||Location||Texas, Wyoming, Oklahoma, Maryland; United States|
Acrocanthosaurus is commonly referred to as the “high-spined lizard.”
The genus consists of only one species, Acrocanthosaurus atokensis, and its first fossils were discovered in the early 1940s.
Subsequent discoveries indicated that the creature was widely distributed across what we now call North America.
Based on these discoveries, paleontologists concluded that the Acrocanthosaurus lived around 113-110 million years ago, during the Early Cretaceous.
It was a bipedal carnivore with distinctive neural spines.
Moreover, it was one of the largest theropods, so its discovery is a significant addition to what paleontologists already knew about the Theropoda clade.
In this article, we’ll share some essential details about the species, including its appearance, behavior, diet, reproduction, and evolution.
We will also explore some notable appearances of Acrocanthosaurus in media.
Acrocanthosaurus was a large theropod, with paleontologists estimating its skull length to be around 1.23-1.29 meters (4-4.2 feet).
Can you imagine that only the skull was larger than some small dinosaurs?!
The body length reached approximately 11-11.5 meters (36-38 feet).
However, paleontologists suggest that these size estimations are based on the largest specimens found, and not all Arcocanthosaurus dinosaurs were this big.
The species is also thought to have weighed roughly 4.4-6.6 metric tons (4.9-7.3 short tons).
For comparison, we have examined the sizes of other dinosaurs within the same family as the Acrocanthosaurus and concluded that the species we’re discussing today was indeed pretty large!
For example, the largest member of the family was probably the Giganotosaurus, just as its name suggests, and it measured 12-13.2 meters (39-43 feet) long.
Some scientists even argued that this theropod is larger than the well-known Tyrannosaurus! This demonstrates that Acrocanthosaurus was not much smaller than the Giganotosaurus!
Meraxes, another relative of the high-spined lizard, was almost equally large, reaching a length of up to 9-11.6 meters (30-38 feet).
The same goes for Mapusaurus, which measured 11-12.2 meters (36-40 feet) long.
The family also had smaller specimens – the Shaochilong was only 5-6 meters (16-20 feet).
In short, we can safely conclude that the Acrocanthosaurus and its relatives were among the world’s largest theropods!
But what about its overall appearance? What made it unique? Here’s what we found out about the Acrocanthosaurus:
- It had a long, narrow skull and featured a large opening in front of the eye socket, which aimed to reduce weight.
- Its brain was very similar to other allosauroid brains, resembling those of Giganotosaurus and Carcharodontosaurus.
- The brain had a slight S-shape, indicating it was similar to a crocodile brain rather than a bird brain.
- It had nineteen teeth on the upper jaw, all curved, serrated, and wider than in other species.
- It featured a row of tall neural spines extending from the vertebrae of its neck, back, hips, and tail; this is considered the species’ most distinctive characteristic.
- It had a long, heavy tail used for maintaining balance.
- It was bipedal and had short forelimbs, each having three digits extending in claws.
- Its hind limbs were long and robust; the femur was longer than the tibia and the metatarsals, suggesting it wasn’t a good runner.
- Each foot had four digits, although only three were functional; the first was smaller and didn’t touch the ground.
Habitat and Distribution
Acrocanthosaurus fossils have been discovered in multiple formations, making it somewhat difficult to outline a precise habitat for the species.
Moreover, since it was a large prehistoric creature, it likely moved around and inhabited various ecosystems.
Here are the locations where the fossils have been found:
- The Twin Mountains Formation, northern Texas
- The Cloverly Formation, north-central Wyoming
- The Antlers Formation, southern Oklahoma
- The Arundel Formation, Maryland
It is thought that the Twin Mountains Formation and Antlers Formation were characterized by floodplains that drained into a shallow inland sea, which eventually became the Western Interior Seaway.
The Cloverly Formation is also thought to have been a floodplain environment, and most of the fossils discovered there were found in lacustrine, pedogenic, and overbank deposits.
The Glen Rose Formation, a marine environment, overlies the Twin Mountains Formation.
Paleontologists discovered multiple dinosaur footprints at this formation located in central Texas.
Although no other fossils were associated with them, scientists have concluded that the footprints probably belonged to Acrocanthosaurus specimens, as the formation is geographically close to the Twin Mountains Formation and the Antlers Formation.
Since this species is considered the largest theropod known to have lived in the area, the footprints from the Glen Rose Formation were attributed to it.
Behavior and Diet
As mentioned previously, Acrocanthosaurus was probably a slow-moving dinosaur or, at the very least, not a proficient runner.
This is indicated by the fact that its femur (thigh bone) was longer than the tibia (the leg bone below the knee) and the metatarsals (foot bones).
Despite its potentially limited running ability, Acrocanthosaurus was an efficient predator, especially since it’s known to have likely had a good sense of smell. Its forelimbs also were of help in the process.
Paleontologists reached this conclusion after studying the range of motion of Acrocanthosaurus forelimbs.
Here comes the most interesting part!
Studies showed that while these dinosaurs couldn’t swing their arms in full circles as we can, they could swing them backward at an angle of 109° from the vertical.
On the other hand, forward swinging was possible only at 24° from the vertical.
Besides, they were unable to extend their arms fully, and excessive flexing was not possible.
The dinosaurs could extend the digits backward until they almost touched the wrist.
All of this suggests that while hunting and catching prey, the Acrocanthosaurus likely used its head first, but once it captured prey with its jaws, it used its forelimbs and the claws on the first two digits to hold the prey tightly against its body.
It might have dispatched it using its jaws or torn it apart using its claws.
Another interesting behavioral trait is the possibility that Acrocanthosaurus moved in packs.
However, this is valid only if the footprints found in Glen Rose Formation belong to Acrocanthosaurus specimens.
These footprints were associated with several dinosaurs, which likely followed a herd of sauropods, indicating that hunting in small packs might’ve been characteristic of the species.
However, this is just a theory, and further evidence is required to confirm it officially.
On the other hand, one certainty is that the species was a carnivore and likely preyed on large sauropods and ornithopods
Acrocanthosaurus, like all dinosaurs, reproduced by laying eggs.
The males had two testes and a retractable penis, while the females had paired ovaries and two oviducts.
Therefore, unlike modern birds that have only one functional oviduct and lay a single egg, dinosaurs lay two eggs at a time.
What nests Acrocanthosaurus dinosaurs laid their eggs and whether they were incubated are unknown.
However, paleontological research shows that baby dinosaurs likely required around 12 years to become fully grown adults.
Other studies suggest a much longer period, around 18-24 years.
As such, although many baby dinosaur species were born precocial, meaning they were functional at birth and didn’t require adult help, baby Acrocanthosaurus may not have been so.
Some studies on carcharodontosaurids suggest that they probably lived up to 50 years.
Evolution and History
The Acrocanthosaurus has long been compared to the Allosaurus and was, in fact, originally placed in the same family as the latter, Allosauridae.
It was then associated with spinosaurids because of the long spines on the vertebrae.
However, further studies showed that it had more in common with members of the Carcharodontosauridae family than those in the Allosauridae and Spinosauridae.
As such, it is now closely related to dinosaurs like Concavenator, Taurovenator, Veterupristisaurus, Giganotosaurus, and Mapusaurus.
Nevertheless, the debate didn’t end here, as some researchers suggested that the members of the Carcharodontosauridae family were more closely related to abelisaurids, not allosaurids, because of some cranial features.
Studies on carcharodontosaurids suggest that the members of this family originated in Europe and subsequently reached southern continents and North America.
The first fossils indicating that this carcharodontosaurid reached North America were discovered in the early 1940s in Oklahoma’s Antlers Formation.
Then, a partial skeleton was found in Texas’ Twin Mountains Formation, and a more complete skeleton was recovered yet again from the Antlers Formation.
Other fossils found in the Cloverly Formation were described in 2012. In Maryland’s Arundel Formation, however, only several teeth were found.
Multiple other fossil discoveries throughout the western United States were also attributed to the Acrocanthosaurus, indicating that it might have had a much wider distribution.
However, they were never officially confirmed to have belonged to these creatures.
Interactions With Other Species
If we guide ourselves by what lived in the Antlers, Twin Mountains, and Cloverly Formations (where most fossils were found), we’d suggest that the high-spined lizard lived in the same ecosystem as the following creatures:
- Sauroposeidon, a sauropod dinosaur
- Tenontosaurus, an ornithopod dinosaur
- Atokasaurus, a scincomorph lizard
- Ptilotodon, a teiid lizard
- Astrodon, a sauropod dinosaur
- Deinonychus, a dromaeosaurid dinosaur
- Naomichelys, a helochelydrid turtle
- Astroconodon, a semi-aquatic mammal
- Albanerpeton, a salamander-like lissamphibian
- Zephyrosaurus, an ornithischian dinosaur
- Microvenator, an oviraptorosaurian theropod
Scientists suggest that the primary prey for Acrocanthosaurus were large sauropods and ornithopods.
More precisely, it is thought to have fed on dinosaurs like Astrodon, which measured up to 66 feet in length, making it much larger than the predator we are discussing today.
It might have also preyed on Sauroposeidon, which could reach around 89-112 feet, nearly three times the size of Acrocanthosaurus!
The fact that these two giant dinosaurs were herbivores suggests that they probably didn’t have well-developed escaping and defensive techniques, making them susceptible to being caught and preyed upon by Acrocanthosaurus.
The Acrocanthosaurus, as we are discussing today, shared its habitat with other carnivorous dinosaurs like Deinonychus, indicating that there may have been some competition between them.
Acroncanthosaurus has been the subject of numerous studies, focusing on various aspects such as its skull, brain, forelimb structure, function, and classification within the Allosauridae or Carcharodontosauridae family.
Other studies have explored the species’ geographic range of this species and other aspects of its evolution.
Needless to say, further research is inevitable, as there’s so much yet to be discovered about this enormous dinosaur.
The species is also well-known in popular culture, particularly due to its appearance in Jurassic World Evolution video game series, being among the series’ largest theropod dinosaurs.
Additionally, the “high-spined lizard” appears in the video game Warpath: Jurassic Park, as well.
Moreover, it has its episode in Monsters Resurrected, where it is depicted as a top predator.
You might’ve also seen it in Prehistoric Washington DC, a show on Discovery Channel, where it’s portrayed as a predator of Sauroposeidon and Astrodon.
These are only a few notable media appearances, highlighting that Acrocanthosaurus has earned popularity as a prehistoric character in the world of entertainment.
The discovery of the Acrocanthosaurus provided paleontologists with essential pieces of information about theropods.
The study of the species’ forelimb structure and function is an incredible addition to various textbooks on famous prehistoric creatures!
Here’s a recap of what we learned in this article.
The Acrocanthosaurus lived during the Early Cretaceous and was probably widespread throughout North America, thus sharing its habitat with many other prehistoric creatures.
It was an apex predator and likely fed on sauropods and ornithopods. Above all, it was among the largest theropods and had tall, distinctive neural spines.
Is Acrocanthosaurus bigger than T-Rex?
The T-Rex was bigger than the Acrocanthosaurus.
While the latter measured approximately 11-11.5 meters (36-38 feet) in length, the former could reach a length of 12.3–12.4 m (40.4–40.7 ft).
Additionally, the T-Rex was taller than the Acrocanthosaurus.
Is Acrocanthosaurus bigger than Spinosaurus?
The Acrocanthosaurus was smaller than the Spinosaurus, as the latter could reach 15 meters (49 feet) in length, while the former was only 11-11.5 meters (36-38 feet) long.
Who would win in a fight, Acrocanthosaurus or T-Rex?
If an Acrocanthosaurus were to confront a T-Rex, the fight would likely be intense, as both predators were excellent fighters and possessed well-developed defensive techniques.
Considering that the Acrocanthosaurus could hunt and kill gigantic sauropods, a T-Rex shouldn’t be a problem, right?!
Well, it might sound so, but the bite force of a T-Rex is about twice the bite force of an Acrocanthosaurus.
So, if the T-Rex managed to bite the high-spined lizard, the latter stands no chance.
As such, although both are great fighters, we’d say that the T-Rex would have more chance of winning.