Acrocanthosaurus

Acrocanthosaurus Was an Apex Predator in its Ecosystem

When it comes to popularly recognized dinosaur species, the Acrocanthosaurus is most certainly not one of the most well known of species. This North American theropod however, was a significant species within its own ecosystem and in this article we will take a look at everything you could want to know about this giant predator. From physical appearance to what these carnivores fed on, we will cover it all in the article below.

What is Acrocanthosaurus?

Acrocanthosaurus was a theropod that lived throughout what is now known as North America during the early Cretaceous period some 116 to 110 million years ago. This rather large dinosaur is recognized by the appearance of large spines that are found along the vertebrae bones on its back which were believed to support a thick layer of muscle. While this predator may not have measured up to other large dinosaurs of the time, in terms of its own ecosystem, the Acrocanthosaurus is seen as a top predator.

What Did Acrocanthosaurus Look Like?

As already mentioned above, Acrocanthosaurus had a series of extended neural vertebrae which supported a thick layer of muscle which ran from the back of the neck to just over the pelvis. This dinosaur was one of the largest theropods known to date measuring in at approximately 40 feet in length and weighing between 6 and 7 metric tons! The skull of Acrocanthosaurus is particularly large, measuring in at just over 4 feet long. The skull of Acrocanthosaurus is characterized by the presence of a particularly large fenestrae – or sinus like hole designed to lighten the weight of the skull. One distinguishing factor in the Acrocanthosaurus skull when compared to the skulls of other large predators like Carcharodontosaurus is that the nasal bone and the outside of the upper jaw bone do not possess a rough texture.

Acrocanthosaurus is also characterized by having a thick brown that is rather pronounced over the eye, this brow is a result of the postorbital and lachrymal bones meeting. When it comes to teeth, there is no definitive count for the bottom jaw of Acrocanthosaurus, but each side of the top jaw of this terrifying meat eater features 19 teeth. Each of Acrocanthosaurus’ teeth were curved and serrated in order to help with the tearing of flesh from prey items.

Acrocanthosaurus as a Hunter

Acrocanthosaurus is recognized for being at the top of its ecosystem in terms of large predators; however, these big carnivores were not fast movers. The large tail of the Acrocanthosaurus allowed for the large bipedal dinosaur to maintain its center of balance as it moved; however, there are a number of reasons why this large hunter was a slow mover. Primarily, like most theropods, Acrocanthosaurus had particularly small forelimbs which would not have been conducive to self preservation were the dinosaur to trip or fall during the hunt. Additionally the structure of the legs themselves was not built to allow the Acrocanthosaurus to run at a decent pace. The femur of Acrocanthosaurus was much longer than the tibia and metatarsals which indicates that it was not capable of running at any significant speed.

Acrocanthosaurus as an Allosauroidea

Acrocanthosaurus is a member of the Carcharodontosauridae family in the suborder Theropoda. Acrocanthosaurus is also classified as a member of the superfamily Allosauroidea in the infraorder Tetanurae. Dinosaurs in the Allosauroidea superfamily are characterized by the presence of ridges on the snout in addition to tall neural spines that can be found along the neck vertebrae. Whether or not you consider the Acrocanthosaurus to be a member of the Carcharodontosauridae family or the Allosauroidea superfamily differs on which defining characteristics of the family you recognize in the species. Regardless of this however, the Acrocanthosaurus is most definitely recognized as a theropod.

The Discovery of Acrocanthosaurus

The first discovery of Acrocanthosaurus was actually a simultaneous discovery of the holotype and the paratype in 1950. The first specimens were located in the Antlers Formation which is located in Oklahoma. The first two specimens of Acrocanthosaurus were far from complete; however, the two partial skeletons and single piece of skull material was enough for paleontologists to begin classification of the theropod species. It wasn’t until forty years later in the 1990’s that two more specimens of Acrocanthosaurus were discovered and provided much more detailed information on the species. One of the two specimens was a partial skeleton that only had a select portion of the skull; this specimen was located in the Twin Mountains Formation in Texas. The second, much more complete Acrocanthosaurus specimen was found once again in the Antlers Formation in Oklahoma and is the largest of all Acrocanthosaurus specimens found to date. This near complete specimen that includes a complete skull and a complete forearm is currently on display in the North Carolina Museum of Natural Sciences in Raleigh, North Carolina.

The Forearm of Acrocanthosaurus

One of the most confusing features of this large dinosaur for many less experienced dinosaur lovers is the short forearms that are characteristic of many theropod species. The small forelimbs only known purpose for this large dinosaur species was for predatory purposes. The wrists of Acrocanthosaurus were particularly stiff which served to strengthen the arms and prevent significant injury when holding prey items. As with many similarly structured dinosaur species, paleontologists hypothesize that the forelimbs of Acrocanthosaurus were not afforded a large range of motion and as such they would have been useless in capturing prey. Researchers believe rather, that Acrocanthosaurus utilized its jaws to capture prey and used its short forelimbs to hold prey items close to the body to prevent escape while tearing in to it with its large and powerful jaws. Another hypothesis states that Acrocanthosaurus perhaps utilized its jaws to hold prey items while using the large claws on its forearms to tear in to prey.

The structure of the smaller forearms of Acrocanthus indicates that measures were taken to ensure that this carnivore was able to utilize its small hands while feeding without worrying too much about injury. Each of the digits on the small forelimbs show evidence of being able to hyperextend completely which ensured that while the digits were small, they would not become injured when used to hold struggling prey. In addition to the digits being designed to bend all the way backwards, the structure of the claws on each of these digits was such that if prey items were to struggle while in Acrocanthosaurus’ grasp, they would become more injured. The first digit on each claw was directed towards the other digits and it featured the largest claw that curved toward the “hand” area. This design ensured that any prey that was still alive when held in Acrocanthosaurus claws would surely impale itself on the large claw while struggling to escape. This design supports the theory that prey was held while still alive in addition to the theory that the claws were used to shred prey as it was held in the jaws.

The Brain of Acrocanthosaurus

Utilizing CT scanning, in 2005, researchers were able to create a cast of the inside of the Acrocanthosaurus’ brain cavity. Creating a cast of the inside of the skull of the Acrocanthosaurus enables researchers to see just how much space was available within the skull for the brain, cerebrospinal fluid and meninges. Taking an endocast of the brain cavity enables researchers to compare the brain of Acrocanthosaurus to other theropods to see just where this carnivorous giant fits in. When compared to other theropods brains’ the Acrocanthosaurus brain is most like that of allosauroid theropods like Giganotosaurus and Carcharodontosaurus. This evidence tends to point to the idea that Acrocanthosaurus should be characterized as a carcharodontosaurid.

Mapping the brain of Acrocanthosaurus proved to tell more about the Acrocanthosaurus in terms of how it fits in to the evolutionary scheme of things. The s-shaped brain that shows little in terms of cerebral hemisphere expansion which means that in terms of evolution the Acrocanthosaurus is more similar to a crocodile than it is to a bird. Scanning of the Acrocanthosaurus brain also shows that this large carnivore possesses large olfactory bulbs meaning that there was little prey could do to hide from this dinosaur’s sense of smell! Much like many other large theropods it is most likely that Acrocanthosaurus depended upon its sense of smell when hunting for prey rather than its eyesight- in fact it is likely that this large dinosaur did not have particularly good eyesight.

The Paleoecology of Acrocanthosaurus

Acrocanthosaurus specimens have been found throughout the United States with fossils being located in the Antlers formation of Oklahoma and the Twin Mountains Formation in Texas. It is also believed that a set of fossilized footprints in the Glen Rose Formation in Texas belong to the Acrocanthosaurus. The specimens and evidence of the Acrocanthosaurus that have been discovered to date can be dated by paleontologists by examining other paleontological evidence within the same rock formations. Utilizing this evidence in addition to geological rock dating, researchers are able to determine that Acrocanthosaurus most likely roamed the Earth during both the Aptian and the Albian stages of the Early Cretaceous period. By dating the Acrocanthosaurus to such a timeframe, paleontologists are able to discover just what type of territory that this giant theropod lived in. Since areas like the Glen Rose Formation were coastal during the Aptian and Albian stages of the early Cretaceous period it is believed that this carnivore prowled low lying shorelines for prey.

The Impressive Acrocanthosaurus

The Acrocanthosaurus was impressive both in size and in terms of the amount of control it was able to exert over other species in its ecosystem. From what paleontologists are able to decipher from the remains of this giant species, Acrocanthosaurus held such an impressive position in its environment that it tackled even the most enormous prey items like the giant sauropod Sauroposeidon. While this meat eater may not be the most recognized of all the Cretaceous period dinosaurs, or even the largest, it certainly was one of the most feared in its own ecosystem.