Acrocanthosaurus: Cretaceous Therapod

Acrocanthosaurus was a large carnivorous therapod dinosaur that lived during the early Cretaceous Period between 115 and 105 million years ago. Incomplete remains of acrocanthosaurus have been unearthed in Oklahoma, Texas, and Utah. One complete skull and several fragmentary bones from the body have provided an overall estimate for what the dinosaur may have looked like. Possible footprints of acrocanthosaurus have been unearthed in Texas, and reveal the presence of many similar dinosaurs. This could mean that acrocanthosaurus could have hunted in packs, but also suggests that separate animals might have passed the same way at a different point in time. Currently, there is not enough evidence to offer conclusive support for either contention.

Acrocanthosaurus was a large carnosaur, reaching lengths of between 30 and 40 feet. It was a saurischian hipped dinosaur and resembled other top dinosaur predators like allosaurus and albertosaurus. It had an extremely large head, about four and a half feet in length, with 68 serrated teeth used for shearing flesh off of prey. It was a heavy therapod, weighing in at around two and a half tons. Unlike Tyrannosaurs, acrocanthosaurus had powerful arms that contained three instead of two fingers. With improved mobility and torque accompanying the longer length, these could have aided in tearing flesh off of carcasses.

The most striking feature of acrocanthosaurus is the presence of long dorsal spines on the back. These were up to a foot and a half long, nearly three times higher than the vertebrae upon which they sat. This means that acrocanthosaurus could have sported either a webbed sail or a camel-like hump on its back. The sail would have been short compared to other dorsal-spined dinosaurs like spinosaurus, and thus might have been unsuited for temperature regulation. It has long been speculated that sail-backs have used their sails for controlling body temperature. The presence of a camel-like hump would seem more probably, perhaps acting as a place to store fat and nutrient resources for the animal.

Like other large carnosaurs, acrocanthosaurus had a higher brain-to-body ratio than other dinosaurs, particularly herbivores. The complete skull has provided scientists with a more intricate glimpse into the possible brain structure of the therapod. The olfactory bulbs were large, which would have indicated a keen sense of smell-something essential in predators with a wide territorial range. A reconstruction of the inner ear canal through computer imaging reveals that acrocanthosaurus would have held its head at a 25 degree angle below horizontal. Finally, the brain would have been shaped more like that of a crocodile than a bird, which was a divergent trait from other therapods like allosaurus.

Acrocanthosaurus is one of the only known large therapod of the early Cretaceous period. It might have died out due to competition from larger predators like Tyrannosaurs that appeared later in the Cretaceous.