Acrocanthosaurus

Acrocanthosaurus: A Giant Predator of the Cretaceous

Imagine a world where giant predators roamed the land, hunting in packs and stalking their prey with deadly precision. One such creature was Acrocanthosaurus, a colossal theropod that dominated its environment during the late Cretaceous period.

The Rise of Acrocanthosaurus

Acrocanthosaurus first appeared on the scene around 113 to 110 million years ago. This giant predator was one of the largest theropods, reaching lengths of 11-11.5 meters and weighing a hefty 4.4-6.6 metric tons. Its presence in North America was confirmed with the discovery of a partial skeleton from the Cloverly Formation in Wyoming in 2012.

Where Did Acrocanthosaurus Roam?

Was Acrocanthosaurus confined to one region, or did it roam freely across North America? The answer is that it was quite widespread. It inhabited both the western and eastern regions of what we now call North America. In 2024, a juvenile specimen was found near Sauroposeidon in Maryland, confirming its presence there.

The Anatomy of a Predator

Acrocanthosaurus had a long, low, and narrow skull with a large antorbital fenestra. Its nasal bones featured characteristic ridges, and the lacrimal and postorbital bones formed a thick brow over its eye. The largest known specimen had an estimated skull length of 1.23-1.29 meters and a body length of 11-11.5 meters.

The dentary bone was squared off at the front edge, while the jaw became deep. Nineteen curved, serrated teeth lined each side of the upper jaw, with a horizontal ridge on the surangular bone under the skull articulation shared with Giganotosaurus. The neural spines on its vertebrae were tall and prominent, more than 2.5 times the height of the vertebrae from which they extended.

How Did Acrocanthosaurus Move?

The skeleton was typical allosauroid, with a bipedal posture, long heavy tail, relatively shorter forelimbs, and robust hind leg bones. The feet had four digits each, but the first digit did not make contact with the ground. The forelimbs were not used for locomotion but served a predatory function.

The study found that the forelimbs would have hung from the shoulders with the humerus angled backward slightly in a resting position. The skeleton was typical allosauroid, with a bipedal posture, long heavy tail, relatively shorter forelimbs, and robust hind leg bones. The feet had four digits each, but the first digit did not make contact with the ground.

Acrocanthosaurus in the Fossil Record

The largest known specimen had an estimated skull length of 1.23-1.29 meters and a body length of 11-11.5 meters, with a body mass estimate ranging between 4.4-6.6 metric tons. The brain and inner ear structure were similar to allosauroids, with large olfactory bulbs indicating good sense of smell.

The forelimbs couldn’t swing forward to scratch the neck but could retract strongly, holding prey against the body and preventing escape. The wrist bones didn’t fit precisely, suggesting stiffness in movement. The middle digit converged towards the first when flexed, and claws had unique flexing and extending abilities.

Acrocanthosaurus as a Predator

What did Acrocanthosaurus prey on? It was one of the largest theropods and likely an apex predator that hunted sauropods, ornithopods, and ankylosaurs. The Glen Rose Formation revealed large three-toed theropod prints, including those belonging to several individuals moving in the same direction as up to twelve sauropod dinosaurs.

The presence of Acrocanthosaurus in the Arundel Formation suggests that it had managed to spread across the continent before the seaway could impede its movement. Potential prey animals included sauropods like Astrodon or Sauroposeidon, and large ornithopods like Tenontosaurus.

Conclusion

In conclusion, Acrocanthosaurus was a formidable predator that roamed the land during the late Cretaceous period. Its presence in North America, from Wyoming to Maryland, speaks volumes about its adaptability and dominance as one of the largest theropods of its time.