Acrocanthosaurus

Acrocanthosaurus was a common carnivorous (meat-eating) dinosaur in North America during the mid Cretaceous period, between approximately 125 and 100 million years ago. It lived in North America - fossils of the animal have been mainly found in the US states of Oklahoma and Texas, but fossilized teeth have been found as far East as Maryland.

Acrocanthosaurus was up to 40 feet (12 meters) long, and weighed approximately 2.4 tons.

One usual feature of Acrocanthosaurus is the large neural spines on the vertebrae of the neck, back, hips and upper tail. It is not thought that it had a sail on its back like Spinosaurus (which was unrelated, and had much larger neural spines), but rather it is thought the spines had attachments for powerful muscles, similar to those found in modern bison. Its not entirely clear what the purpose of these spines and muscles were - possibilities include fat storage, communication, or temperature regulation.

Acrocanthosaurus was a carnivore, but is not believed to have been a fast runner. Its forelimbs and shoulders are also unusual, and seem to have been very strong, had lots of cartilage, but been quite stiff with very limited movement. It is thought that the forelimbs hung down and inwards, and would not have been used for seizing prey. Acrocanthosaurus may instead have seized prey with its jaws, and used its forelimbs to prevent the prey escaping. It is also possible that Acrocanthosaurus may have held the prey in its jaws, and used the claws in its forelimbs to tear gashes into the prey.