Allosaurus

What it was like

Allosaurus was a large, agile hunter with a light, strong skull lined with rows of sharp, serrated teeth. It grew up to about 9.5 meters (31 feet) long and could weigh around 2 metric tons. Its arms were small next to its powerful legs but ended in sharp, curved claws.

It probably preyed on large plant eaters such as stegosaurs and sauropods. Scientists still debate whether Allosaurus hunted alone or sometimes gathered around the same carcass or prey.

Its world

Allosaurus lived from about 155 to 143 million years ago, spanning the Late Jurassic and Early Cretaceous, in what is now the western United States and Portugal. Its bones come mainly from the Morrison Formation, alongside plant eaters like Stegosaurus, Camarasaurus, Brachiosaurus, and Diplodocus, and other hunters such as Ceratosaurus and Torvosaurus. Allosaurus was the most common large predator in this habitat, so its bones turn up wherever the Morrison rock is exposed.

How it was found

Marsh named Allosaurus in 1877. It is one of the best-known Jurassic predators, with about 137 fossil finds recorded, giving paleontologists an unusually full picture of how it looked and moved. Few other dinosaurs from this period are known from so many separate skeletons.