An allosaurus was a large, powerful meat-eating dinosaur that lived about 150 million years ago during the Jurassic Period. Picture a hunter the size of a school bus, walking on two strong back legs, with sharp teeth and claws designed for attacking prey. Allosaurus was one of the top predators of its time, hunting plant-eating dinosaurs like Stegosaurus in what is now North America.

The name allosaurus means “different lizard” because when scientists first discovered its fossils in the 1870s, its bones looked different from other dinosaur fossils they'd found. Allosaurus had a distinctive skull with bony ridges above its eyes, giving it a fierce appearance. While not as famous as Tyrannosaurus rex, allosaurus was actually more common and lived millions of years earlier.

Scientists have found so many allosaurus fossils that we know more about how it lived than most other dinosaurs. Some fossil sites show evidence that allosaurus may have hunted in groups, working together to take down larger prey. These discoveries help us understand not just what dinosaurs looked like, but how they actually behaved in their ancient world.