Ask aDino Field Guide ← Jurassic

Artist's reconstruction · realistic art coming in a later version

Allosaurus

AL-uh-SOR-us

“Different Lizard”

Jurassic
When
Late Jurassic
Where
North America
Size
Up to 39 ft long
Diet
Meat

7 Facts

1–7
  1. Allosaurus was the top predator of the Late Jurassic in North America.
  2. Its name means “Different Lizard” because its backbones weren’t like any known dinosaur when it was discovered.
  3. It had a pair of short bony ridges above its eyes, almost like little horns.
  4. Its teeth were curved and serrated like steak knives, made for slicing meat.
  5. It hunted big plant-eaters — including Stegosaurus, whose tail spikes sometimes fought back.
  6. It could open its jaws very wide and may have used its head like a hatchet to strike prey.
  7. One of the most complete Allosaurus skeletons is a famous fossil nicknamed “Big Al.”