Allosaurus fragilis AL-oh-SOR-us
"Different lizard"
You 1.8 m (5.9 ft) tall
Allosaurus 9 m (29.5 ft) long
6 people holding hands
- Length
- 9 m (29.5 ft) — About 9 m long, ~2 tonnes — the lion of the Late Jurassic.
- Period
- Late Jurassic (155–145 Mya)
- Place
- North America · Western United States · Portugal
- Food
- Carnivore — Large prey — Stegosaurus, Camptosaurus, possibly young sauropods.
Allosaurus was the top predator of the Late Jurassic. More than 60 individuals have been found at the Cleveland-Lloyd Quarry in Utah, making it the best-known large theropod by sheer number of bones. Allosaurus skulls had brow horns above the eyes and could open very wide — paleontologists nicknamed its bite the ‘hatchet jaw’ because it may have swung its head downward like an axe.
What we know
- Over 60 individuals known from the Cleveland-Lloyd Quarry alone.
- Two short brow horns above the eyes — likely display structures.
- Strong neck muscles allowed a downward axe-like bite, unlike T. rex's crushing bite.
- Lived alongside Stegosaurus, Apatosaurus, Diplodocus, Brachiosaurus.
What we guess
- Whether Cleveland-Lloyd is a predator trap, a die-off site, or a pack burial.
- How big the bite force was — much lower than T. rex, but a different killing style.
- Whether brow horns were for ramming, display, or shading the eyes.