Dinosaur Encyclopedia · Pack 4
Allosaurus
AL-oh-SORE-us
For younger explorers (ages 4–7)
Allosaurus facts for kids
01
Allosaurus could open its mouth very wide — like an alligator snapping down on prey!
02
It had bumpy ridges above its eyes, like little orange eyebrows made of bone.
03
Scientists found a bone spur on one Allosaurus that showed it had been stabbed by a Stegosaurus tail spike — and survived!
For older explorers (ages 8–12)
Advanced Allosaurus science
Biomechanical studies suggest Allosaurus attacked by driving its upper jaw down like an axehead, not by crushing like T. rex.
The Cleveland-Lloyd Quarry in Utah has produced over 10,000 Allosaurus bones — the highest density of large theropod fossils ever found.
An Allosaurus fossil known as 'Big Al' showed 19 bone injuries healed during its lifetime — evidence of a dangerous life hunting large prey.
Latest science
Allosaurus: The Axe-Headed Predator of the Morrison Formation
For decades, scientists assumed large theropods like Allosaurus hunted like modern big cats — biting into prey with brute force. Then a 1998 study by Emily Rayfield and colleagues changed the picture: CT scans and biomechanical modeling revealed that Allosaurus's skull was actually structurally weak compared to T. rex's. It couldn't sustain the crushing bite forces a lion uses.
Instead, Allosaurus likely attacked with a hatchet-style blow: it drove its upper jaw down and forward into prey, creating slashing wounds rather than crushing ones. This 'puncture-and-pull' or 'hatchet' attack would allow Allosaurus to wound enormous sauropods like Brachiosaurus and let blood loss do the rest — a very different predation style from T. rex.
Allosaurus is extraordinarily well-represented in the fossil record. The Cleveland-Lloyd Dinosaur Quarry in Utah alone has yielded over 10,000 bones from at least 46 individual Allosaurus specimens, making it one of the most densely studied large theropods in the world.
Journal Citation
Rayfield, E.J. et al. (2001). Cranial design and function in a large theropod dinosaur. Nature, 409, 1033–1037.
Jurassic neighbors
Who lived alongside Allosaurus?
Brachiosaurus
herbivoreA giraffe-like giant up to 26 meters long — Allosaurus's most impressive (and dangerous) prey.
Stegosaurus
herbivoreThe plated herbivore that shared the Morrison Formation — its spiked tail (the 'thagomizer') was Allosaurus's biggest hazard.
Diplodocus
herbivoreA whip-tailed giant reaching 27 meters — one of the longest animals that ever lived, also hunted by Allosaurus.
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