← Rex's Notes
Allosaurus
The Jurassic's main predator.
Said: AL-uh-SOR-us
Era: Jurassic · 155 to 145 million years ago
Diet: Carnivore
Habitat: Floodplain forests of western North America
Size: about the length of a delivery truck.
What it was like
Allosaurus had a mouth that could open extra wide, almost 90 degrees, like a snake. It used its head like a hatchet, swinging it down at prey.
What we know now
Unlike T. rex, which delivered crushing bite force, Allosaurus had a relatively weak bite but a hatchet-style attack: it used neck musculature to drive serrated upper teeth down through flesh. The Cleveland-Lloyd quarry holds dozens of Allosaurus specimens; the current leading interpretation is drought-driven mass mortality at a shrinking watering hole, rather than the older 'predator trap' idea. Distinct ridges above the eyes; juvenile and adult skulls differ markedly.
Notes
- Most common large theropod in the Morrison Formation.
- Some specimens show healed Stegosaurus thagomizer wounds.
- Three forward-curving claws on each hand.