Ceratosaurus nasicornis seh-RAT-oh-SOR-us
"Horned lizard"
You 1.8 m (5.9 ft) tall
Ceratosaurus 6 m (19.7 ft) long
as long as 4 people standing fingertip to fingertip
- Length
- 6 m (19.7 ft) — About 6 m long, ~700 kg — smaller than Allosaurus but distinctive.
- Period
- Late Jurassic (155–145 Mya)
- Place
- North America · Western United States · Tanzania · Portugal
- Food
- Carnivore — Smaller prey, possibly including fish — long flexible body and tall teeth suggest river hunting.
- Clade
- Ceratosauria Dinosauria Saurischia Theropoda Horned theropods: Ceratosaurus, Carnotaurus.
A Late Jurassic predator with a blade on its snout and bone studs down its back.
Ceratosaurus had a short horn on its nose and small horns over its eyes — features that made it stand out from the other big Jurassic predators it shared turf with. It was smaller and rarer than Allosaurus in the Morrison Formation, with a more flexible body and an unusual row of bony plates running down its back.
More about Ceratosaurus
Discovery
Marsh first described the genus from a nearly complete skeleton found at Garden Park. That specimen (USNM 4735) is the holotype and still the most complete skeleton known from the genus.
The name comes from Greek, combining "horn" and "lizard", a nod to the prominent horn on the midline of its snout.
How did Ceratosaurus actually use those long teeth?
Its deep jaws carried proportionally very long, blade-like teeth. Studies in 1998 and 2007 suggested the narrow skull was suited for quick slashing strikes, comparable to a Komodo dragon. In 2026, Taylor Oswald and Brian Curtice argued the very long teeth worked like those of sabre-tooth cats to quickly kill smaller prey, possibly including Dryosaurus, Camptosaurus, and juvenile sauropods.
For the curious → Did this dinosaur live outside North America?
A partial specimen described in 2000 from the Lourinha Formation of Portugal provides evidence for the genus in Europe. Fragmentary remains have also been reported from Tanzania, Uruguay, and Switzerland, but most paleontologists currently do not accept those as Ceratosaurus.
What we know
- Single nasal horn and two small brow horns — display structures, not weapons.
- Row of small bony plates (osteoderms) along the back.
- Four-fingered hand — primitive compared to allosaurs and tyrannosaurs.
- Lived alongside Allosaurus in the Morrison Formation but was less common.
What we guess
- Whether it competed with Allosaurus or specialized in different prey.
- Whether the unusually long, blade-like teeth indicate fish-catching like Spinosaurus.
- The exact purpose of the back osteoderms — armor, display, or thermoregulation.