Name means: Horn Reptile


Species: nasicornis

Range: Late Jurassic (Tithonian, 150-145 MYA) from Utah, Wyoming, Colorado, Oklahoma, possibly Portugal and Tanzania

Size estimate: 18-22 ft length, 1000-2200 lbs

Discovery: Othniel Charles Marsh, 1884

Classification: dinosauria, saurischia, therapoda, ceratosauria, ceratosauridae


Three large carnivores dominated western North America during the Jurassic period. Ceratosaurus was the smallest of the three, and in some ways it was also the most unusual. Its hands included three claws but four fingers. The “horns” that earned it the name “Ceratosaurus” were shaped more like crests. Their thin, fragile build made them better for showing off than fighting. Its unique look may have scared off rivals or threats, or impressed mates. Other parts of the skull suggest it may have survived alongside Allosaurus and Torvosaurus by hunting different prey. Its deeper skull and large, blade-shaped teeth could signal a preference for certain food. In addition to these odd features, Ceratosaurus grew bony plates along its back for defense or showing off.


Ceratosaurus belongs to a widespread but mysterious branch of the theropod group called ceratosauria. Remains of this group occur as far away as Australia and Madagascar. Many of them preserve too poorly or  include too few bones for description as valid species. Its closest relative, Genyodectes from Argentina, is known from only the tips of its jaws. Later members of the group include Carnotaurus, the bizarre Masiakasaurus from Madagascar, and the short-snouted Rugops from Africa.