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Allosaurus (Al-loh-sore-us), Strange Lizard, lived in the Late Jurassic of North America. It is the most common predator from the Morrison Formation. All other theropod dinosaurs are rare.

Content List

1. Genera & species

2. Characteristics

a. Size

b. Behavior

3. History of Discovery

4. Paleoenvironment

5. References.

Genera and Species

Classification: Theropoda, Tetanurae, Carnsauria, Allosauridae

Species: A. fragilis, A. jimmadseni, A. europaeus, A. maximus, A. amplexus, A. atrox, A. ferox, A. tendagurensis.

Senior synonyms: Allos. atrox, Allos. whitei , Allos. Lucaris, A.europaeus), Creosaurus atrox, Labrosaurus ferox, L. fragilis, L. lucaris, Antrodemus fragilis, Antro. lucaris, Antro. atrox, Antro. trihedrodon, Camptonotus amplus, Camptosaurus amplus, Laelaps trihedrodon, possibly Dryptosaurus trihedrodon, Hypsirophus trihedrodon and Apatodon mirus.


Allosaurus had 2 bony bumps above and ahead of their eyes, 2 smaller ones behind them and a low, narrow, bony ridge from eyes to snout. Its skull was deep, and the jaws contained an impressive array of flattened, serrated teeth. The forelimbs were muscular and ended in 3 fingered hands with powerful grasping claws, while the hind limbs were massive but capable of rapid movement.


Length 10 - 12 m (33 - 40 ft). Weight 1 - 1.7 tons.


It probably preyed upon the smaller camasaurs and diplodocids along with stegosaurs and camptosaurs. Fossil evidence from bones of Ceratosaurus and Torvosaurus show Allosaur tooth marks so they could have suppressed other carnivores like lions do today. Footprint evidence shows up to three allosaurs patrolling the same area so group behavior is possible.

History of Discovery

Discovered by Marsh in 1877 and known from 3 complete skulls, partial and complete skeletons of at least 60 animals, many isolated bones


Found in North America (Utah and Colorado USA) in semi-arid plains with a short rainy season crossed by braided rivers. Forests are restricted to river and lakes.


1. Paul, G. (2010). The Princeton Field Guide to Dinosaurs (pp. 10-12). Princeton, New Jersey: University Press Princeton.

2. Worth, G. (1999). The Dinosaur Encyclopaedia (pp. 10-12). Scarborough, Western Australia: HyperWorks Reference Software.