Allosaurus in a dry and sandy landscape


Allosaurus were big, mean killing machines that reigned supreme during the late Jurassic period. They were the most common huge predators in North America 140 million years ago, reaching an impressive 12 metres in length and weighing up to four tonnes. These carnivorous dinosaurs could rip and tear chunks out of the large plant-eating sauropods and stegosaurs of the time. The enormous jaw was filled with long, serrated, back-curving teeth. Near perfect examples of this classic shaped theropod dinosaur were discovered in Wyoming and called Big Al and Big Al Two. Allosaurus fossil remains are extremely rare outside America.

Scientific name: Allosaurus

Rank: Genus

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Allosaurus size

An illustration showing allosaurus's size relative to humans.

A comparison of allosaurus's size in relation to humans.


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Additional data source: Animal Diversity Web

When they lived

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Jurassic period Jurassic period
The Jurassic began after the mass extinction event that ended the Triassic. Life, however, was quick to recover from this blow and the Jurassic eventually became host to the most diverse range of organisms that Earth had yet seen.

BBC News about Allosaurus

  • Who buys a dinosaur skeleton? The BBC's Olivia Lang reports on the trend of collecting dinosaur fossils, as Sothebys auction house puts a partially complete Allosaurus skeleton up for sale in Paris.

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