Dino Index

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Latin Name Allosaurus
Everyday Name Allosaurus
Length 12 meters
Height 5 meters
Weight 1,400 kilo
Diet carnivore
Period Jurassic
Pronunciation Aah - Low - Sor - Us

Allosaurus

Of the many Jurassic dinosaurs, the most famous predators are the allosaurs.

Allosaurus is maybe the best known predator of the Jurassic Period - in fact it was the number one predator of that time - so it is a natural place to start learning about Jurassic dinosaurs.  It belongs to the theropod group of dinosaurs. (the theropods are the group that later became modern birds!) They usually had hollow thin walled bones, three main fingers on the hand (the fourth and fifth are smaller in size), sharp recurved teeth, and claws on all their hands and toes.

My son and I learned about Allosaurus first in the BBC classic Walking with the Dinosaurs - Time of the Titans film (watch a bit here).   They captured my imagination as they tried to attack a brachiosaur in the film - unsuccessfully.  Many of the sauropods of the period were very large and perhaps fended off such attacks easily but there is evidence that Allosaurus attacked Stegosaurus.  One was injured by a Stegosaurus, perhaps when it tried to attack it (...successfully-??), and in another instance a Stegosaurus has a wound that fits well with Allosaurus teeth.

What did they eat?  

Allosaurus looks like a meat eater - a carnivore.  The teeth are large and sharp and curve inward, so animals cannot escape after they are bitten.

  But the jaws were not very strong- not strong enough to crush bones, like the jaws of Tyrannosaurus rex. Some scientists believe that Allosaurus attacked with an open mouth and chopped at prey with its teeth. Also, since Allosaurus was not terribly large, some scientists think they attacked young sauropods before they became too large, or perhaps they hunted in packs.   Another  suggestion was that they did not actually kill their prey but just bit off chunks of flesh in an attack and that was enough to feed them. 

They have been estimated to run at speeds of 30 of perhaps even as high as 55 kmph, but their field of vision suggests that they were ambush predators.

Allosaurus has been found in several locations in North America, and even 95% complete skeletons of the Allosaurus have been found. One  site in Utah had the remains of hundreds of Allosaurus mixed with bones of the sauropods Camarasaurus, and Apatosaurus.   Since the Allosaurus size suggests that they were not very fast, hunting sauropods helps explain how they could be successful without being very fast, since the sauropods also were not very fast.

Small Arms

Paleontologists have been puzzled for a long time about the small size of the arms.  They were powerful, and strong enough to hold prey and at the same time bite it, so they may have been used for attacking. allosaurus
There are three claws at the end of these arms, so they  appear very good for gripping things, too.

If that is the case, then theyu may have had an advantage over the larger Tyrannosaurus rex that appeared in the Cretaceous period.

Allosaurus model in dinosaur park

Something Strange

Allosaurus had crests, or ridge bones in front of the eye sockets.  Scientists don't know why they had these crests, but some think maybe they were for making signals to other Allosaurus.  For instance, they might have identified if it was male or female, or perhaps they acted as protection for the eyes when the Allosaurus fought with other animals.

Where they are found

Allosaurs have been found in the Western United States, Portugal, Australia, and Tasmania.  There are several known kinds of Allosaurus (seven generally recognized, and perhaps as many as twelve), the most well known being Allosaurus fragilis.


This dinosaur used to be known as Antrodemus, and was reclassified in the 1970's.  These dinosaurs lived for about  25 years, and they regularly shed their teeth (but then, so do crocodiles!).   the most famous Allosaur is Big Al, discovered in 1991.