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[al' u sah' rus] the biggest meat-eater in North America during the late Jurassic Period, about 154 to 144 million years ago


Allosaurus was up to 38 feet long and 16.5 feet tall, and weighed about 3,000 pounds. It had a 3-foot-long skull with two short brown horns and bony knobs and ridges above its eyes and on top of the head. Its arms were short and had three-fingered hands with sharp claws that were up to 6 inches long.



Allosaurus was equipped with sharp, pointed teeth in large, powerful jaws. It probably ate large, plant-eating dinosaurs. An Apatosaurus vertebra was found with Allosaurus tooth marks on it. It may have hunted in groups.

Fossil History

Allosaurus was named by paleontologist Othniel C. Marsh in 1877. The first virtually complete skeleton was discovered in Colorado, in 1883. Since then over 60 Allosaurus fossils have been found, mostly in Colorado, but also in other locations in western North America. Allosaurus fossils may have also been found in Australia, Africa and Portugal, but identification is not yet complete.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Archosauria
order Saurischia
suborder Theropoda
infraorder Carnosauria
family Allosauridae
genus & species
Allosaurus amplexus
(1878, originally called Epanterias)
Allosaurus atrox
(1878, originally called Creosaurus)
Allosaurus ferox
Allosaurus fragilis (1896, type species)


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The Robinson Library >> Paleontology

This page was last updated on 09/28/2018.