What is Allosaurus?
{{italictitle}} {{taxobox | name = ''Allosaurus'' | image = Allosaurus in Bałtow white background.jpg | image_width = 200px | image_caption = | status = [[Extinct]] | fossil_range = [[Upper Jurassic|U.J.]]-[[Lower Cretaceous|L.K.]] {{fossil range|155|120}} | regnum = [[Animal]]ia | phylum = [[Chordate|Chordata]] | classis = | superordo = [[Dinosaur]]ia | ordo = [[Saurischia]] | subordo = [[Theropoda]] | familia = [[Allosauridae]] | genus = '''''Allosaurus''''' | genus_authority = [[Othniel Charles Marsh|Marsh]], 1877 | subdivision_ranks = | subdivision = }} [[File:AllosaurusAMNH5753.jpg|thumb|220px|The skeletal mount of AMNH 5753, posed as scavenging on a ''Haplocanthosaurus priscus.'']] [[File:Allosaurus4.jpg|thumb|220px|1919 painting of an ''Allosaurus'' scavenging on a dead ''Haplocanthosaurus''.]] '''''Allosaurus''''' was a large [[theropod]] [[dinosaur]] from the [[Jurassic]] period, a [[predator]]y [[carnivore]]. ''Allosaurus'' averaged 8.5 [[metre]]s (28&nbsp;ft) in length, though some remains suggest it could reach over 12 meters (39&nbsp;ft). Its three-fingered forelimbs were smaller than its large hind legs, and the body was balanced by a long, heavy tail.<ref name=JM76>Madsen, James H, Jr. 1993 [1976]. ''Allosaurus fragilis'': a revised osteology. 2nd ed, ''Utah Geological Survey Bulletin'' '''109'''. Salt Lake City: Utah Geological Survey.</ref> It weighed 2.3 tons. It is the most common large predator found in the [[Morrison Formation]] of [[Colorado]]. This formation was laid down 155 to 145 million years ago, in the Jurassic. ''Allosaurus'' was at the top of the [[food chain]]. It probably preyed on large herbivorous dinosaurs and perhaps even other predators, including ''[[Ceratosaurus]]'' and ''[[Marshosaurus]]''. Potential prey included [[ornithopod]]s, [[stegosaur]]s, and [[sauropod]]s. Some paleontologists think ''Allosaurus'' had cooperative [[behavior]], and hunted in packs. Others believe they may have been aggressive toward each other. Groups have been found together in the foss