Allosaurus (Al-oh-soar-us) was a carnivorous dinosaur that lived 150 million years ago during the Jurassic Period of North America. It was a contemporary of Brontosaurus, Stegosaurus, and Camptosaurus, as well as the smaller carnosaur Ceratosaurus. Allosaurus was 30 to 40 feet long with a 3 foot skull. The forelimbs of Allosaurus were reduced in size (as in other carnosaurs), but were quite functional and armed with large hook-like claws with which to grasp prey. There were three fingers on each hand and the claws that they bore grew as long as 10 inches. The hind limbs were also powerful and, in addition to walking, were probably used for seizing and rending prey. The teeth of Allosaurus were sharp and distinctly recurved and, like most theropods, serrated. There was a distinct horn-like structure in front of and above the eye, the function of which (if any) is unknown. There were also paired ridges that ran along the top of the skull from the nasal region to the "horns."
Allosaurus is one of the dinosaurs that is best known to science thanks to a large deposit of bones discovered in the Cleavland-Llyod Quarry of Utah. Disarticulated remains of at least 44 individuals were found there, ranging from small juveniles to full-size adults. Thousands of individual Allosaurus bones have also been collected from various other sites across western North America, including Colorado, Utah, Wyoming, and Montana.
Brontosaurus tail bones have been found with peculiar grooves that have been identified as Allosaurus tooth marks. Since Allosaurus was probably not large enough to bring down one of these huge dinosaurs by itself, it has been speculated that they either hunted in packs or simply scavenged the larger carcasses. There seems little doubt, however, that Allosaurus was an active hunter of the more moderate-sized dinosaurs with which it lived.
Allosaurus Skeleton and Reconstruction