Allosaurus was a carnivorous (meat-eating) dinosaur that lived in what is now North America during the Late Jurassic period, about 150 million years ago.

The name Allosaurus means "strange lizard" or "different lizard". It was given this name because it looked different from other dinosaurs of its time.

The first Allosaurus specimen ever discovered was a broken tailbone that was found in Colorado in 1869. More fragments were found in 1877.

An almost complete Allosaurus skeleton was collected between 1883 and 1884.

In 1991, a 95% complete Allosaurus skeleton, named "Big Al" was discovered in Wyoming.

Allosaurus was a theropod, an order of dinosaurs that also includes Tyrannosaurus.

Allosaurs were about 28 feet long on average, but some may have reached as long as 40 feet.

Allosaurus walked on two legs. It had a heavy tail, which it used for balance, short arms and three fingers on each hand.

Its head was three feet long, and its teeth were two to four inches long.

Allosaurus is believed to have had a lifespan from 20 to 30 years.

Some paleontologists believe that adult allosaurs cared for their young and brought them food.

Fossils of many differnt allosaurs have been found gathered together at the same site. At one site in Utah, sixty individuals were found.

Paleontologists are not certain whether this means that allosaurs were social animals that hunted in packs, or whether they were solitary hunters who were in the same place because they were scavenging from the same kill.