The Allosaurus was a large bipedal carnosaurian theropod, which means it was a predatory hunter that moved on two legs with a body shape characterized by hollow bones and 3-toed limbs.  

While it was a top of the food chain predator during the late-Jurassic period, it was already long extinct – for about 83 million years – by the time the Tyrannosaurus Rex ruled the world.

The name “Allosaurus” means “different lizard” which refer to its unique concave, or curved, spine, that ran on both sides and contained shallow cavities, giving the Allosaurus an almost hourglass shape — while these features reduced the bones strength, it made a much lighter and quicker dinosaur. The hollow spaces in the neck and spine are also found in modern birds and believed to have contained air sacs for breathing.

Allosaurus is the most common dinosaur fossil found in Cleveland-Lloyd Quarry in Utah, a site that has the heaviest concentration of Jurassic dinosaur bones in the world, though the bulk of Allosaurus fossils come from the Morrison Formation, a huge rock named after Morrison, Colorado and which extends through the Western United States and is believed to be up to 155 million years old.

Cleveland-Lloyd quarry in Utah

At an estimated 30 to 40 feet long and 12 to 16 feet high, and weighing around 3000 lbs at maturity, the Allosaurus was impressive, especially with its horns that protruded above each eye. But what made it a fierce dinosaur was its 60, D-shaped, sharp teeth that made its bite deadly.

Allosaurus teeth

Despite its massive build, this species fast: running up to 21 MPH. It was believed to have eaten large herbivore, or plant-eating, dinosaurs, and may have even tangled with the mighty stegosaurus whose back was covered with armor-like plates and had a tail that could whip its flesh ripping spikes.

The Mighty Stegosaurus


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