Atlascopcosaurus was a small herbivorous dinosaur. At only 6-10 feet in length and about 125-150 pounds, it would have been easy prey for a larger predator. It's only means of escape would have been it's speed. Atlascopcosaurus has been estimated to run up to 25 miles per hour. Atlascopcosaurus lived about 100 million years ago in Australia.