Supersaurus, SOO pur sawr uhs, was one of the largest dinosaurs that ever lived. It measured from 100 to 130 feet (30 to 40 meters) long, stood about 27 feet (8.2 meters) tall at the hips, and may have weighed more than 40 tons (36 metric tons). This enormous reptile lived about 150 million years ago, during the late Jurassic Period. It inhabited what is now the western United States.