In the late Jurassic period, this fleet-footed planteater, known as Dryosaurus altus, needed those powerful hindquarters to scurry away from its many predators.
Philip Currie of the University of Alberta in Canada speculated that pack hunting could have allowed Mapusaurs to prey on the biggest known dinosaur, Argentinasaurus, a 37.5m-long (125ft) plant-eater.