Monolophosaurus, artwork. Monolophosaurus (meaning 'single-crested lizard') was a bipedal carnivorous theropod dinosaur that lived around 170 million years ago (middle Jurassic) in what is now China. When alive, an adult would have measured over 5 metres in length, and weighed roughly 700 kilograms. It had a distinctive crest on top of its skull and was thought to have lived in or around water.