Monolophosaurus (/ˌmɒnoʊˌlɒfoʊˈsɔːrəs/ MON-o-LOF-ə-SAWR-əs;[1] meaning "single-crested lizard") is an extinct genus of tetanuran theropod dinosaur from the Middle Jurassic Shishugou Formation in what is now Xinjiang, China.[2][3] It was named for the single crest on top of its skull. Monolophosaurus was a mid-sized theropod at about 5 metres long.