Guanglong wucaii (Pronounced GWON-long woo-kay-eye) is named from the Chinese words guan, meaning ‘crown’, and long, meaning ‘dragon’, in reference to its flashy head-crest, the most elaborate of any known theropod dinosaur. The species name comes from the Chinese word wucai meaning ‘five colours’ and refers to the multi-hued rocks at Wucaiwan, the badlands where the fossils were found.
Guanlong wucaii is one of the most primitive tyrannosaurs known. It hunted its prey 95 million years before T. rex lived. Guanlong was a relatively small theropod, reaching 3–3.5 m (9.8–11.5 ft) in length and 125 kg (276 lb) in body mass. Its fossils were found in the Shishugou Formation dating to about 160 million years ago, in the Oxfordian stage of the Late Jurassic period, 92 million years before its well-known relative Tyrannosaurus. This bipedal saurischian theropod shared many traits with its descendants, and also had some unusual ones, like a large crest on its head. Unlike later tyrannosaurs, Guanlong had three long fingers on its hands.