A basal tyrannosauroid dinosaur from the Late Jurassic of China

An ornamented dinosaur The tyrannosaurid dinosaurs were a successful group of large carnivores that peaked in terms of size with Tyrannosaurus rex . The fossil record for the group through the Jurassic is sparse but the discovery of a rich deposit of fossils from the Upper Jurassic (about 155 million years old) of the Junggar Basin in northwestern China is filling the gap. One of the most significant finds is described in this issue, a small carnivorous dinosaur about 3 metres long with an elaborate head-crest unlike anything seen in other dinosaurs. It could be an exaggerated sexual ornament, in the same vein as the antlers of the Irish elk or the long tail of the male peacock. The tyrannosauroid fossil record is mainly restricted to Cretaceous sediments of Laurasia, although some very fragmentary Jurassic specimens have been referred to this group 1 , 2 . Here we report a new basal tyrannosauroid, Guanlong wucaii gen. et sp. nov., from the lower Upper Jurassic of the Junggar Basin 3 , 4 , northwestern China. G. wucaii is the oldest known tyrannosauroid and shows several unexpectedly primitive pelvic features 5 , 6 . Nevertheless, the limbs of G. wucaii share several features with derived coelurosaurs 7 , 8 , 9 , and it possesses features shared by other coelurosaurian clades 10 . This unusual combination of character states provides an insight into the poorly known early radiation of the Coelurosauria. Notably, the presumed predatory Guanlong has a large, fragile and highly pneumatic cranial crest that is among the most elaborate known in any non-avian dinosaur and could be comparable to some classical exaggerated ornamental traits among vertebrates.