Yutyrannus, name meaning "feathered tyrant", is a dinosaur genus that contains a single type species, Yutyrannus huali, named and described in 2012. The generic name is derived from Mandarin Chinese yu, “feather” and Latinised Greek τύραννος, tyrannos, “tyrant”, a reference to the fact it is a feathered member of the Tyrannosauroidea. The specific name consists of the Mandarin huáli, “beautiful”, in reference to the beauty of the plumage.
Yutyrannus was a gigantic bipedal predator. The holotype has a known length of 9 metres (30 ft) and an estimated weight of 1,414 kg (3,120 lb). Its skull has an estimated length of 905 millimetres. The skulls of the paratypes are eighty and sixty-three centimetres long and their weights have been estimated at 596 and 493 kilogrammes respectively.
The describers established some diagnostic traits of Yutyrannus, in which it differs from its direct relatives. The snout features a high midline crest, formed by the nasals and the premaxillae and which is covered by large pneumatic recesses. The postorbital has a small secondary process, jutting into the upper hind corner of the eye socket. The outer side of the main body of the postorbital is hollowed out. In the lower jaw, the external mandibular fenestra, the main opening in the outer side, is mainly located in the surangular.
While it has been known since 2004, upon the description of Dilong, that at least some tyrannosaurs possess filamentous “stage 1″ feathers, according to the feather typology of Richard Prum, Y. huali is currently the largest known species of dinosaur with direct evidence of feathers, forty times heavier than the previous record holder, Beipiaosaurus. The feathers were long, up to twenty centimetres, and filamentous. Because the quality of the preservation was low, it could not be established whether the filaments were simple or compound, broad or narrow. The feathers covered various parts of the body. In addition, the two adult specimens had distinctive, “wavy” crests on their snouts, on both sides of a high central crest, which were probably used for display. The presence of feathers on a large basal tyrannosauroid suggests the possibility that later tyrannosaurids were also feathered, even when adult, despite their size.
Yutyrannus was by the describers assigned to the Tyrannosauroidea in 2012. A cladistic analysis showed it occupied a rather basal position, below Eotyrannus in the evolutionary tree, but above forms such as Dilong, Guanlong and Sinotyrannus.
Darren Naish pointed out that the species resembles carcharodontosaurs and allosaurus such as Concavenator, especially in some for a tyrannosaurs unusual features of the skull, such as the pneumatic recesses on the snout crest, the secondary postorbital process and the form of the postorbital boss.
The presence of specimens of a different age allows to determine the ontogeny. During growth the lower legs, the feet, ilium and the forelimbs became relatively smaller. The skull on the other hand, grew more robust and deeper.