Dilong

Dilong (which means 'emperor dragon') is a genus of small, tyrannosauroid dinosaur. The only species is Dilong paradoxus. It is from the Lower Cretaceous Yixian Formation near Lujiatun, Beipiao, in the western Liaoning province of China. It lived about 130 million years ago. It was described by Xu Xing and colleagues in 2004.

Dilong paradoxus is one of the earliest and most primitive known tyrannosauroids and had a covering of simple feathers or protofeathers, and scales. See Feathered dinosaurs.

The name is derived from the Chinese 帝 dì meaning 'emperor' and 龙/龍 lóng meaning 'dragon'. "Di", "emperor", refers to the relationship of this animal to Tyrannosaurus rex, the "king" tyrannosaurid. "Long" is used to name Chinese dinosaurs in much the same way that the Latin -saur(us) is in the West. The specific name, paradoxus, is a Latinisation of the Ancient Greek παράδοξον meaning 'against received wisdom'.

The type specimen is IVPP 14243 (Institute of Vertebrate Paleontology and Paleoanthropology in Beijing), a nearly complete, semi-articulated, skull and skeleton. Referred material includes IVPP 1242, a nearly complete skull and presacral vertebrae, TNP01109 (Tianjin Museum of Natural History), a partial skull, and IVPP V11579, another skull which may belong to D. paradoxus or may be a related species. The type specimen of Dilong was about 1.6 m in length, but it is thought to be a juvenile and may have been over 2 meters long when grown.

The feathers were seen in fossilized skin impressions from near the jaw and tail. They are not identical to modern bird feathers, lacking a central shaft and most likely used for warmth, since they could not have enabled flight. Adult tyrannosaurs, found in Alberta and Mongolia have skin impressions which appear to show the pebbly scales typical of other dinosaurs. Xu et al. (2004) speculated that the tyrannosauroids may have had different skin coverings on different parts of their bodies - perhaps mixing scales and feathers. They also speculated that feathers may correlate negatively with body size - that juveniles may have been feathered, then shed the feathers and expressed only scales as the animal became larger and no longer needed insulation to stay warm.

Turner and colleagues, in 2007, reanalyzed the relationships of coelurosaurian dinosaurs, including Dilong, and found that it was not a tyrannosauroid. Rather, they placed Dilong two steps above the tyrannosauroids in their phylogeny; more advanced than Coelurus, but more primitive than the Compsognathidae.