The type specimen is IVPP 14243 (Institute of Vertebrate Paleontology and Paleoanthropology in Beijing), a nearly complete, semi-articulated, skull and skeleton.

Adult tyrannosaurs, found in Alberta and Mongolia have skin impressions which appear to show the pebbly scales typical of other dinosaurs.

[2] When Dilong was first described, it was considered one of the earliest and most primitive members of Tyrannosauroidea, the group that includes the later, larger tyrannosaurids such as Tyrannosaurus rex.

At least one later study, by Turner and colleagues in 2007, reanalyzed the relationships of coelurosaurian dinosaurs, including Dilong, and found that it was not a tyrannosauroid.

[7] Proceratosaurus bradleyi Kileskus aristotocus Guanlong wucaii Sinotyrannus kazuoensis Juratyrant langhami Stokesosaurus clevelandi Dilong paradoxus Eotyrannus lengi Bagaraatan ostromi Raptorex kriegsteini Dryptosaurus aquilunguis Alectrosaurus olseni Xiongguanlong baimoensis Appalachiosaurus montgomeriensis Alioramus altai Alioramus remotus Tyrannosauridae In a 2014 study, Dilong was found to be a proceratosaurid.

[8] However, in an analysis by Brusatte et al. in 2016, both parsimony and Bayesian phylogenetic analyses placed Dilong outside of Proceratosauridae, as a slightly more advanced tyrannosauroid.