Classification
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. Rather, they placed Dilong two steps above the tyrannosauroids in their phylogeny; more advanced than Coelurus, but more primitive than the Compsognathidae. However, other studies continued to find Dilong as a tyrannosauroid, and some (such as Carr & Williamson 2010) found Dilong to fall within Tyrannosauroidea, not among the more advanced coelurosaurs.
Read more about this topic: Dilong (dinosaur)