Gruiformes is an order in the class Aves.
The Hoatzin was formerly placed in this order but it was moved by Clements to the Cuculiformes and later to Opisthocomiformes. The Seriemas were also placed here, but are now moved into their own family, Cariamidae. The same happened to the Bustards (now in Otidiformes), the Mesites (now in Mesitornithiformes) and the Kagu and the Sunbittern (now in Eurypygiformes). The Buttonquails (Turnicidae) are now placed within the Charadriiformes.