A large order of birds containing the gallinaceous, or chickenlike, birds. They are found worldwide, although several of the subgroups have a more limited distribution. Part of the superorder Neognathae, the galliforms are closely related to the anseriforms and are often placed with them in a separate group, the Galloanserae. The gallinaceous birds include the most important domesticated birds, the chicken (Gallus gallus) and the turkey (Meleagris gallopavo); the rapidly breeding Japanese quail (Coturnix japonica) is an important species for much scientific work. The hoatzin of South America is often classified as a galliform suborder, but here it will be treated as a distinct order, the Opisthocomiformes.