Ostrich (Struthioniformes)

Struthioniformes is a order of flightless birds, containing the extant ostriches and their extinct relatives.  Other ostriches are also among the largest bird species ever.

The first species of Struthio appear during the Miocene epoch, though various Paleocene, Eocene, and Oligocene fossils may also belong to the family. Ostriches are classified in the ratite group of birds, all extant species of which are flightless, including the kiwis, emus, and rheas. Traditionally, the order Struthioniformes contained all the ratites. However, recent genetic analysis has found that the group is not monophyletic, as it is paraphyletic with respect to the tinamous, so the ostriches are usually classified as the only members of the order, though the IUCN uses a broader classification and includes all "ratites" and tinamous in Struthioniformes.