Common ostrich other members of Palaeognathae and thus the flighted tinamous are the sister group to the extinct moa. It is distinctive in its appearance, with a long neck and legs, and can run for a long time at a speed of or even up to about , the fastest land speed of any bird. The common ostrich is the largest living species of bird and lays the largest eggs of any living bird (extinct elephant birds of Madagascar and the giant moa of New Zealand laid larger eggs). The common ostrich's diet consists mainly of plant matter, though it also eats
Largest prehistoric animals "Argentavis magnificens" which a wingspan of , and a body weight of . The largest-known waterfowl of all time belonged to the Dromornithidae (e.g. "Dromornis stirtoni"). The largest-known of Ciconiiformes was "Leptoptilos robustus", standing tall and weighing an estimated . The largest-known of the hesperornithines was "Canadaga arctica" at long. The largest-known diatryma was "Gastornis" tall, with large individuals up to tall. The largest-known teratorn and the largest flying bird ever was "Argentavis". The immense bird had a wingspan estimated up to and a weight up to . It was as high as an adult human when standing. The largest-known-ever