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 organisms the giant moa ("Dinornis maximus"), part of the moa family of New Zealand that went extinct around 1500 AD. This particular species of moa stood up to tall, but weighed about half as much as a large elephant bird or mihirung due to its comparatively slender frame. The heaviest bird ever capable of flight was "Argentavis magnificens", the largest member of the now extinct family Teratornithidae, found in Miocene-aged fossil beds of Argentina, with a wingspan up to , a length of up to , a height on the ground of up to and a body weight of at least