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 along with the closely related "Eotriceratops xerinsularis" both with estimated lengths of . Ojoceratops and several other ceratopsians rival them in size. The very largest-known ornithopods, like "Shantungosaurus" were as heavy as medium-sized sauropods at up to , and in length. The largest-known birds of all time might have been the elephant birds of Madagascar. Of almost the same size was the Australian "Dromornis stirtoni". Both were about tall. The elephant birds were up to and "Dromornis stirtoni" was up to in weight. The tallest bird ever was the giant moa ("Dinornis maximus") at tall. The largest-known flight-capable bird was