Largest organisms is frequently poorly documented and many are subject to conjecture and estimation. The largest living bird, a member of the Struthioniformes, is the common ostrich ("Struthio camelus"), from the plains of Africa and Arabia. A large male ostrich can reach a height of and weigh over . A mass of has been cited for the common ostrich but no wild ostriches of this weight have been verified. Eggs laid by the ostrich can weigh and are the largest eggs in the world today. The largest bird in the fossil record may be the extinct elephant birds ("Aepyornis") of Madagascar, which
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