The Encyclopedia Americana (1920)/Ratitæ
RATITÆ, ră-tī'tē, a group of birds broadly characterized as having a non-carinate sternum and little or no power of flight. The group originally was one of the two grand divisions of Aves, embracing all those whose sternum had no keel, as opposed to Carinatæ; but this character alone will not define the Ratitæ as at present constituted by the researches of Gadow and accepted by ornithologists generally. Its place is as a subdivision of the Neornithes (q.v.) co-ordinate with the Odontolcæ (hesperornis, etc.) and the Carinatæ; and the sum of many anatomical peculiarities distinguishes the group, which consists of the ostriches, cassowaries, kiwis, moas, rocs (Æpyornis), and perhaps some of the fossil birds of Patagonia whose relationships are not yet perfectly clear. The conspicuous feature of all these is the rudimentary condition of the wings, so that the ratites are well-designated flightless birds, the disappearance of the tail and the great prominence of the functions and development of the legs and feet. These features are believed to be the result of changes, very long continued, from ancestors which possessed the power of flight and have lost it by disuse, and in adaptation to life upon plains and deserts. This group was introduced by Merrem in his ‘Attempt at a Natural System of Birds,’ and contains his genus ‘Struthio,’ since divided. Consult Evans, ‘Birds’ (1900); Newton, ‘Dictionary of Birds’ (1893-96); Stejneger, ‘Standard Natural History’ (Vol. IV, 1885).