|Palaeognathae is one of 2 living clades of birds – the other being Neognathae. Palaeognathae contains five extant branches of flightless lineages (plus two extinct clades), termed ratites, and one flying lineage, the Neotropic tinamous. Recent research has indicated that paleognaths are monophyletic but the traditional taxonomic split between flightless and flighted forms is incorrect; tinamous are within the ratite radiation, meaning flightlessness arose independently multiple times via parallel evolution.
There are three extinct groups that are undisputed members of Palaeognathae: the Lithornithiformes, the Dinornithiformes (moas) and the Aepyornithiformes (elephant birds)
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