Palaeognathous Birds

Abstract

The Tinamiformes were long considered to be the sister group of the flightless palaeognathous birds, which were classified as “ratites”. However, current molecular analyses congruently supported a clade including the Tinamiformes, Casuariiormes, and Apterygiformes. Accordingly, flightlessness must have evolved independently within several palaeognathous lineages, as has already been assumed by some earlier authors. The distribution of extant palaeognathous birds is mainly restricted to the Southern Hemisphere, but several fossil taxa were reported from the Paleogene of Europe and North America. Most interesting from an evolutionary point of view are various long-legged, crane-like birds from Eurasia and North America, which are likely to be stem group representatives of the Struthioniformes. Rheiformes and Casuariiformes have a Paleogene fossil record in their current ranges, whereas Paleogene fossils of the Tinamiformes, Dinornithiformes, Apterygiformes, and Aepyornithiformes have not yet been found.