||The English used in this article may not be easy for everybody to understand. (May 2012)|
Neognaths (Neognathae) are birds within the subclass Neornithes of the class of birds. The Neognathae include virtually all living birds; their sister taxon Palaeognathae contains the tinamous and the flightless ratites.
There are nearly 10,000 species of neognaths. Since the late Cretaceous, from which the earliest fossils are known, they have undergone an adaptive radiation producing the diversity of form, function, and behavior that we see today. The Passeriformes (perching birds) are the largest order of land vertebrates, containing some 60% of living birds and being more than twice as specious as rodents and about 5 times as specious as Chiroptera (bats and flying foxes) which are the largest orders of mammals. On the other hand, there are some very small orders, usually birds of very unclear relationships like the puzzling Hoatzin.
The neognaths have fused metacarpals, an elongate third finger, and 13 or fewer vertebrae. They differ from the Palaeognathae in features like the structure of their jawbones. "Neognathae" means "new jaws", but ironically it seems that the supposedly "more ancient" paleognath jaws are among the few apomorphic (more derived) features of this group as compared to the neognaths.