What is "neognathae"

Neognaths (Neognathae) are birds within the subclass Neornithes of the class Aves. The Neognathae include virtually all living birds; exceptions being their sister taxon ( Palaeognathae), which contains the tinamous and the flightless ratites.

There are nearly 10,000 species of neognaths. Since the late Cretaceous period, from which the earliest fossils are known, they have undergone adaptive radiation producing the diversity of form, function, and behavior that we see today. It includes the order Passeriformes (perching birds), the largest clade of land vertebrates, containing some 60% of living birds and being more than twice as speciose as rodents and about five times as speciose as Chiroptera (bats), which are the largest clades of mammals. There are also 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 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.