neornithes

Neornithes is the crown group of modern birds, comprising all living birds and their closest extinct relatives that share a common ancestor with today’s birds. In contemporary classifications, Neornithes includes two major lineages: Palaeognathae, which contains the flightless ratites and the flight-capable tinamous, and Neognathae, which encompasses the vast majority of living birds, including waterfowl, shorebirds, raptors, songbirds, and penguins.

Palaeognathae is defined by a paleognathous palate and typically more primitive skeletal features, while Neognathae is distinguished by a more derived palate and the broad morphological and ecological diversity seen in most modern birds. Together, these two lineages form the extent of extant avian diversity and their closest extinct relatives.

Origin and fossil record: Neornithes are believed to have arisen in the Late Cretaceous, with diversification accelerating after the Cretaceous–Paleogene boundary. The fossil record shows early neornithine lineages emerging in the late Mesozoic, followed by rapid expansion and global distribution in the Cenozoic, contributing to the wide range of forms observed today.

Diversity and ecology: Today, Neornithes comprises roughly 10,000 described living species, occupying nearly every ecological niche from aquatic to terrestrial and from tiny insectivores to large herbivores and predators. Although many Neognathae are capable of flight, several lineages, including some ratites and some penguins, have reduced or lost flight, illustrating the group’s broad evolutionary experimentation and adaptability.