Neornithes

Neornithes is the crown group of birds: the last common ancestor of all living birds and every descendant of that ancestor. It includes all living bird species and some extinct relatives.

Aves: Aves is the bird clade, commonly defined to include all living birds and their extinct descendants. Neornithes is the crown group within the broader bird lineage.
Phylogenetics: Phylogenetics is the study of evolutionary relationships among organisms using shared evidence. It provides the methods for reconstructing relationships among living birds and fossils.
Palaeognathae: Palaeognathae is a major living bird lineage that includes ostriches, emus, kiwis, and tinamous. Its members represent one of the deepest divergences among living Neornithes.
Avian phylogenomics: Avian phylogenomics uses large-scale genomic data to infer evolutionary relationships among birds. Genome-wide studies have revised hypotheses about the deepest splits within Neornithes.
Crown group: A crown group consists of the last common ancestor of living members of a lineage and all its descendants. This definition distinguishes Neornithes from extinct bird lineages outside its crown.
Avian evolution: Avian evolution is the history of evolutionary change along the lineage leading to modern birds. Neornithes is the surviving crown branch of that long evolutionary history.
Neognathae: Neognathae is the major bird lineage containing all living birds other than palaeognaths. It accounts for most living bird diversity within Neornithes.
Avian molecular dating: Avian molecular dating estimates when bird lineages diverged using genetic data and fossil calibrations. Different calibrations and models yield differing dates for the origins of crown birds.
Avialae: Avialae is the theropod dinosaur clade containing birds and their closest relatives. Neornithes occupies a nested position within this larger evolutionary branch.
Cretaceous–Paleogene extinction event: The Cretaceous–Paleogene extinction event occurred about 66 million years ago and eliminated non-avian dinosaurs and many other groups. The surviving Neornithes lineages diversified after this major extinction.

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