Evolution of birds extinction event 66 million years ago, giving rise to ostriches and relatives (Paleognathae), ducks and relatives (Anseriformes), ground-living fowl (Galliformes), and “modern birds” (Neoaves). Phylogenetically, Aves is usually defined as all descendants of the most recent common ancestor of a specific modern bird species (such as the house sparrow, "Passer domesticus"), and either "Archaeopteryx", or some prehistoric species closer to Neornithes (to avoid the problems caused by the unclear relationships of "Archaeopteryx" to other theropods). If the latter classification is used then the larger group is termed Avialae. Currently, the relationship between dinosaurs, "Archaeopteryx", and modern birds is still under
Specimens of Archaeopteryx other "Archaeopteryx" specimens. The left wing preserves the better plumage and shows flight feathers firmly connected to the arms. Though the wings overlap each other enough that assigning feather attachment points to individual bone regions is not possible, it does appear, consistent with other specimens and modern relatives, that the long primary feathers are attached to the second manual digit. The feathers of the right wing are considerably more damaged; so many feathers are missing that only a few can be definitively linked to the ulna, designating them as secondary remiges. One small feather is isolated next to the right