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 under his control and full exposed, his subsequent study and monograph was the first comprehensive description of an "Archaeopteryx" specimen that had not been disarticulated. The Berlin specimen of "Archaeopteryx" is to date the most complete existing specimen of this genus, and is widely regarded as one of the most beautiful fossils in the world. Its well-preserved skeleton and the preserved feathers of its wings and tail have made it of considerable interest to a wide range of scientific study, beginning with Wilhelm Dames and Carl Vogt shortly following its discovery. This iconic fossil preserves the animal with an articulated