Archaeopteryx = Dinosaur-bird

A genus of fossil birds in the extinct order Archaeopterygiformes, characterized by flight feathers like those of modern birds. Archaeopteryx is generally accepted as the oldest known fossil bird. It represents a unique snapshot of evolution; most of its skeletal characters are shared with small carnivorous dinosaurs, yet it has fully feathered modern wings. Archaeopteryx is effectively a flying dinosaur—an ancient bird about the size of a modern magpie.

Archaeopteryx is known from one feather impression and seven skeletons, discovered over the course of 150 years from the Altmuhl Valley in Bavaria, Germany. All have been found in lithographic limestone of uppermost Jurassic (Tithonian) age, approximately 147 million years old, and were excavated from several locations that lie within a 15-mile radius of the town of Solnhofen. The Solnhofen Lithographic Limestone preserves exceptionally fine detail, including the impressions of feathers; the animal carcases sank into fine plastic sediment on a shallow lagoon bed and were buried in anaerobic conditions.

The original specimen, the impression of a single feather preserved as part and counterpart, was discovered in 1861 and named Archaeopteryx lithographica by H. von Meyer. A few months later, a nearly complete skeleton was discovered and subsequently sold to the Natural History Museum in London. A second, complete specimen was discovered in 1877 and eventually acquired by the Berlin Natural History Museum. It was named as a different species, Archaeopteryx siemensii, by W. Dames in 1897 and as a separate genus Archaeornis by B. Petronievics in 1925, although it is widely regarded as a smaller individual of A. lithographica. Five additional well-documented skeletons of Archaeopteryx have been discovered since the 1950s. Not all are complete, but all show some evidence of feather impressions. The identity of three skeletons were not recognized at first.

A fragment collected in 1855 showing feather impressions, claws, and a knee joint was named as a pterosaur (a flying reptile) by von Meyer in 1859; its correct identity was not realized until 1970. Two specimens had been known for many years and misidentified as examples of the small theropod dinosaur, Compsognathus. The largest (sixth) specimen has been described as a separate genus and species,Wellnhoferia grandis, on the basis of size and distinctive manual (hand) and pedal (foot) morphology. The most recent discovery in 1993 was named A. bavarica by P. Wellnhofer based principally on its longer limb proportions. Eighth and ninth specimens are also known to exist, but they have not been described.