Evolution of birds Evolution of birds The evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropoda dinosaurs named Paraves. Birds are categorized as a biological class, Aves. For more than a century, the small theropod dinosaur "Archaeopteryx lithographica" from the Late Jurassic period was considered to have been the earliest bird. Modern phylogenies place birds in the dinosaur clade Theropoda. According to the current consensus, Aves and a sister group, the order Crocodilia, together are the sole living members of an unranked "reptile" clade, the Archosauria. Four distinct lineages of bird survived the Cretaceous-Tertiary
Specimens of Archaeopteryx totaling 1,756 Solnhofen specimens - was purchased the following year. In this way the London Museum came to acquire a truly important collection of fossils, many of them quite rare or undescribed at the time. Wellnhofer remarks that it was likely not the price that kept the Bavarian State Paleontological Collection in Munich from acquiring the fossil, but rather the hesitating attitude of Andreas Wagner which delayed any action. Following Wagner's death in 1861, negotiations with Häberlein certainly would have been all the more difficult. In the wake of this important transaction of the first "Archaeopteryx" body fossil, many German