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
Dinosaur vision Dinosaur vision Dinosaur vision was, in general, better than the vision of most other reptiles, although vision varied between dinosaur species. Coelurosaurs, for example, had good stereoscopic or binocular vision, whereas large carnosaurs had poor binocular vision, comparable to that of modern alligators. Most carnosaurs, including "Carcharodontosaurus" and "Allosaurus", did not have very good binocular vision, comparable to modern alligators. They possessed binocular vision which was restricted to a region only 20° wide, which is understandable, as they hunted mostly large and slow prey. Their keenest sense was probably smell. Deinonychosaurs, like "Stenonychosaurus" and "Velociraptor", had better binocular vision than