page_title: Evolution of reptiles
section_title: Bird evolution
hierarchical_section_title: Evolution of reptiles / Rise of dinosaurs / Bird evolution
caption_attribution_description: English: Archaeopteryx lithographica, specimen displayed at the Museum für Naturkunde in Berlin. (This image shows the original fossil - not a cast.) Deutsch: Archaeopteryx lithographica, Exemplar im Museum für Naturkunde in Berlin. (Dieses Bild zeigt das Original-Fossil, keinen Abguss.)
context_page_description: Reptiles arose about 310–320 million years ago during the Carboniferous period. Reptiles, in the traditional sense of the term, are defined as animals that have scales or scutes, lay land-based hard-shelled eggs, and possess ectothermic metabolisms. So defined, the group is paraphyletic, excluding endothermic animals like birds and mammals that are descended from early reptiles. A definition in accordance with phylogenetic nomenclature, which rejects paraphyletic groups, includes birds while excluding mammals and their synapsid ancestors. So defined, Reptilia is identical to Sauropsida.
  Though few reptiles today are apex predators, many examples of apex reptiles have existed in the past. Reptiles have an extremely diverse evolutionary history that has led to biological successes, such as dinosaurs, pterosaurs, plesiosaurs, mosasaurs, and ichthyosaurs.
context_section_description: The main points to the transition from reptile to bird are the evolution from scales to feathers, the evolution of the beak (although independently evolved in other organisms), the hallofication of bones, development of flight, and warm-bloodedness.
  The evolution of birds is thought to have begun in the Jurassic Period, with the earliest birds derived from theropod dinosaurs. Birds are categorized as a biological class, Aves. The earliest known species in Aves is Archaeopteryx lithographica, from the Late Jurassic period. Modern phylogenetics place birds in the dinosaur clade Theropoda. According to the current consensus, Aves and Crocodilia are the sole living members of an unranked clade, the Archosauria.
  Simplified cladogram from Senter (2007).
caption: An Archaeopteryx specimen in Berlin.
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