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Birds are living dinosaurs. They descend from theropods, the group of two-legged, mostly meat-eating dinosaurs that included Tyrannosaurus and Velociraptor, and they are the only dinosaur line that survived the asteroid impact 66 million years ago.

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The link was first suggested in the 1860s. In 1861 a skeleton of Archaeopteryx, a magpie-sized animal with feathered wings, teeth and a long bony tail, was found in limestone quarries near Solnhofen in Germany, and the British biologist Thomas Henry Huxley soon argued that birds were close to dinosaurs such as Compsognathus. The idea faded, then returned after 1969, when John Ostrom of Yale described Deinonychus, a nimble predator with a strikingly bird-like skeleton. The decisive evidence came from China. In 1996 palaeontologists described Sinosauropteryx, the first of many non-flying dinosaurs found with feathers. Birds share many features with their theropod relatives, including hollow bones, a wishbone and sitting on their eggs in nests. All of today's more than 11,000 bird species belong to that surviving line.

Türkçe oku
Kuşlar yaşayan dinozorlardır. Soyları teropodlara, yani Tyrannosaurus ve Velociraptor gibi iki ayak üstünde yürüyen, çoğu etçil dinozorlara dayanır. 66 milyon yıl önceki göktaşı çarpmasından sağ çıkan tek dinozor soyu da kuşlardır.

Kuşlarla dinozorlar arasındaki bağ ilk kez 1860'larda dile getirildi. 1861'de Almanya'da, Solnhofen yakınlarındaki kireçtaşı ocaklarında bir Archaeopteryx iskeleti bulundu. Saksağan büyüklüğündeki bu hayvanın tüylü kanatları, dişleri ve uzun, kemikli bir kuyruğu vardı. İngiliz biyolog Thomas Henry Huxley kısa süre sonra kuşların Compsognathus gibi dinozorlara çok yakın olduğunu savundu. Fikir zamanla unutuldu, ama 1969'da yeniden gündeme geldi. O yıl Yale Üniversitesi'nden John Ostrom, Deinonychus'u tanımladı; bu çevik avcının iskeleti şaşırtıcı ölçüde kuşa benziyordu. Belirleyici kanıt Çin'den geldi: 1996'da tanımlanan Sinosauropteryx, sonradan birçoğu bulunacak tüylü ama uçamayan dinozorların ilkiydi. Kuşlar teropod akrabalarıyla pek çok özelliği paylaşır: İçi boş kemikler, lades kemiği ve yuvada yumurtaların üstüne kuluçkaya yatmak bunlardan birkaçıdır. Bugün yaşayan 11.000'i aşkın kuş türünün hepsi, hayatta kalan bu soydan gelir.

Sources and further reading

Background reading: Origin of birds
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