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Origin and early evolution of birds


First online

The origin and early evolution of birds: discoveries, disputes, and perspectives from fossil evidence
Zhonghe Zhou

Published online: 8 September 2004

Abstract: The study of the origin and early evolution of birds has never produced as much excitement and public attention as in the past decade. Well preserved and abundant new fossils of birds and dinosaurs have provided unprecedented new evidence on the dinosaurian origin of birds, the arboreal origin of avian flight, and the origin of feathers prior to flapping flight. The Mesozoic avian assemblage mainly comprises two major lineages: the prevalent extinct group Enantiornithes, and the Ornithurae, which gave rise to all modern birds, as well as several more basal taxa. Cretaceous birds radiated into various paleoecological niches that included fish- and seed-eating. Significant size and morphological differences and variation in flight capabilities, ranging from gliding to powerful flight among early birds, highlight the diversification of birds in the Early Cretaceous. There is little evidence, however, to support a Mesozoic origin of modern avian groups. Controversy and debate, nevertheless, surround many of these findings, and more details are needed to give a better appreciation of the significance of these new discoveries.

(A nice summary of the issues, that includes a honorary mention of many [but not all] Mesozoic avians, including their ecology and relationships; and a section on arborealiy in theropods. _Shenzhouraptor_ and _Yandangornis_ do not rate a mention; but _Jeholornis_ does. This paper also opines that the evidence supporting the dinosaurian origin of birds is "overwhelming". TW)

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