Origin and early evolution of birds

[Tim Williams <twilliams_alpha@hotmail.com>]

Naturwissenshaften

First online

Review
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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