The origin and early evolution of birds: discoveries, disputes, and perspectives from fossil evidence
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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.
Keywords
Early Cretaceous Yixian Formation Early Bird Theropod Dinosaur Modern BirdNotes
Acknowledgements
I thank the following persons for providing valuable suggestions and field support for my work on Mesozoic birds over the past years: Meemann Zhang, Lianhai Hou, Fan Jin, Jiangyong Zhang, Xiaolin Wang, Xing Xu, Fucheng Zhang, Yaoming Hu, Yuanqing Wang, Yuan Wang, Chun Li, and Zilu Tang from the IVPP. I also benefited from help and valuable discussions on early avian evolution with many other colleagues during the course of my research over the past years: Larry D. Martin, Alan Feduccia, Luis M. Chiappe, Lawrence Witmer, John Ostrom, Peter Wellnhofer, Evgeny Kurochkin, Storrs Olson, Jim Farlow, Andrzej Elzanowski, Mark Norell, Philip Currie, Paul Sereno, Julia Clarke, Jim Clark, Joel Cracraft, Catherine Forster, Jacques Gauthier, Per Ericson, Stefan Peters, Desui Miao, and Rick Prum. Fan Jin and Jiangyong Zhang also provided insights on the recognition of fish remains in the stomach of Yanornis. Yutong Li, Yan Li, and Huaquan Shou prepared many of the specimens. I also benefited greatly from invaluable critical comments from four anonymous referees. Paul Barrett provided some advice on the final manuscript and improved the English. This work was supported by the National Natural Science Foundation of China, Special Funds for Major State Basic Research Projects of China (TG2000077700), and the Chinese Academy of Sciences.
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