Abstract: The study of the origin and early evolution of modern birds has never produced as much excitement and public attention as in the over 100 years old. Paleontological studies showed that modern avian groups probably first appeared in the Paleocene and experienced an explosive radiation in the early Cenozoic. Modern birds are the only group of Mesozoic birds to have survived after the K/T extinction event, and recent ornithurine discoveries lend further support to the Cenozoic origin of the modern avian groups. The fossil birds of the early Cenozoic (Paleogene—Neogene) are clearly attributable to the modern birds, and the earliest well estabished record of most traditional orders and families of modern birds occur then. Thus, studies on Mesozoic—Cenozoic avian not only help us to understand the early evolutionary radiation and the history of diversification of birds, but also illuminate the origin and early evolution of modern avian groups.

Key words: modern birds, origin, evolutionary radiation