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New bird evolution papers cont.

A third article in Acta Zoologica Sinica relating to the evolution of birds, in the same volume as the other two. Acta Zoologica Sinica. 50(6): 913-920

ABSTRACT: Over the last decade, more Mesozoic birds have been discovered from the Early Cretaceous of Liaoning Province in northeast China than from any other region on earth. Chinese Mesozoic birds represent the earliest significant avian diversification yet known after the oldest known bird Archaeopteryx appeared in the fossil record about 20 million years earlier. They not only include a long-tailed form reminiscent of dinosaurian ancestry but also comprise many other special or derived forms, such as the oldest-known beaked bird, the largest Early Cretaceous bird, the most primitive enantiornithine bird and the best preserved ornithurine bird, with a flight apparatus nearly identical to that of modern birds. Remarkable evolutionary, morphological and ecological differentation, such as in flight, size and diet, are well documented by the Chinese fossils. The long-tailed, basal bird Jeholornis bears a remarkable resemblance to dromaeosaur dinosaurs, thus providing important clues in support of the dinosaurian origin of birds. Chinese Early Cretaceous birds, as well as arboreal dinosaurs of the same age in China, also provide compelling evidence for the arboreal hypothesis of the origin of avian flight. The 'Dinosaur-trees-down' hypothesis, which combines the dinosaurian origin of birds and the arboreal hypothesis of avian flight, is thus well collaborated. Because feathers were present in various dinosaurs, the association of endothermy with feathers becomes purely speculative; endothermy probably did not develop in birds until the Early Cretaceous.