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Summary
A new study of the lung structures of sectioned crocodiles and other reptiles has shown that they resemble the images of several flattened fossil dinosaurs from China. On page 1267, this lung evidence is used to argue not only that dinosaurs were incapable of the high rates of gas exchange needed for warm-bloodedness, but also that their bellowslike lungs could not have evolved into the high-performance lungs of modern birds. The new evidence challenges two of the reigning hypotheses concerning dinosaurs: that they were warm-blooded, and that they gave rise to birds. Some call this report part of a "one-two punch to the dinosaur origins of birds hypothesis," but others still think there's persuasive evidence that birds are descendants of dinosaurs.
