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New doubts arise over the dinosaur-bird link
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That birds descended directly from dinosaurs is one of the most strongly accepted hypotheses in evolution. However, there is mounting evidence to suggest that the theory is simply not correct. In fact, an important piece of information exposed by Oregon State University (OSU) researchers may truly force other scientists to reevaluate the dinosaur-bird link.
Because of flying, birds have extremely unique physiologies. The lungs of birds are particularly unusual because they allow nearly 20 times more oxygen to pass through to the body as compared to cold-blooded reptiles. It is not surprising, then, that birds had to evolve special support systems to aid such different lungs.
In addition to super lungs, birds have an immobile thigh bone. The locked femur has been known for some time, but the role it actually plays in aiding flight is the subject the new discovery. Researchers found that it is the “fixed position of bird bones and musculature that keeps their air-sac lung from collapsing when the bird inhales.” [EurekAlert]
An immobile femur is something has never been seen in any land animal from humans all the way back to dinosaurs. According OSU professor of zoology John Ruben, "This discovery probably means that birds evolved on a parallel path alongside dinosaurs, starting that process before most dinosaur species even existed.” [EurekAlert]
Lung function is a pivotal battle in the dinosaur-bird link war. For decades, scientists have been pointing to similarities in lung function as evidence that dinosaurs and birds are directly related. However this new evidence, published in Journal of Morphology, undercuts that belief. As Ruben stated, “Theropod dinosaurs [like the tyrannosaurus] had a moving femur and therefore could not have had a lung that worked like that in birds. Their abdominal air sac, if they had one, would have collapsed.” [EurekAlert]
So if birds did not descend from dinosaurs, where did they come from? A more recent theory states that dinosaurs and birds are still related, but in a way that is more like siblings. It is thought that they both evolved from a common ancestor, the reptilian thecondonts. At some point, the thecondonts broke off into separate evolutionary chains, giving rise to birds and dinosaurs as unique lineages.
As a last word (and in one of the more amusing, if terrifying, comments made by a scientist), Ruben stated, "A velociraptor did not just sprout feathers at some point and fly off into the sunset.” [EurekAlert]
More science news: Life may have originated billions of years earlier * New theory states Neanderthals were eaten by humans * Weak individuals hear dangerous sounds differently * More
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