Birds not descended from dinosaurs, say researchers

Posted by Emma Woollacott

Corvallis, Oregon – Birds probably aren't descended from theropod dinosaurs after all, according to controversial new research from Oregon State University.


The conclusion is based on a new discovery about how birds breathe and have a lung capacity that allows for flight.


It's been known for decades that the femur in birds is largely fixed. What the Oregon researchers have discovered, however, is that it's this fixed position of bird bones and musculature that keeps the air-sac lung from collapsing when the bird inhales.


"This is fundamental to bird physiology," said Devon Quick, an OSU instructor of zoology who completed this work as part of her doctoral studies. "It's really strange that no one realized this before. The position of the thigh bone and muscles in birds is critical to their lung function, which in turn is what gives them enough lung capacity for flight."


However, every other animal that has walked on land, the scientists said, has a moveable thigh bone that is involved in motion – including dinosaurs.


The implication, the researchers said, is that birds almost certainly did not descend from theropod dinosaurs such as tyrannosaurus or allosaurus.


Other discoveries have also cast doubt on the supposed line of descent. "For one thing, birds are found earlier in the fossil record than the dinosaurs they are supposed to have descended from," Ruben said. "That's a pretty serious problem."


The newest findings, the researchers said, are more consistent with birds having evolved separately from dinosaurs. It is possible, they said, that birds and dinosaurs may have shared a common ancestor, such as the small, reptilian "thecodonts," which may then have evolved on separate evolutionary paths into birds, crocodiles and dinosaurs.


OSU has been calling into question the link between dinosaurs and birds since the early 1990s, and this latest conclusion is likely to ruffle a few feathers.


"Frankly, there's a lot of museum politics involved in this, a lot of careers committed to a particular point of view even if new scientific evidence raises questions," Ruben claimed.


The study is published in The Journal of Morphology, and was funded by the National Science Foundation.