Thursday, June 11, 2009

Birds and Dinosaurs: Related?

Science Daily reported on a new study which alleges that birds are probably not descended from dinosaurs:

"It's been known for decades that the femur, or thigh bone in birds is largely fixed and makes birds into "knee runners," unlike virtually all other land animals, the OSU experts say. What was just discovered, however, is that it's this fixed position of bird bones and musculature that keeps their air-sac lung from collapsing when the bird inhales.


"Warm-blooded birds need about 20 times more oxygen than cold-blooded reptiles, and have evolved a unique lung structure that allows for a high rate of gas exchange and high activity level. Their unusual thigh complex is what helps support the lung and prevent its collapse.

...

"The implication, the researchers said, is that birds almost certainly did not descend from theropod dinosaurs, such as tyrannosaurus or allosaurus. The findings add to a growing body of evidence in the past two decades that challenge some of the most widely-held beliefs about animal evolution."

I'm not exactly sure how this follows, and of course I don't have the credentials to assess this debate, but I do wonder what the dino-bird theorists would have to say about this.

4 comments:

Marc said...

At the end of the article it says
''"We aren't suggesting that dinosaurs and birds may not have had a common ancestor somewhere in the distant past," Quick said. "That's quite possible and is routinely found in evolution. It just seems pretty clear now that birds were evolving all along on their own and did not descend directly from the theropod dinosaurs, which lived many millions of years later."

I don't think this has hit the scienceblogs yet I'd like to see their take on it

Jonathan said...

I'm going to have to search for the link, but there was a fossil found not too terribly long ago of a theropod dinosaur that has soft-tissue preservation showing it had an air-sac lung. So, these guys are kind of screwed.

Jonathan said...

Okay, I have the citation now. It's from an article in Nature. It's not on soft-tissue, but an analysis of vertebrae. It does show that the dinosaur had unidirectional lungs, though.

O'Connor and Claessens, Basic avian pulmonary design and flow-through ventilation oin non-avian theropod dinosaurs, Nature 436, 253 - 256 (2005)

AIGBusted said...

Interesting, Jonathan.

Props to you for remembering the discovery!