Washington, June 10 (ANI): Scientists have made a fundamental new discovery about how birds breathe and have a lung capacity that allows for flight, which means it's unlikely that birds descended from any known theropod dinosaurs.
The conclusions, by researchers at Oregon State University (OSU), US, add to other evolving evidence that may finally force many paleontologists to reconsider their long-held belief that modern birds are the direct descendants of ancient, meat-eating dinosaurs.
"It's really kind of amazing that after centuries of studying birds and flight, we still didn't understand a basic aspect of bird biology," said John Ruben, an OSU professor of zoology.
"This discovery probably means that birds evolved on a parallel path alongside dinosaurs, starting that process before most dinosaur species even existed," he added.
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, according to OSU experts.
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. "This is fundamental to bird physiology," said Devon Quick, an OSU instructor of zoology.
"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," Quick added.
However, every other animal that has walked on land, the scientists said, has a moveable thigh bone that is involved in their motion, including humans, elephants, dogs, lizards and, in the ancient past - dinosaurs.
According to the researchers, the implication is that birds almost certainly did not descend from theropod dinosaurs, such as tyrannosaurus or allosaurus.
The newest findings are more consistent with birds having evolved separately from dinosaurs and developing their own unique characteristics, including feathers, wings and a unique lung and locomotion system, they added. (ANI)