they're strikingly similar. There is also evidence that dinosaurs sat on their eggs, just like birds. Specifically, birds are believed to be descendants of a type of dinosaur known as maniraptoran therapods. But as with all orthodoxies, there is dissent. Two scientists at Oregon State University have published a paper in the Journal of Morphology arguing that dinosaurs did not have bird-like lungs. 'No known therapod dinosaur could possibly have ventilated a birdlike lung,' said zoologist John Ruben, who co-authored the study with colleague Devon Quick. They researched the skeletal-muscular structure supporting the air sacs that enable a bird to breathe. No such anatomy is known in therapod dinosaurs, Ruben said. 'It's far more like that the two groups share a common ancestor and for at least some period of time evolved in parallel,' Ruben said. The birds-are-dinosaurs model is popular because 'it allows people to think that somehow velociraptor sprouted feathers and flew off in the sunset and now is flying around your back yard.' But Jack Horner, curator of paleontology at the Museum of the Rockies in Montana, said the criticism is based on a misunderstanding of how we can tell species are related. 'Differences don't matter,' Horner said. 'It doesn't matter how many differences there are between birds and dinosaurs because there are hundreds of similarities.' There is no other animal in the fossil record more closely related to birds than therapod dinosaurs, he said, and the hypothesis is based on hundreds of characteristics. 