Theropod Quotes
When people look of non-avian dinosaur they're thinking of extrapolating a cow up to that size. Mammals are much much denser than birds are, because a lot of the skeletons of sauropods (the big, long-necked ones-Apatosaurus, Brachiosaurus and the like) and theropod dinosaurs are just air. Theropods don't have solid bones like we do; they have hollow bones. Sauropods don't, but they have tremendous air sacs that fill up a lot of their bodies. And thus they weigh way less than a mammal scaled up to that size.
Mark Norell
... if you saw a baby tyrannosaur you would probably think it was a weird looking bird. A full grown one might have had feathers too, maybe not on its whole body though, maybe more of an ornamental display sort of feathers. So traits in the theropod dinosaurs were more birdlike than say, crocodiles.
Mark Norell
