Conversely, it shows that birds really are the descendants of dinosaurs. The new finds raise a deeper problem, the same raised by the discovery of any transitional form between what we have hitherto thought of as distinct categories, such as 'bird' and 'dinosaur'. It forces us to think very hard about what we mean by the term 'bird'. This seems like a silly question. Of course everybody knows what a bird is.
Birds are animals with beaks and feathers.
They eat birdseed and make ugly white streaks down the sides of buildings. We are so convinced that we know what birds are that we hardly give them a second thought. But this cosy familiarity hides a dangerous fallacy. Once we admit this possibility, we must see that the many adaptations of the modern bird skeleton to make it a better airframe could have evolved among the ancestors of birds, for different reasons. Velociraptor , for example, had a furcula, flexible wrists and hollowed bones, but it wasn't a bird, and couldn't fly.