T Rex is a tetanuruan coelurasaur, not as you may think, a descendant of the carnasaurs, such as alasaurus. This makes it more closely related to the birds and maniraptorans, so inside every bird there is a T-rex trying to get out. There is a theory that the later feathered dinosuars, such as dynonichcus, velociraptor, etc, were actually flightless birds. This would explain how there was a bird, archaeopteryx, present in the easly createacous, yet the apparently obvious precursors of the avian line only appeared just before the end of the age of the dinosaurs.