As organisms evolve, any genes that are no longer used arn't removed, they are simply 'switched off' This means we still have the inactive genes of fish, amphibians reptiles, apes and every other stage of evolution that we went through to get to where we are now, including single-celled protazoa that are both animal & vegitable!
It's even possible to get some of these domant genes to 'wake' up.
Birds are directly decended from the same branch of psudoreptillians that the dinosaurs belonged to and some evolved more recently than others.
The Ground Hornbill of Africa is a large predatory bird living on the plains of Africa which runs down and eats small mammals & reptiles.
With a little gene therepy, it is possible to turn this bird into a 'living dinosaur'- as the domant genes activate, the bird grown teeth in its bill, and a long scaly tail.