Pedomorphosis is an evolutionary process through which descendants end up looking like the juveniles of their ancestors. There are many known examples of this in the fossil record, e.g. amongst trilobites and amphibians.
Now, a study by Bhullar and colleagues in Nature show that birds skulls are morphologically similar to baby dinosaur skulls, indicating that birds are not only descendants of dinosaurs, but they have retained a juvenile morphology. One of the traits typical of baby dinosaurs is a large eye socket, and this is also typical for adult birds. While the morphology of baby dinosaur skulls were very different from those of their adults, baby birds have skulls that are virtually similar to adult birds. This has allowed birds to take a faster and more direct route to adulthood.
You can read more and view pictures of the skulls on Dinosaur tracking.