Updated February 05, 2015 with a revised illustration of the chicken skull following further study. See comparisons on the blog post dated 02/05/2015.
The chicken (Gallus gallus) was recently added to the large reptile tree. Like most birds several skull bones fuse in adults. Other bones are greatly reduced, losing their old theropod dinosaur appearance. The antorbital fenestra is confluent with the orbit. The ascending process of the jugal is unossified. Like mammals, birds have a greatly enlarged brain and cranium and that coincides with a reduced quadrate.
This is an example of how DGS (digital graphic segregation) can help illustrate a very common taxon. Earlier mistakes were examples of naiveté as I have avoided studying bird skulls until just recently.