Skull shape variation in the dog. Above are shown extreme examples of brachycephalic breeds (on top, from left to right: Pug, Japanese Chin, Brussels Griffon, French Bulldog, Neapolitan Mastiff) and dolichocephalic breeds (on bottom, from left to right: German Shepherd Dog, Bull Terrier, Saluki, Ibizan Hound, Collie) (images: Mary Bloom, AKC).