Brachycephalic (Wikipedia) dogs are dogs that have a relatively broad, short skull (typically with the breadth at least 80 per cent of the length). Brachycephalic literally means "short-headed". Popular brachycephalic breeds include English and French bulldogs (Wikipedia), bull mastiffs, Boston terriers (Wikipedia), boxers, pugs (Wikipedia), shih tzus, Lhasa apsos and Pekingese, among others. The term can also be applied to mixed breed dogs that inherited this trait from brachycephalic ancestors. Brachycephalic dogs tend to have extremely shortened snouts that make them almost appear flat-faced, which differentiates them from some breeds that simply have shorter snouts.