In fact the blanket breed name «pit bull» refers to many different breeds with boxy heads and bulky bodies including the American Pit Bull Terrier, American Staffordshire Terrier, Bull Terrier and Staffordshire Bull Terrier or a mix of any. (onegreenplanet.org)
The American Boxer is a term for a relatively new variety of dog with a slightly smaller, sleeker appearance and less boxy head than the traditional German Boxer. (cuteness.com)