Simplify the following text for a Grade 7 native English-speaking person.
Original: These early `` proto-staffords '' provided the ancestral foundation stock for the Staffordshire Bull Terrier , the Bull Terrier , the American Pit Bull Terrier and American Staffordshire Terrier .
Simplified: It is related to the bull terrier . Its appearance is similar to the American Staffordshire Terrier and American pit bull terrier , but it is smaller than both of them .