Note from Mom: I let someone lead me to believe that Opie was a Hybrid - not that it matters - that just means he would be half and half of the 2 main types of American Bulldogs - but to know for sure that he is all one type is good to know, too.
So here is a little history on the 2 main types of American Bulldog.
Johnson: is the classic and larger of the 2 bulldog types. They generally stand 23 - 27 inches at the withers and can weigh any where from 70 - 120 pounds. They have heavier bones, wider chests and resemble the English bulldog in the face with a boxier head. Actually they were crossed with the English Bulldog. They have an undershot bite but their teeth usually don't show. These are around today thanks to John Johnson - otherwise they would be extinct. He gets the credit for breeding and keeping this beautiful dog in existence.
Scott: is more the "standard" type. Smaller, more athletic. Typically weighing 60 - 100 pounds. Sometimes they are mistaken for the American Pit Bull Terrier. They usually have a reverse scissors bite - meaning their lower teeth touch the sides of the upper teeth on the outside. Alan Scott is the man responsible for this breed type.
This picture is a better one of a Scott type -