Are the Bullenbeisser and Mexican Hairless Dog both dogs?
Bullenbeisser The Bullenbeisser (also known as the German Bulldog) was a breed of dog known for its strength and agility. The breed was closely related to the Bärenbeisser (some believe that the two breeds were the same; the names mean "bull-biter" and "bear-biter," respectively), and the Boxer. It was, in all its aspects, similar to the present Alano Español (Spanish Bulldog) and very alike to the Dogo Argentino, not only in aspect, but also in usage. There were two regional varieties, the Brabanter Bullenbeisser and the Danziger Bullenbeisser. The breed is now extinct.
Molera A molera is a "hole" in a Chihuahua's head; it is the same as a fontanelle in human babies. Historically, the Chihuahua as developed in Mexico and the United States has displayed a "hole in the head". In times past, this has been accepted as a mark of purity for this dog breed, and it is still mentioned in most Chihuahua breed standards the world over. The bones of the head in all foetuses are not firmly knitted together, but in most mammals, the different bones of the skull join with cartilaginous sutures as the animal matures. The Chihuahuas' moleras vary in size and shape, occurring on the top of the head where the parietal and frontal bones come together.