The pyrenean mastiff and tosa inu are both in all of my dog breed encyclopedias. They are real breeds.
The Irish staff, roman rottie, and a few others are purebreds that are bred for different looks, (taking oversized purebreds and breeding them ext.).
The bulldogs are mixes and the page even says this.
The chonquing dog is an old breed, which may or may not still be in existence. I've heard of it several times. One of my encyclopedias says its extinct.