there are over 701 dog breeds in the world and thousands of variations. Sometimes people breed dogs, such as silver labs to make money. A silver lab i a rare breed they tell people who want an unusual dog. Really it is either a purebred lab with a default or a mix of lab and something else that they can pass of as purebred. AKC doesnt check these things when handing out registration papers. As for long and short coated varieties of breeds, almost every breed has both varieties or more. Its just that the akc doesnt register all varieties.