Black spots on a dog's tongue are actually quite common and are not indicative of breed purity. They are usually just pigmentations and don't have any bearing on a dog's lineage or breed.
Many dog breeds, including mixed breeds, can have black spots on their tongues. Some breeds are known to have more prominent black spots, like:
* Chow Chows
* Doberman Pinschers
* Great Danes
However, even within these breeds, some dogs may have more spots than others.
It's important to remember that breed purity is determined by pedigree and lineage, not physical characteristics like tongue spots. If you're interested in a dog's breed, you should look at its pedigree papers or contact a reputable breeder.