I found your black tongue debate site and was interested.  Chows are not super rare in our area, and they can be clever at getting out of peoples'
yards, but they are not so common that it is likely that every mixed breed dog at the local shelter with some spots on its tongue is a chow mix.

I always heard that many breeds of dog could have some splotching on the tongue, but the only breeds that typically have entirely black tongues,
as opposed to black spots, are the chows/shar-peis/foo dogs etc.  So a lot of the dog people I know assume that mixes with spots on their tongues could be
almost anything, but a dog with a mostly black tongue was very possibly a mix of one of the "black tongue" breeds at least.  They have DNA tests now for
helping to find what breeds may be in a mixed breed dog. They vary greatly as to how many breeds they are supposed to find, ranging from about 60 up to
over 170. I'm not sure what the accuracy really is for different ones of these, as I've seen some results that are.....hard to believe.  But genes can do strange
things when they get shuffled up and mixes don't always look like what they are.

One of my dogs (Roxy) is a solid black dog that has a mostly black/blue tongue/lips/mouth, but some pink on it on the sides.  The shelter said she was a "border
collie mix" according to the owners who refused to come bail her out the third time she was picked up off the street (funny how she's never wandered off from
us in 10 years).  It is very possible she has border collie or some other herding breed in her, but I suspect she may be part chow as well.  In addition to the mostly
black tongue, she has a tail that curls up over her back sometimes, a generally "spitzy" appearance and a ruff, though her coat texture is quite different from a
chow's and her muzzle and face are not as heavy and wrinkly as most chows.  She can get a certain expression on her face when she is being thoughtful that
is rather "chowish" sometimes.    Her shoulder and rear leg angulation are more "upright" than most herding breeds but less so than most chows.  She's a little
under 40 pounds.

Two of our other dogs, Astra and Simon, are also mystery mixes and they have some spotting on their tongues, but they do not look as "chowish" to me as Roxy does. 
They looks like they could be mixes of lots of breeds, and if there is any chow/shar-pei in there with either of them, it is probably a small part of the whole. 
Astra is the black and tan dog and is very fluffy and soft and slightly wavy (like puppy down).  I can't think of any breed with a coat quite like hers, but there was a
paper in Science a while back that stated that most of the amazing variation in coat length and texture in dogs comes from various combinations of a pretty small
number of genes, so she may have just gotten an interesting mix of genes.  I don't have a great picture of Simon that shows his tongue, but he is the large yellow
dog and has a fair amount of splotching on his tongue. Maybe there's some lab is in there, but he doesn't act much like the labs I've known (no interest in water or in retrieving).

I am a biology instructor and so I have been curious about the genetics of the all black tongue color.  It appears to be pretty true breeding in chows (and is a breed
standard requirement) but seems to be highly variable in its appearance in mixed breed dogs that are known to have one chow parent.  Maybe more than one set
of genes controls tongue color and there are issues like incomplete dominance at work with some of them.  I've never found any discussion anywhere on the webs
of the actual inheritance pattern of the blue/black tongue in chows.  Hope I didn't blast you with TMI, but dog genetics interests me.  And I dislike "breedism" in
any case, as there are just so many variables besides a dog's breed or mix that determines whether the dog will be aggressive or not.
Erica,  Sacramento, CA
 

I was told my dog, Rosco,  was a
Lab-Weimariner Mix.  Now I am not so sure.
Either way he is a sweetheart.
Heather,   Keller TX

Our Rottweiler Charlie was a rescue from Galveston Texas, we're now in NH.  He appears to be a full Rott but has very long straight hair and the black spotted tongue.  He’s very compact at 79lbs & 1 yr.  He’s extremely agile which makes me think he’s part cheetah with that tongue of his. 
Laura, NH

Every "dog genius" told me my dogs had Chow in them. Since I didn't know, I searched the web and found a lot of sites that debunk that myth. Thank you for posting yours. Here is my shot of both brothers. Lefty is the one on the right and Ritey is the one on the left. Ritey has a black spot way on the back of his tongue (you can just barely see it in the photo) and some under his tongue. You can obviously see Lefty's spots. And the spots have been growing as fast as the pups have too. At first Ritey didn't have any spots and Lefty's were just small dots.
Brady, Melrose FL

Below is Maki, whom I thought might be a 
dwarf Chow. Her coat was just starting to grow 
back after I adopted her as a mostly naked dog  
from the pound. It turned out she had advanced 
thyroid cancer and  only lived a couple months. 
She was about half the size of a normal  
Chow and quite old
Linda Richmond CA

Rena, Newport News, VA

This is my 6 month papered AKC Newfoundland Mungo who has a spotted tongue. At 8 wks,  he had 3 small spots,
now he has multiple spots that keep growing. I was pissed that people kept insisting he was a Chow-Newf mix because of his tongue. Silly people just cant understand that is just a
discoloration
Rachel & Mungo, Salt Lake City, Utah

Max Allentown PA