This is a mastif-rhodesian ridgeback mix I was evaluating for our adoption program. After two minutes he flopped over to get his tummy rubbed, and his face just sort of collaped because all of the wrinkles. He is a charming dog, and we had no problem finding a new home for him. Oh, he was named "Bumper" because he would use his head to "bump" his kennel door open. He only weighed about 120 lbs. at the time.
That is a wonderful expression you have captured there, he certainly looks a big dog. I would have preferred it not to be laying across the crack in the floor. But you can ask it too move for the next shot, he/she scares the life out of me.