Dogs have relatively smaller skulls, smaller brains, and smaller teeth as compared to wolves. Smaller brains require lesser calories for dogs to survive. The paw of a dog is half the size of that of a wolf, and its tail curls upwards, unlike that of a wolf. Dog teeth have less complicated cusp patterns and a much smaller tympanic bulla as compared to wolves.
Wolves have a longer muzzle and legs. They have a narrow chest with forelegs pressed into it. Elbows point inwards and feet point outwards. Also, wolves have a pre-caudal gland at the base of their tail used to release a pheromone onto another wolf, marking that wolf as a member of a particular pack. This gland is no longer functionary in dogs.
http://missionwolf.org/page/wolf-dog-difference/
Skull of an gray wulf vs an mastiff