Snarl (open/closed) since there are two different ways a canine can technically look when they snarl, for screenshot purposes, there should also be an 'ears back' and 'ears forward' for the same reason, because defensive/offensive snarls are totally different, and it all has to do with body language.
Snarl(closed) - a canine pulls its lips back and it's teeth are clenched shut, this is more or less defensive.
Snarl(open) - Open jaws, similar to the above and can be considered offensive, since the open jaws would, to most, be a 'get away from me or i rip off your face' in comparison to the closed snarl where it's just 'get away from me'.
^ both would have sound effects, possibly looping. per say, a cornered canine and three attackers, it'd fit the moment to have a consistent, seamless snarl.
Instead of the combat system, why not just have biting emotes? other than people being morons with it, it'd not cause the person to 'die' and respawn or anything.
