So I imported some model into blender just to see how the person that made it rigged it and shit and it looks good..one thing that confuses me is that the model has all the mouth visemes (shape keys whatever) all set up and they work okay....yet the model itself has no jaw bones? like I can't actually mess with the mouth in pose mode at all due to no bones...yet it has mouth shape keys?

how does that even work? I thought you needed a bone to control movement?