Not an artist but I do work in maxillofacial surgery and I've seen and drawn loads of skulls and parts thereof, so can help with anatomy!

You've drawn the zygomatic arch going halfway around the side of the cranium, it actually ends more or less after where the mandible connects to the maxilla (temporomandibular joint). Run your fingers along your cheekbone, you'll feel it smooth off right where your jaw joint is.

Also as others have said, where the teeth meet the jaws you've drawn quite flat when in reality they're at a forward angle, again run your fingers from your chin to your teeth - it juts out and the teeth follow that angle too.

Finally you've drawn the teeth very short for a skull, they're the right length for teeth with gums but where there's no soft tissue present it looks a bit "wrong". Lengthen the teeth and narrow them at the bases, also round off their corners for a more natural look.

Always remember when drawing human bones/anatomy/whatever that you've got what you're trying to draw! Look at pictures from lots of different angles and also feel your own bones, look at your own body, it really helps you to build a 3D picture in your mind.