Haven't tried removing the jaw. Should be able to with an xacto blade. I'm not sure but I think it's just styrofoam or something very similar. Might do one later tonight.
It might be fatter. These are pretty damn close to human sized. Well, at least my size. I will have to pick up a few more. Just in case members here would like one and can't find em. Once I cut the jaw off I'll post a pic.
Sorry for the Double Post, but remember to paint the Gold Tooth and Neural Implants in. But the Weird thing about the Skulls in Halo is that the Skull is actually Captain Keyes Skull(Read it up on Halopedia) and I never recalled Keyes Having a Gold Tooth.