Mutant Jawbones and Pristine Finger Bones do drop in Gunthak at the castle.
The culprit that drops em are Mutant... (three different types) in front door first trio of mobs to the right B4 ya go up the steps. Will B a mutant _____ , a Lugguld _____ , and another mutant ______. Pull to right wall in the cubbie between 2 pillars... Gravy !
Mutant Jawbones have not been cycled yet, no idea what they go to.... c'mon people..give us a job... LOL !