Which bit under the head are you referring to? I see his jaw and then just where the hood comes together again.
Good, could easily be better =)
Generally, you show too much. Suggest, play with contrast and darkness. Try a more diagonal, triangular composition by leaving some of the robe in shadow.
Whatever is visible just below the head isn't readable and hinders the skull readability too. If it's anything inside such as bones, they should be in shadow anyway.
The arms look wrong: the way he's holding the shaft, his left elbow should be visible below his right hand.
Those hands should be the place of choice to suggest some bones!
The scythe blade might have a sharp bright edge.
Guess you're right, that's a jaw. Somehow it looks wrong to me.