If you look at the high resolution version of my sig image, you can see some lighting things occurring that are throwing it off. The photo at low res gives the impression that the shadow is his jawline, but if you look at the high resolution, there's more to his jaw with a faint glow there that lines up with the glow under his chin. I also thing it's just the way the extreme highlight on the left side of his face and the shadowing on the right are making a V shape out of the midtone area of his face
I really like how the snarl turned out, I was hoping for it, I was nervous because if done wrong it could look quite silly but it really captures that way his mouth gets quite nicely.