Fish!

I know, it seems like a strange thing to look at. But I thought, as the dagon is an aquatic species I thought I may have to look at mouths of other species similar, even as sightly similar as a fish.
I chose to look at trout and pike as these have large opened mouths.

I have found some difficulty when sketching the Dagons mouth before hand, I found it hard creating a wide open mouth that would look like it could match up when closed. Looking at these shows me ways of drawing the jaw in such a way that it would work and how the teeth would come out of the mouth.