Assuming our dragons still follow most basic natural laws (in order for them to be easier to suspend disbelief with), the triangle-shaped head implies a triangular prism[*], and not just a head that fits in a triangle shape…
But alas, perspective has never been an ally of mine… :/
*a bit of Googling later, I found that I actually meant (for the most part) a tetrahedron, though in some cases a triangular prism would probably have sufficed as well, especially since it’s easier to draw.
