I didn't use a reference, but the exact anatomy is not the point of my edit. (it's more about technique than it is about the subject matter here. I kinda fudged your design into something I like, it's cool, it's cool
)
What I wanted to get across was contrast. I'm not a fan of dithering
, but I used it to show you when it's appropriate. Your colors are so close together you could have just smooth shaded. When you need to dither is when the two colors are so far apart they create an unwanted visual schism on your piece. So you mix the two in a checker pattern [or other atrocious way
] and the two colors have a baby.
Also, try to build form rather than shape. If you make forms clear, it does the job of any outline you make plus some.