I've ALWAYS had trouble with drawing wings. I could never work out which direction they went or how they're supposed to look. But this helped IMMENSELY! Thank you so much! I would have never thought of using bat wings as a guide. XP
the human to wing concept can actually be made better. since the part of the arm on a human with 2 pones connected to the wrist can be transformed even farther.
rather then say that the wing also has these 2 bones working in sync. make it 1 bone going to the wrist. and the other drops down to be the anchor for mid-wing flap. then fuse the fingers and all the rest is there already.