It's a really quick/rough one covering some basics but I hope it helps. =]
I really wanna stress the spinal curve, which is also known as an action line, it's especially helpful when you want to have a sense of movement and energy in your poses and can be applied to anything, not just dragons =]
It's better than starting head first, because you can plan its size and place on a page and you'd be able to know when you're gonna run outta room long before the sketch is finished.
Yes, circles and stick limbs do help map out the anatomy. It may look a bit tedious and unnecessary, but they are the foundations/bones on which you build the body on and are helpful to figure out the pose before you go into detail, as well as keeping things in proportion.
The bat-like wing IS like a human arm and thus has the same range of movement at its joints as your shoulder, elbow, wrist, and fingers- think of your fingers being much longer
Again, I hope this is helpful
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