Most professional artists use reference pictures almost every time they draw something. Expecially if it's something they haven't drawn before. The most important thing to realize that you don't need to know WHAT you're drawing, it's what you're DRAWING. That means, that if you want to make a wolf, you don't draw a wolf. You draw what a wolf looks like, feels like, acts like. You have to know the anatomy, behavior, muscles, texture, weight, and so on. That's what's most important if you want it to look realistic, and believable. Otherwise, it's not gonna look like a wolf, only what you think a wolf looks like. I hope that makes sense. If you know that, then it doesn't matter what medium you're using. You could do just as well with photoshop as with a simple pen and paper.