You probably have thought that animals—like dogs, cats, and horses— look way different than people.  Especially their legs!!  Well, this may come as a big surprise to you— but dogs, cats and horses (mammals) look more like people than you think!!  In fact, the skeleton of a human and any mammal are very similar.  One of the main reasons that  the legs look so different is that most mammals walk on their tiptoes.  Once you realize that fact, the legs are not so much a mystery anymore!  Look closely at this drawing of a human skeleton and compare it to the dog skeleton.

I just went on a walk with my dog, and as I watched his back legs as he walked, realizing his “heel” was always six inches off the ground, the more I realized that his legs looks a lot like a human leg!! The main difference is that my dog’s upper leg (thigh) is on the side (and part of) of his body, and what I see as his leg is really his lower leg and foot.  It took me quite awhile studying this and drawing the skeleton to understand it, and learn how to draw it.  But it is worth learning.  It will help you draw animals and fantasy creatures much better if you can memorize the bone structure of animals (since many fantasy creatures are based on the construction of humans and animals)!