How does an elephant lie down? It pulls itself forward, lowering its rear half onto the knees, then settling the front half on the elbows. (Link to video)
A free website called ReferenceReference has a wealth of stock video clips of such animal actions. Most clips are a few seconds long, and they're intended as reference for animators.
But illustrators will find them fascinating too, because it's really important to know where a pose is coming from and where it's going.
Most of the clips show human action. There are several categories for fighting poses, including hand-to-hand, weapons, kick boxing, and defense. Typically they're shot against a simple background, with a grid to show the perspective of the floor.
There are also clips in categories like dance, contortionist, and push-pull-lift. The actors are divided into men, women, and children, with a variety of ages and ethnicities.
In addition to full-figure actions, there are close-up actions and facial expressions. Often the same action is presented from the front and side views at the same time so that you can get a clear spatial sense of what's going on.
For any actual illustration or animation job, of course, you will probably want to cast and direct your own models, but this resource is useful for generating ideas, for understanding basic principles, or for getting yourself out of habits.
And it's a good supplement to Muybridge's Human Figure in Motion or the Books of art poses.