First, explore the world until you find some bones. Turn on Freecam via the console (CTRL+Shift+C and type freecam and press ENTER) and use the bones. Immediatly pause the game once the icon appears showing you the type of item you received. Now use your mouse wheel to scroll out far enough that you and the bones disappear. Once you've zoomed out, immediately zoom back in and the bones will respawn. Repeat this as necessary until the bones completely vanish, letting you know you've received all the creature parts from those size bones.
You can do this with any size bones!