Hello everyone, I found this glitch many years ago but never posted it, and I haven't seen it posted anywhere else.
What you need to do is find a skeleton in the creature stage and dig it up.
During the animation for digging it up, pause the game and activate freecam.
Zoom out with freecam until the skeleton is no longer rendered
Zoom back in, and the skeleton will be back, and ready to be dug up again.
Repeat until satisfied
With a big enough skeleton, you can use this glitch to get all of the parts in very little time at all
Freecam does not disable achievements, so don't worry about that