One trick that particle effects use is to have 3-4 images that have 3-4 coins each. When shown briefly and moving/rotated/scaled and with the coins images layered on top of each other, it can be difficult to notice that some of the coins are on the same image.
Another thought is that if there is not much else going on at the time this effect is shown, then it may not matter that a skeleton uses many bones. Having a skeleton with many bones can be acceptable while having many skeletons with many bones may not.
