The Chinese government has strict control over the media in their country, and Magic card art is no exception. Along with overtly sexual or violent illustrations, human skeletons are not permitted on the cards.
In order to comply to these strict regulations, art often has to be completely redone, but in some cases the original can be altered enough to pass. The above example shows how the Unworthy Dead from Urza's Saga were given some flesh and muscle to cover their exposed bones for the Chinese version.
The redone Unworthy Dead art was then used again for the Chinese Sixth Edition Drudge Skeletons. As a rule, art is never used twice on different cards, but when the government gets involved, rules sometimes need to be broken. (The English 6E Skeletons is to the right; altering that art was probably too daunting a task under the deadlines.)