inconsistency with weapons of dragon slaying (they are vilnerable, while dragon zombies and skeletons aren't), and because their description indicates that they're made of pieced-together bones from many different dragons (so limiting them to one species of dragon seems wrong).

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@7262 c06c8d41-db1a-0410-9941-cceddc491573