Shapeshifter is just a creature type, and NO creature type has any inherrent additional effects of meanings since Champions of Kamigawa (which did away with Walls inherrently being unable to attack, which was made into the defender ability, and Legend becoming the supertype Legendary thus decoupling the legend rule from that creature type). A shapeshifter is not a Skeleton nor any other creature type. It is the CHANGELING ABILITY that makes SOME shapeshifters all creature types. But merely being a shapeshifter has no effect or inherrent meaning within the game. Super-Skull is a Skull, a Shapeshifter, and a Villain, and nothing else.