Quote Originally Posted by PArcher View Post
4's horns are furry and there are four of them, coming from the side of his head. Neither Primal nor minion have that.

The picture at the top of this page also much more clearly shows the horns being much more similar to 6's. Its highly likely the Allagans mutilated them to fit the Coils on him properly, if it isn't just a Dragon->Primal change
That or the Ascian-summoned version of Bahamut deviated in appearance somewhat from the original Bahamut. Tiamat called it "a mockery of my beloved."