This is a beautiful US ammonite. It is a Scaphites sp. from South Dakota. This specimen is unusual because of its natural red iridescence - most ammonites from this locality are white. The ammonite has detailed ribbing and the tiny inner whorls are even preserved. It displays well in the natural block of Fox Hills matrix that is chock full of fossil bivalves. This is a very pretty ammonite from the high plains of South Dakota.