This skull, some 9.6 inches long, is carved from an Ammonite fossil. In India the skulls are associated with the God Vishnu and are used in various ceremonies. The name Ammonite actually comes from teh Greek ram-horned God called Ammon.
I think these skulls are wonderful inspiration for GMs. There are plenty of fantasty creatures that would “carve up” nicely and create relics to mystify the players. If you fancied you could even buy this skull from Skullis or another of their selection.