An unusual item from an unusual shark. Actually, its a type of guitarfish (related to rays) that has characteristics of both sharks and rays, hence the common name, shark ray. This creature has a broad flattened head with gills on the underside -- typical of a ray, but it has a more pronounced lower lobe on the tail.

This is from the dorsal ridge just above and behind their head, before the dorsal fin. Check out the massive dermal denticles. Very unusual item.