An unusual jaw 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.
The teeth are a crushing type dentition -- perfect for feeding on crabs and other shellfish.There is an area in the lower jaw that has a deformity.
A very unusual jaw for your collection.