This 6.5 inch (16.5 cm) fossil is a stellar example of a Hybodont (Hybodus Obtusus) Shark Dorsal Spine. Mined from the famous Kem Kem formation in South Eastern Morocco, this specimen has maintained its denticles--the tooth-like formations that make these fossils sometimes mistaken for jaws! 

Hybodus Obtusus was a small shark from the Late Cretacious that only grew to 2 meters in length, and would have been a very fast, opportunistic predator. 

It is relatively rare for non-tooth shark material to be preserved in this condition, this fossil very nearly was kept for our personal collection!