This is an interesting fossil - its a fossilized dorsal fin spine from HYBODUS, an extinct shark that lived during the Cretaceous period approximately 110 million years ago. This shark had 2 dorsal fins, each with a bony spine like this one, that is thought to have served a defense purpose for the shark. This spine measures approximately 3 3/4 inches long, and it was found in Morocco, North Africa.
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