To understand how tooth strength evolved in giant sharks, we studied fossil teeth from the extinct megatooth shark Otodus megalodon and its ancestor, O. obliquus. Using micro–X-ray fluorescence (µ-XRF), we mapped zinc levels across the tooth crowns of both shark species. In contrast, O. obliquus teeth did not show clear zinc reinforcement along the edges, although zinc levels were also lower near the base of the tooth. Publication: On the Cutting Edge: Otodus megalodon Strengthened Tooth Edges Through Zinc Incorporation in Enameloid. https://palaeo-electronica.org/content/Luke Schwenk ([email protected])Dr. Geoffrey Bowers ([email protected])Dr. Victor Perez ([email protected])Dr. Stephen J. Godfrey ([email protected])