Deep-Sea Ghost Sharks Grow Teeth on Their Foreheads, and Scientists Finally Know Why

Male ghost sharks use tooth-studded rods on their foreheads for mating. Male “ghost sharks,” eerie deep-sea fish known as chimaeras and closely related to sharks and rays, have a strange rod that projects from their foreheads and is covered with sharp, retractable teeth. Distinguishing teeth from skin denticlesSpecialists in shark evolution and anatomy were fascinated by the tooth-covered rods emerging from the foreheads of ghost sharks. CT scans of the fossils and modern chimaeras gave the scientists unprecedented, detailed insights into the development of the tenaculum teeth, which looked remarkably similar to the teeth of today’s sharks. The tenaculum teeth express genes found only in true teeth, never in shark skin denticles.