Caught male Spotted Ratfish (Hydrolagus colliei) showing the [extended/erect] frontal clasper (tenaculum) on the front of the head. Credit: Gareth J. Fraser, University of Florida ========================================================================== Male ghost sharks use tooth-studded rods on their foreheads for mating. Fossil and genetic evidence prove they are true teeth, showcasing evolutionary flexibility. 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. New research shows these are not simple imitations but actual rows of teeth that develop outside the mouth. The...