A mace-like spiny-headed rod found on the mid-dorsal surface of heads of male Holocephali. Thought to aid in holding the female during copulation. [ http://fishbase.org/glossary/Glossary.php?q=tenaculum http://en.wikipedia.org/wiki/Chimaera#Description_and_tastes http://www.fishbase.org/glossary/Glossary.php?q=cephalic+clasper ]