Cow sharks

Cow sharks are a shark family, the Hexanchidae, characterized by an additional pair or pairs of gill slits. Its 37 species are placed within the 10 genera Gladioserratus, Heptranchias, Hexanchus, Notidanodon, Notorynchus, Pachyhexanchus, Paraheptranchias, Pseudonotidanus, Welcommia, and Weltonia.