The order Hexanchiformes contains two families. The Frilled sharks, or Chlamydoselachidae, and the Cow sharks, or Hexanchidae.
These sharks can be found all over the world in tropical, temperate and boreal waters. They prefer deep, cold habitats mostly in the tropics. However, they can be found inshore in temperate temperatures as well.
Hexanchiformes typically have 6 or 7 gill slits. Their vertebral column extends all the way to the caudal fin’s long dorsal lobe. They have one spineless dorsal fin over or behind the pelvic fins.