Frilled sharks, Order Chlamydoselachiformes, are among the oldest living species of sharks, with fossil evidence dating to 95 million years ago. Some paleontologists suggest it is a living cladodont shark, a shark that existed as long ago as 380 million years.

Frilled Shark (Chlamysoselachus anguineus). Illustration: R. Aidan Martin

Frilled sharks are so unusual that the 2 known species known are placed by some biologists in their own order (as we do, here). Historically, Frilled sharks have been considered a Family within the order of Hexanchiformes, or Cow sharks.

Frilled sharks resemble eels, with a long, thin body followed by a long tail fin. It has six gill slits which are covered with the frilly skin that gives it its name.