The frilled shark is so unique that scientists place it in its own family. And though they are usually categorized in the same order as cowsharks (Hexanchiformes), some scientists say the frilled sharks should have a separate order as well.
Like cowsharks, frilled sharks are members of some of the most ancient groups of sharks still in existence. Both have extra gills, big mouths, eyes on the sides of their heads, spineless back fins, and an unusual arrangement of vertebrae.
The fossil record for frilled sharks dates back to 95 million years ago, though some paleontologists believe they are closely related to sharks that lived as long as 300 million years ago. The frilled shark is one of the few sharks adapted to its challenging deep-water habitat. Without the competition faced by sharks living closer to the surface, the frilled shark has retained many primitive-seeming features. As the only surviving species in its family, it’s often called a “living fossil.”
Until recently, only one living species of frilled shark was known to science. But in 2009, it was confirmed that a specimen caught off the coast of Namibia was in fact a distinct species. Named the Southern African frilled shark, this new frilled shark species is slightly smaller than its close cousin, with a longer head and longer gill slits. It’s found from southern Angola to southern Namibia.