Sharks evolved about 400 million years ago and so they have had a lot of time to adapt and change to their environment. Their great diversity is familiar to us all: from the fearsome gape of the Great White to the bizarre, almost laughable appearance of the Hammerhead. Sharks as a whole group have been called living fossils, though the term is probably best applied to specific species which have changed very little through time and have few relatives.
Recently, two amazing discoveries of living fossil sharks were made off of the coast of Japan. On January 21, 2007, staff at Awashima Marine Park in Shizuoka, southwest of Tokyo, were alerted by fishermen to a 'strange eel-like fish with razor sharp teeth'. The 1.6 meter long female frilled shark appeared to be in poor health so was captured by park staff who placed it in a salt water tank. Unfortunately, the fish died a few hours after capture.
The frilled shark (Chlamydoselachus anguineus) was discovered in Japanese waters in the 19th century and superficially, looks less like a shark and more like an eel. Its distinctive 'shark' features include its eponymous protruding gill slits which form a frill around its neck The frilled shark usually live at depths of 600 to 1,300 meters, feeding on small deep water fishes and squid. Park staff believe the animal came to the surface because it was unwell and disoriented.
More recently, another strange creature, a 1.3 metres long goblin shark was caught swimming in Tokyo Bay. It was transferred to an aquarium but also died a short time later. The goblin shark (Mitsukurina owstoni) has a long pointed, rostrum and dwells at similar depths to the frill shark feeding on small fishes and crustaceans. The most striking feature of this odd animal is the snout which is thought to be an electrosensory device used to detect prey for capture.
Both the frilled and goblin sharks are so rare that only a few have ever been documented and studied since thier discovery in the 1800s. Their homes are so deep in the oceans that we cannot easily study their habitat, life history and reproductive habits. Ironically though we cannot reach them, it is likely that the polluting effects of our lifestyles reach their environment. But since we cannot determine if their populations are threatened by our actions they are not currently given protected status.