The Dwarf Lanternshark

  The dwarf lantern shark is the smallest known species of shark. It grows to roughly twelve centimetres long - about the length of a ballpoint pen. These reclusive micro-sharks at depths of four hundred and forty metres, meaning that they are not often encountered by humans.
  Wether this shark is endangered or of least concern, no one knows. Their range is small - nearly as small as they are! - and fisheries in the areas where they live have repoted netting them as bycatch. They have been classed as data deficient by SHARKDEFENSE.
  These deep-sea-nipprs rise to the Sunlight Zone by night to hunt in schools of several hundred specimens, catching solitary fish and sometimes small sharks, like dogfish.

The minute range of the dwarf lantern shark.

A dwarf lantern shark spotted in the Twilight zone by
a very lucky diver.