Which tiny deepwater species is often cited as the world's smallest shark?

Which tiny deepwater species is often cited as the world's smallest shark? The dwarf lanternshark is often cited as the world's smallest shark.

The species, Etmopterus perryi, is a member of the dogfish shark family Etmopteridae. It lives on upper continental slopes in the Caribbean Sea, especially off Colombia and Venezuela, where it has been reported from roughly 283 to 439 metres deep. Its small size and deep habitat make it rarely encountered by people.

Dwarf lanternsharks are bioluminescent. Photophores on the underside produce light, probably helping camouflage the shark against the faint downwelling light seen from below. The species is dark brown and has distinctive black ventral markings, along with a long, flattened head and two dorsal fins equipped with spines.

Adults reach about 20 centimetres in commonly quoted measurements, although reported maximum lengths vary slightly. The title of smallest shark is not completely absolute: the spined pygmy shark and pygmy ribbontail catshark reach similarly tiny sizes, and reproductive maturity is difficult to compare. Even so, dwarf lanternshark is the standard answer in general references and trivia questions.