Spined pygmy shark

Spined pygmy shark
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Order:	Squaliformes
Family:	Dalatiidae
Genus:	Squaliolus
Species:	S. laticaudus
Binomial name
Squaliolus laticaudus H. M. Smith and Radcliffe, 1912
Range of the spined pygmy shark
Synonyms
Squaliolus sarmenti Noronha, 1926

The spined pygmy shark (Squaliolus laticaudus) is a species of squaliform shark in the family Dalatiidae found widely in all oceans. Growing no larger than roughly 28 cm (11 in), it is one of the smallest sharks alive, with this record beaten by the dwarf lanternshark. This shark has a slender, cigar-shaped body with a sizable conical snout, a long but low second dorsal fin, and an almost symmetrical caudal fin. Its sister species S. aliae and it are the only sharks with a spine on the first dorsal fin and not the second. Spined pygmy sharks are dark brown to black, with numerous bioluminescent organs called photophores on their ventral surface. The shark is believed to use these photophores to match ambient light conditions, which break up its silhouette and help the shark to avoid being seen by predators below.

Usually inhabiting nutrient-rich waters over upper continental and insular slopes, the spined pygmy shark feeds on small bony fishes and squid. Like its prey, it is a diel vertical migrator, spending the day at close to 500 m (1,600 ft) deep and moving towards a depth of 200 m (660 ft) at night. Reproduction is presumably aplacental viviparous, with females giving birth to litters of up to four pups. This diminutive shark has no economic value. The International Union for Conservation of Nature has assessed this species as of Least Concern, as it faces little threat from commercial fisheries and has a wide distribution.