Pyroteuthis is a genus of squid

Squid

Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...

 in the family Pyroteuthidae

Pyroteuthidae

Fire squid are species belonging to the family Pyroteuthidae. The family comprises two genera. Species are diurnally mesopelagic, however migrate into surface waters during the night. The family is characterised by the tentacles, which have a permanent constriction and bend near the base; and...

. It is differentiated from the genus Pterygioteuthis

Pterygioteuthis

Pterygioteuthis is a genus of squid in the family Pyroteuthidae. Members are differentiated from the genus Pyroteuthis due to size and head shape. The genus is characterised by the presence of a lidded photophore over each eye.-External links:*...

by size, head shape and behaviour. Species within the genus are separated by the arrangement of tentacular

Tentacle

A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...

 photophores; the shape of the hectocotylus

Hectocotylus

A hectocotylus is one of the arms of the male of most kinds of cephalopods that is modified in various ways to effect the fertilization of the female's eggs. It is a specialized, extended muscular hydrostat used to store spermatophores, the male gametophore...

, and the shape of the hectocotylus hooks. With the exception of the Tropical Eastern Pacific

Tropical Eastern Pacific

The Tropical Eastern Pacific is one of the twelve marine realms that cover the shallow oceans of the world. The Tropical Eastern Pacific extends along the Pacific Coast of the Americas, from the southern tip of the Baja California Peninsula in the north to northern Peru in the south...

, the genus is circumpolar in tropical and temperate oceans. The species P. addolux

Pyroteuthis addolux

Pyroteuthis addolux is a species of squid in the family Pyroteuthidae. It is distinguished from other members of the genus Pyroteuthis by the shape of photophores on the tentacles and the shape of the hectocotylus. The hectocotylus is located on arm IV, containing 10 proximity hooks, and 6–15...

is the only member to occur in the North Pacific.