Lycoteuthids are mostly small, muscular squids occupying mesopelagic depths during the day and migrating into near-surface waters at night. They are tropical and subtropical in distribution but are not known from the North Pacific. They possess a large variety of luminous organs. Oval photophores are found on the tentacles, eyeballs and viscera in all species and on the arms, head, mantle and fins in some. Strong sexual dimorphism in general morphology occurs in some species.

Diagnosis

A member of the enoploteuthid families ...

• without hooks.
• with photophores on viscera, eyeballs and in tentacles.

Chun (1903) erected the family Thaumatolampadidae for the species now known as Lycoteuthis lorigera. In 1908 Pfeffer placed this species in the subfamily Lycoteuthinae of the Onychoteuthidae.Berry (1914) removed the lycoteuthids from the Enoploteuthidae and erected the family Lycoteuthidae for them. Since the Name Thaumatolampadidae had not been used for nearly 50 years Voss (1962) stated that this name should not be maintained regardless of possible priority. Berry (1916) erected the family Lampadioteuthidae for Lampadioteuthis megaleia. Naef (1923) included the Lycoteuthinae as a subfamily of the Enoploteuthidae.Voss(1956) maintained the separate familial status for the Lycoteuthidae and in 1962 maintained the subfamilial status for the Lampadioteuthinae.

A list of all nominal genera and species in the Lycoteuthidae can be found here. The list includes the current status and type species of all genera, and the current status, type repository and type locality of all species and all pertinent references.

1. Arms
   1. Arms with biserial suckers; hooks absent.
      
      
2. Tentacle
   1. Tentacular clubs with quadraserial suckers; hooks absent.
      
      
3. Tail
   1. Tail slender, long or short, without vesicles, extends well posterior to gladius.
      
      
4. Photophores
   1. Ocular: 4 or 5 oval photophores present on eyeball.
   2. Viscera: anal, branchial, postero-abdominal organs present on viscera. Abdominal photophores present in most species.
   3. Tentacles: 2-5 spherical organs embedded in tentacles.
      

      Figure. Ventral view of Lycoteuthis diadema" showing photophore terminology. Drawing from Chun (1910), labels added.

Comments

A variety of other photophores are found in specific genera or species.

Comparisons of subfamilies:

	Hectocotylus	Abdominal photophores	Ocular photophores	Rostrum on gladius
Lampadioteuthinae	Present	Absent	Four	Present
Lycoteuthinae	Absent	Present	Five	Absent

A single species, Lampadioteuthis megaleia, exists in the Lampadioteuthinae. The three genera of the Lycoteuthinae can be separated as follows:

	Male genitalia	Greatly elongated arms (males)	Large photophore at posterior mantle apex	Photophores on arms II and III
Lycoteuthis	Paired	Arms II	No	Subterminal, many
Nematolampas	Single	Arms III*	No	Subterminal, single or many
Selenoteuthis	paired	None	Yes	Terminal, single

*Nematolampas venezuelensis also has long arms II but not as long as arms III.