Members of the Sepiolinae are neritic and benthic sepiolids. The subfamily has a world wide distribution except for waters of the Americas. Their highest diversity appears to be in the eastern Atlantic Ocean and Mediterranean Sea.

Brief diagnosis:

A sepiolid ...

• with dorsal mantle fused to head.
• without ventral mantle shield.

1. Arms
1. Interbrachial web weakly developed between arms I-III.
2. Suckers in 2-4 series except at tip where there may be more.
3. Left dorsal arm of male hectocotylized (see details under Comments below).


2. Tentacles
1. Tentacular clubs expanded.
2. Keel along full length of club.


3. Mantle
1. Dorsal mantle fused to head.


4. Gladius
1. Gladius reduced or absent.


5. Viscera
1. Bursa copulatrix present near female genital opening.


Figure. Ventral view of the mantle cavity of Sepiola robusta, mature female. Nidamental glands are colored yellow; the bursa copulatrix is colored brown. The photophores are blue. Note that the bursa extends over the base of the gill and onto the muscular mantle. Drawing modified from Naef (1921-23).

6. Photophores
1. Photohores, when present, usually (see exception in Rondeletiola) with separate bean-shaped lenses and reflectors on lateral lobes of ink sac.
   
   
   

   Figure. Ventral view of the visceral photophores of Euprymna scolopes. Only the ends of the bean-shaped reflectors can be seen due to expansions of the ink sac over the mid-regions. The lenses that cover the reflectors are transparent and cannot be seen. © 2004 Richard E. Young

Comments

The Sepiolinae comprise two natural groups: Euprymna and the remaining Sepiola-like species. Eupyrmna is distinguished, among other features, by the presence of four sucker series on the arms and a hectocotylus (left arm I) that is less specialized in lacking a "copulatory apparatus." The Sepiola-like species have arm suckers in two series except at the tips of arms IV where more may be present and a distinct type of hectocotylus. The latter hectocotylus (left arm I) consists of 1-4 normal suckers at the base of the arm, followed by a "copulatory apparatus" that includes modified sucker stalks without suckers, followed by a relatively normal distal portion (Naef 1921-23).

A distinct feature of the Sepiolinae is the presence of the bursa copulatrix in females. This is a folded pocket of the lining of the mantle cavity near, and often covering, the oviducal opening but is not part of the latter which may have its own flutted lips. The bursa is an attachment site for spermatangia. Other sepiolids a wrinkled skin in this region and the bursa is a great elaboration of this wrinkled area (Naef, 1921-23).

The following table compares the genera of the Sepiolinae.

	Arm sucker series*	Visceral photophores	Club sucker series	Gladius
Euprymna	4**	Yes	>20**	Present
Inioteuthis	2	No	8-16	Absent
Rondeletiola	2	Yes	8-16	Absent
Sepietta	2	No	16-32	Very weak
Sepiola	2	Yes	<9	Present

*Non-hectocotylized arm; excludes tips of arms IV.
**Except E. phenax (2 sucker series on arms, 12-14 on clubs).

The subfamily does not occur in waters of the Americas. Young (et al., 1998) speculate that the group evolved after the shallow water bridge across the high North Atlantic was obliterated.

View Sepiolinae Tree

We follow the phylogeny of Naef (1921-23) with the exception that we place Sepiolina in the Heteroteuthinae.