Promachoteuthis sulcus (first known as Promachoteuthis sp. C on this page) is known from a single, small (25 mm ML, sex unknown) but distinctive individual from great depths in the south Atlantic Ocean.

Brief diagnosis:

A promachoteuthid...

• with nuchal fusion between head and mantle.
• with arm suckers much larger than club suckers.
• with tentacle base wider than arm base.
• with recessed club base and aboral tentacle groove.

1. Arms
   1. Arm suckers much larger than club suckers.
   2. Suckers in three series on all arms.
      

      Figure. Oral view of brachial crown of P. sulcus, holotype. The squid seems to have a set of dentures. The "dentures" are the circular, folded lips, of which only the upper and lower portions can be seen. The lips surround the beaks which are not visible in this photograph. Photograph by R. Young.

2. Tentacles
   1. At base tentacle thick, about 2x diameter of arm III.
   2. Tentacle stalk with deep groove on aboral surface.
   3. Club suckers tiny (0.014 mm diam), in numerous irregular rows.
   4. Sucker-bearing club recessed at tapering, proximal end; surrounding lateral and aboral tissue with thick folds.
   5. Tentacles heavily pigmented at base but not forming a well-defined band.
      

      Figure. Tentacular club of P. sulcus, holotype, preserved. Top - Oral view of the distal portion of the club, holotype. Bottom - Oral view of the proximal portion of the tentacular club. Photographs by R. Young.

3. Head
   1. Head fused to mantle in nuchal region.
      

      Figure. Side view of the head and anterior mantle of P. sulcus showing nuchal fusion. Photograph by R. Young.

4. Fins
1. Fins terminal with anterior and posterior lobes. Each fin approximately circular in outline.


Figure. Ventral and dorsal views of the fins of P. sulcus. Photograph.

Comments

More details of the description of P. sulcus can be found here.

Clubs were slightly abraided so the number of suckers in a transverse series could not be determined. The largest number of those present was 12 suckers across. The specimen is an immature female. The mantle was cut open prior to fixation by a previous investigator. The label in the specimen jar states that the ML is 40 mm; the squid currently measures 25 mm ML.

Type locality: 36°49'S, 12°17'W off Tristan Da Cunha, south Atlantic Ocean. Captured from WALTHER HERWIG at 1750-2000 m depth (open net).

Holotype for Promachoteuthis sulcus Young et al., 2007
Catalog Number: USNM 730702
Collection: Smithsonian Institution, National Museum of Natural History, Department of Invertebrate Zoology
Sex/Stage: female; immature
Preparation: Alcohol (Ethanol)
Year Collected: 1971
Locality: Tristan Da Cunha, Tristan Da Cunha Islands, South Atlantic Ocean
Depth (m): 1750 to 2000
Vessel: Walther Herwig R/V

Depth range based on 1 specimen in 1 taxon.
Water temperature and chemistry ranges based on 1 sample.

Environmental ranges
  Depth range (m): 1875 - 1875
  Temperature range (°C): 2.700 - 2.700
  Nitrate (umol/L): 28.259 - 28.259
  Salinity (PPS): 34.757 - 34.757
  Oxygen (ml/l): 4.735 - 4.735
  Phosphate (umol/l): 1.945 - 1.945
  Silicate (umol/l): 57.898 - 57.898
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.