Euprymna Steenstrup, 1887

Sanchez, Gustavo, Jolly, Jeffrey, Reid, Amanda, Sugimoto, Chikatoshi, Azama, Chika, Marlétaz, Ferdinand, Simakov, Oleg & Rokhsar, Daniel S., 2019, New bobtail squid (Sepiolidae: Sepiolinae) from the Ryukyu islands revealed by molecular and morphological analysis, Communications Biology 2 (465), pp. 1-15 : 4-5

Euprymna Steenstrup, 1887

Gender feminine. Type species, by subsequent designation, Inioteuthis morsei Verrill, 1881 . Recent. Western Pacific and eastern Indian Oceans.

Diagnosis. (Amended from Norman and Lu47 and Reid39, and after Bello, personal communication.) Broad ligament between head and mantle; commissure greater than one-third of head width. Transverse suckers in two or more rows on normal (nonhectocotylised) arms. Stalked suckers in six or more transverse rows on tentacular clubs. Left arm 1 hectocotylised in mature males; distally with lengthened, columnar sucker pedicels, closely packed to form longitudinal “palisades”, bearing at tip embedded toothed suckers that are partially covered by fleshy cap, number of palisades proximally equal to that of regular sucker rows but reduced toward distal tip of arm; pedicels not bearing discretely demarcated rounded suckers; basal part of hectocotylised arm with normal suckers and sometimes with 1–2 finger-like papillae in ventral sucker row, sometimes bearing tiny sucker(s). Enlarged arm suckers usually present in male and sometimes present in females. Paired kidney-shaped light organs in mantle cavity, ventral, and closely adherent to ink sac. Gladius absent.

Remarks. Given that some Euprymna are now known to have biserial arm suckers, members of the genus Sepiola seem superficially to conform to this diagnosis. However, these two taxa (i.e., Euprymna and Sepiola ) clearly differ based on molecular traits

and in a number of other important characters in detail. The modification of the hectocotylus is quite distinct. In Sepiola , the hectocotylised left dorsal arm is thicker than the right and strongly recurved aborally in preserved specimens. The palisade columnar suckers in the hectocotylus distal portion are unique for Euprymna . Sepiola as well as all the other Sepiolinae genera bear regular suckers in the distal part of the hectocotylus. Some of them may be enlarged in some species, their stalks may be also lengthened and/or swollen, but no other Sepiolinae species have columnar stalks with embedded suckers at their tips. Although the suckers are positioned on enlarged and elongate pedicels in both taxa, the suckers are ovoid and discrete in Sepiola , while in Euprymna the suckers are partially capped or encased by the pedicels and the chitinous rims are usually narrow. Most remarkably, in Sepiola , instead of a finger-like papilla at the base of the hectocotylus (as seen in most Euprymna species) there is a distinct fleshy mound that may bear hook-like projections. The third arms of Sepiola males are thick and strongly curved orally in some species; in Euprymna the third arm pair of males is not swollen and recurved. Sepiola generally have two rows of suckers on each arm (as do some species of Euprymna ), but some species have 4–8 rows of suckers on the distal tips of the fourth (ventralmost) arm pair. Euprymna may have two or more rows of arm suckers but if four or more rows are present, they are not confined to a single arm tip. In addition, the tentacular club is recurved and relatively short in Euprymna and longer and much less curved in Sepiola with a much narrower keel. The fins in Sepiola are large and round, while in Euprymna the fins are narrower and more elongate in outline.