Stemonosudis Harry, 1951

Ho, Hsuan-Ching, Russell, Barry, Graham, Ken & Psomadakis, Peter N., 2019, Review of the Stemonosudis rothschildi species complex, with descriptions of two new species from the Indo-west Pacific Ocean (Aulopiformes: Paralepididae), Zootaxa 4702 (1), pp. 216-229 : 217-218

Stemonosudis Harry, 1951

Stemonosudis Harry, 1951:32 (Type species: Macroparalepis intermedius Ege, 1933 ).

Distinguishing features. A genus of the subfamily Paralepidinae with body generally relatively slender; anus clearly situated before dorsal-fin origin; jaws slender; nostrils above posterior the end of maxilla (but unknown in some species because of a lack of adult specimens), and some are slightly further forward (i.e. three species treated in present study); ventral adipose fin well-developed between anus and origin of anal fin; anal-fin rays 34–50 (except S. molesta with 30); vertebrae more than 84 (usually more than 90).

Remarks. Prior to the present study, total of 12 nominal species were recognized in the genus Stemonosudis . The two new species described herein raise the number to 14. However, based on the examination of the type specimens of most of species, some may be reassigned to other genera, such as Lestidiops .

Harry (1951, 1953) listed many characters in his diagnosis of Stemonosudis . However, most of them are commonly shared by other genera. Stemonosudis is similar to Macroparalepis Ege, 1933 in having a very slender body, but Macroparalepis has the anus well behind the tip of the anal fin, no ventral adipose fin and 24–28 anal-anal fin rays, whereas Stemonosudis has the anus just situated above posterior tip of pelvic fin, ventral adipose fin well-developed between anus and AFO, and more than 34 anal-fin rays (except for one species with 30).

Of all the other genera in the Lestidiinae, Stemonosudis is most similar to Dolichosudis Post, 1969 . Based on observations by the first author, no distinguishable character has been found between these two genera, except for the uniformly blackish color in adults of Dolichosudis , compared with an uneven color pattern, such as saddles, in Stemonosudis . These two genera are likely to be synonyms.

Stemonosudis also shares most characters with members of Lestidiops Hubbs, 1916 . The two genera can be separated mainly by body shape (much more slender and narrow in Stemonosudis than in Lestidiops ), shapes of jaws (more slender in Stemonosudis than in Lestidiops ), and position of nostrils (above or behind posterior end of maxilla in Stemonosudis and well in front in Lestidiops ). However, the three species treated here have moderately slender bodies and jaws and their nostrils are slightly in front of the end of the maxilla, conditions that are “intermediate” between these of the two genera. Further studies are needed in order to assess the validity of the two genera, and the species assigned to them may change.