Hymenogadus Gilbert & Hubbs, 1920

Schwarzhans, Werner, 2014, Head and otolith morphology of the genera Hymenocephalus, Hymenogadus and Spicomacrurus (Macrouridae), with the description of three new species, Zootaxa 3888 (1), pp. 1-73 : 23-24

Hymenogadus Gilbert & Hubbs, 1920

Hymenogadus Gilbert & Hubbs, 1920: 521 , as subgenus of Hymenocephalus Giglioli, 1884 , type species by original designation Hymenocephalus gracilis Gilbert & Hubbs, 1920 .

Hymenogadus: Okamura, 1970: 58 .

Hymenocephalus: Marshall & Iwamoto, 1973: 602 ; Sazonov & Iwamoto, 1992: 55; Iwamoto & Merrett, 1997: 518.

Diagnosis. Modified from Okamura (1970). First spine of dorsal fin serrated. Ventral striae consisting of fine parallel lines of dark, alternating with silvery pigment associated with a light-producing function on abdominal wall, parts of chest, and shoulder girdle, not joint at median line behind pelvic fin bases. Head cavernous, with moderately thin skin cover. Median and lateral processes of snout sharply pointed, not plate-like. Gill rakers 10–19. Additional diagnostic features from axial skeleton and head morphology are: 11–12 precaudal vertebrae (based on radiographs). Widening of sensory canal systems on head; development of incipient infranasal, infraorbital and preopercular supporters; Hymenocephalus -like snout with broad, blunt, soft tip. Additional diagnostic features from otolith morphology are: Moderately elongate shape of otoliths (OL:OH = 1.25–1.55); elevated, but short predorsal lobe; ventral sulcus margin at collum indented; pseudocolliculum indistinct, short.

Comparison. Hymenogadus resembles Spicomacrurus in a number of aspects, such as body shape, extent of ventral striae not joined behind the pelvic fin bases, otolith with an indented ventral sulcus margin at the collum, and short, indistinct pseudocolliculum. Certain other characters remind of the status seen in Hymenocephalus , such as the widening of the sensory canal system on the head, albeit covered by a thicker more robust skin than in Hymenocephalus , the lack of the spatulate nasal bones, the incipient developments of infranasal, infraorbital and preopercular supporters and the expanded, though short predorsal lobe in the otoliths.

Species. Two species, one nearly cosmopolitan ( H. gracilis ), except for Hawaii, where it is replaced by the second, probably endemic species ( H. tenuis ).