Hymenogadus tenuis ( Gilbert & Hubbs, 1917 )

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 : 26

Hymenogadus tenuis ( Gilbert & Hubbs, 1917)

Figs. 6J–L , 7

Hymenocephalus tenuis Gilbert & Hubbs, 1917: 173 (type locality: Hawaii, off southern Oahu ).

Material examined. The unique holotype: USNM 78177 , 75 mm TL, south coast of Oahu, Hawaii, 485–512 m, Albatross , 5 June 1902 .

Diagnosis. Pelvic fin rays 8; pectoral fin rays 12; barbel short, 12% HL, reaching vertical through anterior edge of orbit; gill rakers 10; OL:OH = 1.3, from x-ray.

Comparison. See H. gracilis .

Description. Head morphology ( Fig. 6J–K ): Head slender with projecting, broad, soft-tipped snout. No scale pockets visible on head, but present on nape. Snout length 20% HL, orbit diameter 38% HL, interorbital width 40% HW. Barbel 12% HL, reaching vertical through anterior edge of orbit. Frontal, infraorbital, supraorbital and postorbital canals widened (infraorbital, supraorbital and postorbital widths 5–12% HL), covered by thin, but mostly preserved skin; preopercular and supratemporal canals fully skin covered and indistinct. Infranasal supporter small; infraorbital supporter narrow, not expanded below rear part of orbit; preopercular supporter narrow, pointed, short, 4% HL. No pores visible.

Otolith morphology ( Fig. 6L ): No otolith was extracted from the unique holotype, but a high quality x-ray shows an otolith with a very similar outline and similar proportions (OL:OH = 1.3) to those of H. gracilis , but seemingly with a more symmetrical and not-inclined predorsal lobe.

Distribution ( Fig. 7 ). Apparently endemic to Hawaii.

Figures

FIGURE 6. Heads and otoliths of the species of Hymenogadus: A–I—Hymenogadus gracilis, A–D—ZMH 111113, A—Dorsal view of head, B—Ventral view of head and trunk, C–D—Lateral views of head, E—Inner face of otolith, coll. Schwarzhans (leg. IRSNB), F–H—USNM 131873, F—Anterior view of otolith, G—Inner face of otolith, H—Ventral view of otolith, I—ZMH 107658, inner face of otolith. J–L—Hymenogadus tenuis, holotype, J—Lateral view of head, K—Dorsal view of head, L—Radiograph of head depicting otolith.

FIGURE 7. Geographical distribution of the species of Hymenogadus.