Hymenocephalus antraeus Gilbert & Cramer, 1897

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 : 47-49

Hymenocephalus antraeus Gilbert & Cramer, 1897

Figs. 22A–G , 27

Hymenocephalus antraeus Gilbert & Cramer, 1897: 428 (type locality: 21°08’N, 157°49’W).

Material examined. 9 specimens; 6 specimens LACM 57119 , 120 + – 171 mm TL, off Hawaii, R / V Townsend Cromwell TC 52–88 ; 3 specimens USNM 47735 (syntypes), 130–145 mm TL, 21°08’N, 157°49’W, 627 m .

Diagnosis. Pelvic fin rays 11–12, mostly 12; pectoral fin rays 13–15, rarely 16; snout barely projecting, short, 15–18% HL; barbel short, 3–4% HL; orbit diameter large, 35–40% HL; infraorbital width 8–10% HL; preopercular supporter moderately long, with obtuse angle at rear margin, 5–7% HL; gill rakers 21–24; ventral striae reaching to ½ from pelvic fin bases to periproct; otolith with high predorsal lobe, colliculi separated, narrowly placed across collum with occasional tendency to partly join, terminating at some distance from anterior and posterior rims of otolith; OL:OH = 0.95–1.1; TCL:PCL = 1.6–1.7.

Comparison. Hymenocephalus antraeus differs from other members in the antraeus Group primarily in the larger orbit (35–40% HL vs 30–35% HL), higher number of pelvic fin rays (11 to mostly 12 vs 7–11), narrow infraorbital width (8–10% HL vs 10–16% HL), and presence of an obtuse angle at the rear margin of the preopercular supporter (vs. straight in all other members of the group). The last character is shared with species of the striatulus Group, from which H. antraeus differs in its short, barely projecting snout (15–18% HL vs 20–25% HL), large orbit (except for H. striatulus ), and long pseudocolliculum (TCL:PCL = 1.6–1.7 vs 1.7–2.8).

Description. Head morphology (n = 2) ( Fig. 22A–B ): Snout short, rounded, barely projecting, 15–18% HL, orbit diameter large, 35–40% HL, interorbital width 50–60% HW. Barbel short, 3–4% HL, not reaching vertical through anterior edge of orbit. Head canals well developed, variably large, infraorbital width narrow, 8–10% HL, supraorbital canal with 6 segments, width 11–13% HL, supratemporal canal moderately developed, above segment 4 of supratemporal canal, preopercular canal width 11–13% HL, postorbital-preopercular interspace 7–8% HL. Infranasal supporter small; infraorbital supporter short, expanding only beyond rear part of orbit, 40–50% OD; preopercular supporter moderately long, 5–7% HL, rear margin with obtuse angle.

Otolith morphology (n = 4) ( Fig. 22C–G ): Otolith large; OL:OH = 0.95–1.1; OH:OT = 3.5. Dorsal rim with a distinct, broad, somewhat irregularly formed predorsal lobe with pointed tip, distally marked by small incision; posterior tip shifted above sulcus termination; ventral rim deep, regularly curved, smooth, deepest anterior of the middle; anterior rim high, subvertical to nearly vertical. Inner face slightly convex, with median sulcus. Ostial and caudal colliculi moderately small, narrowly placed across collum, terminating at some distance from anterior and posterior tips of otolith; pseudocolliculum long. CCL:OCL = 0.95–1.15; TCL:PCL = 1.6–1.7. Dorsal depression small; ventral furrow distinct, moderately close to ventral rim. One otolith was found with nearly joined colliculi ( Fig. 22G ). Together with one other case observed in H. nascens , this is the only instance of incipient joining of colliculi in the otoliths of species of Hymenocephalus .

Distribution ( Fig. 27 ). Apparently endemic to Hawaii.

Figures

FIGURE 22. Hymenocephalus antraeus: A–B—LACM 57119-1, A—Lateral view of head, B—Dorsal view of head. C–G—Otoliths, USNM 47735, C, E, G—Inner faces, D—Anterior view, F—Ventral view.

FIGURE 27. Geographical distribution of Hymenocephalus antraeus, H. hachijoensis, H. heterolepis and H. punt.