Spicomacrurus adelscotti ( Iwamoto & Merrett, 1997 )

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 : 20

Spicomacrurus adelscotti ( Iwamoto & Merrett, 1997)

Figs. 3C–D , 4A–B , 5

Hymenocephalus (Spicomacrurus) adelscotti Iwamoto & Merrett, 1997: 514 (type locality: 11°54’S, 179°31’W); Iwamoto & Williams, 1999: 176.

Material examined. 1 specimen WAM P.28073-004, 154+ mm TL, 17°45’S, 118°32’E, 600– 690 m .

Diagnosis. Pelvic fin rays 9; nasal bones closely adjoining along mesial edges, forming three horizontal platelike processes; OL:OH = 1.75.

Comparison. Spicomacrurus adelscotti most closely resembles S. kuronumai , differing in the number of pelvic fin rays (9 vs 8), the more elongate head shape (head length: height = 2.1 vs 1.7) and the more elongate otolith (OL:OH = 1.75 vs 1.45–1.6). The occiput does not show any relict of scales or scale pockets as do the studied specimens of S. kuronumai .

Description. Head morphology ( Figs. 3C–D ): Head length to height about 2.1 with relatively firm head bones and platy spatulate nasal bones closely adjoining along mesial edges. No indication of scales on head. Snout length 26% HL, orbit diameter 29% HL, interorbital width 40% HW. Barbel 18% HL, reaching vertical through center of orbit. Infraorbital, supraorbital and preopercular canal systems narrow with widths <8% HL, covered by rather thick, firm skin. One small pore visible in anterior section of infraorbital skin. Preopercular angle broad, not projecting.

Otolith morphology ( Fig. 4A–B ): Thin, elongate otoliths with slightly convex inner and slightly concave outer face. OL:OH = 1.75; OH:OT = 4. Predorsal lobe moderately developed, narrow; ventral rim shallow; anterior tip blunt, posterior tip moderately pointed. Sulcus slightly supramedian with narrow, ventrally-indented collum. Colliculi large, reaching close to anterior and posterior rims of otolith, caudal colliculum about 1½ times the length of ostial colliculum; pseudocolliculum indistinct, short; TCL:PCL = 9. Dorsal depression large; ventral furrow distinct, turning upwards and away from ventral rim posteriorly.

Distribution. ( Fig. 5 ) Known from only two specimens, the holotype off northern Fiji, and the examined specimen from off Western Australia.

Figures

FIGURE 3. Heads of the species of Spicomacrurus: A–B—Spicomacrurus dictyogadus, holotype, MNHN 2009-1455, redrawn from Iwamoto, Shao & Ho (2011), A—Lateral view, B—Dorsal view. C–D—Spicomacrurus adelscotti, WAM P.28073-004, C—Lateral view, D—Dorsal view. E–F—Spicomacrurus kuronumai, E—Lateral view, NSMT P46796, F—Dorsal view, NSMT P103488. G–H—Spicomacrurus mccoskeri, MNHN 1994-0881, G—Lateral view, H—Dorsal view.

FIGURE 4. Otoliths of the species of Spicomacrurus: A–B—Spicomacrurus adelscotti, WAM P.28073-004, A—Inner face, B—Ventral view. C–D—Spicomacrurus mccoskeri, MNHN 1994-0881, C—Inner face, D—Ventral view. E–G—Spicomacrurus kuronumai, E–F—NSMT P46796, E—Inner face, F—Ventral view, G—NSMT P103488, inner face.

FIGURE 5. Geographical distribution of the species of Spicomacrurus.