Coryphaenoides altipinnis Günther, 1877

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 147-149

Coryphaenoides altipinnis Günther, 1877

[Japanese name: Hokake-dara]

( Figs. 95D , 96 ; Appendix 3-5E)

Coryphaenoides altipinnis : G̹nther, 1877:439 [original description; holotype: BMNH 1887.12.7.90, from “south of Japan ” (southeast of Boso Peninsula), Challenger sta. 237, in 1875 ftm (3429 m)]; Jordan & Snyder 1901:120 (listed; Japan); Jordan & Gilbert in Jordan & Starks 1904:608 [after G̹nther (1877, 1887)]; Jordan et al. 1913:416 (listed; Japan; new Japanese name: “Hokake-dara”); Okada & Matsubara 1938:449 (in key; Japan); Kuroda 1951:391 (questionable; listed; Suruga Bay); Kuroda 1952:176 (questionable; 1 spec. from Suruga Bay); Matsubara 1955:1309 (in key; Japan); Okamura 1970a:129 [brief description after G̹nther (1877, 1887)]; Tominaga & Uyeno 1981:488 (listed; Japan); Okamura 1984b:95, pl. 345, fig. G (compiled); Okamura 1988:95, pl. 345, fig. G (compiled); Nakabo 1993:364 (in key; Japan); Nakabo 2000:428 (in key; Japan); Nakabo 2002:428 (in key; Japan); Motomura 2020:39 (listed; Japan).

Macrurus altipinnis : G̹nther 1887:138, pl. XXXIX, fig. A [description; in part, holotype, BMNH 1887.12.7.90; other spec. represent C. nasutus and Nezumia proxima ].

Coryphaenoides (Coryphaenoides) altipinnis: Okamura 1970b : table 1 (listed; Japan).

Coryphaenoides altipennis [sic]: Eschmeyer 1998:79 (listed); Nakabo & Kai 2013:504 (in key; Japan).

Diagnosis. Pelvic-fin rays 9. Snout short, slightly protruding beyond upper jaw. No prominent modified scales on head ridges and tip and lateral angles of snout. Mouth large, posterior margin of upper jaw almost reaching vertical through hind rim of orbit; upper-jaw length 41% HL; lateral corner of mouth not restricted by skin folds. Outermost gill slit moderately wide, length 24% HL. Barbel short, length 9% HL.Teeth small, conical, in broad tapered bands in both jaws, outer premaxillary series enlarged. Body scales covered with short, greatly reclined, needle-like spinules in narrowly divergent rows; tip of last spinule in each row barely extending beyond posterior scale margin. Transverse scale rows below first dorsal-fin midbase 11. Snout almost fully scaled. Interdorsal space less than first dorsal-fin base length. Height of first dorsal fin 93% HL; second spinous ray slightly elongate, finely serrated along its leading edge; first dorsal-fin rays II,13.

Material examined. 1 specimen. Holotype of Coryphaenoides altipinnis: BMNH 1887.12.7.90 (1, 102 mm HL, 473+ mm TL), southeast of Boso Peninsula , Chiba, Pref., Japan, 34.6167ºN, 140.5333ºE, 1875 ftm (3429 m), Challenger sta. 237, trawl, 17 Jun. 1875.

Counts and measurements. Counts: first dorsalfin rays II,13; pectoral-fin rays i21; pelvic-fin rays 9; gill rakers on first arch (outer/inner) 8–10/14, on second arch 12–13/14; longitudinal scales 38; transverse scale rows below first dorsal-fin origin 15, below first dorsal-fin midbase 11, below second dorsal-fin origin 12.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 25 (32); orbit diameter 25 (32); postorbital length 54 (69); postrostral length 77; orbit–preopercle distance 48 (62); suborbital width 11 (14); upper-jaw length 41 (54); length of rictus 35 (45); length of premaxillary tooth band 33 (42); preoral length 10 (13); distance between tip and lateral angle of snout 13 (16); snout width 21 (27); internasal width 17 (22); interorbital width 25 (32); body width over pectoral-fin bases 49 (63); body depth at first dorsal-fin origin 77 (99); body depth at anal-fin origin 56 (72); prepelvic length 100 (130); preanus length 163 (211); preanal length 168 (217); isthmus–pelvic distance 46 (59); pectoral-fin length 56 (72); predorsal length 106 (137); height of first dorsal fin 93 (120); length of first dorsal-fin base 31 (40); interdorsal length 27 (35); length of gill slit 24 (31); length of posterior nostril 8 (10); barbel length 9 (12).

Redescription of holotype. General features are shown in Fig. 96 . Body deepest at first dorsal-fin origin, progressively tapering to long tail. Trunk short, deep, compressed, width over pectoral-fin bases 1.6 in depth at first dorsal-fin origin. Head large, HL about 4.7 in TL; head bones moderately stout; flesh firm. Dorsal contour of head steeply elevated from snout tip to above nasal fossa, then straightened from this point to first dorsal-fin origin. Snout short, conical in preserved specimen, but probably more or less inflated when fresh; its tip low, slightly protruding beyond upper jaw, ventral contour oblique; snout length equal to orbit diameter. Orbit moderately large, circular, greatest diameter 2.2 in postorbital length. Interorbital space broad, width equal to orbit diameter. Mouth large, oblique, subinferior, upper-jaw length 0.6 in orbit diameter; posterior margin of maxillary almost reaching vertical through hind rim of orbit; lateral corner of mouth not restricted by lip folds; lips thin. Suborbital region moderately flat, only weakly ridged. Preopercle large, hind margin inclined from vertical, forming broad lobe posteroventrally; preopercular ridge poorly marked. Interopercle mostly hidden behind preopercle. Subopercle and opercle smoothly adjoined, forming posterior margin of gill cover. Gill membranes narrowly connected across isthmus; gill opening wide, extending ventrally to below posterior margin of lower jaw. Outermost gill slit moderately wide, length equal to orbit diameter. Gill rakers developed into small tubercles, tipped with short, slender spines. Barbel short, slender, length 2.7 in orbit diameter.

Anus immediately anterior to anal-fin origin; periproct poorly developed. Ventral light organ absent.

Teeth short, conical, slightly incurved, in long tapered band in both jaws. Premaxillary teeth arranged in about 5 rows at widest point near symphysis, in about 2 rows posteriorly; outermost series enlarged; posterior margin of tooth band almost reaching lateral corner of mouth. Dentition in lower jaw similar to that in premaxillary, but no teeth especially enlarged; mandibular band much shorter than premaxillary band.

Body scales small, thin, highly deciduous, covered with short, greatly reclined, needle-like spinules in narrowly divergent, discrete rows ( Fig. 95D ); those on dorsum below interdorsal space with about 5 spinule rows; length of spinules gradually increasing posteriorly, but last spinule in each row barely extending beyond posterior scale margin; lateral buttresses not developed; reticulate structure absent. Body fully and uniformly scaled except for fins.

Neither head ridges nor tip and lateral angles of snout armed with coarsely modified tubercles. Head almost fully scaled; naked areas confined to nasal fossa, anterior portion of mandibular rami, lips, chin barbel, and gular and branchiostegal membranes; ventral surface of snout completely scaled, except for narrow naked area above upper lip.

Cephalic sensory canals broad; infraorbital and mandibular canals probably with small open pores. Lateral line complete, not interrupted throughout.

First dorsal-fin origin slightly posterior to pectoralfin base; second spinous ray of first dorsal fin slightly prolonged, its tip extending to base of 9th second dorsalfin ray when lain back; height of first dorsal fin 3.0 times as long as its base length; leading edge of second spinous ray finely serrated. Second dorsal-fin origin more or less above anal-fin origin; interdorsal space 0.9 times as long as first dorsal-fin base length. Pectoral fin long, but its tip not reaching vertical through anal-fin origin. Pelvic fin inserted slightly anterior to pectoral-fin base, outermost elongate (its tip slightly damaged). Anal fin well developed, much deeper than second dorsal fin.

Color when fresh. Unknown.

Color in alcohol ( Fig. 96 ). Head and body uniformly pale brown; fins darker; gular and branchiostegal membranes mostly pale, posterior margins of gill membranes prominently blackish.

Size. To at least 47 cm TL.

Distribution. So far known only from the holotype collected from off the Boso Peninsula at a depth of 3429 m (Appendix 3-5E). Very rare.

Remarks. Coryphaenoides altipinnis was originally described by G̹nther (1877) from the “south of Yeddo” (= southeast of the Boso Peninsula), Japan, at a depth of 3429 m (Challenger sta. 237). According to G̹nther (1887), only a single specimen was collected from the type locality (BMNH 1887.12.7.90, holotype; Fig. 96 ). He (1887) also reported two additional specimens from off Japan at a depth of 1034 m (Challenger sta. 235), both of which were re-identified in this study, one as a different species of Coryphaenoides (probably C. nasutus ; BMNH 1887.12.7.91, 27.0 mm HL, 128+ mm TL) and the other as Nezumia proxima (BMNH 1887.12.7.92, 24.0 mm HL, 149+ mm TL). Unfortunately, no additional specimens were discovered during the course of this study. The paucity of available materials could be attributable to its apparent preference for very deepwater habitats. Because G̹nther’s (1877, 1887) description is brief, the holotype is redescribed here for future studies. It should be noted that the original spelling of the specific epithet is “ altipinnis ”, instead of “ altipennis ”.

Based on a 386 mm TL specimen, Kuroda (1952) reported C. altipinnis from Suruga Bay (see also Kuroda 1951). Citing Kuroda’s record, Shinohara & Matsuura (1997) included this species in their list of deep-sea fishes occurring in this area. Although Kuroda’s specimen is presumably lost, it was likely a misidentification, considering that the specimen was obviously collected by local fisheries confined to upper slope depths.

Relationships and comparisons. Coryphaenoides altipinnis belongs to the subgenus Coryphaenoides (sensu Iwamoto 1990) , and is closely similar to C. cinereus ( Gilbert, 1896) and C. filifer ( Gilbert, 1896) . The absence of prominent modified scales on the snout readily distinguishes the species from the latter two (vs. snout tipped with large prominent tubercles). It further differs from these two species in that the tip of the pectoral fin does not reach a vertical through the anal-fin origin (vs. extending to or beyond this level), and in having more scale rows below the first dorsal-fin origin (15 vs. 10– 14 in C. cinereus and 8.5–13.5 in C. filifer ). Regarding morphometric characters, it differs from C. cinereus and C. filifer in the preoral length (10% HL vs. 13–19% and 11–13%), postorbital length (54% HL vs. 43–52% and 48–53%), and pectoral-fin length (56% HL vs. 60–68% and 56–70%); from C. cinereus in the snout length (25% HL vs. 26–29%) and snout width (21% HL vs. 34–30%); and from C. filifer in the orbit–preopercle distance (48% HL vs. 42–46%).

Okamura (1970a:136) suggested a close similarity between C. altipinnis and C. spinulosus ( Gilbert & Burke, 1912) , the latter of which is regarded here as a junior synonym of C. acrolepis ( Bean, 1884) . Coryphaenoides altipinnis is readily distinguished from C. acrolepis by several meristic characters, including first dorsal-fin rays (II, 13 in C. altipinnis vs. II, 8–11 in C. acrolepis ), outer gill rakers on the first arch (8–10 vs. 3–7), and transverse scale rows (below first dorsal-fin origin 15 vs. ±14; below first dorsal-fin midbase 11 vs. 7–10; below second dorsal-fin origin 12 vs. 6.5–11). It further differs from C. acrolepis in having a shorter snout (snout length 25% HL vs. 27–32%; preoral length 10% HL vs. 13–21%), a smaller barbel (9% HL vs. 11–19%), a longer postorbital (54% HL vs. 42–51%) and orbit–preopercle distance (48% HL vs. 35– 43%), a broader interdorsal space (27% HL vs. 8–21%), and a wider gill slit (24% HL vs. 15–21%). Body-scale structure is also different between the two species, with C. altipinnis having much weaker spinulation than C. acrolepis ( Fig. 95D vs.A–C). In addition, cephalic sensory canals are completely closed in C. altipinnis except for a few tiny pores on the mandibular and infraorbital canals, whereas in C. acrolepis , small pores are serially present along all canals.

Figures

FIGURE 95. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of two species of Coryphaenoides. (A–B) Co. acrolepis, BSKU 103028, 138 mm HL; (C) Co. acrolepis, USNM 74397, holotype of Chalinura spinulosa, not measured due to its poor condition; (D) Co. altipinnis, BMNH 1887.12.7.90, holotype, 102 mm HL. (A, C–D) Views from above; (B) oblique view. [Photos: (A–B) NSMT; (C–D) N. Nakayama]

FIGURE 96. Holotype of Coryphaenoides altipinnis. BMNH 1887.12.7.90, 102 mm HL, 473+ mm TL, southeast of Boso Peninsula, Chiba Pref., Pacific, 3429 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]