Coelorinchus smithi Gilbert & Hubbs, 1920

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 128-135

Coelorinchus smithi Gilbert & Hubbs, 1920

[Japanese name: Kishu-hige]

( Figs. 52B , 53 E–F, 54B, 85–87; Tables 3 , 5 ; Appendix 3-5B)

Coelorhynchus commutabilis (not Smith & Radcliffe in Radcliffe 1912): Smith & Radcliffe in Radcliffe 1912:128, pl. 29, fig. 2 (original description; part of “typical examples”, Indonesia and Philippines).

Coelorhynchus smithi Gilbert & Hubbs, 1920:493 , fig. 20 [original description; holotype:USNM78212,from“between Gillolo and Makyan Islands”, Albatross sta. 5621, 0º15ʹ00ʺN, 127º24ʹ35ʺE, in 298 ftm (545 m); 18 paratypes]; Okamura 1963a:27, fig. 5 (first record from Japan; description; 40 spec. from Aichi, Mie, and Kochi Pref.; new Japanese name: “Kishû-hige”); Kamohara 1964:96 (listed; Kochi Pref.); Okamura 1970a:179, pl. XXXIX, text-figs. 75–77 (description; biological notes; 63 spec. from Pacific off southern Japan from Heta to Totoro); Kuroda 1971:56 [listed from Suruga Bay after Okamura (1970a)]; Tominaga & Uyeno 1981:488 (listed; Japan); Yatou 1982:171, 353, fig. 103 (description; 8 spec. from Tosa Bay; photo based on BSKU 29521); Ozawa 1983:13 (listed; off Makurazaki, Kagoshima Pref., East China Sea).

Coelorhynchus (Oxymacrurus) smithi: Okamura 1970b : table 1 (listed; Japan).

Coelorinchus smithi: Yatou 1984:231 , 368, fig. 164 (brief description; 10 spec. from Okinawa Trough; photo based on BSKU 29588); Okamura 1984b:97, pl. 83, fig. C (compiled); Okamura 1988:97, pl. 83, fig. C (compiled); Okamura 1997:127, fig. 15 (compiled); Shao et al. 2008b: table 2 (8 spec. from northeastern and southwestern Taiwan, and South China Sea); Nakabo & Kai 2013:510 (in key; Japan); Iwamoto et al. 2015:67 (brief description; 7 spec. from northeastern and southwestern Taiwan); Motomura 2020:38 (listed; Japan).

Caelorinchus smithi: Nakabo 1993:369 (in key; Japan); Shinohara & Matsuura 1997:291 (listed; Suruga Bay); Nakabo 2000:433 (in key; Japan); Shinohara et al. 2001:305 (18 spec. listed from Tosa Bay); Nakabo 2002:433 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Shinohara et al. 2005:417 (listed; Ryukyu Islands); Suetsugu & Ohta 2005: table 3 (listed; Enshu-nada); Furuhashi et al. 2010: table 2 (38 spec. listed from northern Okinawa Trough); Iwatsuki et al. 2017:32 (listed; Hyuga-nada).

Caelorinchus (Oxymacrurus) smithi: Chiou et al. 2004a : table 1 (listed; Taiwan).

Diagnosis. Light organ externally represented by short naked fossa immediately anterior to anus, its anterior margin falling far short of line connecting inner pelvicfin bases. Underside of head almost completely scaled except for narrow naked area above upper lip and anterior portions of mandibular rami; dorsal surface of snout fully scaled (narrow naked clefts rarely present along each side of mid rostral ridge). Snout long, sharply pointed, length 69–96% PRL; dorsal profile of snout moderately concave in lateral view; terminal scute moderately short, diamondshaped, dorsoventrally flattened, length 11–24% PRL; lateral nasal ridge completely supported by nasal bone, only slightly convex in dorsal view, giving attenuated appearance to snout. Anus slightly separated from analfin origin. Premaxillary teeth small, conical, arranged in short, uniformly wide band, none distinctly enlarged (outer series slightly larger); posterior margin of tooth band falling far short of lateral corner of mouth. Body scales covered with short, reclined, keel-like spinules in widely divergent, coarsely saw-toothed ridges; every spinule row complete, extending to posterior scale margin; spinules in each row greatly overlapping, increasing in height posteriorly; buttresses narrowly developed. Occipital scales covered with short, moderately reclined, keel-like (rarely knife-like) spinules in 4 or more widely divergent, saw-toothed rows. Orbit diameter 43–52% PRL; suborbital width 19–23% PRL; internasal width 28–37% PRL; interorbital width 33–42% PRL; pelvic-fin length 53–74% PRL; pectoral-fin length 60–76% PRL; transverse scale rows below first dorsal-fin midbase 3.5– 5.5, below second dorsal-fin origin 4–6. Body generally darker dorsally, paler ventrally; about 2 faint saddles dorsally on tail (much prominent in smaller specimens); lips white; oral cavity blackish; gular and branchiostegal membranes pale to dusky; first dorsal, pectoral, and pelvic fins generally dusky to dark.

Material examined. 55 specimens. Holotype of Coelorhynchus smithi: USNM 78212 (80.7 mm HL, 261+ mm TL), Molucca Sea, between Gilolo and Makyan Islands,Indonesia, western Pacific, 0.2500ºN, 127.4097ºE, 298 ftm (545 m), Albatross sta. 5621, 12-ft Agassiz beam trawl, 28 Nov. 1909. Non-types : Japan: KPM-NI 24972 (1, 110 mm HL, 407+ mm TL), off Okinawa, 600 m, long line, coll. K. Yunokawa, 2009 ; KPM-NI 28333 (1, 135 mm HL, 528+ mm TL), ca. 25 km southeast of Agunijima Island , East China Sea , 26.4120ºN, 127.3947ºE, 774–780 m, R/ V Tansei-maru, cr. KT-08-33, sta. AG-1, 3-m beam trawl, coll. T. Sato, 17 Dec. 2008 ; KPM-NI 28341 (1, 71.1 mm HL, 256+ mm TL), KPM-NI 28342 (1, 58.7 mm HL, 207+ mm TL), ca. 9 km east of Aguni-jima Island , East China Sea , 26.5700ºN, 127.3307ºE, 583–589 m, R/ V Tansei-maru, cr. KT-08-33, sta. AG-6, 3-m beam trawl, coll. T. Sato, 17 Dec. 2008 ; BSKU 29588 (1, 102 mm HL, 382+ mm TL), northwest of Miyako-jima Island , Okinawa Trough, 25.7917ºN, 124.5117ºE, 500–550 m, F/ V Yuryo-maru, No. 8, sta. 1-T9, bottom trawl, coll. T. Kitajima, 15 Sept. 1979 ; BSKU 32512 (1, 102 mm HL, 308+ mm TL), northwest of Miyako-jima Island , Okinawa Trough, 25.7917ºN, 124.5117ºE, 500–550 m, F/ V Yuryomaru, No. 8, sta. 1-T9, bottom trawl, coll. M. Hirose and T. Kume, 10 Oct. 1979 ; BSKU 32583 (1, 84.0 mm HL, 313+ mm TL), northwest of Miyako-jima Island , Okinawa Trough, 25.7900ºN, 124.3900ºE, 600 m, F/ V Yuryomaru, No. 8, sta. 1-T13, bottom trawl, coll. T. Kitajima, 20 Sept. 1979 ; BSKU 29637 (1, 93.2 mm HL, 332+ mm TL), northwest of Miyako-jima Island , Okinawa Trough, 25.7900ºN, 124.3333ºE, 600 m, F/ V Yuryo-maru, No. 8, sta. 1-T13, bottom trawl, coll. T. Kitajima, 20 Sept. 1979 ; BSKU 29844 (1, 68.1 mm HL, 236+ mm TL), northwest of Amami-oshima Island , Okinawa Trough, 30.0115ºN, 127.8387ºE, 400–420 m, F/ V Yuryo-maru, No. 8, sta. 3- T4, bottom trawl, coll. H. Maeda, 26 Oct. 1979 ; BSKU 97991 (1, 45.3 mm HL, 152+ mm TL), south of Muroto , 33.0790ºN, 134.1645ºE, 414–513 m, R/ V Tansei-maru, cr. KT-05-29, sta. K-500, beam trawl, coll. H. Endo et al., 17 Nov. 2005 ; BSKU 77899 (1, 67.6 mm HL, 217+ mm TL), Tosa Bay , 33.2083ºN, 133.6433ºE, 364–382 m, FRV Kotaka-maru, otter trawl, coll. H. Endo, 27 Sept. 1999 ; BSKU 112076 (1, 82.9 mm HL, 311 mm TL), Tosa Bay , 33.1428ºN, 133.6248ºE, 450–490 m, FRV Kotaka-maru, 1 Aug. 1988 ; BSKU 69308 (1, 80.0 mm HL, 274+ mm TL), Tosa Bay , 33.1800ºN, 133.6217ºE, 412–423 m, FRV Kotaka-maru, otter trawl, 8 Sept. 1998 ; BSKU 43829 (1, 56.0 mm HL, 211+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 11 Jun. 1987 ; BSKU 40217 (1, 80.9 mm HL, 239+ mm TL), BSKU 40218 (1, 67.4 mm HL, 210+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 25 Jul. 1984 ; BSKU 51398 (1, 42.9 mm HL, 136+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 27 Sept. 1999 ; BSKU 65947 (1, 97.2 mm HL, 346+ mm TL), BSKU 97954 (1, 74.7 mm HL, 275+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 9 May 2000 ; BSKU 40335 (1, 77.8 mm HL, 271+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 9 Oct. 1984 ; BSKU 10041 (1, 64.3 mm HL, 201+ mm TL), BSKU 10045 (1, 66.9 mm HL, 239+ mm TL), BSKU 10046 (1, 59.3 mm HL, 214 mm TL), Mimase fish market, coll. T. Kamohara, 10 Feb. 1961 ; BSKU 4382 (1, 49.4 mm HL, 179+ mm TL), BSKU 4383 (1, 75.7 mm HL, 264+ mm TL), Mimase fish market, coll. T.Kamohara, 19 Dec. 1954 ; BSKU 8834 (1, 84.9 mm HL, 304+ mm TL), Mimase fish market, coll. T. Kamohara, 30 Jan. 1951 ; BSKU 12747 (1, 65.5 mm HL, 226+ mm TL), Mimase fish market, coll. Y. Mishima (= Y. Machida), 15 Feb. 1967 ; BSKU 13782 (1, 64.2 mm HL, 246 mm TL), Mimase fish market, coll. Y. Mishima (= Y. Machida), Jan.–Mar. 1968 ; BSKU 106852 (1, 77.0 mm HL, 281 mm TL), Mimase fish market, F/ V Kosei-maru, 15 Apr. 2012 ; BSKU 102699 (1, 51.6 mm HL, 180+ mm TL), BSKU 102700 (1, 51.5 mm HL, 157+ mm TL), BSKU 102702 (1, 59.8 mm HL, 192+ mm TL), BSKU 102703 (1, 56.4 mm HL, 199+ mm TL), BSKU 102705 (1, 60.0 mm HL, 207+ mm TL), Mimase fish market, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama, 21 Feb. 2010 ; BSKU 102690 (1, 72.9 mm HL, 267+ mm TL), Mimase fish market, F/ V Kosei-maru, tr. 3, bottom trawl, coll. N. Nakayama, 21 Feb. 2010 ; BSKU 13918 (1, 64.4 mm HL, 232+ mm TL), Mimase fish market, Jan. 1968 ; BSKU 13881 (1, 66.1 mm HL, 229+ mm TL), Mimase fish market, Mar. 1968 ; BSKU 44652 (1, 58.7 mm HL, 216 mm TL), off Okitsu, Tosa Bay , 200–230 m, 20 Apr. 1988 ; BSKU 29521 (1, 79.0 mm HL, 271+ mm TL), Tosa Bay , 32.9833ºN, 133.4833ºE, 453 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, cr. 4- Ky, sta. T18, bottom trawl, coll. O. Okamura et al., 21 Dec. 1979 ; BSKU 30481 (1, 74.2 mm HL, 254+ mm TL), Tosa Bay , 32.9833ºN, 133.4833ºE, 453 m, F/ Vs Shinseimaru, No. 53 and Kyoyo-maru, No. 2, tr. 17, beam trawl, coll. O. Okamura et al., 21 Dec. 1979 ; BSKU 13107 (1, 72.1 mm HL, 282 mm TL), BSKU 13108 (1, 67.2 mm HL, 249 mm TL), ca. 15 km east of Cape Ashizurimisaki , Tosa Bay , 420–555 m, 2–6 Jun. 1968 ; * BSKU 71585 (1, 34.5 mm HL, 123+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 9 May 2000 ; * BSKU 112398 (1, 94.5 mm HL), * BSKU 112402 (1, 88.0 mm HL, 302+ mm TL), * BSKU 112403 (1, 55.5 mm HL, 213 mm TL), off Susaki, Tosa Bay , F / V Kosei-maru, bottom trawl, coll. N. Nakayama, 4 Mar. 2014 ; MSM 13-10 (1, 93.9 mm HL, 333+ mm TL), southeast of Fuji River , Suruga Bay , 35.1013ºN, 138.6823ºE, 502–529 m, 1.3-m larval net, 26 Jan. 2010 ; FRLM 3736 (1, 83.6 mm HL, 322+ mm TL), off Goza, Kumano-nada, long line, coll. Fisheries Research Institute of Mie Pref., 13 Oct. 1982 ; BSKU 19190 (1, 62.9 mm HL, 226+ mm TL), south of Miura Peninsula , Sagami Bay , 35.1250ºN, 139.5100ºE, 700 m, FRV Soyo-maru, sta. 181, beam trawl, 10 Mar. 1961. Philippines: BSKU 15694 (1, 95.6 mm HL, 322+ mm TL), Sulu Sea, 8.3467ºN, 118.3300ºE, 738 m, R/ V Hakuho-maru, cr. KH-72-1, sta. 13, 3-m beam trawl, coll. O. Okamura, 27 May 1972 ; BSKU 15665 (1, 59.3 mm HL, 169+ mm TL), BSKU 15666 (1, 57.8 mm HL, 195+ mm TL), BSKU 15667 (1, 65.6 mm HL, 199+ mm TL), BSKU 15668 (1, 54.2 mm HL, 158+ mm TL), Sulu Sea, 8.3167ºN, 118.1517ºE, 495–500 m, R/ V Hakuho-maru, cr. KH-72-1, sta. 12, 3-m beam trawl, coll. O. Okamura, 27 May 1972.

Redescription based on Japanese specimens. General features are shown in Figs. 54B and 85 . Counts and measurements are given in Tables 3 and 5 . Body deepest at first dorsal-fin origin, gradually tapering from this level to long, laterally compressed tail. Trunk short, moderately compressed, width over pectoral-fin bases 1.1–1.4 in depth below first dorsal-fin origin. Head large, HL about 3.1–3.9 in TL. Snout long, sharply pointed, protruding well beyond upper jaw, length 1.4–2.0 times as long as orbit diameter; dorsal contour of snout moderately concave in lateral view; lateral nasal ridge completely supported by nasal bone; anterolateral margins of snout only slightly convex when viewed dorsally, giving attenuated appearance to snout. Orbit large, its greatest diameter 0.9–1.2 in postorbital length (1.4 in largest specimen; KPM-NI 28333, 135 mm HL). Interorbital space broad, flat, width 1.2–1.4 in orbit diameter. Mouth moderately large, inferior, protrusible, upper-jaw length 1.1–1.4 in orbit diameter (0.9 in largest specimen); posterior margin of maxilla extending to vertical through hind 1/3 of orbit or beyond; lateral corner of mouth barely restricted by skin folds; lips thin, slightly papillose near tooth bands. Suborbital region divided by longitudinal bony ridge passing from tip of snout to posteroventral angle of opercle; its upper half almost vertical, lower half sharply inclined mesially. Preopercle large, posterior margin inclined, forming moderately angular lobe at posteroventral corner. Subopercle produced into narrowly pointed tab posteroventrally; posterior margin deeply concave. Gill membranes broadly connected across, and attached mesially to isthmus, with free posterior fold. Outer gill slit moderately restricted by skin folds, length 2.1–3.3 in orbit diameter (1.5 in largest specimen). Gill rakers small, low, tubercular, armed with short, fine spines; no rakers on outer side of first arch and inner side of fourth arch; gill filaments moderately long. Chin barbel short, slender; length 2.8–4.9 in orbit diameter (2.4 in largest specimen).

Anus only slightly separated from anal-fin origin by a few scale rows. Light organ externally represented by short naked fossa anterior to anus; its anterior margin extending to about posterior 1/3 of distance from outer pelvic-fin bases to anus, and falling far short of line connecting inner pelvic-fin bases.

Teeth small, sharp, conical, gently incurved, in narrow bands in both jaws. Premaxillary teeth in short, uniformly wide band, with about 6–7 tooth rows near symphysis; posterior margin of tooth band falling far short of lateral corner of mouth; teeth becoming progressively smaller inwardly, with outer series only slightly larger. Mandibular teeth uniformly small, in narrow tapered band, with about 5 tooth rows near symphysis; posterior margin of tooth band extending beyond lateral corner of mouth. All teeth deeply embedded in thick layer of gum papillae.

Scales on body large, thin, moderately deciduous, covered with short, reclined, keel-like spinules in widely divergent rows ( Fig. 53 E–F); in 92.5 mm HL specimen (BSKU 112399), those on dorsum below interdorsal space with 6 rows of spinules; middle row usually with about 6–7 spinules, but not especially high or enlarged compared with adjacent rows; every spinule row complete throughout; spinules forming angle of about 45º to scale surface; spinules greatly overlapping, closely adjoined to one another, but their distal tips occasionally free, forming saw-toothed ridges that give spiny appearance to body surfaces; height of spinules increasing posteriorly, with last spinules in each row extending moderately beyond posterior scale margin; lateral buttresses of spinules narrowly developed; reticulate structures absent on unexposed potion. Body fully scaled except for fins and ventral light organ.

Scales on head ridges thickened and coarsely spinulated; those on median rostral ridge covered with radiating rows of spinules.Terminal snout scute moderately short, diamond-shaped, dorsoventrally flattened, its length 2.1–4.0 in orbit diameter. Supraoccipital scute stout, prominent, armed with divergent rows of spinules; posttemporal scutes thickened, but not especially enlarged, armed with single row of spinules. Occipital scales covered with short, moderately reclined, keel-like (rarely knife-like) spinules in widely divergent rows ( Fig. 52B ); spinules in each row connected basally to one another, forming saw-toothed ridges, and their height gradually increasing posteriorly; scales on dorsal surfaces of snout posterior to lateral nasal ridges armed with divergent rows or cluster of short, erect, needle-like or knife-like spinules. Other scales on head variable in size, generally similar to those on body, but spinules much shorter and more erect; those on opercle, preopercle, and postorbital and supratemporal canals largest. Nasal fossa usually heavily scaled anteroventrally. Dorsal surfaces of snout fully scaled, without prominent naked clefts along each side of median rostral ridge. Underside of head completely scaled except for narrow naked area above upper lip, anterior portions of mandibular rami, and posteroventral margins of preopercles; scales on ventral surfaces of head small, non-imbricate, covered with small cluster of short, erect, knife-like spinules.

No open pores along cephalic sensory canals. Free neuromasts on head not prominently marked. Anterior nostril small and circular; posterior large, bean-shaped; septum between nostrils forming anteriorly opened hood. Lateral line complete, not interrupted throughout.

Origins of first dorsal and pelvic fins on about same vertical; first dorsal fin moderately high, its height 2.3–3.2 times as long as its base length; second spinous ray not elongated, smooth along its leading edge (a few rudimentary denticles rarely present distally); its tip usually extending to second dorsal-fin origin or beyond when laid back. Interdorsal space 1.2–2.2 times as long as first dorsal-fin base length. Second dorsal fin originating posterior to anal-fin origin (above base of 3rd–9th anal fin rays). Pectoral-fin base slightly anterior to vertical through pelvic-fin base. Outer pelvic-fin ray prolonged, with fine distal tip.

Color when fresh ( Fig. 85 ). Head and body dark brown dorsally, whitish ventrally (especially lower 1/3 of body), but ventral parts moderately darker in large specimens; about 2 faint, dark saddles on tail in smaller specimens ( Fig. 85A ), first below about second dorsal-fin origin, second further posterior on tail, separated from first by distance about equal to postorbital length; gill cover slightly shiny, except for large specimens; lips white, gill and branchiostegal membranes pale to dusky; light organ and periproct dull black; first dorsal fin uniformly dark, but whitish apically; pectoral and second dorsal fins generally dusky; pelvic fin dark, but outermost ray whitish; second dorsal and anal fins dusky to dark, much darker posteriorly.

Color in alcohol.Head and body generally dark brown dorsally; lower 1/3 of body distinctly paler; abdomen slightly dark in ventral view; 2 faint, dark saddles on tail (especially marked in small specimens, and often difficult to distinguish in large specimens); lips white; oral and gill cavities blackish; gill rakers and filaments light tan, arches dark dusky; gular and branchiostegal membranes pale to dusky; first dorsal, pectoral, and pelvic fins generally uniformly dark, but outer pelvic-fin rays paler distally; second dorsal and anal fin heavily peppered; anal fin prominently blackish posteriorly.

Size. To at least 53 cm TL ( KPM-NI 28333 , 528 + mm TL, Okinawa Trough , Japan) .

Distribution. Widely distributed from Japan to Australia, including Taiwan, the Philippines, and Indonesia, at depths of 196–1110 m ( Gilbert & Hubbs 1920; Iwamoto & Williams 1999; Iwamoto & Graham 2001). In Japan and adjacent waters, the species is known from the Pacific off southern Japan northward to the Boso Peninsula (139.89ºE), Okinawa Trough, and northern South China Sea, at depths of 196‾ 780 m ( Shao et al. 2008b; this study; Appendix 3-5B). Common.

Remarks. Coelorinchus smithi was originally described by Gilbert & Hubbs (1920) based on 19 specimens collected from Indonesia and the Philippines, with the type locality in the Molucca Sea ( Fig. 86 ). These specimens were previously included in the type series of C. commutabilis Smith & Radcliffe in Radcliffe, 1912. Coelorinchus smithi was first reported from Japanese waters by Okamura (1963a).

Comparisons of specimens collected from Japan with those from the East Indies (holotype and 5 Philippine specimens) revealed subtle differences in fresh coloration and pectoral-fin ray counts. In the Japanese specimens, the ventral half of the body is whitish ( Fig. 85 A–F) except for one large specimen examined (KPM-NI 24972, 407+ mm TL; Fig. 85G ), whereas the whole body is uniformly and intensely dark in similar-sized specimens from the Philippines ( Fig. 87 ). Unfortunately, the color of the 261+ mm TL holotype is somewhat faded ( Fig. 86 ), but the dark coloration of East Indies’ specimens was also depicted in the original description, where Gilbert & Hubbs (1920:497) stated that the overall coloration of the type specimens was “brown, usually darker than in C. commutabilis ; it is darker above than below” (for C. commutabilis see the Relationships and comparisons given below). Iwamoto & Merrett (1997:489) pointed out that “color can be quite variable within a species, especially from one region to another, and it appears to be influenced considerably by the substratum”. However, the difference between the two populations of C. smithi is too distinctive to be ascribed to intraspecific variation. In addition, the Japanese specimens commonly have two faint saddles on the tail (indistinct in large individuals), of which one is situated below the second dorsal-fin origin, and the other is separated from the first saddle by a distance about equal to the postorbital length ( Fig. 85A ). These saddles are absent in the Philippine specimens examined (unknown in the holotype due to discoloration), but Gilbert & Hubbs (1920:497) also noted the presence of similar markings in the original description. Moreover, counts of pectoral-fin rays are slightly higher in the Japanese specimens than in the holotype and the Philippine specimens examined [i16– i20 (usually i18 or i19, modally i19) vs. i14–i18 (modally i16 or i17); Table 5 ], although their ranges overlap. The modal difference in the fin-ray counts further suggests that the Japanese population represents a distinct species or subspecies with allopatric distribution from the true C. smithi . A redescription based on the Japanese specimens examined is provided here for future investigations, and a molecular study will help to elucidate their taxonomic status.

Relationships and comparisons. Coelorinchus smithi belongs to the C. japonicus group (sensu stricto; see the Relationships of C. japonicus ), and closely resembles C. commutabilis known from the East Indies. When similar-sized specimens are compared, the Japanese C. smithi examined readily differ from the holotype of C. commutabilis (USNM 72945, 93.7 mm HL; examined here) in that the ventral half of the body is distinctly paler ( Fig. 85 vs. body uniformly dark), but otherwise they are similar to each other. According to Gilbert & Hubbs (1920:497) C. smithi (from the East Indies)is distinguished from C. commutabilis by having “constantly larger scales” and “several carinae instead of a median keel of the scales of occipital ridges”. However, examinations of their holotypes along with additional specimens of C. smithi revealed no significant differences in the numbers of transverse scale rows (below first dorsal-fin origin 4.5– 6 vs. 5.5 in C. smithi and C. commutabilis respectively; below first dorsal-fin midbase 4–4.5 vs. 4.5; and below second dorsal-fin origin 4.5–6 vs. 5.5). The holotype of C. commutabilis is also differentiated in that most scales on the parietal ridges (“occipital ridges” of Gilbert & Hubbs 1920) are covered with only a few rows of stout spinules, whereas those of C. smithi are generally armed with multiple rows so as to give a highly spinulated appearance to the scales. The difference in spinulation of the modified scales may warrant the recognition of separate species, but further verification based on more specimens of C. commutabilis is required.

The Japanese population of C. smithi is also similar to C. charius Iwamoto & Williams, 1999 known from off Western Australia, both of which are characterized by their paler body color and the presence of faint saddles on the tail when young. An examination of the holotype and 18 paratypes of C. charius (51.3–98.2 mm HL) revealed that these species are difficult to distinguish from each other by counts and measurements, squamation, and scale spinulation. However, a subtle difference was found in the saddle pattern of small specimens. In the young C. smithi examined, only two saddles were present dorsally on the tail ( Figs. 54B , 85A ), whereas similar-sized C. charius specimens had more than five saddles ( Iwamoto & Williams 1999: fig. 9b). Although this difference is pronounced only in small specimens, it indicates the specific separation between Japanese C. smithi and C. charius .

Coelorinchus sereti Iwamoto & Merrett, 1997 known from the tropical southwestern Pacific is another species closely related to C. smithi . They are quite similar in overall appearance, with no pronounced differences in counts and measurements, except for the pelvic-fin length (53–74% PRL in C. smithi vs. 72–90% in C. sereti ). However, the shape of the snout is substantially different between the two species. In C. smithi , the dorsal contour of the snout is moderately concave in lateral view ( Figs. 85A, D, G , 86A , 87A, C ), whereas that of C. sereti is gently convex ( Iwamoto & Merrett 1997: fig. 15a). Also, when viewed dorsally ( Figs. 85B, E , 86B ), the snout of C. smithi is progressively attenuated toward its tip, giving a sharply pointed appearance, whereas the leading edges of C. sereti are broadly convex anteriorly, giving a much wider appearance to the snout ( Iwamoto & Merrett 1997: fig. 15aʹ).

In Japanese waters, C. smithi is likely to be confused with C. nox sp. nov., but they are distinguished by the combination of squamation and coloration (see the Relationships and comparisons of the latter). Coelorinchus smithi also resembles C. japonicus ( Temminck & Schlegel, 1846) , with which it has often been confused in museum collections. However, it differs notably from the latter species in that the occipital scales are covered with four or more widely divergent rows of spinules (vs. uniserial, rarely 2–3 narrowly divergent rows). As noted by Okamura (1963a:31), the ventral light organ of C. smithi is much broader and more prominent compared with that of C. japonicus ( Fig. 85C, F vs. Fig. 51C ). In addition, C. smithi tends to have relatively fewer scales below the second dorsal-fin origin (4–6, modally 5) than C. japonicus (5–7.5, modally 6).

Figures

FIGURE 51. Preserved specimen of Coelorinchus japonicus. BSKU 45514, 222 mm HL, 665+ mm TL, off Tosa-Shimizu, Kochi Pref., Pacific. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]

FIGURE 52. Photographs showing spinulation of the occipital scales in two species of Coelorinchus. (A) C. japonicus, BSKU 44422, 118 mm HL; (B) C. smithi, BSKU 65947, 97.2 mm HL. Preserved specimens. [Photos: N. Nakayama]

FIGURE 53. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of three species of the Coelorinchus japonicus group. (A–B) C. japonicus, BSKU 109017, 128 mm HL; (C–D) C. leptorhinus, BSKU 99870, 96.5 mm HL; (E–F) C. smithi, BSKU 65947, 97.2 mm HL. (A, C, E) Views from above; (B, D, F) oblique views. [Photos: NSMT]

FIGURE 54. Preserved juvenile specimens of two species of Coelorinchus. (A) C. japonicus, BSKU 110419, 29.0 mm HL, 112+ mm TL, Suruga Bay, (B) C. smithi, BSKU 71585, 34.5 mm HL, 123+ mm TL, Tosa Bay. Lateral views. [Photos: N. Nakayama]

FIGURE 85. Fresh specimens of Coelorinchus smithi. (A–C) BSKU 112403, 55.5 mm HL, 213 mm TL, Tosa Bay off Susaki, Kochi Pref., Pacific, ca. 400 m depth; (D–F) BSKU 112402, 88.0 mm HL, 302+ mm TL, collected with BSKU 112403; (G) KPM- NI 24972, 110 mm HL, 407+ mm TL, off Okinawa-jima Island, Okinawa Pref., 600 m depth. (A, D, G) Lateral, (B, E) dorsal, and (C, F) ventral views. [Photos: (A–F) N. Nakayama; (G) H. Senou]

FIGURE 86. Holotype of Coelorhynchus smithi (= Coelorinchus smithi). USNM 78212, 80.7 mm HL, 261+ mm TL, between Gilolo and Makyan Islands, Indonesia, Molucca Sea. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]

FIGURE 87. Fresh specimens of Coelorinchus smithi. (A–B) BSKU 15665, 59.3 mm HL, 169+ mm TL, Sulu Sea, 495–500 m depth; (C–D) BSKU 15694, 95.6 mm HL, 322+ mm TL, Sulu Sea, 738 m depth. (A, C) Lateral and (B, D) ventral views of the head and trunk. [Photos: BSKU]