Coelorinchus anatirostris Jordan & Gilbert, 1984

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 27-38

Coelorinchus anatirostris Jordan & Gilbert in Jordan & Starks, 1904

[Japanese name: Nezumi-hige]

( Figs. 18–20 , 21A , 22–25 ; Table 1 ; Appendix 3-1C)

Coelorhynchus anatirostris Jordan & Gilbert in Jordan & Starks, 1904:619, unnumbered fig. (original description; holotype: USNM 51471, from Misaki); Jordan et al. 1913:418, fig. 388 (listed; Japan; new Japanese name: “Nezumi-hige”); Schmidt 1931:155 (brief description; 3 spec. from Nagasaki); Kamohara 1934a:54 (listed; Kochi); Okada & Matsubara 1938:450 (in key; Japan); Kamohara 1938:73 (1 spec. from Kochi Pref.); Kamohara 1950:277 (listed; Kochi and Wakayama Pref.); Kuroda 1951:391 (listed; Suruga Bay); Kamohara 1952:99 (spec. from Kochi Pref.); Kuroda 1952:177 (2 spec. from Suruga Bay); Matsubara 1955:1313 (in key; Japan); Kamohara 1958:73 (listed; Kochi Pref.); Okada et al. 1959:83 (listed; Kumano-nada); Kamohara 1964:95 (listed; Kochi Pref.); Matsubara 1965:506 (compiled; Japan); Okamura 1970a:186, pl. VIII, text-fig. 80 (description; 72 spec. from Pacific off southern Japan from Heta to Tosa Bay; C. productus a junior synonym of C. anatirostris ); Kataoka & Tomida 1981:78 (listed; Mie Pref.); Tominaga & Uyeno 1981:488 (listed; Japan); Okamura 1982:171, 352, fig. 102 (brief description; 2 spec. from Tosa Bay; photo based on BSKU 29586); Ozawa 1983:13 (listed; off Makurazaki, Kagoshima Pref., East China Sea).

Coelorhynchus antirostris [sic]: Franz 1910:27 (misspelled; 1 spec. from Aburatsubo); Matsubara et al. 1951:42 (misspelled; listed; Mie Pref.).

Coelorhynchus productus Gilbert & Hubbs, 1916:175 , pl. 9, fig. 1 [original description; holotype: USNM 76865, from “Suruga Gulf” (= Suruga Bay), Albatross sta. 5059; 6 paratypes from Suruga Bay]; Okada & Matsubara 1938:450 (in key; Japan; new Japanese name: “Tengu-hige”); Kamohara 1950:277 (listed; Kochi and Wakayama Pref.); Kuroda 1951:391 (listed; Suruga Bay); Kamohara 1952:99 (spec. from Kochi Pref.); Matsubara 1955:1313 (in key; Japan); Kobayashi 1956:72 (listed; Enshu-nada); Kamohara 1958:73 (listed; Kochi Pref.); Kamohara 1964:95 (listed; Kochi Pref.); Matsubara 1965:506 (compiled; Japan).

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

Coelorinchus anatirostris: Yatou 1984:233 , 368, fig. 165 [brief description; 9 spec. from Okinawa Trough; photo based on BSKU 37101 (from Mimase fish market)]; Okamura 1984b:97, pl. 83, fig. E (compiled); Okamura 1988:97, pl. 83, fig. E (compiled); Iwamoto 1990:141, fig. 346 (synopsis); Okamura 1997:127, fig.11 (compiled); Shao et al. 2008b:table 2 (5 spec. listed from northeastern and southwestern Taiwan); Nakabo & Kai 2013:511 (in key; Japan); Fukui et al. 2015:182, fig. 9 (13 spec. from off Kuro-shima Island, Kagoshima Pref., East China Sea); Iwamoto et al. 2015:50 (brief description; 20 spec. from northeastern and southwestern Taiwan, and South China Sea); Motomura 2020:38 (listed; Japan).

Coelorinchus productus: Yatou 1984:233 , 369, fig. 166 (brief description; 6 spec. from Okinawa Trough; photo based on BSKU 29638); Okamura 1988:435, pl. 373, fig. I (compiled); Iwamoto 1990:179, fig. 406 (synopsis); Okamura 1997:127, fig. 12 (compiled); Shao et al. 2008b: table 2 (5 spec. listed from northeast of Taiwan); Nakabo & Kai 2013:511 (in key; Japan); Iwamoto et al. 2015:66 (brief description; 5 spec. from northeastern Taiwan); Motomura 2020:38 (listed; Japan).

Caelorinchus productus: Nakabo 1993:370 (in key; Japan); Shinohara & Matsuura 1997:291 (listed; Suruga Bay); Nakabo 2000:434 (in key; Japan); Shinohara et al. 2001:304 (listed; Tosa Bay); Nakabo 2002:434 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Chiou et al. 2004a:44, fig. 11 (brief description; 2 spec. from Da-xi; first record from Taiwan); Shinohara et al. 2005:417 (12 spec. listed from Ryukyu Islands); Suetsugu & Ohta 2005: table 2 (listed; southeast of Boso Peninsula).

Caelorinchus anatirostris: Nakabo 1993:370 (in key; Japan); Shao 1993:168, fig. 37-6 (compiled; Taiwan; photo spec. is C. multispinulosus ); Shinohara & Matsuura 1997:290 (listed; Suruga Bay); Nakabo 2000:434 (in key; Japan); Shinohara et al. 2001:304 (26 spec. listed from Tosa Bay); Nakabo 2002:434 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Shinohara et al. 2005:416 (11 spec. listed from Ryukyu Islands); Senou et al. 2006:420 (listed; Sagami Sea); Furuhashi et al. 2010: table 2 (268 spec. listed from northern Okinawa Trough).

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

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

Caelorinchus gilberti (not Jordan & Hubbs 1925): Shinohara et al. 2005:416 (3 spec. listed from Ryukyu Islands ) .

Diagnosis. Light organ externally represented by short, narrow, naked streak immediately anterior to anus, its anterior margin falling far short of line connecting inner pelvic-fin bases. Underside of head almost completely naked; dorsal surface of snout fully scaled, except narrow naked clefts along each side of median rostral ridge. Nasal fossa usually heavily scaled. Snout long, sharply pointed, length 60–88% PRL, becoming proportionally shorter with growth; dorsal profile of snout slightly concave in lateral view.Terminal snout scute short, broad, arrowheadshaped, dorsoventrally flattened, length 7–18% PRL. Scales on median rostral ridge covered with divergent rows of spinules. Lateral nasal ridge completely supported by nasal bone, not strongly convex when viewed dorsally. Anus slightly separated from anal-fin origin. Premaxillary teeth small, conical, arranged in short, uniformly wide band, none especially enlarged; posterior margin of tooth band falling far short of lateral corner of mouth. Body scales covered with short, reclined, keel-like spinules in narrowly divergent saw-toothed ridges; every spinule row complete, extending to posterior scale margin; spinules in each row greatly overlapping, closely adjoined to one another, but generally free at tips; buttresses narrowly developed. Occipital scales covered with short, reclined, keel-like spinules in narrowly divergent, saw-toothed rows. Orbit diameter 45–52% PRL; postorbital length 50–56% PRL; orbit–preopercle distance 52–60% PRL; height of first dorsal fin 85–107% PRL; interdorsal length 33–54% PRL; pyloric caeca 21–26. Free neuromasts on underside of head tiny, immaculate, difficult to distinguish; dark hair-like papillae absent on underside of head. Body darker dorsally, paler ventrally, without either blotches or saddles; underside of head dusky; lips white; oral cavity blackish; gular and branchiostegal membranes pale; pelvic fins dusky.

Material examined. 56 specimens. Holotype of Coelorhynchus anatirostris: USNM 51471 (93.7 mm HL, 395 mm TL), Misaki, Kanagawa Pref., Sagami Bay , Japan, date unknown . Holotype of Coelorhynchus productus: USNM 76865 (79.9 mm HL, 304 mm TL), off Fuji River, Shizuoka Pref., Suruga Bay , Japan , 35.0917ºN, 138.6639ºE, 197–297 ftm (361–544 m), Albatross sta. 5059, 9-ft Albatross-Blake beam trawl, 13 Oct. 1906 . Paratypes of C. productus: USNM 76872 (1, 55.6 mm HL, 233+ mm TL), off Fuji River, Suruga Bay , 35.1014ºN, 138.6722ºE, 221–293 ftm (405–536 m), Albatross sta. 5066, 9-ft Albatross-Blake beam trawl, 15 Oct. 1906 ; CAS-SU 22977 (2, 68.2– 68.2 mm HL, 260+– 286 mm TL) , USNM 76873 (3 of 4, 53.0– 58.5 mm HL, 186+–243+ mm TL, counts and measurements taken on 2 of 3), collected with holotype. Non-types: Japan: BSKU 29744 (1, 80.2 mm HL, 269+ mm TL), north-northeast of Miyako-jima Island, Okinawa Trough , 25.9833ºN, 125.8500ºE, 430 m, F/ V Yuryo-maru, No. 8, sta. 2-T3, bottom trawl, coll. H. Maeda, 10 Oct. 1979 ; BSKU 34351 (1, 58.1 mm HL, 199+ mm TL), northwest of Kumejima Island, Okinawa Trough , 27.0083ºN, 125.8417ºE, 410–420 m, F/ V Yuryo-maru, No. 8, sta. 5-T3, bottom trawl, coll. K. Uchida, 10 Dec. 1979 ; BSKU 29586 (1, 94.3 mm HL, 359+ 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 32516 (1, 91.6 mm HL, 318+ 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. M. Hirose and T. Kume, 10 Oct. 1979 ; BSKU 29638 (1, 68.7 mm HL, 226+ 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 106770 (1, 72.7 mm HL, 278+ mm TL) , BSKU 106821 (1, 62.5 mm HL, 219+ mm TL) , BSKU 106823 (1, 63.8 mm HL, 250+ mm TL) , BSKU 106824 (1, 55.7 mm HL, 210+ mm TL), southeast of Shimokoshiki-jima Island, East China Sea , 31.5658ºN, 129.8915ºE, 380 m, F/ V Maruko-maru, tr. 1, bottom trawl, coll. N. Nakayama et al., 24 Apr. 2012 ; BSKU 106807 (1, 91.3 mm HL, 370+ mm TL) , BSKU 106808 (1, 68.2 mm HL, 260+ mm TL) , BSKU 106809 (1, 75.3 mm HL, 281+ mm TL) , BSKU 106811 (1, 62.1 mm HL, 240 mm TL), southeast of Shimokoshiki-jima Island, East China Sea , 31.5652ºN, 129.8878ºE, 407 m, F/ V Maruko-maru, tr. 3, bottom trawl, coll. N. Nakayama et al., 24 Apr. 2012 ; BSKU 106777 (1, 58.9 mm HL, 230+ mm TL) , BSKU 106779 (1, 57.1 mm HL, 191+ mm TL) , BSKU 106794 (1, 55.4 mm HL, 208+ mm TL) , BSKU 106796 (1, 51.0 mm HL, 195+ mm TL) , BSKU 106797 (1, 68.4 mm HL, 259+ mm TL), southeast of Shimokoshiki-jima Island, East China Sea , 31.5560ºN, 129.8847ºE, 415 m, F/ V Marukomaru, tr. 4, bottom trawl, coll. N. Nakayama et al., 24 Apr. 2012 ; KAUM-I. 32206 (1, 85.5 mm HL, 338+ mm TL), off Nomaike , Kagoshima, 31.5000ºN, 129.8833ºE, 370–400 m, trawl, coll. M. Yamashita and Y. Ohashi, 10 Sept. 2010 ; BSKU 109032 (1, 90.6 mm HL, 354+ mm TL) , BSKU 109033 (1, 79.7 mm HL, 318+ mm TL) , BSKU 109034 (1, 56.1 mm HL, 207+ mm TL) , BSKU 109038 (1, 89.9 mm HL, 382+ mm TL), west of Sanposone , 32.2872ºN, 129.0732ºE, 351–389 m, T/ V Nagasakimaru, cr. N365, sta. B4, 3-m ORE beam trawl, coll. N. Nakayama, 19 Nov. 2012 ; BSKU 109019 (1, 62.2 mm HL, 256+ mm TL), west of Okikasayama Bank , 32.1503ºN, 129.0072ºE, 499–504 m, T/ V Nagasaki-maru, cr. N365, sta. C5, 3-m ORE beam trawl, coll. N. Nakayama, 19 Nov. 2012 ; NSMT-P 65673 (1, 74.4 mm HL, 310+ mm TL), west of Yaku-shima Island, East China Sea , 30.4467ºN, 128.2367ºE, 499–500 m, FRV Yoko-maru, sta. D9, bottom trawl, coll. T. Kubodera et al., 10 Nov. 2002 ; BSKU 29821 (1, 86.4 mm HL, 358+ mm TL) , BSKU 34038 (1, 96.7 mm HL, 388+ mm TL), west of Yaku-shima Island, Okinawa Trough , 30.4433ºN, 128.0177ºE, 410–430 m, F/ V Yuryo-maru, No. 8, sta. 3-T7, bottom trawl, coll. H. Maeda, 28 Oct. 1979 ; BSKU 27989 (1, 106 mm HL, 383+ mm TL), northwest of Amami-oshima Island, Okinawa Trough , 28.8333ºN, 127.2333ºE, 700–740 m, F/ V Ryoanmaru, No. 28, tr. 59, bottom trawl, coll. Y. Kinoshita and S. Hagino, 16 Mar. 1978 ; BSKU 27927 (1, 94.9 mm HL, 377+ mm TL), northwest of Amami-oshima Island, Okinawa Trough , 28.7500ºN, 127.1167ºE, 520–542 m, F/ V Ryoan-maru, No. 28, tr. 58, bottom trawl, coll. Y. Kinoshita and S. Hagino, 16 Mar. 1978 ; BSKU 112539 (1, 100 mm HL, 399+ mm TL), off Aki, Tosa Bay , 380 m, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama et al., 12 Mar. 2014 ; BSKU 70897 (1, 85.6 mm HL, 359 mm TL), Tosa Bay , 33.2250ºN, 133.6933ºE, 440–460 m, FRV Kotaka-maru, otter trawl, 24 Aug. 2000 ; BSKU 71581 (1, 79.2 mm HL, 317+ mm TL) , BSKU 97956 (1, 83.5 mm HL, 318+ mm TL) , BSKU 97957 (1, 85.1 mm HL, 326+ mm TL) , BSKU 97958 (1, 73.3 mm HL, 309+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 9 May 2000 ; BSKU 77981 (1, 79.5 mm HL, 292+ mm TL) , BSKU 77982 (1, 81.3 mm HL, 314+ mm TL), Tosa Bay , 33.2000ºN, 133.6317ºE, 370–380 m, FRV Kotaka-maru, otter trawl, 8 Sept. 1998 ; BSKU 43815 (1, 78.9 mm HL, 310+ mm TL) , BSKU 43832 (1, 51.1 mm HL, 206+ mm TL), Tosa Bay , 400 m, FRV Kotaka-maru, otter trawl, 11 Jun. 1987 ; BSKU 4385 (1, 98.4 mm HL, 427 mm TL), Mimase fish market, bottom trawl, coll. T. Kamohara, 19 Dec. 1954 ; BSKU 37101 (1, 77.0 mm HL, 301+ mm TL), Mimase fish market, bottom trawl, coll. Y. Machida, 20 Apr. 1982 ; BSKU 102701 (1, 58.5 mm HL, 204+ mm TL), Mimase fish market, F/ V Kosei-maru, bottom trawl, coll. N. Nakayama, 21 Feb. 2010 ; BSKU 102691 (1, 78.4 mm HL, 312 mm TL), Mimase fish market, F/ V Koseimaru, tr. 3, bottom trawl, coll. N. Nakayama, 21 Feb. 2010 ; BSKU 102003 (1, 73.1 mm HL, 283+ mm TL), Mimase fish market, F/ V Seiryo-maru, bottom trawl, 7 Dec. 2009 ; BSKU 110034 (1, 74.2 mm HL, 294+ mm TL), Suruga Bay , 34.7127ºN, 138.4553ºE, 262–434 m, F/ V Hinode-maru, sta. 1, bottom trawl, coll. N. Nakayama and R. Misawa, 23 Apr. 2013 ; * BSKU 50891 (1, 21.7 mm HL, 88+ mm TL), Numazu fish market, coll. S. Ohashi, 15 Feb. 2009 . Taiwan: ASIZP 65573 (1, 98.2 mm HL, 352+ mm TL), Gwu-san Island , Yilan, 606–653 m, bottom trawl, coll. H.-M. Yeh, 17 Apr. 2003 . Chesterfield and Bellona Plateaus : CAS 86496 (1, 81.9 mm HL, 288+ mm TL), 19.6808ºS, 158.7683ºE, 600–615 m, MUSORSTOM 5, sta. CC383, 21 Oct. 1986 .

Redescription based on Japanese specimens. General features are shown in Figs. 18–20 , 21A . Counts and measurements are given in Table 1 . Body deepest at first dorsal-fin origin, gradually tapering to long, laterally compressed tail. Trunk short, moderately compressed, width over pectoral-fin bases 1.0– 1.3 in depth below first dorsal-fin origin. Head large, HL about 3.3–4.3 in TL. Snout long, protruding greatly beyond upper jaw, length usually 1.4–1.8 times as long as orbit diameter (1.2 times in BSKU 4385); dorsal contour of snout slightly concave in lateral view; lateral nasal ridge completely supported by nasal bone; anterolateral margins of snout moderately convex when viewed dorsally. Orbit large, greatest diameter 1.0– 1.2 in postorbital length. Interorbital space almost flat, width 1.1–1.5 in orbit diameter. Mouth moderate in size, inferior, protrusible, upper-jaw length 1.0– 1.4 in orbit diameter; posterior margin of maxilla extending to vertical through midorbit or beyond, but not reaching hind margin of orbit; lateral corner of mouth moderately 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 prolonged ventrally as slender flap; posterior margin deeply concave. Gill membranes broadly connected across, and attached mesially to isthmus, with slight posterior free fold. Outer gill slit moderately restricted by skin folds, length 2.3–3.2 in orbit diameter. Gill rakers small, low, tubercular, armed with short, fine spines; no rakers on outer side of first arch (a few rudimentary rakers occasionally found in large specimens) and inner side of fourth arch; gill filaments moderately long. Chin barbel slender, tapering into filamentous tip; length usually 2.6– 5.6 in orbit diameter (6.5 in USNM 76872, paratype of C. productus ).

Anus slightly separated from anal-fin origin by a few scale rows. Light organ externally represented by short, narrow, naked streak anterior to anus; its anterior margin reaching about midway between anus and outer pelvic-fin bases, and falling far short of line connecting inner pelvicfin bases. Pyloric caeca 24–26, rete-gas gland complexes 4 (based on BSKU 106823 and 109038).

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, and none especially enlarged. Mandibular teeth in broad tapered band, with about 5 tooth rows near symphysis, none especially enlarged; band narrowing abruptly, and its posterior margin extending beyond lateral corner of mouth. All teeth deeply embedded in thick layer of gum papillae.

Body scales large, thin, not deciduous, covered with narrowly divergent rows of short, reclined, keel-like spinules ( Fig. 22 A–D); in 90.1 mm HL specimen (BSKU 109032), those on dorsum below interdorsal space with 7–9 spinule rows; middle row longest with about 6–8 spinules, but not especially high or enlarged compared with adjacent rows; every spinule row complete throughout; spinules forming angle of about 40º to scale surface; spinules greatly overlapping, closely adjoined to one another, but distal tips usually free, forming saw-toothed ridges that give spiny appearance to body surfaces; spinules increasing in height posteriorly, with last in each row extending slightly beyond posterior scale margin (last spinule rarely falling short of scale margin in large specimens; Fig. 22 A–B); buttresses of spinules narrowly developed; no reticulate structures on unexposed potion. Body fully scaled except for fins and ventral light organ.

Scales on head ridges coarsely modified; those on median rostral ridge covered with divergent rows of spinules. Terminal snout scute short, broad, arrowheadshaped, dorsoventrally flattened, its length 2.8–6.5 in orbit diameter. Supraoccipital scute stout, enlarged, armed with single row of spinules; posttemporal scutes thickened, but not especially enlarged. Occipital scales covered with short, reclined, keel-like spinules in narrowly divergent rows ( Fig. 22 E–F); spinules slightly adjoined basally to one another, and increasing in height posteriorly; scales on dorsal surfaces of snout posterior to leading edges armed with divergent rows or small cluster of short, erect, knife-like spinules. Other scales on head variable in size, generally similar to those on body, but spinules more erect; those on opercle, preopercle, and postorbital and supratemporal canals largest. Nasal fossa usually heavily scaled anteroventrally (scales rarely absent especially in small specimens). Dorsal surfaces of snout fully scaled; naked clefts along each side of median rostral ridge only slightly developed. Underside of head almost completely naked; small scaly patches often present on ventral surfaces of preopercles and above posterior margins of lower jaws.

No open pores along cephalic sensory canals. Free neuromasts on ventral surface of head tiny, poorly marked, not discernible. Anterior nostril small and oval; posterior large, bean-shaped. Lateral line complete, extending from upper margin of opercle to tip of tail.

Origins of first dorsal and pelvic fins on about same vertical; first dorsal fin moderately high, its height 2.3–3.4 times as long as its base length; second spinous ray not elongated, smooth along its leading edge (1–2 rudimentary denticles rarely present distally); its tip extending to second dorsal-fin origin or beyond when laid back. Interdorsal space 0.9–1.5 times as long as first dorsal-fin base length. Second dorsal fin originating above or posterior to anal-fin origin. Pectoral-fin base slightly anterior to vertical through pelvic-fin base. Outer pelvicfin ray slightly prolonged, filamentous at tip.

Color when fresh ( Fig. 18 ). Dorsum body purplish gray, ventral half whitish without prominent silvery reflection; abdomen generally pale even in ventral view; opercle iridescent soon after capture; first dorsal darker apically, but otherwise paler; pectoral and pelvic fins dusky; distal margin of anal fin narrowly blackish posteriorly.

Color in alcohol ( Figs. 19–20 , 21A , 24 ). Head and body darker dorsally, paler ventrally; abdomen dark violet, but chest paler; lips white; oral and gill cavities blackish; gill rakers and filaments light tan, arches pallid; gular and branchiostegal membranes pale; first dorsal fin paler basally, darker distally, second spinous ray blackish; second dorsal fin immaculate; anal fin paler anteriorly, but prominently darker posteriorly; pectoral and pelvic fins generally dusky.

Size. To about 43 cm TL (BSKU 4385, 427 mm TL, off Kochi, Japan).

Distribution. Distributed in Japan and Taiwan as well as in the tropical southwestern Pacific including Vanuatu and the Chesterfield Islands ( Iwamoto & Merrett 1997; Merrett & Iwamoto 2000; Shao et al. 2008b; Nakayama 2019). Depth range 110–1160 m. In Japan and adjacent waters, known from off the Pacific coasts of southern Japan northward to the Miura Peninsula (139.62ºE), Okinawa Trough, south of Jeju Island in Korea, and the northern South China Sea (Appendix 3-1C). One of the most abundant species of Coelorinchus found at upper slope depths off southern Japan.

Nomenclatural discussion. Coelorinchus anatirostris was originally described from a single 395 mm TL specimen collected from Misaki, Sagami Bay, Japan ( Fig. 19 ). Subsequently, Gilbert & Hubbs (1916) described C. productus based on seven specimens collected from Suruga Bay, Japan (186+– 304 mm TL; Fig. 20 ), suggesting its close relationship with C. anatirostris . According to Gilbert & Hubbs (1916), C. productus is distinguished from C. anatirostris by having the following combination of features: snout longer, sharply pointed in dorsal view (vs. duckbill-shaped in C. anatirostris ); orbit smaller, 1.8 in snout length, slightly less than distance from pelvic-fin base to anus (vs. 1.5); barbel shorter, about 6 in orbit diameter (vs. almost equal to half eye); maxillary 4.6 in HL (vs. 4); gill membranes without free fold; body scales with 3–5 spinule rows (vs. 6–9); scales atop head not similar to those on body, with 1–3 spinule rows.

The taxonomic status of C. productus has been controversial over the past few decades. Okamura (1970a), who examined paratypes of this species and many Japanese specimens of C. anatirostris , concluded that the two species are synonymous, considering that the differences reported by Gilbert & Hubbs (1916) are simply attributed to size-related or individual variations. However, Yatou (in Okamura & Kitajima 1984) resurrected C. productus and distinguished the two species by the combination of the barbel length (1/4–1/3 times as long as orbit diameter in C. productus vs. 1/3 times or more in C. anatirostris ) and preoral length (HL 2.4–2.6 times as long as preoral length vs. 2.6–3.0 times). Subsequently, many authors followed Yatou’s (1984) conclusion (see the synonym list), but Fukui et al. (2010) re-synonymized the species with C. anatirostris based on selected measurements and an analysis of 16s rRNA sequences. Most recently, Iwamoto et al. (2015) continued to recognize C. productus as valid, but noted that the problem needs further investigation.

An examination here of the types of both C. anatirostris and C. productus and an additional 46 specimens from Japan reconfirmed their conspecificity. All measurements of the holotype of C. productus fall within, or only slightly outside of the range of variation of C. anatirostris ( Table 1 ), except for the snout length (88% PRL vs. 60–84%) and preoral length (81% PRL vs. 50–79%). However, these subtle differences are of little significance when referring to ontogenetic variation of the snout in C. anatirostris . In C. anatirostris , the snout becomes shorter and broader with growth ( Fig. 23A ), giving significant change to the head appearance ( Fig. 24 ). Furthermore, the shape of the snout is variable even in a comparison with similar-sized specimens (see Fig. 24 : BSKU 77981 vs. BSKU 77982; BSKU 4385 vs. BSKU 27989). These variations influenced other measurements, because the head length was traditionally used as a standard of comparison in grenadiers.

As noted by Gilbert & Hubbs (1916), type specimens of C. productus have a somewhat shorter barbel than the holotype of C. anatirostris (8–11% PRL vs. 12%). However, the barbel length relative to HL tends to become longer with growth ( Fig.23B ),and the difference is unclear when the variation of C. anatirostris is considered (9–18% PRL). Unfortunately, the distal portion of the chin barbel is slightly damaged in the holotype of C. productus .

Gilbert & Hubbs (1916) distinguished C. productus from C. anatirostris in having “scales with 3 to 5, instead of 6 to 9, divergent spinous ridges, those on the top of the head not similar to those on body, bearing but one to three ridges”. However, the number of spinule rows tends to increase with growth in grenadiers ( Iwamoto & Merrett 1997:509) and the character should be used only for comparisons of similar-sized specimens. Specimens in the type series of C. productus are significantly smaller than the holotype of C. anatirostris (53.0– 79.9 mm HL vs. 93.7 mm HL), and the differences in squamation appear to reflect size-related variation.

Meristic data also show no significant differences between the two species. Therefore, this study supports Fukui et al. ’s (2010) conclusion that C. productus is a junior synonym of C. anatirostris .

Comments on type specimens. In the original description of C. productus, Gilbert & Hubbs (1920) designated six specimens collected from the Albatross sta. 5059 and 5066 as paratypes of the species. However, seven specimens being referable to C. anatirostris collected from these stations were found among the USNM and CAS fish collections. Of these, the smallest one from sta. 5059 (USNM 76873, 1 of 4, 93+ mm TL) is herein considered a non-type, because it is obviously smaller than the size range of the C. productus paratypes given in the original description (190–286 mm TL).

Remarks. Okamura (1970b: fig. 14N) provided a figure of the premaxillary tooth band of C. anatirostris , where the outermost series was illustrated as being distinctly enlarged. His figure seems to be diagrammatic, considering that the specimens examined in this study lack greatly enlarged teeth on the upper jaw. In C. anatirostris , the premaxillary teeth are arranged in a short, uniformly wide band, with tooth size gradually decreasing inward. In addition, inner rows are deeply embedded in a thick layer of gum papillae, which gives a larger appearance to the outermost series.

Chiou et al. (2004b; as C. productus ) reported two Taiwanese specimens (ASIZP 61326 and ASIZP 61327, 278– 296 mm TL) as having 11–12 pelvic-fin rays. However, the number is almost always seven (rarely six) in Coelorinchus , and a brief examination of the voucher specimens confirmed that Chiou et al. ’s (2004b) counts were erroneous (those specimens have seven pelvic-fin rays). Chiou et al. (2004b) also noted their specimens as having 3.5–4 scale rows below the first dorsal-fin origin and the length of the light organ 2.8–3 times as long as the orbit diameter. Although their scale counts are slightly lower than those of C. anatirostris in this study (4.5–6.5), the difference appears to reflect different methods of counting. Further, the length of the light organ given by Chiou et al. (2004b) should be read as the length is 2.8–3 in the orbit diameter.

Coelorinchus anatirostris has a disjunct distribution between the northwestern Pacific from Japan to Taiwan and the southwestern Pacific. A single specimen collected from the Chesterfield and Bellona Plateaus (CAS 86496, 81.9 mm HL, 288+ mm TL) was examined to compare with the northwestern Pacific population. As pointed out by Iwamoto & Merrett (1997:489), the New Caledonian specimen has a distinctly paler color, but otherwise they are closely similar to each other. A further in-depth comparison should be done with more specimens from the southeastern Pacific.

Relationships. Coelorinchus anatirostris belongs to a group of Coelorinchus species characterized by the following combination of features: light organ short, its anterior margin falling far short of pelvic-fin bases; lateral nasal ridge completely supported by nasal bone, not strongly convex when viewed dorsally; premaxillary teeth in short, uniformly wide band; underside of head completely to broadly naked; body scales covered with widely divergent rows of spinules, and every row complete throughout; buttresses of body-scale spinules scarcely to only narrowly developed; no prominent markings on body ( Nakayama & Endo 2017; this study). It corresponds with one of two subgroups of the C. japonicus group as redefined by Nakayama & Endo (2017), comprising the following eight species in which the underside of the head is completely or almost completely naked: C. anatirostris ; C. goobala Iwamoto & Williams, 1999 from the eastern Indian Ocean off Australia; C. hige Matsubara, 1943 from Japan to Taiwan (a senior synonym of C. asteroides Okamura, 1963 ); C. lanceolatus sp. nov. from Japan; C. okamurai Nakayama & Endo, 2017 from the Timor Sea; C. radcliffei Gilbert & Hubbs, 1920 from the Philippines and Indonesia; C. shcherbachevi Iwamoto & Merrett, 1997 from the tropical southwestern Pacific; and C. weberi Gilbert & Hubbs, 1920 from the Philippines. For convenience of comparison, this group is called here the C. anatirostris group.

Coelorinchus chilensis Gilbert & Thompson in Thompson, 1916, known from the southeastern Pacific, is superficially similar to the aforementioned species, but differs notably in having the lateral nasal ridge incompletely supported by the nasal bone, and in lacking any prominent external evidence of the light organ anterior to the anus.

Comparisons. Among the C. anatirostris group, C. anatirostris is closely related to C. weberi , with which it shares most of the diagnostic features used to distinguish the species from its congeners. Gilbert &Hubbs (1920:378, table 3) assumed that C. weberi is a possible sibling species of either C. anatirostris or C. productus (the last of which was then considered valid, but herein regarded as a junior synonym of C. anatirostris ; see the Nomenclatural discussion). Coelorinchus weberi is currently known only from the holotype collected at the Babuyan Channel off northern Luzon, the Philippines. In their key to species of the genus ( Gilbert & Hubbs 1920:425), C. anatirostris runs to the couplet j, where it is substantially separated from C. weberi by having a larger orbit, with its diameter being about equal to the postorbital length (vs. 1.35 in postorbital) and 1.9 in the snout length (vs. 1.5–1.8). An examination of the holotype of C. weberi (USNM 78225, 86.7 mm HL) confirmed their differences in the orbit diameter (45–52% PRL in C. anatirostris vs. 44% in C. weberi ; Fig. 25A ) and postorbital length (50–56% PRL vs. 58%; Fig. 25B ) as well as the orbit–preopercle distance (52–60% PRL vs. 62%; Fig. 25C ). However, the two species differ most notably from each other by coloration of the cephalic neuromasts. In C. anatirostris , the free neuromasts on the underside of the head are difficult to distinguish as they are unpigmented, whereas each neuromast of C. weberi is marked with two small black dots, and easily discernible without a microscope. The latter species will be fully redescribed in a forthcoming paper by the present author.

Coelorinchus shcherbachevi is another species that is closely similar to C. anatirostris , and is known only from four large specimens (118–132 mm HL, 435+– 550+ mm TL) collected from the Loyalty Ridge, New Caledonia ( Iwamoto & Merrett 1997; Merrett & Iwamoto 2000) and an additional record from the western Coral Sea ( Last et al. 2014). The holotype (MNHN 1996-966, 126+ mm HL) and one of the paratypes (CAS 90995, 123 mm HL) were examined in the course of this study. Its distinctness from C. anatirostris was well documented in the original description given by Iwamoto & Merrett (1997). Coelorinchus anatirostris is clearly distinguished from C. shcherbachevi by having keel-like spinules on the body scales (vs. broadly triangular, somewhat pyramidal in C. shcherbachevi ) and poorly developed sensory organs on the underside of the head (vs. dark hair-like papillae densely scattered, with prominent flap-like black neuromasts). As discussed by Iwamoto & Merrett (1997), the number of spinule rows on the body scales also appears to be a good diagnostic character between the two species, especially when similar-sized specimens are compared. In the Japanese specimens of C. anatirostris examined, the number increases with size, with one of the largest specimens (BSKU 4385, 98.4 mm HL) having eight rows of spinules ( Fig. 22A ). However, the C. shcherbachevi specimens examined had only four or five rows despite their large size, and the number is considerably fewer than in the C. anatirostris specimens examined. This study also confirmed that the two species are further distinguished from each other by the orbit diameter (45–52% PRL in C. anatirostris vs. 43–44% in C. shcherbachevi ), orbitpreopercle distance (52–60% PRL vs. 61–63%), upperjaw length (37–45% PRL vs. 45–47%), interorbital width (34–43% PRL vs. 42–43%), isthmus–pelvic distance (41–57% PRL vs. 59–63%), height of first dorsal fin (85– 107% PRL vs. 80%), length of gill slit (15–22% PRL vs. 23–28%), and coloration (paler ventrally vs. uniformly dark). However, these differences should be verified when more specimens of C. shcherbachevi become available, because ontogenetic variations of that species have been poorly understood.

Among Japanese congeners, C. anatirostris is most similar to C. lanceolatus sp. nov., but is readily distinguished from the latter by its shorter snout (60–88% PRL vs. 107%) and higher first dorsal fin (85–107% PRL vs. 84%). Coelorinchus anatirostris is also likely to be confused with C. hige (a senior synonym of C. asteroides Okamura, 1963 ; see the Nomenclatural discussion on the latter species), and they occur together in the northwestern Pacific (Appendix 3-1C and 3-2E). It differs primarily from C. hige in that the occipital scales are covered with keel-like spinules in narrowly divergent, saw-toothed rows (vs. needle-like spinules in widely divergent, comblike rows) and the nasal fossa is usually scaled ventrally (vs. completely or almost completely naked). A further comparison between the two species is discussed under the Relationships and comparisons of C. hige .

Figures

FIGURE 18. Fresh specimens of Coelorinchus anatirostris. (A) BSKU 109032, 90.6 mm HL, 354+ mm TL, Okinawa Trough, East China Sea, 351–389 m depth; (B) BSKU 109033, 79.7 mm HL, 318+ mm TL, collected with BSKU 109032; (C–E) BSKU 102003, 73.1 mm HL, 283+ mm TL, Mimase fish market, Kochi, Pacific. (A–C) Lateral views; (D) dorsal and (E) ventral views of the head and trunk. [Photos: N. Nakayama]

FIGURE 19. Holotype of Coelorhynchus anatirostris (= Coelorinchus anatirostris). USNM 51471, 93.7 mm HL, 395 mm TL, Sagami Bay off Misaki, Kanagawa Pref., Pacific. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]

FIGURE 20. Preserved specimen of Coelorinchus anatirostris. USNM 76865, holotype of Coelorhynchus productus, 79.9 mm HL, 304 mm TL, Suruga Bay, Shizuoka Pref., Pacific, 544–361 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. [Photos: N. Nakayama]

FIGURE 21. Preserved juvenile specimens of two species of Coelorinchus. (A) C. anatirostris, BSKU 50891, 21.7 mm HL, 88+ mm TL, Numazu fish market, Shizuoka Pref., Pacific; (B) C. hige, BSKU 50881, 30.0 mm HL, 108+ mm HL, off Nomaike, Kagoshima Pref., East China Sea. Lateral views. [Photos: N. Nakayama]

FIGURE 22. Scanning electron micrographs showing scales of Coelorinchus anatirostris. (A–B) BSKU 4385, 98.4 mm HL; (C–F), BSKU 97958, 73.3 mm HL. (A–D) Scales from the dorsum below the interdorsal space; (E–F) from the top of the head between the parietal ridges. (A, C, E) Views from above; (B, D, F) oblique views. [Photos: N. Nakayama]

FIGURE 23. Scatter diagrams showing relationships of the (A) snout length and (B) barbel length (as % PRL) to PRL (mm) in Coelorinchus anatirostris (circles) and C. productus (squares). Arrows indicate holotypes.

FIGURE 24. Variation of the snout shape in Coelorinchus anatirostris. [Photos: N. Nakayama]

FIGURE 25. Scatter diagrams showing relationships of the (A) orbit diameter, (B) postorbital length, and (C) orbit–preopercle distance (as % PRL) to PRL (mm) in Coelorinchus anatirostris (circles) and C. weberi (squares). Arrows indicate holotypes.