Coelorinchus leptorhinus Chiou, Shao & Iwamoto, 2004

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 96-97

Coelorinchus leptorhinus Chiou, Shao & Iwamoto, 2004

[No Japanese name]

( Figs. 53 C–D, 64–65; Appendix 3-3F)

Caelorinchus tokiensis (not Steindachner & D̂derlein 1887): Shao 1993:170 (compiled; Taiwan) [fide Chiou et al. 2004a: table 1].

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

Caelorinchus leptorhinus Chiou, Shao & Iwamoto, 2004b:299 , figs. 1–3 [original description; holotype: ASIZP 61344 , from Ta-shi (= Da-xi, northeastern Taiwan); 23 paratypes from northeast of Taiwan].

Coelorinchus leptorhinus: Shao et al. 2008b : table 2 (23 spec. listed from northeastern and southwestern Taiwan); Ho & Shao 2011:36 (type catalog); Iwamoto et al. 2015:59 (brief description; 54 spec. from northeastern and southwestern Taiwan).

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. Snout completely scaled dorsally, mostly naked ventrally; underside of head posterior to hind margins of lateral nasal ridges almost completely scaled. Snout very long, sharply pointed, length 69–99% PRL; dorsal profile of snout concave in lateral view; terminal scute short, diamond-shaped, dorsoventrally flattened; lateral nasal ridge completely supported by nasal bone. Anus only slightly separated from anal-fin origin. Premaxillary teeth small, conical, arranged in moderately wide tapered band, with outer series distinctly enlarged; posterior margin of tooth band extending beyond midway of rictus. Body scales covered with short, reclined, keel-like spinules in divergent saw-toothed ridges; every spinule row complete, extending to posterior scale margin; spinules in each row greatly overlapping, increasing in height posteriorly; buttresses barely developed. Occipital scales covered with keel-like spinules in narrowly divergent rows. Orbit diameter 36– 41% PRL; suborbital width 14–18% PRL; internasal width 19–24% PRL; interorbital width 27–31% PRL; pectoralfin length 72–97% PRL; transverse scale rows below first dorsal-fin midbase 5.5–6.5. Head and body uniformly dark brown, but lips pale to dusky; all fins blackish.

Material examined. 11 specimens. Holotype of Caelorinchus leptorhinus: ASIZP 61344 (234 mm HL, 811+ mm TL), Da-xi fish market, Yilan, northeastern Taiwan , 24.9105ºN, 122.0636ºE, 400–600 m, beam trawl, coll. M.-L. Qiu, 15 Mar. 1999 . Paratypes of C. leptorhinus: ASIZP 61345 (1, 119 mm HL, 388+ mm TL), Nan-fang-ao fish market, Yilan, 15 Dec. 1999 ; ASIZP 61347 (3, 171– 176 mm HL, 507+–645+ mm TL), Da-xi fish market, Yilan, 24.9105ºN, 122.0636ºE, bottom trawl, coll. M.-L. Qiu, 30 May 2001 . Non-types: Taiwan: * BSKU 99870 (1, 96.5 mm HL, 367+ mm TL), Da-xi fish market, Yilan, coll. M.-Y. Lee, 30 Jun. 2009 ; FAKU 204420 (1, 131 mm HL, 470 mm TL), FAKU 204421 (1, 107 mm HL, 411 mm TL), FAKU 204422 (1, 112 mm HL, 424+ mm TL), FAKU 204423 (1, 96.5 mm HL, 302+ mm TL), FAKU 204424 (1, 80.6 mm HL, 245+ mm TL), Dong-gang fish market, Pingtung, bottom trawl, coll. N. Nakayama, 27 Feb. 2017 .

Counts and measurements. Based on 10 specimens (80.6–234 mm HL, 245+–811+ mm TL). Counts: first dorsal-fin rays II,8–9; pectoral-fin rays i16–i19; pelvicfin rays 7; gill rakers on first arch (outer/inner) 0/8–9, on second arch 6–7/8–9; longitudinal scales 43–51; transverse scale rows below first dorsal-fin origin 5.5–8, below first dorsal-fin midbase 5.5–6.5, below second dorsal-fin origin 6–8, above anal-fin origin 21–22.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 41–50 (69–99); orbit diameter 20–21 (36–41); postorbital length 30–38 (59–65); postrostral length 50– 59; orbit–preopercle distance 31–39 (61–68); suborbital width 7–11 (14–18); upper-jaw length 24–31 (47–53); length of rictus 18–26 (35–43); length of premaxillary tooth band 15–20 (28–34); preoral length 27–40 (45–79); length of terminal snout scute 6–9 (11–19); length of lateral nasal ridge 21–34 (35–67); length of suborbital ridge 88–95 (149–189); snout width 18–21 (30–40); internasal width 11–14 (19–24); interorbital width 14–18 (27–31); occipital width 6–7 (11–13); body width over pectoral-fin bases 26–39 (51–66); body depth at first dorsal-fin origin 33–48 (66–80); body depth at anal-fin origin 29–37 (58–65); prepelvic length 103–115 (175– 212); preanus length 124–139 (220–256); preanal length 133–147 (234–269); isthmus–pelvic distance 27–35 (50– 62); isthmus–anus distance 46–56 (88–106); isthmusanal distance 55–65 (105–116); pelvic–anal distance 29– 40 (56–67); anus–anal distance 8–11 (14–19); pelvic-fin length 27–36 (51–65); pectoral-fin length 37–57 (72–97); predorsal length 86–110 (146–210); height of first dorsal fin 35–37 (60–71); length of first dorsal-fin base 13–17 (25–29); interdorsal length 24–37 (44–63); length of gill slit 9–14 (18–24); length of posterior nostril 7–8 (12–14); barbel length 7–14 (15–24).

Size. Attains at least 81 cm TL ( ASIZP 61244 , holotype, 811+ mm TL) .

Distribution. So far known only from the East and South China Seas off Taiwan at depths of about 100–650 m ( Shao et al. 2008a, 2008b; Appendix 3-3F). Common.

Comments on type specimens. Coelorinchus leptorhinus was originally described from northeastern Taiwan based on 23 specimens collected at the Da-xi fish market, Yilan ( Chiou et al. 2004b; Fig. 65 ). Ten paratypes registered in the Academia Sinica , Taipei ( ASIZP 61346 ) were not found among the collection during the author’s visit in 2012 and 2017 .

Remarks, relationships, and comparisons. Morphology of the species was detailed in the original description given by Chiou et al. (2004b). No specimens of C. leptorhinus have been collected within Japan’s EEZ, although it is commonly found in the Da-xi fish market in northern Taiwan. The species belongs to the C. japonicus groups (sensu stricto; see the Relationships of C. japonicus ), and is unlikely to be confused with Japanese congeners in that the underside of the snout is broadly naked (vs. completely and uniformly scaled, except for narrow naked areas above upper lip and along ventromedial line). It further differs from Japanese species of the C. japonicus group in having a relatively smaller orbit [36–41% PRL vs. 39–52%, 45–52%, and 43–52% in C. japonicus ( Temminck & Schlegel, 1846) , C. nox sp. nov., and C. smithi Gilbert & Hubbs, 1920 respectively], longer pectoral fin (72– 97% PRL vs. 55–71%, 57–69%, and 60–76%), narrower suborbital (14–18% PRL vs. 18–23%, 18–23%, and 19– 23%), internasal (19–24% PRL 26–33%, 27–31%, and 28– 37%), and interorbital regions (27–31% PRL vs. 31–38%, 39–41%, and 33–42%). This species is also distinguished from C. nox and C. smithi in having more scales below the first dorsal-fin midbase (5.5–6.5 vs. 3.5–4.5 and 3.5–5.5 in C. nox and C. smithi respectively).

Figures

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 65. Holotype of Caelorinchus leptorhinus (= Coelorinchus leptorhinus). ASIZP 61344, 234 mm HL, 811+ mm TL, Dong-gang fish market, southern Taiwan, South China Sea. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]