Coelorinchus sheni 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 : 126-127

Coelorinchus sheni Chiou, Shao & Iwamoto, 2004

[Japanese name: Tora-hige]

( Figs. 42 C–D, 82–84; Appendix 3-5A)

Caelorinchus sheni Chiou, Shao & Iwamoto, 2004a:37 , figs. 1–4 [original description; holotype: ASIZP 61348 , from off Tashi (= Da-xi, northeastern Taiwan); 2 paratypes from Taiwan; “ Caelorinchus (Oxygadus) sheni ” in table 1].

Coelorinchus sheni: Shao et al. 2008b : table 2 (3 spec. listed from northeastern and southwestern Taiwan); Iwamoto et al. 2015:67 (brief description; 13 spec. from northeastern and southeastern Taiwan); Ho & Shao 2011:36 (type catalog); Nakayama et al. 2018:122, figs. 1–2 (description; 1 spec. from Japan; comments on type specimens; new Japanese name: “Tora-hige”); Motomura 2020:38 (listed; Japan).

Diagnosis. Light organ externally represented by short, narrow, naked streak immediately anterior to anus (difficult to distinguish in some specimens), its anterior margin falling far short of line connecting inner pelvicfin bases. Underside of head completely and uniformly covered with scales, except for anterior portions of mandibular rami; top of snout completely scaled; nasal fossa scaled ventrally. Snout long, sharply pointed, length 57–73% PRL, its dorsal profile straight or slightly convex in lateral view; terminal scute pointed distally, arrowheadshaped; lateral nasal ridge incompletely supported by nasal bone. Anus immediately anterior to anal-fin origin, but they slightly separated by a few scale rows. Premaxillary teeth in long, tapered band, with outer series prominently enlarged; posterior margin of tooth band reaching near 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 overlapping but free at tips, gradually increasing in height posteriorly; buttresses poorly developed. Occipital scales covered with 2–4 divergent rows of spinules. Preoral length 37–59% PRL; barbel length 13–21% PRL. About 6 dark saddles on body (faint in large individuals); ventral margins of saddles extending beyond mid-lateral axis of body; lips paler; oral cavity blackish; gular and branchiostegal membranes dusky.

Material examined. 11 specimens. Holotype of Caelorinchus sheni: ASIZP 61348 (115 mm HL, 412+ mm TL), off Da-xi, Yilan, northeastern Taiwan , East China Sea , 24.91°N, 122.06°E, 400–600 m depth, F/ V Gin Ton Long, bottom trawl, coll. by M.-L. Qiu, 30 May 2001 . Paratypes of C. sheni: ASIZP 61232 (1, 249 mm HL, 868+ mm TL), off Lauto, southeastern Taiwan , ca. 22.6667ºN, 121.6667ºE, rod and reel, 1 Mar. 1999 ; CAS 215541 (1, 112 mm HL, 424+ mm TL), Da-xi fish market, Yilan, northeastern Taiwan , East China Sea , coll. M.-L. Chiou and H.-C. Ho, date unknown. Non-types : Japan: OCF-P 3492 (1, 196 mm HL, 692+ mm TL), Izena Bank , northwest of Ie-jima Island , 27.1343ºN, 127.2403ºE, 650 m, coll. T.Arakaki, 15 Sept. 2016 . Taiwan: BSKU 116417 (1, 154 mm HL, 558+ mm TL), Da-xi fish market, Yilan, coll. H.-C. Ho, 18 Jun. 2014 ; ASIZP 70210 (6, 41.3–98.8 mm HL, 86+–380+ mm TL), Da-xi fish market, Yilan, coll. M.-L. Qiu, 25 Jun. 2005 .

Counts and measurements. Based on 11 specimens (41.3–249 mm HL, 86+–868+ mm TL). Counts: first dorsal-fin rays II,8–9; pectoral-fin rays i17–i20; pelvicfin rays 7; gill rakers on first arch (outer/inner) 0–3/8–9, on second arch 6–8/9–10; longitudinal scales 33–43; transverse scale rows below first dorsal-fin origin 5.5– 6.5, below first dorsal-fin midbase 4–5.5, below second dorsal-fin origin 5–6, above anal-fin origin 20.5–24.5; pyloric caeca 46–58.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 36–43 (57–73); orbit diameter 21–27 (33–44); postorbital length 35–42 (58–66); postrostral length 58– 63; orbit–preopercle distance 36–46 (59–76); suborbital width 12–15 (21–25); upper-jaw length 27–37 (45–59); length of rictus 21–31 (36–49); length of premaxillary tooth band 16–22 (28–35); preoral length 24–35 (37–59); length of terminal snout scute 3–6 (5–10); length of lateral nasal ridge 19–27 (30–44); length of suborbital ridge 88–97 (139–163); snout width 23–29 (37–47); internasal width 17–21 (26–34); interorbital width 23–26 (37–43); occipital width 9–11 (14–18); body width over pectoral-fin bases 36–50 (59–79); body depth at first dorsal-fin origin 54–65 (90–107); body depth at anal-fin origin 43–54 (71– 89); prepelvic length 102–114 (168–192); preanus length 129–148 (214–244); preanal length 133–154 (222–252); isthmus–pelvic distance 28–39 (46–64); isthmus–anus distance 52–74 (86–122); isthmus–anal distance 58–80 (96–131); pelvic–anal distance 32–46 (52–75); anus–anal distance 5–46 (7–72); pelvic-fin length 33–56 (54–93); pectoral-fin length 45–52 (77–86); predorsal length 105– 112 (173–183); height of first dorsal fin 42–50 (69–82); length of first dorsal-fin base 17–21 (29–34); interdorsal length 12–28 (20–46); length of gill slit 13–19 (22–32); length of posterior nostril 7–9 (12–15); barbel length 8– 13 (13–21).

Size. Attains about 87 cm TL ( ASIZP 61232 , paratype, 868+ mm TL, southwestern Taiwan).

Distribution. Known from the southern East China Sea off Taiwan and Japan, and also southeastern Taiwan (Appendix 3-5A). Depth range 400–650 m (based on specimens associated with reliable depth records; see Nakayama et al. 2018). Very rare.

Remarks. Coelorinchus sheni has been well described by previous authors, and thus does not need repeating here. This species was originally described by Chiou et al. (2004a) based on three specimens collected from Taiwan ( Figs. 83–84 ). Recently, Iwamoto et al. (2015) reported additional specimens from the type locality (Da-xi fish market), and Nakayama et al. (2018) newly recorded this species from Japanese waters based on a single specimen collected from the East China Sea off Ie-jima Island, Okinawa Pref. Nakayama et al. (2018) also emended localities of type specimens of the species. One of the paratypes (ASIZP 61232), which was previously not found among the collection of the Academia Sinica, Taipei ( Nakayama et al. 2018), was rediscovered during the author’s visit in November 2017 ( Fig. 84 ).

Relationships and comparisons. Coelorinchus sheni is a member of the C. tokiensis group (see the Relationships of C. hexafasciatus ), and most closely related to C. quadricristatus (Alcock in Wood-Mason & Alcock, 1891), which is distributed in the Indian Ocean. The two species are unique within the group in that the terminal snout scute is sharply pointed. They also differ from all but C. celaenostoma McMillan & Paulin, 1993 and C. osipullus McMillan & Iwamoto, 2009 in that the underside of the head is completely scaled. Coelorinchus sheni readily differs from C. quadricristatus in having a shorter snout [36–43% HL vs. as long as a half HL (fide Alcock in Wood-Mason &Alcock 1891:119)] and a deeper body [depth below first dorsal-fin origin 1.3–1.6 times as long as snout length vs. “greatest height of the body barely equal to length of the snout” ( Alcock 1899:106)]. Furthermore, saddles of C. sheni extend ventrally beyond the mid-lateral axis of the body ( Fig. 83 ), whereas those of C. quadricristatus reach only this level (see Alcock 1892: pl. III, fig. 1).

Figures

FIGURE 42. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of three species of the Coelorinchus tokiensis group. (A–B) C. hexafasciatus, BSKU 29452, paratype, 167 mm HL; (C–D) C. sheni, CAS 215541, 112 mm HL; (E–F) C. tokiensis, BSKU 26104, paratype of C. longicephalus, 202 mm HL. (A, C, E) Views from above; (B, D, F) oblique views. [Photos: (A–B, E–F) N. Nakayama; (C–D) NSMT]

FIGURE 83. Holotype of Caelorinchus sheni (= Coelorinchus sheni). ASIZP 61348, 115 mm HL, 412+ mm TL, Da-xi fish market, northeastern Taiwan, East China Sea. (A) Lateral, (B) dorsal, and (C) ventral views. Preserved condition. [Photos: N. Nakayama]

FIGURE 84. Paratype of Caelorinchus sheni (= Coelorinchus sheni). ASIZP 61232, 249 mm HL, 868+ mm TL, off Lauto, southeastern Taiwan. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. [Photos: N. Nakayama]