Coelorinchus Giorna, 1809

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 25-27

Genus Coelorinchus Giorna, 1809

[Japanese name: Tojin-zoku]

Coelorinchus Giorna, 1809:179 [type species: Lepidoleprus caelorhincus Risso, 1810 (= Coelorinchus caelorhincus ), by subsequent designation by Fowler (1936)].

[?] Krohnius Cocco, 1844:22 (type species: Krohnius filamentosus Cocco, 1844 , by monotypy).

[?] Coccolus Bonaparte, 1846:47 , 97 (type species: Coccolus annectens Bonaparte, 1846 , by monotypy).

Paramacrurus Bleeker, 1874:370 (type species: Lepidoleprus australis Richardson, 1839 , by original designation).

Oxymacrurus Bleeker, 1874:370 (type species: Macrurus japonicus Temminck & Schlegel, 1846 , by original designation).

Abyssicola Goode & Bean, 1896:417 (type species: Macrurus macrochir G̹nther, 1877 , by original designation).

Quincuncia Gilbert & Hubbs, 1920:432 (as subgenus of Coelorhynchus ; type species: Coelorhynchus argentatus Smith & Radcliffe in Radcliffe, 1912, by original designation).

Oxygadus Gilbert & Hubbs, 1920:515 (as subgenus of Coelorhynchus ; type species: Macrurus parallelus G̹nther, 1877 , by original designation).

Mahia McCann & McKnight, 1980:53 (type species: Mahia matamua McCann & McKnight, 1980 , by original designation).

Diagnosis. Infraorbital and preopercular ridges tightly adjoined, forming continuous bony ridge; preopercular ridge elongate posteroventrally, sharply pointed at angle. Snout long, acute in lateral view in most species, tipped with stout scute. Scales on head ridges usually coarsely modified. Pelvic-fin rays almost always 7 (rarely 6); pelvic fin inserted below or posterior to vertical through pectoral-fin base. Leading edge of second spinous ray of first dorsal fin smooth (a few denticles occasionally found in distal portion in small individuals). Anus usually abutting or only slightly separated from anal-fin origin; periproct absent or rudimentary. Light organ present in most species. Chin barbel present and variously developed. No gill rakers on outer side of first gill arch (a few rudimentary rakers rarely found in large adults). Body scales large, spinules variable in shape; reticulate structure absent on unexposed portion (except for C. immaculatus Sazonov & Iwamoto, 1992 ). Grooved lateral line complete. Cephalic sensory canals without open pores. Branchiostegal rays 7. Color variable, some species with prominent body markings.

Remarks. Following Art. 32.5.2 of the ICZN (1999) and comments by Iwamoto (2008a), the original spelling of the generic name “ Coelorinchus ” is corrected to “ Coelorinchus ”; other subsequent spellings, including “ Caelorinchus ”, “ Coelorhynchus ”, and “ Caelorhynchus ”, are all considered here as incorrect subsequent spellings [see also Art. 33.3 of the ICZN (1999)]. Coelorinchus is by far the largest genus of the family, including about 120 valid species, with many species awaiting description ( Iwamoto & Williams 1999; Iwamoto et al. 2006, 2015; Nakayama & Endo 2017). Of these, 25 species are herein recorded form Japan and adjacent waters. According to a recent molecular phylogeny ( Roa-Varón & Ortí 2009), Macrourus Bloch, 1786 [“ Macrurus ” appeared in early literature but should be regarded as an incorrect subsequent spelling of this name; see also Art. 33.3 of the ICZN (1999)] is deeply nested within Coelorinchus , suggesting that the two genera are synonymous. In terms of morphology, Coelorinchus differs from Macrourus in that the second spinous ray of the first dorsal fin is smooth along its leading edge (vs. serrated in Macrourus ), but otherwise they are very similar. A more in-depth study is therefore required to revise their taxonomic status.

Key to species of Coelorinchus from Japan and adjacent waters

1a Anus distinctly separated from anal-fin origin, situated about midway between inner pelvic-fin bases and anal-fin origin .. .............................................................................................. 2

1b Anus immediately anterior to or only slightly separated from anal-fin origin....................................................................... 3

2a Mandibular teeth in 2 irregular rows; lateral nasal ridge soft, incompletely supported by nasal bone; suborbital ridge distinctly curved anteriorly in lateral view; body scales covered with moderately erect, knife-like to keel-like spinules in widely divergent rows................................... C. macrochir

2b Mandibular teeth in narrow band; lateral nasal ridge stout, completely supported by nasal bone; suborbital ridge straight from tip of snout to preopercle in lateral view; body scales covered with greatly reclined, needle-like spinules in tightly packed parallel rows............................................................. 5

3a Light organ externally discernible, its anterior margin extending to line connecting outer pelvic-fin bases or beyond (duct connecting anterior and posterior fossae often difficult to distinguish externally in species of the C. hubbsi group; see the Relationships of C. brevirostris ) .................................... 4

3b Light organ either discernible or not evident externally; if discernible, its anterior margin not reaching (usually far posterior to) line connecting outer pelvic-fin bases ........... 14

4a Lateral nasal ridge completely supported by nasal bone; anterior margin of light organ extending to line connecting outer pelvic-fin bases or only slightly beyond; snout relatively short, length 50–66% PRL ................................................... 5

4b Lateral nasal ridge incompletely supported by nasal bone; anterior margin of light organ extending well beyond line connecting outer pelvic-fin bases and almost reaching isthmus; snout relatively long, 60–90% PRL....................... 6

5a Small rudimentary dark spot between lateral line and pectoral-fin base (often difficult to distinguish or absent); anterior margin of light organ extending anteriorly beyond line connecting outer pelvic-fin bases; anus only slightly separated from anal-fin origin; barbel length 12–19% PRL .. ................................................................................ C. jordani

5b Prominent large dark blotch between lateral line and pectoral-fin base; anterior margin of light organ situated on line connecting outer pelvic-fin bases; anus situated about midway between inner pelvic-fin bases and anal-fin origin; barbel length 7–13% PRL ............................... C. kishinouyei

6a Anterior rays of second dorsal fin distinctly shorter than those of anal fin; interdorsal space usually greater than first dorsalfin base length; premaxillary teeth in long, tapered band, with posterior margin of tooth band almost reaching lateral corner of mouth ............................................................................... 7

6b Anterior rays of second dorsal fin about equal in height to those of anal fin; interdorsal space usually less than first dorsal-fin base length; premaxillary teeth in short, uniformly wide band, with posterior margin of tooth band falling far short of lateral corner of mouth.......................................... 10

7a Underside of head posterior to vertical through midorbit heavily scaled, but mandibular rami mostly naked anteriorly; spinules on body scales trihedral ................... C. formosanus

7b Underside of head including mandibular rami usually completely naked (a few scales or rudimentary scaly patches occasionally found on ventral surfaces of preopercles); spinules on body scales needle-like or narrowly triangular ... .............................................................................................. 8

8a Short black hair-like papillae (not free neuromasts) densely scattered over underside of head; spinules on body scales narrowly triangular; length of gill slit 26–29% PRL ............. .......................................................................... C. kamoharai

8b Short black hair-like papillae (not free neuromasts) absent on underside of head; spinules on body scales needle-like; length of gill slit 20–26% PRL........................................................ 9

9a Spinules on body scales arranged in subparallel to narrowly divergent rows; dark body markings not prominent, often difficult to distinguish; height of first dorsal fin 58–70% PRL; barbel length 11–18% PRL ............................ C. longissimus

9b Spinules on body scales arranged in quincunx order; dark vermiculations or small irregular spots prominently marked dorsally on body; height of first dorsal fin 81–100% PRL; barbel length 16–24% PRL ..................... C. multispinulosus

10a Body pale overall, lacking prominent markings; second spinous ray of first dorsal fin greatly elongate, height of first dorsal fin 139–220% PRL; when viewed dorsally lateral contour of snout broadly convex anteriorly, giving spadeshaped appearance to snout; chin barbel short, length 4–10% PRL; spinules on scales anterior to light organ rudimentary. ......................................................................... C. brevirostris

10b Body with prominent dark saddles, diagonal bars or blotch present on body, or if markings absent, body uniformly dark overall; first dorsal fin high, but second spinous ray not especially elongate, height of first dorsal fin 80–130% PRL (except for C. cingulatus , 107–156% PRL); when viewed dorsally, distal portion of snout narrowly attenuated, giving sharply pointed appearance to snout (except for juveniles); chin barbel moderately developed, length 9–19% PRL; spinules on scales anterior to light organ not rudimentary .... ............................................................................................. 11

11a Longitudinally elongate dark blotch between lateral line and pectoral fin, extending from above pectoral-fin base to below about second dorsal-fin origin; narrow dark stripe extending mid-laterally from pectoral-fin base to middle of tail or beyond..................................................................... C. hubbsi

11b Body color different from above........................................ 12

12a Prominent dark blotch between lateral line and pectoral-fin base; fine dark vermiculations over dorsal surface of head (uniformly dark brown in preserved specimens) ................... ......................................................................... C. matsubarai

12b No prominent dark blotch between lateral line and pectoralfin base; fine dark vermiculations absent on dorsal surface of head .................................................................................... 13

13a Second spinous ray of first dorsal fin greatly elongate (except for juveniles), height of first dorsal fin 107–156% PRL; snout length 79–86% PRL; dorsal profile of snout distinctly concave in lateral view; barbel length 10–13% PRL ..... C. cingulatus

13b Second spinous ray of first dorsal fin not elongate, height of first dorsal fin 92–106% PRL; snout length 60–72% PRL; dorsal profile of snout almost straight to gently concave in lateral view; barbel length 13–17% PRL .......... C. fuscigulus

14a Body scales covered with keel-like spinules in divergent rows; every spinule row complete, extending to posterior scale margin, giving harsh appearance to body surface; middle row not especially high and enlarged compared with adjacent rows; light organ externally discernible; anus slightly separated from anal-fin origin by a few scale rows ........... 15

14b Body scales covered with shield-like spinules in parallel to subparallel rows; lateral rows often incomplete, not extending to posterior scale margin; middle row notably higher, giving striated appearance to body surface; no external evidence of light organ; anus abutting anal-fin origin........................... 24

15a Underside of head mostly or completely scaled ................ 16

15b Underside of head almost entirely naked (oval scaly patches present on lower surfaces of preopercles in C. hexafasciatus and C. tokiensi s)................................................................. 20

16a About 6 prominent dark saddles on trunk and tail; lateral nasal ridge incompletely supported by nasal bone............. C. sheni

16b Dark saddles usually absent on body, if present, not prominent and restricted to tail; lateral nasal ridge completely supported by nasal bone...................................................................... 17

17a Underside of snout broadly naked (small to moderate scaly patches often present); internasal width 19–24% PRL, interorbital width 27–31% PRL ...................... C. leptorhinus

17b Underside of snout almost completely scaled, naked area confined along ventromedial line and/or narrow band above upper lip; internasal width 26–37% PRL, interorbital width 31–42% PRL ...................................................................... 18

18a Occipital scales usually covered with single row of spinules (rarely 2–3 rows)................................................ C. japonicus

18b Occipital scales covered with 4 or more rows of spinules..... ............................................................................................ 19

19a Spinules on occipital scales needle-like, erect, completely free from one another in each row, forming comb-like ridges; head and body uniformly dark brown ............ C. nox sp. nov.

19b Spinules on occipital scales keel-like (rarely knife-like), moderately reclined, basally adjoined from one another in various degrees in each row, forming saw-toothed ridges; in Japanese specimens, head and body darker dorsally, but distinctly paler ventrally.......................................... C. smithi

20a Several dark saddles on trunk and tail; lower surfaces of preopercles scaled; lateral nasal ridge incompletely supported by nasal bone; outer series of premaxillary tooth band enlarged .............................................................................. 21

20b No prominent dark saddles on trunk and tail; lower surfaces of preopercles completely or almost completely naked; lateral nasal ridge completely supported by nasal bone; outer series of premaxillary tooth band not enlarged ............................ 22

21a Snout relatively short, length 57–70% PRL............................ ..................................................................... C. hexafasciatus

21b Snout relatively long, length 70–85% PRL......... C. tokiensis

22a Spinules on occipital scales needle-like, forming comb-like ridges; nasal fossa usually naked (a few scales rarely found anteroventrally); interdorsal length 51–71% PRL ...... C. hige

22b Spinules on occipital scales keel-like, forming saw-toothed ridges; nasal fossa usually heavily scaled (only sparsely scaled in some specimens); interdorsal length 33–54% PRL ............................................................................................ 23

23a Snout relatively short, length 60–88% PRL; length of terminal snout scute 7–18% PRL; height of first dorsal fin 85–107% PRL ................................................................. C. anatirostris

23b Snout very long, length 107% PRL; length of terminal snout scute 27% PRL; height of first dorsal fin 84% PRL .............. ........................................................... C. lanceolatus sp. nov.

24a Underside of head almost entirely naked; nasal fossa usually lacking scales; free neuromasts on underside of head modified into prominent, knob-like or flap-like projections ................. ................................................................................ C. gilberti

24b Underside of head almost completely scaled; nasal fossa usually heavily scaled; free neuromasts on underside of head not especially enlarged....................................................... 25

25a Occipital scales covered with divergent rows of spinules ...... ............................................................................ C. divergens

25b Occipital scales covered with single row of spinules ............ ....................................................................... C. parallelus