Macrouridae Bonaparte, 1831

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 15-16

Family Macrouridae Bonaparte, 1831 (sensu Iwamoto et al. 2015)

[Japanese name: Sokodara-ka]

Diagnosis. Two dorsal fins well separated; first dorsal fin high and short-based; second dorsal fin long-based, poorly developed throughout its length; anal fin similar to, but usually much deeper than second dorsal fin; pelvic fin well developed with 5 or more soft rays; tail greatly elongate, without either caudal fin or caudal peduncle (pseudocaudal occasionally present and variously developed); mouth usually inferior to subterminal (rarely terminal); outermost gill slits restricted by skin folds attached to upper and lower ends of gill arch; gill rakers tubercular, not slender or lath-like; posttemporal fossa absent; body scales almost always ctenoid.

Remarks. This study confirms the occurrence of 76 grenadier species belonging to 18 genera from Japan and adjacent waters, of which 70 species in 15 genera are recognized within Japan’s EEZ.

Key to genera of grenadiers from Japan and adjacent waters

1a Infraorbital and preopercular ridges tightly adjoined, forming continuous bony ridge; preopercular ridge elongate posteroventrally and sharply pointed at posteroventral angle; snout long, protruding well beyond upper jaw, acutely pointed in lateral view in most species ......... Coelorinchus (25 spp.)

1b Infraorbital ridge not connected with preopercular ridge, separated by distinct gap; preopercular ridge not elongate posteroventrally nor sharply pointed at posteroventral angle; snout relatively short, moderately to scarcely protruding beyond upper jaw, conical to broadly rounded in lateral view .............................................................................................. 2

2a Anus (or periproct, if developed) abutting or only slightly separated from anal-fin origin.............................................. 3

2b Anus (or periproct, if developed) distinctly separated by several scale rows from anal-fin origin............................... 11

3a Gular region covered with net-like pattern or striation of black epithelium; broad areas of fine (microscopic), parallel, black lines (ventral striae) extending on ventral surfaces of chest, shoulder girdle, and belly, and along each side of isthmus; small lens-like structure of light organ on chest .................. 4

3b Gular region uniformly pale, dusky, dark, or blackish; ventral striae absent; no lens-like structure of light organ on chest anterior to pelvic fins ........................................................... 6

4a Gular region covered with net-like pattern of black epithelium; nasal bones stout, forming 3 horizontally flattened projections; outer pelvic-fin ray flattened, with narrow ribbon-like flange on free distal portion ........... Spicomacrurus ( S. kuronumai )

4b Gular region covered with striated pattern of black epithelium; nasal bones weak, usually paper-thin, not forming horizontal projections; outer pelvic-fin ray not flattened distally ......... 5

5a Second spinous ray of first dorsal fin smooth along its leading edge; trunk moderately deep, laterally compressed in cross section .......................................... Hymenocephalus (6 spp.)

5b Second spinous ray of first dorsal fin serrated along its leading edge; trunk shallow, almost cylindrical in cross section ......... .................................................... Hymenogadus ( H. gracilis )

6a Ventral aspects of body well forward so that anal-fin origin distinctly anterior to hind margin of first dorsal-fin base; scales on infraorbital ridge modified into coarsely spinulated, adherent scutes ............... * Sphagemacrurus ( S. pumiliceps )

6b Ventral aspects of body not well forward, and anal-fin origin below or posterior to hind margin of first dorsal-fin base; scales on infraorbital ridge normal or only slightly thickened .............................................................................................. 7

7a Second spinous ray of first dorsal fin smooth along its leading edge; periproct large, occupying more than half of distance between inner pelvic-fin bases to anal-fin origin; scales along anterior part of anal-fin base enlarged ................................... ...................................................... Trachonurus ( T. villosus )

7b Second spinous ray of first dorsal fin serrated along its leading edge; periproct small, its anterior margin far posterior to midway between inner pelvic-fin bases and anal-fin origin; scales along anterior part of anal-fin base not especially enlarged ................................................................................ 8

8a Head massive, soft, inflated, and broad; scales along anterior part of second dorsal-fin base enlarged.................................. ....................................................... Cetonurus ( C. globiceps )

8b Head not inflated, moderately compressed laterally; scales along anterior part of second dorsal-fin base not especially enlarged ................................................................................ 9

9a Periproct absent or rudimentary; reticulate structure absent on unexposed portion of body scales; branchiostegal rays 6 ...... ...................................................... Coryphaenoides (15 spp.)

9b Periproct narrow but distinct; reticulate structure broadly developed on unexposed portion of body scales; branchiostegal rays 7–8.............................................................................. 10

10a Dorsal surface of snout broadly naked anterior to line connecting lateral angles of snout; underside of head almost completely naked; posterior margin of upper jaw extending to vertical through hind rim of orbit or beyond; spinules on body scales arranged in widely spaced subparallel to slightly divergent rows..................... Asthenomacrurus ( A. victoris )

10b Dorsal surface of snout fully scaled; naked areas on underside of head confined to area above upper lip and anterior portions of mandibular rami; posterior margin of upper jaw not reaching vertical through hind rim of orbit; spinules on body scales arranged in quincunx order ........................................ ....................................................... Pseudonezumia (2 spp.)

11a Premaxillary teeth fang-like, arranged in 1 distinct row; chin barbel absent; trunk strongly compressed............................. ............................................ Odontomacrurus ( O. murrayi )

11b Premaxillary teeth not fang-like, relatively small, arranged in 2 or more rows; chin barbel present, variously developed; trunk moderately compressed ........................................... 12

12a Second spinous ray of first dorsal fin smooth along its leading edge; mandibular teeth arranged in 1 or 2 rows ............... 13

12b Second spinous ray of first dorsal fin variously serrated along its leading edge; mandibular teeth arranged in narrow to wide band...................................................................... 15

13a Mandibular teeth arranged in 2 irregular rows, with inner row slightly enlarged ............................................................ * Ventrifossa (in part; subgenus Atherodus : V. macroptera )

13b Mandibular teeth arranged in 1 distinct row..................... 14

14a Anterior dermal window of light organ large, bean-shaped, laterally expanded; mandibular teeth widely spaced canines; lower portion of gill membranes narrowly scaled along branchiostegal rays ....... Malacocephalus ( M. nipponensis )

14b Anterior dermal window of light organ small and circular; mandibular teeth small, not enlarged, tightly arranged; branchiostegal membranes entirely naked............................. ................................... Pseudocetonurus (P. sp. cf. septifer )

15a Dorsal surface of snout broadly naked anterior to line connecting lateral angles of snout....... Kumba ( K. japonica )

15b Dorsal surface of snout completely or almost completely scaled ................................................................................ 16

16a Scales on infraorbital ridge modified into coarsely spinulated, adherent scutes.................................................................. 17

16b Scales on infraorbital ridge not especially modified ........ 18

17a Anus closer to pelvic-fin bases than to anal-fin origin; ventral aspects of body not positioned forward, and anal-fin origin below or posterior to hind margin of first dorsal-fin base .... .................................................................. Nezumia (7 spp.)

17b Anus closer to anal-fin origin than to pelvic-fin bases; ventral aspects of body positioned forward so that anal-fin origin distinctly anterior to hind margin of first dorsal-fin base ...... ...................................... * Sphagemacrurus ( S. pumiliceps )

18a Posterior margin of upper jaw extending beyond vertical through midorbit; posterior end of premaxillary tooth band extending beyond hind margin of maxillary process............ ................* Ventrifossa (in part; subgenera Sokodara and Ventrifossa : 7 spp.)

18b Posterior margin of upper jaw not or barely reaching vertical through midorbit; posterior end of premaxillary tooth band falling short of hind margin of maxillary process............. 19

19a Reticulate structure present on unexposed portion of body scales; body uniformly dark to blackish; posterior dermal window of light organ scarcely discernible externally ......... .......................................................... Kuronezumia (2 spp.)

19b Reticulate structure absent on body scales; body pale to dusky; posterior dermal window of light organ prominent, much larger than anterior window ........................................ ......................................... Lucigadus ( L. nigromarginatus )