Pseudonezumia japonica Okamura, 1970

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 275-276

Pseudonezumia japonica Okamura, 1970

[Japanese name: Nihon-sokodara]

( Figs. 187 C–D, 188–189; Appendix 3-11E)

Pseudonezumia japonicus Okamura, 1970a:39 , pl. XIII, text-fig. 20 [original description; holotype: BSKU 14203 , from “off Choshi ”, Chiba Pref., 36º19′08ʺN, 141º14′00ʺE (off Mito, Ibaraki Pref.), in 1690 m; new Japanese name: “ Nihonsokodara ”].

Pseudonezumia japonica: Okamura 1970b : table 1 (listed; Japan); Tominaga & Uyeno 1981:489 (listed; Japan); Okamura 1984b:95, pl. 81, fig. K (compiled); Okamura 1988:95, pl. 81, fig. K (compiled); Nakabo 1993:356 (in key; Japan); Nakabo 2000:420 (in key; Japan); Nakabo 2002:420 (in key; Japan); Nakabo & Kai 2013:496 (in key; Japan); Motomura 2020:39 (listed; Japan).

Diagnosis. Underside of snout broadly naked above upper lip; spinules on body scales supported by narrowly developed buttresses; transverse scale rows below first dorsal-fin origin 8.5–12.5, below first dorsal-fin midbase 7–12; orbit diameter 22–28% HL; preoral length 20–26% HL; postorbital length 42–48% HL; orbit–preopercle distance 34–43% HL; interorbital width 29–36% HL; barbel length 8–13% HL; caudal depth at base of 40th anal-fin ray 27–34% HL; body uniformly dusky to paler brown, except for darker abdomen and black periproct.

Material examined. 31 specimens. Holotype of Pseudonezumia japonicus: BSKU 14203 (46.0 mm HL, 303 mm TL), off Mito , Ibaraki Pref., Japan, 36.3189ºN, 141.2333ºE, 1690 m, 3 Dec. 1967. Non-types: Japan: BSKU 56944 (1, 47.2 mm HL, 325 mm TL), BSKU 56945 (1, 43.6 mm HL, 258+ mm TL), BSKU 56946 (1, 46.7 mm HL, 290+ mm TL), BSKU 56947 (1, 44.9 mm HL, 280+ mm TL), BSKU 56948 (1, 48.7 mm HL, 274+ mm TL), BSKU 56949 (1, 38+ mm HL, 274+ mm TL), BSKU 56950 (1, 48.8 mm HL, 302+ mm TL), BSKU 56951 (1, 42.6 mm HL, 306 mm TL), BSKU 56952 (1, ca. 39 mm HL, 253+ mm TL), BSKU 56953 (1, 43.8 mm HL, 214+ mm TL), BSKU 56954 (1, 39.9 mm HL, 287+ mm TL), BSKU 56955 (1, 36.5 mm HL, 244+ mm TL), BSKU 56956 (1, 43.5 mm HL, 285+ mm TL), BSKU 56957 (1, 47.3 mm HL, 289+ mm TL), BSKU 56958 (1, 49.5 mm HL, 332+ mm TL), BSKU 56959 (1, 48.5 mm HL, 286+ mm TL), BSKU 56960 (1, 47.0 mm HL, 224+ mm TL), BSKU 56961 (1, 44.4 mm HL, 307+ mm TL), BSKU 56963 (1, 47.8 mm HL, 331+ mm TL), BSKU 56964 (1, 47.4 mm HL, 215+ mm TL), BSKU 56965 (1, ca. 45 mm HL, 288+ mm TL), BSKU 56966 (1, 43.8 mm HL, 273+ mm TL), BSKU 56967 (1, 43.1 mm HL, 297 mm TL), BSKU 56969 (1, 40.5 mm HL, 272 mm TL), BSKU 56971 (1, ca. 36 mm HL, 218+ mm TL), BSKU 56972 (1, 32.9 mm HL, 165+ mm TL), BSKU 56973 (1, ca. 36 mm HL, 231+ mm TL), BSKU 56974 (1, 41.7 mm HL, 270+ mm TL), BSKU 56975 (1, ca. 43 mm HL, 195+ mm TL), off Hitachi, 36.4205ºN, 141.5420ºE, 1845–1948 m, FRV Wakataka-maru, sta. 62, coll. H. Endo, 10 Nov. 1995 ; BSKU 56976 (1, 50.5 mm HL, 273+ mm TL), off Kamaishi, 39.3797ºN, 143.1282ºE, 1949–2005 m, FRV Wakataka-maru, sta. 59, coll. H. Endo, 7 Nov. 1995.

Counts and measurements. Based on 31 specimens (31.9–50.5 mm HL, 165+–332+ mm TL). Counts: first dorsal-fin rays II,8–10; pectoral-fin rays i14–i19; pelvicfin rays 6; longitudinal scales 49–61; transverse scale rows below first dorsal-fin origin 8.5–12.5, below first dorsal-fin midbase 7–12, below second dorsal-fin origin 9–12; pyloric caeca 8–10.

The following measurements are in% of HL, followed by those in % of PRL in parentheses: snout length 33–38 (48–58); orbit diameter 22–28 (31–40); postorbital length 42–48 (63–69); postrostral length 66–71; orbit–preopercle distance 34–43 (51–61); suborbital width 15–19 (24–28); upper-jaw length 25–33 (37–49); preoral length 20–26 (29–39); snout width 32–40 (47–58); internasal width 26–34 (38–49); interorbital width 29–36 (43–54); body width over pectoral-fin bases 30–56 (45–82); body depth at first dorsal-fin origin 63–89 (101–130); body depth at anal-fin origin 58–76 (86–112); caudal depth at base of 40th anal-fin ray 27–34 (40–49); prepelvic length 93–108 (134–164); preanus length 120–135 (170–198); preanal length 128–142(182–209); isthmus–pelvic distance 23–31 (33–46); isthmus–anus distance 49–62 (69–90); isthmusanal distance 57–71 (80–104); pelvic–anal distance 34– 44 (50–66); anus–anal distance 5–12 (8–18); pelvic-fin length 28–54 (40–81); pectoral-fin length 32–64 (47–91); predorsal length 103–119 (158–174); height of first dorsal fin 71–83 (102–120); length of first dorsal-fin base 19–27 (29–39); interdorsal length 33–48 (48–); length of gill slit 12–17 (19–24); length of posterior nostril 6–11 (9–17); barbel length 8–13 (12–19).

Size. To about 33 cm TL ( BSKU 56958 , 332 + mm TL, off Hitachi , Ibaraki Pref., Japan) .

Distribution. Restricted to Japan (Appendix 3-11E). Depth range 1453‾ 2005 m.

Remarks. For further morphological information see the original description given by Okamura (1970a). Pseudonezumia japonica was described from a single specimen collected from off Mito, Ibaraki Pref., Japan ( Fig. 189 ), as a new genus and species of grenadiers. Okamura (1970a) considered this species to be quite different from other grenadiers in having eight branchiostegal rays (vs. six or seven). However, an examination of additional specimens from the type locality showed that the number is usually seven, and only rarely eight.

Relationships and comparisons. Pseudonezumia japonica is closely similar to P. cetonuropsis ( Gilbert & Hubbs, 1916) also known from Japan. These two species are tentatively regarded as valid in this study, but a further investigation based on additional material may arrive at a different conclusion, namely, P. japonica is synonymized with P. cetonuropsis (see the Relationships and comparisons of the latter species).

Figures

FIGURE 187. Scanning electron micrographs showing body scales (from the dorsum below the interdorsal space) of two species of Pseudonezumia. (A–B) P. cetonuropsis, NSMT-P 78831, 48.8 mm HL; (C–D) P. japonica, BSKU 56976, 50.5 mm HL. (A, C) Views from above; (B, D) oblique views. [Photos: N. Nakayama]

FIGURE 189. Holotype of Pseudonezumia japonicus (= P. japonica). BSKU 14203, 46.0 mm HL, 303+ mm TL, off Mito, Ibaraki Pref., Pacific, 1690 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]