Ventrifossa rhipidodorsalis Okamura 1984

Ventrifossa rhipidodorsalis Okamura, 1984 [Japanese name: Homae-hige]

(Figs. 205 C–D, 214–215; Appendix 3-13C)

Ventrifossa nigrodorsalis (not Gilbert & Hubbs 1920): Okamura 1982:147, 348, fig. 90 [first record from Japan; new Japanese name:“Homae-hige”; brief description; 2 spec. from Tosa Bay; photo based on BSKU 29495 (paratype of V. rhipidodorsalis)]; Ohta 1983: table A (listed; Suruga Bay).

Ventrifossa rhipidodorsalis Okamura, 1984a:205, fig. 146 (original description; holotype: BSKU 27695, from Okinawa Trough, 28º42.0ʹN, 127º09.0ʹE, in 500–535 m; 23 paratypes from Okinawa Trough and Tosa Bay, in 220–650 m); Okamura 1984b:93, pl. 81, fig. D (compiled); Okamura 1988:93, pl. 81, fig. D (compiled); Nakabo 1993:358 (in key; Japan); Okamura 1997:128, fig. 11 (compiled); Nakabo 2000:422 (in key; Japan); Shinohara et al. 2001:306 (listed; Tosa Bay); Nakabo 2002:422 (in key; Japan); Yoda et al. 2002:11 (listed; East China and Yellow Seas); Chiou et al. 2004a:48, fig. 22, table 1 (brief description; 13 spec. from Nan-fang-ao; first record from Taiwan); Shinohara et al. 2005:418 (listed; Ryukyu Islands); Suetsugu & Ohta 2005: table 3 (listed; Enshu-nada); Shao et al. 2008b: table 2 (53 spec. listed from northeastern, southeastern, and southwestern Taiwan, and South China Sea); Furuhashi et al. 2010: table 2 (2 spec. listed from northern Okinawa Trough); Nakabo & Kai 2013:498 (in key; Japan); Iwamoto et al. 2015:115 [brief description; 82 spec. from northeastern Taiwan, Japan (including holotype), and Philippines]; Nakae et al. 2018:219 (1 spec. listed from Amami-oshima Island, Kagoshima Pref.); Motomura 2020:40 (listed; Japan).

Ventrifossa longibarbata (not Okamura 1984a): Okamura 1997:128, fig. 10 [in part, photo based on BSKU spec. (catalog no. unknown)].

Diagnosis. Second spinous ray of first dorsal fin finely serrated along its leading edge; large intense black spot on center of first dorsal fin; anal fin dusky, with narrow blackish margin anteriorly; front of premaxillary ascending process pale; oral cavity pale; median rostral ridge lacking narrow blackish streak; leading edges of snout, supranarial ridges, and suborbital shelves prominently marked with black; dorsum not strongly demarcated in color from rest of body; snout low, slightly protruding beyond upper jaw, preoral length 11–19% HL; no scute-like scale at snout tip; body scales covered with short, moderately erect, needle-like spinules in quincunx order; spinules on scales along second dorsal-fin base not enlarged; body scales moderately small, transverse scale rows below midbase of first dorsal fin 6.5–7.5, below second dorsal-fin origin 6.5–8; longitudinal scales 37–49; area of spinuleless scales posterior to first dorsal-fin base only narrowly developed; outer series of premaxillary teeth slightly enlarged; mandibular teeth arranged in narrow tapered band; suborbital shelf not greatly constricted anteriorly; inner gill rakers on first arch 15–17, outer gill rakers on second arch 14–17; orbit large, greatest diameter 29–35% HL; upper-jaw length 42–47% HL; interorbital space moderately narrow, width 20–27% HL; chin barbel moderately long, length 16–26% HL; pectoral-fin length 57–70% HL.

Material examined. 37 specimens. Holotype of Ventrifossa rhipidodorsalis: BSKU 27695 (62.2 mm HL, 328+ mm TL), west-northwest of Amami-oshima Island, Kagoshima Pref., Japan, Okinawa Trough, East China Sea, 28.7000ºN, 127.1500ºE, 500–535 m, F/ V Ryoanmaru, No. 28, tr. 50, bottom trawl, coll. Y. Kinoshita and S. Hagino, 11 Mar. 1978. Paratypes of V. rhipidodorsalis: * BSKU 29571 (1, 57.2 mm HL, 315+ mm TL), northwest of Miyako-jima Island, Okinawa Trough, 25.7900ºN, 124.3900ºE, 600 m, F/ V Yuryo-maru, No. 8, sta. 1-T13, bottom trawl, coll. T. Kitajima, 20 Sept. 1979; * BSKU 28599 (1, ca. 41 mm HL, 241+ mm TL), northwest of Amami-oshima Island, Okinawa Trough, 29.9500ºN, 128.0000ºE, 585–610 m, F/ V Ryoan-maru, No. 28, tr. 76, bottom trawl, coll. Y. Kinoshita and S. Hagino, 20 Mar. 1978; BSKU 27184 (1, 51.7 mm HL, 269+ mm TL), BSKU 27190 (1, 32.8 mm HL, 187+ mm TL), BSKU 27191 (1, 40.7 mm HL, 225+ mm TL), northwest of Amamioshima Island, Okinawa Trough, 29.4333ºN, 127.5167ºE, 570 m, F/ V Yuryo-maru, No. 8, tr. 22, bottom trawl, coll. Y. Kinoshita and S. Hagino, 5 Feb. 1978; BSKU 27123 (1, 50.1 mm HL, 265+ mm TL), BSKU 27146 (1, 54.2 mm HL, 209+ mm TL), northwest of Amami-oshima Island, Okinawa Trough, 29.3833ºN, 127.5150ºE, 650 m, F/ V Yuryo-maru, No. 8, tr. 21, bottom trawl, coll. Y. Kinoshita and S. Hagino, 5 Feb. 1978; * BSKU 27915 (1, 54.0 mm HL, 229+ mm TL), * BSKU 27916 (1, 46.6 mm HL, 246+ mm TL), BSKU 27917 (1, 30.2 mm HL, 171+ mm TL), northwest of Amami-oshima Island, Okinawa Trough, 28.7500ºN, 127.1167ºE, 520–542 m, F/ V Ryoanmaru, No. 28, tr. 58, bottom trawl, coll. Y. Kinoshita and S. Hagino, 16 Mar. 1978; BSKU 27660 (1, 58.6 mm HL, 313+ mm TL), BSKU 27661 (1, 54.1 mm HL, 226+ mm TL), BSKU 27663 (1, 51.7 mm HL, 264+ mm TL), west of Okinawa-jima Island, Okinawa Trough, 28.7333ºN, 127.0167ºE, 610–640 m, F/ V Ryoan-maru, No. 28, tr. 49, bottom trawl, coll. Y. Kinoshita and S. Hagino, 11 Mar. 1978; BSKU 27694 (1, 66.6 mm HL, 354+ mm TL), BSKU 27696 (1, 47.7 mm HL, 262+ mm TL), * BSKU 27698 (1, 34.3 mm HL, 191+ mm TL), * BSKU 29697 (1, 34.6 mm HL, 201+ mm TL), collected with holotype; BSKU 27858 (1, 42.6 mm HL, 172+ mm TL), BSKU 27861 (1, 58.8 mm HL, 268+ mm TL), * BSKU 27862 (1, 46.3 mm HL, 259+ mm TL), BSKU 27865 (1, 52.8 mm HL, 262+ mm TL), northwest of Amami-oshima Island, Okinawa Trough, 28.5833ºN, 127.0000ºE, 600 m, F/ V Ryoan-maru, No. 28, tr. 57, bottom trawl, coll. Y. Kinoshita and S. Hagino, 16 Mar. 1978; BSKU 30498 (1, 30.8 mm HL, 156+ mm TL), Tosa Bay, 32.9667ºN, 133.5333ºE, 605 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, bottom trawl, coll. O. Okamura et al., 21 Dec. 1979; BSKU 29495 (1, 28.6 mm HL, 168 mm TL), Tosa Bay, 32.9667ºN, 133.5333ºE, 605 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, cr. 4- Ky, tr. 19, bottom trawl, coll. O. Okamura et al., 21 Dec. 1979. Non-types: Japan: BSKU 109208 (1, 46.0 mm HL, 196+ mm TL), off Amami, East China Sea, 28.5679ºN, 127.0421ºE, 607 m, T/ V Nagasaki-maru, cr. N365, sta. J6, tr. 1, 3-m ORE beam trawl, coll. N. Nakayama, 16 Nov. 2012; BSKU 101640 (1, 48.9 mm HL, 282+ mm TL), BSKU 101641 (1, 48.7 mm HL, 270+ mm TL), off Muroto, Tosa Bay, 360–435 m, bottom trawl, 9 Jun. 1968; BSKU 45012 (1, 48.4 mm HL, 276+ mm TL), BSKU 45013 (1, 44.9 mm HL, 247+ mm TL), Tosa Bay, 500 m, FRV Kotaka-maru, otter trawl, 23 Aug. 1988; BSKU 48169 (1, 61.1 mm HL, 343+ mm TL), BSKU 99329 (1, 51.7 mm HL, 293+ mm TL), BSKU 99330 (1, 38.6 mm HL, 212+ mm TL), BSKU 99331 (1, 43.0 mm HL, 255+ mm TL), BSKU 99332 (1, 54.4 mm HL, 313+ mm TL), BSKU 99334 (1, 54.7 mm HL, 308+ mm TL), BSKU 99335 (1, 63.4 mm HL, 336+ mm TL), BSKU 99338 (1, 48.6 mm HL, 269+ mm TL), off Kochi, 600 m, bottom trawl, 24 Mar. 1989.

Counts and measurements. Based on 30 specimens (29–66.1 mm HL, 158+–353+ mm TL). Counts: first dorsal-fin rays II,10–12; pectoral-fin rays i19–i25; pelvic-fin rays 8–10; gill rakers on first arch (outer/inner) 9–16/15–17, on second arch 14–17/14–18; longitudinal scales 37–49; transverse scale rows below first dorsalfin origin 7.5–11.5, below first dorsal-fin midbase 6–7.5, below second dorsal-fin origin 6.5–8.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 26–31 (34–43); orbit diameter 29–35 (38–46); postorbital length 41–48 (54–64); postrostral length 72– 79; orbit–preopercle distance 39–44 (52–60); suborbital width 11–14 (14–19); upper-jaw length 42–47 (56–62); length of rictus 36–40 (48–54); length of premaxillary tooth band 31–35 (40–47); preoral length 11–19 (15–25); distance between tip and lateral angle of snout 13–19 (18–26); snout width 23–31 (30–42); internasal width 18– 22 (23–30); interorbital width 20–27 (27–35); occipital width 12–16 (16–21); body width over pectoral-fin bases 37–65 (50–84); body depth at first dorsal-fin origin 76– 101 (100–130); body depth at anal-fin origin 64–86 (86– 114); prepelvic length 99–117 (127–156); preanus length 106–128 (135–170); preanal length 130–149 (166–198); isthmus–pelvic distance 42–55 (57–73); isthmus–anus distance 51–63 (68–83); isthmus–anal distance 69–87 (93–115); pelvic–anal distance 29–43 (40–58); anus–anal distance 18–30 (25–40); pelvic-fin length 36–47 (45–62); pectoral-fin length 57–70 (75–93); predorsal length 107– 119 (141–157); height of first dorsal fin 71–84 (95–111); length of first dorsal-fin base 25–33 (34–44); interdorsal length 43–64 (58–85); length of gill slit 22–29 (30–38); length of posterior nostril 3–5 (3–7); barbel length 16–26 (21–35).

Size. To about 35 cm TL (BSKU 27694, 353 + mm TL, paratype, Okinawa Trough, Japan).

Distribution. Distributed in the western Pacific from Japan to the Philippines (Chiou et al. 2004a; Shao et al. 2008a, 2008b; Iwamoto et al. 2015; this study); In Japanese waters, known from off the Pacific coasts northward to the Izu Peninsula (138.96ºE) and the Okinawa Trough in the East China Sea (Appendix 3-13C). Depth range 315‾ 1165 m. Uncommon.

Remarks. Ventrifossa rhipidodorsalis was originally described from the Okinawa Trough (type locality) and Tosa Bay by Okamura (1984a), to which the reader can refer for further morphological information. The two paratypes from Tosa Bay were initially reported as V. nigrodorsalis Gilbert & Hubbs, 1920 by Okamura (1982).

Relationships and comparisons. Among northwestern Pacific congeners, this species is most similar to V. nigrodorsalis, but readily differs from the latter in having a black anterodistal margin of the anal fin (vs. uniformly pale), higher counts of gill rakers (15–17 vs. 13–15 on the inner side of the first arch; 14–17 vs. 13–14 on the outer side of the second arch; and 14–18 vs. 12–13 on the inner side of the second arch), a larger mouth (upper-jaw length 42–47% HL vs. 38–40%), and a narrower interorbital space (20–27% HL vs. 27–29%).