Hymenocephalus papyraceus Jordan & Gilbert

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 215-218

Hymenocephalus papyraceus Jordan & Gilbert in Jordan & Starks, 1904

[Japanese name: Kamidara]

( Figs. 141–142 ; Appendix 3-8D)

Hymenocephalus papyraceus Jordan & Gilbert in Jordan & Starks, 1904:614, unnumbered fig. [original description; holotype: USNM 50935, from Sagami Bay, Albatross sta. 3697, in 120–265 ftm (220–485 m)]: Jordan et al. 1913:412, fig. 382 (listed; Japan; new Japanese name: “Kami-dara”); Okada & Matsubara 1938:452 (in key; Japan); Matsubara 1955:1315 (in key; Japan); Matsubara 1965:508 (compiled; Japan); Okamura 1970a:56, pl. XVII, text-fig. 24 [description; 1 spec. from off the east coast of southern Japan, probably in Sagami or Suruga Bays (BSKU 14205)]; Okamura 1970b: table 1 (listed; Japan); Tominaga & Uyeno 1981:489 (listed; Japan); Okamura 1984b:92, pl. 344, fig. I (compiled); Okamura 1988:92, pl. 344, fig. I (compiled); Sazonov 1993:117 (East China Sea); Senou et al. 2006:421 (listed; Sagami Sea); Shinohara & Williams 2006:551, fig. 2-L (listed; Sagami Sea; misspelled “ papiraceus ” in figure legend); Nakabo & Kai 2013:495 (in key; Japan); Schwarzhans 2014:37, fig. 14F–J (description; comparison; in key); Iwamoto et al. 2015:76, fig. 12 (brief description; 1 spec. from Da-xi; first record from Taiwan); Iwatsuki et al. 2017:32 (listed; Hyuga-nada); Motomura 2020:39 (listed; Japan).

Hymenocephalus papiraceus [sic]: Nakabo 1993:355 (in key; Japan); Nakabo 2000:419 (in key; Japan); Nakabo 2002:419 (in key; Japan).

Diagnosis. A species of Hymenocephalus with 11 or 12 pelvic-fin rays; barbel rudimentary, length 2–4% PRL; snout high, not depressed, length 41–52% PRL; orbit diameter 33–46% PRL; interorbital width 37–52% PRL; orbit–preopercle distance 59–71% PRL; suborbital width 22–26% PRL; first dorsal-fin rays II,9–11; pectoralfin rays i12–i15; gill rakers on first arch (outer/inner) 13–18/19–24, on second arch 18–22/15–21; small but prominent black melanophores densely scattered over trunk and tail, giving dark appearance to body; caudal vertebrae barely visible from outside; ostial and caudal colliculi of otolith not fused.

Material examined. 9 specimens. Holotype of Hymenocephalus papyraceus: USNM 50935 (25.1 mm HL, 113+ mm TL), off Manazuru, Sagami Bay, Japan, 35.1333ºN, 139.1667ºE, 120–265 ftm (220–485 m), Albatross sta. 3697, 8-ft Tanner beam trawl, 5 Mar. 1900. Non-types: Japan: BSKU 101959 (1, 32.3 mm HL, 139+ mm TL), east of Yoron-jima Island, 27.1133ºN, 128.6983ºE, 870–945 m, R/V Hakuho-maru, cr. KH-73- 02, sta. 4, 3-m beam trawl, coll. S. Ohta, 24 Feb. 1973; ZMMGU P.18258 (1, 35.0 mm HL, 125+ mm TL), west of Yaku-shima Island, Okinawa Trough, 30.5167ºN, 129.3167ºE, 800–826 m, R/V Vityaz’, cr. 25, sta. 3768, Galatea trawl, date unknown; BSKU 44761 (1, 29.7 mm HL, 176 mm TL), Tosa Bay, 600 m, FRV Kotaka-maru, otter trawl, 16 May 1988; BSKU 44292 (1, 32.2 mm HL, 137+ mm TL), BSKU 44296 (1, 34.6 mm HL, 163+ mm TL), BSKU 44297 (1, 32.9 mm HL, 129+ mm TL), Tosa Bay, 600 m, FRV Kotaka-maru, otter trawl, 17 Nov. 1987; BSKU 20312 (1, 28.5 mm HL, 129+ mm TL), off Atami, Sagami Bay, 35.0783ºN, 139.1467ºE, 450 m, FRV Soyo-maru, sta. T10, beam trawl, 24 Nov. 1972; BSKU 99483 (1, 35.7 mm HL, 177+ mm TL), off Pacific coast of southern Japan, date unknown.

Counts and measurements. Based on 9 specimens (25.1–35.7 mm HL, 113+–177+ mm TL). Counts: first dorsal-fin rays II,9–11; pectoral-fin rays i12–i15; pelvicfin rays 11–12; gill rakers on first arch (outer/inner) 13– 18/19–24, on second arch 18–22/15–21; transverse scale rows below first dorsal-fin origin 3.5, below first dorsalfin midbase 4.

The following measurements are in% of HL, followed by those in % of PRL in parentheses: snout length 30–36 (41–52); orbit diameter 24–31 (33–46); postorbital length 45–50 (63–67); postrostral length 69–75; orbit–preopercle distance 43–49 (59–71); suborbital width 16–19 (22–26); upper-jaw length 45–49 (61–69); length of rictus 38 (53); length of premaxillary tooth band 36–37 (49–50); preoral length 20–29 (28–39); distance between tip and lateral angle of snout 21–26 (28–35); snout width 32–38 (44–53); internasal width 24–29 (34–39); interorbital width 27–36 (37–52); body width over pectoral-fin bases 29–49 (40– 66); body depth at first dorsal-fin origin 66–74 (91–103); body depth at anal-fin origin 40–46 (56–64); prepelvic length 105–122 (144–168); preanus length 152–168 (207– 232); preanal length 154–171 (211–237); isthmus–pelvic distance 44–54 (60–74); isthmus–anus distance 105–120 (140–165); isthmus–anal distance 92–123 (126–169); pelvic–anal distance 53–74 (72–102); pelvic-fin length 59 (79); pectoral-fin length 65 (95); predorsal length 98–107 (135–152); length of first dorsal-fin base 27–34 (36–47); interdorsal length 43–59 (58–); length of gill slit 25–28 (34–39); barbel length 1–3 (2–4).

Size. To at least 18 cm TL (BSKU 99483, 177+ mm TL, off southern Japan).

Development. Endo (2014) provided a brief description of a juvenile (9.6 mm HL) collected from Sagami Bay.

Distribution. Restricted to Japan and Taiwan ( Sazonov 1993; Schwarzhans 2014; Iwamoto et al. 2015; this study; Appendix 3-8D). Capture depths 220‾ 945 m. Uncommon.

Remarks. For further morphological details see the original description ( Jordan & Gilbert in Jordan & Starks 1904) and a redescription given by Sazonov (1993); otolith morphology was fully described by Schwarzhans (2014).

Hymenocephalus papyraceus was originally described from a single specimen collected from Sagami Bay ( Fig. 142 ). Subsequently, Okamura (1970a) reported one additional specimen from “off the east coast of southern Japan ” (probably from Sagami or Suruga Bays). Because his specimen(BSKU 14205) is badly deteriorated, it was impossible to confirm the identification with certainty. Sazonov (1993) also provided a redescription of the species based on a specimen collected from the East China Sea off Yaku-shima Island. During the course of this study, a total of 14 specimens was newly found among the collection of Kochi University (BSKU) and the Natural History Museum and Institute, Chiba (CBM), 11 of which were used in Schwarzhans’ (2014) review of the genus. Iwamoto et al. (2015) also recorded the species from northern Taiwan, based on a single specimen collected from the Da-xi fish market.

Relationships and comparisons. Hymenocephalus papyraceus belongs to the H. aterrimus group as defined by Schwarzhans (2014). This group is substantially consistent with the subgenus Papyrocephalus Gilbert & Hubbs, 1920 , and comprises the following six species: H. aterrimus Gilbert, 1905 (type species of Papyrocephalus ) sporadically recorded from tropical and temperate waters of the world’s oceans, including the Hawaiian Islands (type locality), east and west coasts of Australia, New Caledonian region, and northwestern Atlantic; H. barbatulus Gilbert & Hubbs, 1920 known only from the Philippines; H. fuscus McMillan & Iwamoto, 2014 recently described from New Zealand; H. nesaeae Merrett & Iwamoto, 2000 so far known from Vanuatu; H. papyraceus ; and H. sazonovi Schwarzhans, 2014 probably endemic to the Nazca and Sala y Gomez Ridges.

Hymenocephalus papyraceus is unlikely to be confused with H. barbatulus and H. nesaeae by having 11–12 pelvic-fin rays [vs. 7 in H. barbatulus , 13–14 in H. nesaeae , fide Schwarzhans (2014: table 1)]. This species is somewhat similar to H. aterrimus , H. fuscus , and H. sazonovi in having a uniformly dark tail, but it differs notably from the latter three by its unique pigmentation. Although the ground color of the tail is immaculate in H. papyraceus , small black melanophores are densely scattered over its surface; this intense pigmentation gives a distinctly dark appearance to the tail. Such melanophores are also found in H. aterrimus , H. fuscus , and H. sazonovi , but the ground color (= epidermis except where the melanophores are present) is also uniformly dark, and thus their tail appears to be more blackish compared with that of H. papyraceus . For further comparisons see McMillan & Iwamoto (2014) and Schwarzhans (2014).

In Japan, H. papyraceus may be confused with H. lethonemus Jordan & Gilbert in Jordan & Starks, 1904, but the two species are separable by several meristic and morphometric characters (see the Relationships and comparisons of the latter species).

Figures

FIGURE 141. Fresh specimen of Hymenocephalus papyraceus. BSKU 44761, 29.7 mm HL, 176 mm TL, Tosa Bay, Kochi Pref., Pacific, 700 m depth. Lateral view. [Photo: BSKU]

FIGURE 142. Holotype of Hymenocephalus papyraceus. USNM 50935, 25.1, 113+ mm TL, Sagami Bay, Pacific, 220–485 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]