Ratabulus megacephalus ( Tanaka, 1917 )

Imamura, Hisashi & Gomon, Martin F., 2010, Taxonomic revision of the genus Ratabulus (Teleostei: Platycephalidae), with descriptions of two new species from Australia, Memoirs of Museum Victoria 67, pp. 19-33 : 28-29

Ratabulus megacephalus ( Tanaka, 1917)

Japanese name: Haname-gochi

( Figures 2b , 3b , 4b , 5b , 6b , 8b )

Thysanophrys megacephalus Tanaka, 1917: 11 (original description, fish market in Tokyo); Tanaka, 1931: 37 (list, Japan); Kamohara, 1952: 70 (list, Kochi, Japan).

Thysanophrys (Ratabulus) megacephalus : Kamohara, 1964: 77 (list, Kochi).

Ratabulus megacephalus : Jordan and Hubbs, 1925: 287 (English translation of original description published in Japanese); Okada and Matsubara, 1938: 334 (key and distribution, Tokyo to Kagoshima, Japan); Mori, 1952: 159 (list and distribution, Tongyeong, southern South Korea); Matsubara and Ochiai, 1955: 95, pl. 3 (description, southern Japan and East China Sea); Matsubara, 1955: 1122 (key, short description and distribution, Tokyo Bay, south from Kasumi, Hyogo Prefecture, Korea and East China Sea); Anonymous, 1962: 926, fig. 730 (description, Hainan Island, South China Sea); Ochiai, 1984: 322, pl. 289-E (short description and distribution, southern Japan to East China Sea); Yatou, 1985: 599, 729, pl. 371 (description and distribution, Okinawa Trough); Shao and Chen, 1987: 86, fig. 20 (short description, Taiwan); Shao and Chen, 1993: 258, pl. 65-4 (short description, Taiwan); Imamura, 1996: 207, fig. 62 (list); Imamura, 1997: 220, fig. 5 in 221 page (short description); Lee and Joo, 1998: 220, fig. 4 (description, Pusan); Knapp, 2000: 608 (list, South China Sea); Nakabo, 2002: 618, unnumbered figs (pictorial key and limited meristic values, Pacific coast of southern Japan and East China Sea); Shinohara et al., 2001: 318 (list, Tosa Bay, Japan); Youn, 2002: 259, 570, unnumbered fig. (pictorial key, Tongyeong, southern South Korea); Kim et al., 2005: 237, unnumbered fig. (short description, Tongyeong, southern South Korea).

Ratabulus diversidens (nec McCulloch, 1914): Knapp, 1999: 2410 (description, East and South China seas and northern Philippines) (in part).

Nontypes (location of holotype unknown, Eschmeyer et al., 1998). Twenty-three specimens (83.4–344 mm SL), Northwest Pacific. BSKU 9503, 186 mm SL, fish market, Mimase , Kochi Prefecture, 1 December 1950 ; BSKU 36141, 192 mm SL, fish market, Mimase , Kochi Prefecture, 9 December 1981 ; BSKU 36270, 228 mm SL, fish market, Mimase , Kochi Prefecture, 26 January 1982 ; BSKU 51453, 205 mm SL, fish market, Mimase , Kochi Prefecture, 9 April 2000 ; BSKU 52257, 160 mm SL, Irino fishing port, Hata-gun, Kochi Prefecture, 10 August 2000 ; BSKU 54460, 252 mm SL, fish market, Mimase , Kochi Prefecture, 24 November 2000 ; BSKU 59497 , 83.4 mm SL, Irino fishing port, Hata-gun, Kochi Prefecture, 18 March 2002 ; BSKU 63578, 188 mm SL, Saga fishing port, Hata-gun, Kochi Prefecture, 20 November 2002 ; BSKU 73629 , 88.7 mm SL, Irino fishing port, Hata-gun, Kochi Prefecture, 5 April 2002 ; BSKU 85012, 164 mm SL, Tosa Bay , Kochi Prefecture, 125 m depth, 30 September 1997 , R / V Kotakamaru ; BSKU 87405, 216 mm SL, fish market, Mimase , Kochi Prefecture, 30 March 2000 ; FAKU 12168, 270 mm SL, East China Sea, February 1949 , K. Matsubara and R. Ishiyama ; FAKU 14957 , 14959–14960 , 3 : 283–295 mm SL, Maisaka , Shizuoka Prefecture ; HUMZ 37397, 111 mm SL, no collection data (perhaps Kochi Prefecture ) ; HUMZ 49396, 187 mm SL, fish market, Mimase , Kochi Prefecture, 15 November 1975 ; HUMZ 49470, 187 mm SL, fish market, Mimase , Kochi Prefecture, 17 November 1975 ; HUMZ 200048, 344 mm SL, East China Sea (27°06.31’N, 125°47.32’E – 27°06.11’N, 125°46.24’E), 192– 186 m, 2 June 2007 ; HUMZ 200050, 296 mm SL, collaboration with HUMZ 200048 ; NSMT-P 828, 103 mm SL, Enoura, Izu Peninsula , Shizuoka Prefecture (35°03'N, 138°54'E) ; USNM 329510, 239 mm SL, South China Sea (19°06' 30²N, 112°23'E), 203–218 m, 22 July 1958 ; USNM 383571, 370 mm SL, fish market, Bolinao , Luzon, Philippines, 7–9 October 1995 .

Other material. One specimen. HUMZ 199844, 264 mm SL, East China Sea (26°35.68'N, 125°04.57'E – 26°36.73'N, 125°05.78'E), 192– 186 m, 5 May 2007 (used for description of color when fresh) .

Diagnosis. A species of Ratabulus with 94–112 anteroventrally slanted oblique scale rows above lateral line; snout length 31.2– 35.7% HL, markedly decreasing in length proportionally with growth; pectoral fin length 13.9–17.0% SL; pelvic fin length 19.5–23.1% SL; nasal bone without tubercles; dorsal surface of head and body dark brown, with small, round, dark-brown spots; and pelvic fin with small brown to black spots.

Description. Dorsal fin rays I + VIII + I-11 or 12 or I + IX + 0-11 (I + IX + 0-11 in one, I + VIII + I- 12 in one); anal fin rays 12; pectoral fin rays two or three (usually two) + 9–11 + 6–8 = 19 or 20; pelvic fin rays I, 5; branched caudal fin rays 12 or 13; scales in lateral line 53–55, anterior three or four scales with spine; posteroventrally slanted oblique scale rows above lateral line 71–78; anteroventrally slanted oblique scale rows above lateral line 94–112; gill rakers 1 + 6–8 = 7–9.

See table 1 for selected proportional measurements. Head length 2.4–2.7 in SL. Snout rather long, its length 2.8–3.2 in HL, ratio as %HL markedly decreasing proportionally with growth (fig. 9). Iris lappet broad and simple dorsally and absent ventrally (fig. 5b). Interorbital width 12.8–19.6 in HL. Nasal bone with 0–2 spines, and without tubercles (fig. 4b). Lachrymal with 2–4 spines directed anterolaterally. Preocular spine in front of eye, its base without spines or tubercles. Suborbital ridge with many small to large spines; anteriormost (preorbital) spine usually present. Supraorbital ridge serrated medially and posteriorly or just posteriorly. Postocular spine present. Pterotic ridge with 1–3 spines. Parietal with single spine, followed posteriorly by 0–2 additional spines. Supratemporal usually with a spine, rarely with two. Posttemporal with one or two spines. Preopercle with twp or three spines; uppermost longest, not reaching posterior margin of opercle, bearing one small spine on base laterally. Ridge of lower opercular spine without serrations. Posterior end of maxilla below anterior margin of eye or just posterior to it. Anterior part of upper jaw with conical or small canine teeth in front of long, slender canines, followed by villiform teeth, innermost row with small, slender conical teeth. Lower jaw with narrow band of small conical teeth anteriorly, smallest teeth posteriorly, followed by villiform teeth, innermost a row of moderately long canines. Palatine with moderately broad tooth band; those anterolaterally canines of short to moderate length with moderate to long and slender canines mesially; posterior part of palatine with small conical teeth. Vomer with about 2–5 tooth rows medially; anterior teeth conical or short canines, those medially and posteriorly slender canines of moderate length. Posterior margin of caudal fin mostly straight, slightly concave or slightly rounded in some; caudal fin length 5.2–6.0. Pectoral fin length 5.9–7.2 in SL. Posterior tip of pelvic fin not reaching anal fin origin; pelvic fin length 4.3–5.1 in SL.

Color in alcohol. Head and body dark brown dorsally, pale yellowish ventrally. Dorsal surfaces of head and body with small, round, dark-brown spots; body usually without bands dorsally, but occasionally with indistinct darker bands; longitudinal stripe formed by continuous series of gray spots on side below lateral line. First dorsal fin with dark brown to black submarginal stripe, base clear anteriorly with scattered small dark-brown to black spots; second dorsal with brown to black spots. Anal fin with melanophores along rays. Caudal fin with 5–9 narrow longitudinal black stripes posteriorly; several dark-brown to black spots anteriorly and dorsally. Pectoral and pelvic fins with small dark-brown to black spots (fig. 6b).

Color when fresh from photographs of HUMZ 199844 (fig. 8b). Similar to those in alcohol.

Distribution. East and South China seas, and Northwest Pacific, including southern Japan, Korea, Taiwan, Hainan Island and northern Philippines, at depths of 192–218 m ( Anonymous, 1962; Ochiai, 1984; Shao and Chen, 1987, 1993; Knapp, 1999; Kim et al., 2005) (fig. 1).

Remarks. R. megacephalus is most similar to R. fulviguttatus in having the nasal bone devoid of tubercles (versus tubercles present in R. diversidens and R. ventralis ) (fig. 4) and the dorsal surface of the body with small, round spots (versus without spots) (fig. 2). R. megacephalus differs from R. fulviguttatus in having a proportionally longer snout (31.2–35.7% HL in R. megacephalus versus 30.4–34.8% HL in R. fulviguttatus ) and shorter pectoral fins (13.9–17.0% SL compared to 14.6–16.5% SL) (figs 9–10) at comparable sizes, and the dorsal surface of the head and body dark brown (versus pale brown) (fig. 2). R. megacephalus is also separable from R. ventralis in having shorter pectoral fins (13.9–17.0% SL versus 15.8–18.6% SL) and pelvic fins (19.5–23.1% SL versus 25.3–28.2% SL) (figs 10–11).

Sadovy and Cornish (2000) reported Ratabulus megacephalus from Hong Kong, but their photograph depicts a specimen of Inegocia ochiaii Imamura, 2010 , previously known incorrectly as ‘ Inegocia guttata ’ (e.g. Matsubara and Ochiai, 1955; Ochiai, 1984), a species that has an interopercular flap, and a long and branched iris lappet.

Figures

Figure 2. Lateral views of four species of Ratabulus: a, R. diversidens, AMS I.40494-001, 391 mm SL; b, R. megacephalus, HUMZ 200048, 344 mm SL; c, R. fulviguttatus sp. nov., CSIRO H4031-79, holotype, 262 mm SL; d, R. ventralis sp. nov., CSIRO H6116-02, holotype, 304 mm SL.

Figure 3. Dorsal views of four species of Ratabulus: a, R. diversidens, AMS I.40494-001, 391 mm SL; b, R. megacephalus, HUMZ 200048, 344 mm SL; c, R. fulviguttatus sp. nov., CSIRO H4031-79, holotype, 262 mm SL; d, R. ventralis sp. nov., CSIRO H6116-02, holotype, 304 mm SL.

Figure 4. Dorsal views of anterior head region in four species of Ratabulus: a, R. diversidens, AMS I.11523-010, 190 mm SL; b, R. megacephalus, BSKU 87405, 216 mm SL; c, R. fulviguttatus sp. nov., CSIRO H4031-79, holotype, 262 mm SL; d, R. ventralis sp. nov., CSIRO H6116-02, holotype, 304 mm SL. Arrows show tubercles on nasal bone. Scale bar = 10 mm.

Figure 5. Iris lappet (left eye) of four species of Ratabulus: a, R. diversidens, AMS I.45084-009, 230 mm SL; b, R. megacephalus, BSKU 87405, 216 mm SL; c, R. fulviguttatus sp. nov., CSIRO H4031-79, holotype, 262 mm SL; d, R. ventralis sp. nov., CSIRO H6116-02, holotype, 304 mm SL. Scale bar = 3 mm.

Figure 6. Dorsolateral view of pelvic fin in four species of Ratabulus: a, R. diversidens, CSIRO H630-29, 273 mm SL; b, R. megacephalus, HUMZ 200048, 344 mm SL; d, R. fulviguttatus sp. nov., CSIRO H4031-79, holotype, 262 mm SL; d, R. ventralis sp. nov., CSIRO H6116-02, holotype, 304 mm SL.

Figure 8. Three species of Ratabulus: a, R. diversidens, off Newcastle, New South Wales (33°08'S, 151°56'E), 125–130 m, 7 September 1978, specimen discarded, scale bar = 5 cm, photo by K. Graham; b, R. megacephalus, HUMZ 199844, 264 mm SL, East China Sea (26°35.68'N, 125°04.57'E – 26°36.73'N, 125°05.78'E), 192–186 m, 5 May 2007, photo by Hokkaido University; c, R. fulviguttatus sp. nov., upper specimen CSIRO H1505-15, 189 mm SL, lower specimen H1505-06, 219 mm SL, north of Nickol Bay, Western Australia (19°07'S, 117°06'E – 19°07'S, 117°04'E), 177–184 m depth, 5 October 1988, FRV Soela, photo by CSIRO.