Ratabulus diversidens ( McCulloch, 1914 )

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 : 22-28

Ratabulus diversidens ( McCulloch, 1914)

English name: Freespine flathead

( Figures 2a , 3a , 4a , 5a , 6a , 7 , 8a )

Insidiator diversidens McCulloch, 1914: 148 , fig. 13, pl. 31-fig. 1 (original description, type locality: 11 km northeast of Port Stephens Lighthouse, New South Wales, Australia); McCulloch, 1929: 403 (list and distribution, New South Wales, Australia)

Ratabulus diversidens : Paxton et al., 1989: 470 (list and distribution, Queensland to off Sydney, New South Wales, Australia) (in part); Knapp, 1999: 2410, unnumbered fig. (description, eastern Australia) (in part); Hoese et al., 2006: 944 (list and distribution, Queensland to off Sydney, New South Wales, Australia) (in part).

Lectotype (designated here). AMS E. 2103, 232 mm SL, 11 km northeast of Port Stephens Lighthouse , New South Wales, 87 m, 10 November 1910, FIS Endeavour.

Paralectotypes. Two specimens. AMS E. 1566, 212 mm SL and AMS I. 11254, 245 mm SL, collected with lectotype .

Nontypes. Twenty-three specimens (54.4–391 mm SL) eastern Australia. AMS I.15523-010, 190 mm SL, off Brisbane , Queensland (26°31'S, 153°28'E), 137 m, 26 July 1968 ; AMS I.23993-003, 205 mm SL, Ballina-Tweed Heads , New South Wales (28°13'S, 153°52'E), 201 m, 17 August 1978 , FRV Kapala ; AMS I.25097-007, 2: 118–140 mm SL, east of Brunswick Heads , New South Wales (28°24'S, 153°51'E), 155–174 m, 3 June 1978 , FRV Kapala ; AMS I.25804-019, 278 mm SL, just north of Townsville , Queensland (17°51'S, 147°01'E), 260 m, 9 January 1986 , RV Soela; AMS I.31332-001, 370 mm SL, off Wollongong , New South Wales (34°25'S, 152°00'E), 18–109 m, February 1991 ; AMS I.39088-001, 369 mm SL, 5–6 km offshore, North Head , New South Wales (33°17'S, 151°35'E), 65 m, 31 January 1999 ; AMS I.40494-001, 391 mm SL, off Crowdy Head, New South Wales (31°51'S, 152°45'E), 60–70 m, 2000; AMS I.45084-009, 2 of 5: 182–230 mm SL, northeast of Arrawarra Headland , New South Wales (29°30'S, 153°48'E), 7 May 1971 , FRV Kapala ; CSIRO H 630-29, 273 mm SL, south of Saumarez Reef , Queensland (22°36'S, 153°50'E), 345–350 m depth, 17 November 1985 , FRV Soela; CSIRO H 630-30, 308 mm SL, collaboration with CSIRO H630-29 ; CSIRO H 698-22, 295 mm SL, east of Bowen, Marian Plateau , Queensland (19°29.2'S, 150°16.5'E – 19°29.8'S, 150°17.8'E), 324–328 m, 15 November 1985 , FRV Soela; CSIRO H4268-01 , 204 mm SL, east of Pambula , New South Wales (36°54'S, 149°58'E – 36°55'S, 149°57'E), 42–43 m, 28 April 1996 , FRV Southern Surveyor; NMV A 15248, 290 mm SL, off Lakes Entrance , Victoria (38°07'S, 147°45'E), January 1995 ; NMV A 15249, 283 mm SL, collaboration with NMV A15248 ; NMV A 19471, 349 mm SL, off Lakes Entrance , Victoria (38°17' 52²S, 148°33' 34²E), 90–156 m, 22 October 1997 ; QM I. 2117, 313 mm SL, east of Tweed Heads , New South Wales (28°12'S, 154°54'E), 235 m, 27 July 1982 ; QM I. 18698, 215 mm SL, Queensland (25°27'S, 153°46'E – 25°17'S, 153°43'E), 183–230 m, 14 September 1980 ; QM I.18813, 2: 203–252 mm SL, Queensland (23°50'S, 152°36'E – 23°46'S, 152°32'E), 238–274 m, 23 September 1980 ; QM I. 26624, 274 mm SL, east of Fraser Island , Queensland (26°S, 153.3°E), 30 m, 16 May 1990 ; QM I.34240, 2: 54.4–144 mm SL, southeast of Cape Moreton , Queensland (28°12'S, 154°54'E), 235 m, 27 July 1982 .

Diagnosis. A species of Ratabulus with 80–93 anteroventrally slanted oblique scale rows above lateral line; snout length 29.5– 32.3% HL, slightly decreasing proportionally with growth; pectoral fin length 13.9–15.8% SL; pelvic fin length 22.1–28.5% SL; nasal bone with tubercles in larger specimens; dorsal surface of head with large, pale to dark-brown irregularly shaped spots, body without spots dorsally; pelvic fin with large brown spots.

Description. Dorsal fin rays I+VIII+I-11 (I+VIII+I-10 or 11, 10 in one); anal fin rays 12; branched caudal fin rays 12 (11–13, usually 12 or 13, smallest specimen with 11 rays); pectoral fin rays 2 + 10 + 8 = 20 (2 or 3 + 10 – 12 + 6 to 8 = 19 or 20); pelvic fin rays I, 5; scales in lateral line 54 (53 or 54), anterior 6 (3–7) scales with spine; posteroventrally slanted oblique scale rows above lateral line 75 (71–78); anteroventrally slanted oblique scale rows above lateral line 84 (80–93); gill rakers 1 + 6 = 7 (1 + 5–8 = 6–9).

See table 1 for selected proportional measurements. Head length 2.6 (2.4–2.7) in SL. Snout rather robust, its length 3.2 in HL (3.1–3.3 in HL, ratio as % HL slightly decreasing proportionally with growth) (fig. 9). Iris lappet broad and simple dorsally, absent ventrally (rarely absent dorsally, and usually broad and simple ventrally) (fig. 5a). Interorbital width 14.1 (10.3–22.2) in HL. Nasal bone without distinct spines, but with tubercles (smallest specimen, 54.4 mm SL, with single spine and without tubercles) (fig. 4a). Lachrymal with four (2–7) anterolaterally directed spines. Single (rarely two) preocular spine in front of eye, its base with tubercles (with small spines, or without small spines and tubercles in several specimens). Suborbital ridge roughly serrated by many small to large spines; anteriormost (preorbital) spine small (rarely absent).Supraorbital ridge serrated, except anteriorly. Single postocular spine present. Pterotic with serrated ridge ending in strong spine. Parietal with single spine, followed posteriorly by three small spines on left side and four on right (by 1–5 spines). Supratemporal with serrated ridge (with serrated or smooth ridge) ending in spine. Posttemporal with two spines on left side and one on right (with 1–4 spines, usually one). Preopercle with three (two or three) spines; uppermost longest, not reaching posterior margin of opercle, bearing two small spines on left side and one on right on base laterally (usually one). Ridge of lower opercular spine smooth on left side and serrated on right. Posterior end of maxilla below anterior margin of eye (just beyond it in several specimens). Anterior part of upper jaw with conical teeth (short canines in several specimens) anteriorly, followed by long, slender canines; middle and posterior parts of upper jaw with villiform teeth, but innermost row with small, slender conical teeth. Lower jaw with narrow tooth band containing small conical teeth anteriorly, becoming smaller posteriorly, followed by villiform teeth at end of jaw; innermost row conical (conical teeth to moderately long canines). Palatine with moderately broad tooth band; anterior part of palatine with short canines laterally and moderately long canines mesially (moderate to long and slender canines mesially); posterior part of palatine with small conical teeth. Vomer with about four (about three or four) tooth rows centrally; anterior part of vomer with small conical teeth, middle and posterior parts with moderate to long and slender canines. Posterior margin of caudal fin mostly straight (rarely slightly concave); caudal fin length 5.6 (4.8–6.1) in SL. Pectoral fin length 7.0 (6.3–7.2) in SL. Posterior tip of pelvic fin reaching second (first to third) anal fin ray; pelvic fin length 4.0 (3.5–4.5) in SL.

Color in alcohol (lectotype, fig. 7). Head and body mostly faded. First dorsal fin with dark brown submarginal stripe; second dorsal with scattered small dark brown spots. Caudal fin with five longitudinal black stripes along fin membranes posteriorly. Upper part of pectoral fin with about two dark brown bands. Pelvic fin with large dark-brown spots posteriorly.

Other specimens with head and body pale to dark-brown dorsally, pale yellow ventrally; dorsal surface of head with large irregular pale to dark-brown spots; body without spots, but sometimes with several narrow dark-brown bands dorsally, side with longitudinal stripe formed by continuous gray spots 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 dark brown spots. Anal fin pale or with melanophores along rays. Caudal fin with 4–6 narrow black longitudinal stripes posteriorly; lower stripes tending to merge in some specimens; upper part of fin with several brown spots. Pectoral fin with small dark-brown spots tending to form bands. Pelvic fin with large brown spots (fig. 6a).

Color when fresh based on photograph (fig. 8a). Similar to those in alcohol.

Distribution. Eastern Australia from Townsville, Queensland (17°51'S) to Lakes Entrance, Victoria (38°17' 52²S), recorded at depths of at least 30–345 m ( McCulloch, 1914; Paxton et al., 1989) (fig. 1).

Remarks. Ratabulus diversidens is easily separable from R. megacephalus and R. fulviguttatus in having 80–93 anteroventrally slanted oblique scale rows above the lateral line (versus 94–112 in R. megacephalus and 99–113 in R. fulviguttatus ), the snout length 29.5–32.3% HL, becoming slightly shorter proportionally with growth (versus 31.2–35.7% HL in R. megacephalus and 30.4–34.8% HL in R. fulviguttatus ) (fig. 9), nasal bone with tubercles in larger specimens (versus lacking tubercles in R. megacephalus and R. fulviguttatus ) (fig. 4), the dorsal surface of the head with large, irregularly shaped, pale to dark-brown spots, the body without spots dorsally (versus dorsal surface of head and body with small, round, pale or dark-brown spots in R. megacephalus and R. fulviguttatus ) (fig. 3). R. diversidens resembles R. ventralis in having tubercles on the nasal bone, but differs from it in having a shorter pectoral fin (13.9–15.8% SL in R. diversidens versus 15.8–18.6% SL in R. ventralis ) (fig. 10) and large, irregular spots on the head (versus a head with small, round, brown spots in R. ventralis ) (fig. 3). This species can be separated from the other three by the large brown spots on its pelvic fin (versus having small spots) (fig. 6).

McCulloch (1914) recorded the collection locality of the type specimens of R. diversidens as ‘seven miles S. 21°W. off Port Stephens Lighthouse , New South Wales’, but data with the specimens indicate they were captured 11 km northeast of Port Stephens Lighthouse (S. Reader, pers. comm., 16 May 2006).

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 7. Dorsal (upper) and lateral (lower) views of Ratabulus diversidens, AMS E.2103, lectotype, 232 mm SL, 11 km northeast of Port Stephens Lighthouse, New South Wales.

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.