Platycephalus aurimaculatus Knapp, 1987

Imamura, Hisashi, 2015, Taxonomic revision of the flathead fish genus Platycephalus Bloch, 1785 (Teleostei: Platycephalidae) from Australia, with description of a new species, Zootaxa 3904 (2), pp. 151-207 : 177-180

Platycephalus aurimaculatus Knapp, 1987

Common English name: Toothy flathead ( Figs. 19–20 ; Table 7 )

Platycephalus sp.: Last et al., 1983: 334, fig. 28.23.

Neoplatycephalus sp. 1: May & Maxwell, 1986: 273, unnumbered fig.

Platycephalus (Neoplatycephalus) aurimaculatus Knapp, 1987: 53 (type locality: Bass Strait, east of King Island, Tas, Australia).

Neoplatycephalus aurimaculatus: Knapp, 1991: 29 , tab. 1; Kuiter 1993: 102, unnumbered fig.

Platycephalus aurimaculatus: Kuiter, 1994: 516 , fig. 459; Hoese et al., 2006: 940; Imamura, 2006: 304, tab. 1; Gomon, 2008: 518, unnumbered fig.

Platycephalus conatus (not Waite & McCulloch, 1915): Imamura, 2006: 304, tab. 1 (in part).

Material examined. Holotype: NMV A 1404, 279 mm SL, 60 km east-northeast of Bold Head, King Island, Central Bass Strait, Tas, Australia (39°56’25”S – 39°53’52”S, 144°48’03”E – 144°47’58”E), 29.4-49.4 m depth, 3 Feb. 1981.

Paratypes (4 specimens, 211–322 mm SL, from southeastern Australia): AMS I.26328-001 (ex. NMV A1389), 322 mm SL, off Cape Otway, Bass Strait, Vic (39°05’S, 143°26’E), 82 m depth, 31 Jan. 1981; NMV A3733, 2 specimens, 211–229 mm SL, 3.2 km west of Sandringham, Port Phillip Bay, Vic (37°57’S, 144°57’E), 30 Mar. 1971; USNM 280181, 315 mm SL, Bass Strait, NSW, Feb. 1981.

Other specimens (17 specimens, 121–489 mm SL, from southern Australia): AMS I.21309-001, 377 mm SL, southeast of Bass Strait, Tas (40°25’S, 147°35’E), 46 m depth, 16 Oct. 1979; AMS E. 750, 233 mm SL, Marsden Point, Kangaroo Island, SA (35°34’S, 137°38’E), 19 Aug. 1909; AMS IB. 2118, 296 mm SL, Geelong, Vic (38°10’S, 144°21’E), 11 Apr. 1948; CSIRO 3698, 380 mm SL, south of Point Cuvier, Great Australian Bight, WA (33°37’S, 124°48’E – 33°35’S, 124°47’E), 50 m depth, 29 Nov. 1981; CSIRO H3796-01, 489 mm SL, Disaster Bay, NSW (37°17’– 37°18’S, 149°59’E), 26–33 m depth, 13 Nov. 1996; NMV A1424, 2 specimens, 176–191 mm SL, NMV A 24057, 181 mm SL, 5 km south-southeast of Cape Woolomai, Phillip Island, Vic (38°43’S, 145°34’E), 46 m depth, 17 Jan. 1980; NMV A 1568, 245 mm SL, 46 km east-northeast of North Point, Flinders Island, Eastern Bass Strait, Tas (39°31’21”– 39°34’19”S, 148°24’01”– 148°24’07”E), 19.5–36.5 m depth, 8 Feb. 1981; NMV A1581, 3 specimens, 121–132 mm SL, Vic, 13 Nov. 1979; QM I. 22300, 285 mm SL, NSMT-P 112680, 401 mm SL, Great Australian Bight, SA (32°21.3’S, 130°2.1’E), 62 m depth, 30 Nov. 1975; QM I. 22304, 316 mm SL, Lakes Entrance, Vic (37°53’S, 148°E), 14 Aug. 1984; QM I. 22309, 390 mm SL, Western Port, Vic (38°26’S, 145°08’E), 14 Aug. 1984; WAM P.30105-002, 464 mm SL, Capel, WA (33°25’S, 115°21’E), 6 Sep. 1990.

Diagnosis. A species of Platycephalus with the following combination of characters: second dorsal- and analfin rays usually 14; caudal-fin rays 12–13; pored lateral-line scales 75–90; gill rakers 1–2 + 6–7 = 7–9; orbital diameter 16.3–22.4% HL; interorbital width 7.4–11.7% HL; postorbital length 49.1–56.9% HL; suborbital width 6.7–9.0% HL; occipital region scaled; lower half of suborbital region naked; margin of interopercle smooth; one to three large caniniform teeth anteromedially on upper jaw; all or most pored lateral-line scales with one pair of sensory ducts and exterior openings posteriorly; fleshy sensory tubes from suborbitals and preopercle not covering cheek region; swimbladder absent; abdominal cavity pale, slightly silvery.

Description. Counts and measurements shown in Table 7 . Data for all specimens presented first, followed by holotype condition in parentheses.

SL (mm) 279 211–322 121–489

Counts:

Snout, area anteroventral to eye, anterior one-fourth to entire area of interorbit (anterior half) and lower half of suborbital region naked; occipital region scaled. Interorbit narrower than orbital diameter. Upper iris lappet simple, moderately long; lower weakly convex, or absent (absent). Nasal, preorbital and supplemental preopercular spines absent. One suborbital spine present below posterior margin of eye in smallest 121 mm SL specimen, absent in others. Lower preopercular spine longer than upper, not reaching opercular margin. Interopercular flap absent; margin of interopercle smooth. Maxilla extending beyond anterior margin of pupil; some specimens with maxilla reaching to middle of eye (slightly beyond anterior margin of pupil in holotype). Anteromedial portion of upper jaw with one to three (one) large caniniform teeth. Palatine teeth in two rows, villiform or small conical (small conical) in outer row, small to large caniniform (moderately caniniform) in inner row. Vomerine teeth in a single row. Fleshy sensory tubes from suborbitals and preopercle not covering cheek region. Posterior tip of pelvic fin reaching from anus to base of third anal-fin ray (base of second anal-fin ray). Posterior margin of caudal fin mostly straight, or slightly rounded (mostly straight). Swimbladder absent.

Color in alcohol. In holotype ( Fig. 20 ), ground color of head and body pale brown above, slightly paler below. Dorsal surface of head and body with scattered small white spots. Side of body with greenish-gray band. First and second dorsal fins with melanophores along fin rays. Pectoral fin pale with brown spots tending to form bands; lower margin of pectoral fin paler. Pelvic fin pale brown; its lower margin paler. Anal fin with melanophores along rays. Caudal fin with pale brown spots and bands posteriorly. In other specimens ( Fig. 19 ), first and second dorsal fins with melanophores or small indistinct pale brown spots along fin rays. Caudal fin with dark brown spots, or pale brown spots, bands and/or indistinct markings. Abdominal cavity pale, slightly silvery.

Distribution. Known only from southern Australia, from to Disaster Bay, NSW (149°59’E) to Capel, WA (115°21’E), including Vic, Tas and SA, in bays and coastal waters in depths from 10 to 160 m (e.g., Knapp, 1987; Hoese et al., 2006; Gomon, 2008; this study).

Size. Previously reported maximum length 55 cm SL ( Gomon, 2008). One specimen examined during the present study measured 489 mm SL (565 mm TL).

Remarks. Platycephalus aurimaculatus is most similar to P. conatus and P. richardsoni in having usually 14 anal-fin rays, 12 or 13 caudal-fin rays, the occipital region scaled, the margin of the interopercle smooth and large caniniform teeth anteromedially on the upper jaw, the combination of such characters not occurring in other species of Platycephalus . The present species is easily distinguished from P. conatus and P. richardsoni in lacking a swimbladder (vs. present), and having the lower half of the suborbital region naked (vs. scaled, but scales not developed in 165 mm SL or smaller specimens of P. richardsoni ) and the abdominal cavity pale and slightly silvery (vs. dark brown or black). Postorbital length and suborbital width at any given length may also help to separate P. aurimaculatus and P. conatus (postorbital length 49.1–56.9% HL and suborbital width 6.7–9.0% HL in the former vs. 49.7–56.2% HL and 5.4–9.7% HL, respectively, in the latter), although broad overlaps occur in both proportions ( Fig. 21 ). Platycephalus aurimaculatus is distinguishable from P. richardsoni in having 75–90 pored lateral-line scales (vs. 65–74), 7–9 total gill rakers (vs. 12–17), a narrower interorbit (7.4–11.7% HL in P. aurimaculatus vs. 10.1–15.7% HL in P. richardsoni ) ( Fig. 18 A) and all or most pored lateral-line scales with one pair of sensory ducts and exterior openings posteriorly (vs. most scales with two pairs of ducts and openings).

Figures

FIGURE 18. Comparison of (A) orbital diameter (solid symbols) and interorbital width (open symbols) versus standard length, and (B) postorbital length versus standard length in Platycephalus chauliodous (circles), P. aurimaculatus (diamonds), P. conatus (triangles) and P. richardsoni (squares). Holotypes labeled by capitalized initial of specific names.

FIGURE 19. (A) Dorsal and (B) lateral views of Platycephalus aurimaculatus, CSIRO H 3796 - 01, 267 mm SL, Disaster Bay, NSW.

FIGURE 20. Dorsal view of holotype of Platycephalus aurimaculatus, NMV A 1404, 279 mm SL, King Island, Central Bass Strait, Tas.

FIGURE 21. (A) Comparison of postorbital length and (B) suborbital width versus standard length in Platycephalus aurimaculatus (solid circles) and P. conatus (open circles). H, holotype.

Tables

TABLE 7. Comparison of counts and proportional measurements of Platycephalus aurimaculatus. Holotype Paratypes Non-types NMV A 1404 n = 4 n = 17

D1	I + VIII + 0	I + VIII + 0	Usually I +VIII + 0
			(rarely I + VII + I)
D2	14	13–14	13–15 (usually 14)
A	14	13–14	14–15 (usually 14)
P1	1 + 14 + 5 = 20	1–2 + 11–12 + 5–6 = 18–19	1–2 + 10–15 + 3–7 = 18–20
C	12	12–13	12–13
LLS (spines)	84 (1)	ca. 80–85 (0)	75–90 (0–2, usually 1)
OBS	93	88–97	90–94
GR	1 + 6 = 7	1–2 + 6–7 = 7–9	1–2 +6–7 = 7–9
As % SL:
HL	33.3	32.1–33.8	33.2–35.7
PDL	35.0	34.1–35.4	34.3–37.2
LD1B	21.5	19.4–21.6	17.3–21.7
LD2B	34.2	32.0–33.0	29.9–34.0
LAB	37.2	34.5–36.2	33.0–36.8
SNL	9.4	8.9–9.8	8.9–10.6
OD	6.7	6.2–6.9	5.4–7.9
UJL	12.9	12.1–12.9	12.5–13.9
LJL	17.1	16.8–17.4	16.8–19.4
IW	3.3	2.8–3.4	2.6–4.0
POL	17.5	17.1–18.1	17.1–20.0
SW	2.8	2.5–2.9	2.3–3.1
P1L	15.8	15.5–16.2	14.2–16.9
P2L	27.4	24.1–26.3	23.7–28.1
CL	16.4	–	14.3–19.3
As % HL:
SNL	28.1	27.8–29.4	29.5–29.8
OD	20.0	19.2–20.7	16.3–22.4
UJL	38.6	37.7–38.6	36.0–29.9
LJL	51.2	51.4–52.2	49.5–54.7
IW	9.9	8.5–10.5	7.4–11.7
POL	52.6	51.2–54.4	49.1–56.9
SW	8.5	7.4–8.5	6.7–9.0