Platycephalus australis, Imamura, Hisashi, 2015

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 : 199-203

Platycephalus australis sp. nov.

Proposed common English name: Australian bartail flathead ( Figs. 34–35 , 36 A, 37; Tables 13–14 )

Platycephalus indicus (not Linnaeus, 1758): Paxton & Hanley, 1989: 469; Knapp, 1999: 2409, unnumbered fig. (in part); Hoese et al., 2006: 942.

Material examined. Holotype: WAM P.29859-001, 477 mm SL, Exmouth Gulf, WA, Australia (22°28’S, 114°13’E), 22 May 1988.

*Tending to decrease with growth.

**Nine or 10 caudal-fin rays in specimens <50 mm SL (incompletely branched caudal fin).

Paratypes (11 specimens, from north and northeastern Australia): AMS I.21831-028, 294 mm SL, Arafura Sea (10°53’S, 132°02’E), 36–40 m depth, 14 Nov. 1980; AMS I.34397-046, 273 mm SL, AMS I.34397-075, 214 mm SL, HUMZ 215745 (ex. AMS I.34397-075), 184 mm SL, South Arm Channel, Port Clinton, Qld (23°34.13’S, 150°44.75’E), 10 m depth, 25 Oct. 1993; CSIRO 3916-01, 415 mm SL, west of Weipa, Gulf of Carpentaria, Qld (12°32’S, 141°28’E – 12°31’S, 141°28’E), 22 m depth, 8 March 1995; CSIRO H6714-01, 232 mm SL, southeast of Bowling Green Bay, Qld (19°28’S, 147°32’E – 19°27’S, 147°32’E), 15 m depth, 2 Dec. 2003; NTM S.10414-004, 2 of 7 specimens, 125–126 mm SL, Ludmilla Creek, Darwin, NT (12°25’S, 130°51’E), 0–0.5 m depth, 26 Nov. 1981; NTM S.10738-013, 2 specimens, 123–147 mm SL, Buchanan Island, Bathurst Island, NT (11°49’S, 130°39’E), 18 Nov. 1982; NTM S.17108-012, 229 mm SL, Haycock Reach, Darwin Harbour, NT (12°34.99’S, 130°57.67’E), 8–9 m depth, 28 March 2011.

Non-types (13 specimens, from north and northeastern Australia): AMS I.22720-017, 1 of 2 specimens, 51.4 mm SL, Three Mile Creek, Cape Pallarenda, Townsville, Qld (19°11.14’S, 146°46’E), 0–1 m depth, 8 Oct. 1981; AMS I.25676-002, 310 mm SL, south of Moreton Bay, Qld (27°25’S, 153°20’E), 2 March 1985; NTM S.10414- 0 0 4, 5 of 7 specimens, 63.6–106 mm SL, Ludmilla Creek, Darwin, NT (12°25’S, 130°51’E), 0–0.5 m depth, 26 Nov. 1981; NTM S.10553-007, 6 specimens, 81.5–109 mm SL, East Arm Mudflats, Darwin, NT (12°29.5’S, 130°34’E), 6 Sep. 1982.

Diagnosis. A species of Platycephalus with the following combination of characters: first dorsal fin with a single small isolated spine anteriorly; second dorsal-fin rays 13–14, usually 13: anal-fin rays 13; pectoral-fin rays 19–21, usually 20; gill rakers 1–2 + 3–8 = 4–10 (tending to decrease with growth); postorbital length 51.6–63.6% HL; snout, area anteroventral to eye, interorbit, and occipital region scaled; upper iris lappet usually simple, triangular; a finger-like interopercular flap present; upper jaw without large caniniform teeth; teeth absent on dorsal surface of anterolateral edge of upper jaw; palatine teeth in two rows; vomerine teeth usually in one row; caudal fin with a yellow marking on midline when fresh.

Description. Counts and measurements shown in Table 13 . Data for all specimens, including both non-types and paratypes, presented first, followed by holotype in parentheses.

Body greatly depressed, mostly covered with ctenoid scales, but some cycloid scales on undersurface. Head greatly flattened, length 2.8–3.2 (3.2) in SL; scales covering snout, a small area anteroventral to eye, interorbit, occipital region, nape, and postorbital and opercular regions; suborbital region naked. Snout robust, longer than orbital diameter, length 3.6–4.0 (3.8) in HL. Upper surface of eye without papillae. Upper iris lappet simple, triangular dorsally; lower weakly convex (unobservable in holotype) ( Fig. 35 B). Interorbital width 5.5–15.3 (6.3) in HL, increasing with growth; orbital diameter 5.4–8.0 (8.4) in HL, decreasing with growth; interorbit narrower than orbital diameter in smaller specimens, becoming equal to or wider than orbital diameter by 232 mm SL (including holotype). Spines and ridges on top and side of head weakly developed ( Fig. 35 B). Nasal usually with a single distinct spine in 123 mm SL or smaller specimens (absent in 106 mm SL specimen), a small or rudimentary spine, or spine absent in larger specimens (absent in holotype). Lachrymal with two embedded antrorse spines. Single preocular spine present. Single preorbital spine present or absent in 109 mm SL or smaller specimens, absent in larger specimens (including holotype). Suborbital ridge usually with a spine below and slightly posterior to posterior margin of eye, often with a spine below and slightly anterior to middle of eye in 125 mm or smaller specimens (lacking both spines on right side of 123 mm SL specimen); with or without a spine below and slightly posterior to posterior margin of eye in 175 to 270 mm SL specimens; and without spines in 273 mm SL or larger specimens (including holotype). Supraorbital ridge serrated posteriorly, with one to seven small spines (two on left and one on right in holotype). Single postocular spine present. Pterotic with one to six spines (one). Frontal and supraoccipital with entirely smooth ridges. Parietal with one or two spines (rudimental spine on left, spine absent on right). Supratemporal usually with one spine (sometimes two or zero) in 294 mm SL or smaller specimens (spines absent in 415 mm SL specimen and holotype). Posttemporal usually with one spine; rarely absent in some specimens in 125 mm SL or larger (including holotype). Supracleithrum usually with one spine (spine absent only in holotype). Preopercle with two distinct spines; lower spine slightly longer than upper (including holotype) or spines subequal, not reaching posterior margin of opercle; upper spine with supplementary spine in 147 mm SL or smaller specimens, usually without in 184 mm SL or larger specimens (including holotype) (rudimental supplementary spine in 294 mm SL specimen). Opercle with two spines, lacking prominent ridge. Finger-like interopercular flap present; margin of interopercle not scalloped. Maxilla reaching beyond anterior margin of orbit, length 2.6–2.8 (2.6) in HL, tending to extend posteriorly with growth [just below posterior margin of orbit in largest examined specimen (holotype)]. Teeth in bands on jaws and palatine, a single shallow V-shaped or crescentic patch on vomer (shallow crescentic patch in holotype); tooth band on upper jaw lacking distinct notch mesially. Upper jaw with several large conical or small caniniform (large conical in holotype) teeth anteromedially, villiform teeth anterolaterally, teeth tending to be larger medially; remainder of jaw with small conical and villiform teeth; teeth absent on dorsal surface of anterolateral edge of upper jaw. Lower jaw usually with one villiform tooth row laterally (a narrow villiform band in holotype) and one small to moderate conical tooth row medially, teeth tending to become larger posteriorly; lateral villiform teeth forming two or three rows anteriorly in several paratypes and non-types. Palatine with two tooth rows; inner row with small conical teeth, outer row with small villiform teeth. Vomer with single villiform to moderate conical (moderate conical in holotype) tooth row; some specimens 147 mm SL or larger with additional villiform teeth anteriorly and/or posteriorly (teeth anteriorly in holotype). Lip margins without papillae. Fleshy sensory tubes on suborbitals and preopercle not covering cheek region. Pored scales in lateral line each with a pair of sensory ducts and exterior openings posteriorly. First dorsal fin originating posterior to opercular margin. First and second dorsal fin narrowly separated. Pectoral fin rounded posteriorly, length 5.6–8.1 (7.1) in SL. Posterior tip of pelvic fin reaching between anus and base of fourth anal-fin ray (reaching anal-fin origin), length 4.0–5.1 (4.5) in SL. Caudal fin usually slightly rounded or mostly straight posteriorly (slightly concave in holotype), length 5.5–6.8 (7.2) in SL.

Color in alcohol. In holotype ( Fig. 34 ), body and head brown above, pale below. Head with single indistinct, dark brown band crossing occipital and anterior opercular regions. Side of head with many small dark brown spots. Body with two dark brown bands below second dorsal fin; anterior band broad, posterior band narrow. First and second dorsal, pectoral and pelvic fins with small, dark brownish spots along rays. Pectoral and pelvic fins with paler outer margins. Anal fin pale, with melanophores along membrane between seventh to last fin rays; melanophores thicker posteriorly. Caudal fin with the following markings: a long dark brown band on both the upper and lower portions; short blackish band above long dark brown band on upper portion; short dark brown band below long dark brown band on lower portion; small brownish spots on dorsal portion.

In paratypes and non-types, caudal fin usually with three dark brown or black bands; middle band paler than dorsal and ventral bands. In CSIRO H3916-01 (415 mm SL, paratype) caudal fin with four bands; middle two bands brownish, and dorsal and ventral two bands dark brown.

Color when fresh (based on color photographs; Figs. 36 A, 37). Caudal fin with yellow marking on midline; its size variable, small ( Fig. 36 A), medium ( Fig. 37 A) or large ( Fig. 37 A). Other coloration similar to preserved condition.

Distribution. Known from northern Australia, from Exmouth Gulf, WA (22°28’S) to south of Moreton Bay, Qld (27°25’S) in depths from at least 0.5–36 m (this study).

Size. Recorded maximum length 477 mm SL (554 mm TL) (this study; Fig. 34 ).

Etymology. The specific name australis derived from Latin is proposed in reference to its type locality, Australia.

Remarks. Platycephalus australis sp. nov. has previously been misidentified as Platycephalus indicus , both species being characterized by usually 13 second dorsal- and anal-fin rays, the snout, area anteroventral to the eye, interorbit and occipital region scaled, large caniniform teeth absent on the upper jaw, a finger-like interopercular flap, palatine teeth arranged in two rows and the caudal fin with a yellow marking on the middle when fresh. In fact, the yellow mid-caudal fin marking occurs only in the above two species. However, P. australis sp. nov. is separable from P. i n di c us in having fewer total gill rakers (4–10 in P. australis vs. 7–10 in P. i n di c us, tending to decrease with growth in both species) and a longer postorbital region (51.6–63.6% HL vs. 51.4–61.6% HL) than the latter at a comparable size, although a considerable overlap occurs ( Fig. 38 ). In addition, P. australis sp. nov. differs from P. indicus in having a greater number of pectoral-fin rays (19–21, usually 20 vs. 18-20, usually 19) ( Table 14). The validity of P. australis sp. nov. has also been demonstrated from genetically reconstructed phylogenetic relationships of Platycephalus , showing that “ P. indicus ” from Australia, including a specimen with a yellow marking on the mid-caudal fin (thus probably P. australis sp. nov.) and P. i nd i c u s from the Indian Ocean and Indonesia are included in different monophyletic clades, the degree of speciation between the two species being similar to that of P. conatus and P. richardsoni (sister species) (W. White, personal communication, 20 June 2013). A detailed comparison of P. australis sp. nov. and P. i ndicus is presented in Table 13 .

Among other species with usually 13 second dorsal- and anal-fin rays, P. australis sp. nov. is easily distinguished from P. endrachtensis in having a broader interorbit and longer postorbital region (interorbital width 6.5–18.1% HL and postorbital length 51.6–63.6% HL in P. australis sp. nov. vs. 7.7–12.0% HL and 50.7–56.9% HL in P. endrachtensis ) ( Fig. 30 ), from P. angustus , P. cultellatus , P. f u s cu s, and Platycephalus sp. 1 and sp. 2 (sensu Nakabo, 2002) in having the first dorsal fin with a single small isolated spine anteriorly (usually two in the other species), and from P. westraliae in having a simple triangular upper iris lappet (usually broad and bilobed in P. westraliae ).

Figures

FIGURE 30. Comparison of (A) interorbital width and (B) postorbital length versus standard length (mm) in Platycephalus endrachtensis (solid circles), P. angustus (solid diamonds), P. cultellatus (open circles), P. indicus (open squares), P. australis sp. nov. (solid triangles), P. westraliae (open triangles), Platycephalus sp. 1 (solid squares) and Platycephalus sp. 2 (open diamonds). H, holotype; N, neotype.

FIGURE 34. (A) Dorsal and (B) lateral views of Platycephalus australis sp. nov., WAM P. 29859 - 001, holotype, 477 mm SL, Exmouth Gulf, WA.

FIGURE 35. Dorsal view of (A) head and (B) dorsolateral view of left eye in Platycephalus australis sp. nov., HUMZ 215745, 184 mm SL, South Arm Channel, Port Clinton, Qld, Australia. LA, lachrymal spines; LO, lower opercular spine; PA, parietal spine; PO, postocular spine; POC, preocular spine; POP, preopercular spines; PT, posttemporal spine; PTE, pterotic spines; SC, supracleithral spine; SO, supraocular spines; ST, supratemporal spine; UO, upper opercular spine.

FIGURE 36. Lateral views of (A) Platycephalus australis sp. nov., CSIRO 6731 - 01 (not examined, photo from CSIRO) and (B) Platycephalus indicus, HUMZ 193328, 291 mm SL, Bintan Island, both in fresh condition.

FIGURE 37. Lateral views of caudal fin in (A) Platycephalus australis sp. nov., QM I. 39150, 345 mm SL and (B) QM I. 39151, 358 mm SL (both from Moreton Bay, Qld not examined, photos in fresh condition from QM). Photo of QM I. 39150 (A), originally showing right side of caudal fin, was reversed for comparison.

FIGURE 38. Comparison of (A) total gill raker numbers and (B) postorbital length versus standard length (mm) in Platycephalus australis sp. nov. (solid circles) and P. indicus (open circles). H, holotype.

Tables

TABLE 13. Comparison of counts and proportional measurements of Platycephalus australis sp. nov. and P. indicus.

	P. australis Holotype	Paratypes	Non-types	P. indicus Non-types
SL (mm)	WAM P.29859-001 477	n = 11 123–415	n = 13 51.4–310	n = 41 40.2 –379
Counts: D1 D2	I + VIII + 0 13	I + VII–VIII + 0–I (usually I + VIII + 0) 13	I + VII + I or I + VIII + 0 13	I + VI–VIII + 0–I 13–14 (usually 13)
A P1	13 2 + 13 + 5 = 20	13 2 + 11–14 + 4–7 = 19–21 (usually 20)	13 2–3 + 11–13 + 4–7 = 19–21 (usually 20)	13 1–2 + 10–14 + 4–7 = 18–20 (usually 19)
C LLS (spines) OBS GR	12 68 (1) 85 1 + 4 = 5	11–13 (usually 12) 69–78 (1–2) 80–99 1–2 + 3–7 = 4–9*	11–12 (usually 12) 67–74 (2) 75–97 1–2 + 5–8 = 6–10*	9–12 (usually 12)** 67–84 (1–3) 83–112 1–2 + 6–8 = 7–10*
As % SL: HL	31.7	31.5–33.4	31.6–35.8	29.2–34.7
PDL LD1B LD2B LAB	33.2 20.3 34.0 35.1	31.8–35.0 16.9–20.1 33.9–36.0 36.2–38.5	33.9–37.9 16.5–21.3 31.9–35.7 35.0–37.9	29.9–38.1 14.8–21.8 31.8–36.2 34.1–41.1
SNL OD	8.3 3.8	7.9–8.8 4.1–6.2	8.3–9.8 4.5–7.5	7.6–9.5 3.9–8.5
UJL LJL IW POL	12.3 16.4 5.1 20.2	11.7–12.5 16.0–17.3 3.3–6.0 18.3–20.8	11.5–12.8 16.3–18.2 2.7–5.0 18.4–19.1	10.6–13.2 14.8–18.4 2.5–5.5 16.5–19.3
SW P1L	2.8 14.1	2.6–2.9 12.7–15.8	2.4–2.8 12.4–17.9	2.5–3.1 12.4–17.7
P2L CL As % HL: SNL	22.4 13.8 26.2	19.5–23.8 14.8–17.6 25.0–26.8	19.8–24.7 14.6–18.3 25.9–27.8	21.2–25.6 14.7–19.9 25.3–28.4
OD UJL	11.9 38.7	12.5–18.5 36.0–38.0	14.4–23.4 35.6–38.0	13.0–23.6 35.0–40.4
LJL IW POL SW	51.7 16.0 63.6 8.7	50.5–52.6 10.4–18.1 56.5–63.3 7.8–8.9	48.2–52.7 6.5–15.7 51.6–60.4 6.9–8.6	48.6–54.3 7.2–18.4 51.4–61.6 7.1–10.1