Pterygotrigla (Pterygotrigla) gomoni, Last, Peter R. & Richards, William J., 2012

Last, Peter R. & Richards, William J., 2012, Two new gurnards of the genus Pterygotrigla (Scorpaeniformes: Triglidae) from Australian seas, Zootaxa 3195, pp. 39-50 : 40-43

Pterygotrigla (Pterygotrigla) gomoni sp. nov.

Gomon’s Gurnard

Figs 1–2 , Table 1

Holotype. WAM P 26270–004, 156 mm SL, Indian Ocean, Western Australia, 230 km north-west of Beagle Bay, 15°30’S, 120°58’E, FRV Courageous, shot 0 781, 280– 320 m, Jun. 1978.

Paratypes. 2 specimens. WAM P 26270–004, 2(156–174 mm SL), taken with holotype.

Diagnosis. A species of the genus Pterygotrigla (reaching at least 174 mm SL) with the following combination of characters: snout short, horizontal length about 2.8–3.0 in head length; orbit large, length 2.9–3.1 in head; broad fleshy margin surrounding entire ventral margin of eye; rostral spine slender, tapering, very short, less than half orbit length, about 7–8 in head; head not heavily ossified; interorbital depression strongly concave; parietal not strongly hyperostotic; nuchal spine elongate, narrow based, not recurved, extending to below 2nd or 3rd dorsal-fin spines; cleithral spine relatively weak, not recurved, short, much shorter than nuchal spine and extending to first spines of first dorsal fin; opercular and preopercular spines weak; nasal and postocular spines absent; bucklers poorly developed, embedded, predorsal buckler absent; no dorsal-fin spines thickened, first spine shorter than next 4–5 spines; pectoral fin with 12 connected rays, not greatly elongated, length 29–34% SL, extending to anterior rays of second dorsal fin; vomerine tooth patch well developed; body scales small, cycloid; predorsal, prepectoral and interpelvic spaces, breast, and much of belly naked; preserved coloration pale without evidence of dark markings on body or vertical fins; pectoral-fin inner surface dark, encircled with narrow pale rim, axil of fin black; gill rakers 6–7, short; vertebrae 27.

Description. Dorsal rays IX (VIII), 11 (11); anal rays 12 (12); pectoral rays 12 + 3 (12 + 3); pelvic rays I, 5 (I, 5); principal caudal rays 11 (11–13); lateral-line pores to caudal base about 65 (63–73); gill rakers (excluding rudiments) 7 (6–7); vertebrae 27 (27).

Body moderately elongate, tapering gently posteriorly; trunk deepest anteriorly, maximum depth 4.9 (4.5–4.7) in SL, 1.1 (1.1–1.2) times width across pectoral-fin base; caudal peduncle narrow, subrectangular in cross-section, length 3.2 (2.6–2.8) in caudal-fin length. Head not greatly expanded, robust; surface finely granular, not pitted or covered with rugose striae; its length 3.0 (3.0–3.1) in SL; snout relatively short, deeply concave before orbit in lateral view, its length 3.0 (2.8–3.0) in head length. Rostral spine very short, broad, depressed, weakly ossified (often damaged); apices bluntly pointed, not recurved distally; its length 2.7 (2.4) in snout length, 1.8 (1.9) times its width; spines diverging, directed anterolaterally, interspace between their bases exceeding their length. Nuchal spine narrow based, elongate, slender, pungent, not recurved distally; extending to below 2nd or 3rd dorsal-fin spines, 1.2 (1.1–1.3) times predorsal space; slightly longer than cleithral spine, length 0.8 (0.8–0.9) in length of cleithral spine; much longer than opercular spine, length 1.6 (1.4–1.5) times length of opercular spine; parietal robust but not heavily ossified or forming a broadly elevated ridge above operculum; a weak postorbital groove present. Opercular spine very short, slender, either not reaching or barely extending beyond margin of operculum, length 1.6 (1.5–1.6) in postorbital head length. Preopercular spine single, slender, at posteriormost angle of preoperculum; similar in shape to opercular spine; very short, its length 1.5 (1.7–1.8) in length of opercular spine; spine absent at posteroventral angle of preoperculum; angles separated by a weakly concave margin. Nasal and postocular spines absent. Cleithral spine relatively weak, narrow based, pungent; depressed slightly; short, reaching below first spines of first dorsal fin, length 1.9 (2.1–2.2) times length of preopercular spine, 3.8 (3.4–3.8) in head length. Orbit lateral, large, length 2.9 (3.1) in head length, 1.0 (1.0–1.1) in snout length, 1.0 (1.0–1.1) in postorbital head length; margin of supra-orbital rim elevated, prominent, not obviously indented mid-dorsally. Interorbit deeply concave, width 1.2 (1.3–1.6) in orbit. Cheek depth moderate, height 1.4 (1.2–1.3) in orbital length; its bony portion 76% (76–81%) of its height; a broad fleshy portion surrounding entire ventral margin of eye. Mouth large with broad bands of villiform teeth on premaxilla and dentary; head of vomer with prominent transverse patch of villiform teeth; maxilla reaching anterior margin of orbit or beyond; length of upper jaw 2.2 (2.3–2.4) in head length. Dorsal fins separated slightly, spines partly depressible into a shallow groove; predorsal buckler absent; 9 subdorsal bucklers poorly developed, all fully embedded beneath epithelium; no spines reaching anterior rays of second dorsal fin when depressed; longest dorsal-fin rays subequal in length to 5th spine; dorsal-fin spines mainly smooth, anterior margin of 1st spine and lateral margin of 2nd spine very finely granular; no spines showing evidence of hyperostosis. Anal-fin origin forward of second dorsal-fin origin, inserted marginally more posteriorly; longest ray slightly shorter than length of longest dorsal-fin ray; its base longer than base of second dorsal fin, length 1.2 (1.2) times length of base of second dorsal-fin. Pectoral fin elongate, length 3.2 (2.9–3.5) in SL, reaching to first few rays of anal fin; 1st free pectoral-fin ray very elongate, reaching to origin of anal fin, its length 1.1 (1.1–1.3) in length of pectoral fin. Pelvic fin elongate, length 3.7 (3.8–3.9) in SL, marginally shorter than longest free pectoralfin ray; reaching beyond anus. Caudal fin lunate, tips of lobes narrowly pointed, length 3.6 (3.7–3.8) in SL. Body scales small, cycloid, oval, mostly embedded; scales absent from nape, base of cleithrum, breast, prepectoral and interpelvic areas, and anterior belly.

Coloration. In preservative, types faded, pale without evidence of major markings on most fins and body; a few scattered dark spots faintly visible on dorsum above lateral line. Pectoral-fin inner surface with a blackish basal blotch, upper 8 membranes dark; remaining membranes and fin rays paler, translucent or whitish; outer surface of fin dusky, surrounded by pale rays and membranes. Caudal fin without dark posterior margin. No description or image of fresh material.

Size. Probably a small species, attaining at least 174 mm SL; smallest specimen examined is the holotype, 156 mm SL.

Distribution. Known from the type specimens taken at a single station in the eastern Indian Ocean off Western Australia, 230 km north-west of Beagle Bay at 280–320 m depth ( Fig. 6 ).

Etymology. This species is named after Dr. Martin F. Gomon who has contributed greatly to the understanding of Australian fish systematics, particularly members of the triglid genus Lepidotrigla .

Comparisons. Of the Australian members of the subgenus, Pterygotrigla gomoni shares short and simple rostral spines with P. andertoni and P. pauli , but differs from them in lacking dark spots over the body (persistent in preserved material), and in having a more deeply concave interorbit, a relatively less well developed opercular spine, a narrower cheek relative to orbit length, and a much shorter pectoral fin. Pterygotrigla polyommata is plain coloured but has a more strongly patterned inner surface of the pectoral fin (with rows of yellow spots or lines on bluish grey vs. more uniformly dark in P. gomoni ), a deep notch in the dorsal rim of the orbit (lacking in P. gomoni ), a deeper cheek relative to the orbit length, and a relatively longer opercular spine and pectoral fin. Pterygotrigla polyommata also has a more concave preopercular margin (vs. deeply notched) between its posteroventral angle and its spine. Pterygotrigla ryukyuensis has a more strongly ossified head with a less deeply concave snout, broader-based rostral spines that diverge more strongly posteriorly, well developed bucklers (absent or deeply embedded in P. gomoni ), and a much longer snout with the mouth angle well short of the orbit (vs. maxilla reaching orbit margin or beyond). Of non-Australian members of the subgenus, P. gomoni differs from P. guezei Fourmanoir in Fourmanoir & Guézé 1963, in having a less well ossified head, shorter snout, mouth reaching level of the orbit (rather than falling well short), less well developed bucklers (predorsal bucklers absent rather than well developed in P. guezei ), and a simple, narrow based rostral spine (vs. broader based sometimes with apical serrations).

Figures

FIGURE 1. Illustrations of the holotype of Pterygotrigla gomoni sp. nov. (WAM P 26270 – 004, 156 mm TL): A, lateral view; B, dorsal view of head - a patch of scales shown below the first dorsal fin is representative of other scaled areas.

FIGURE 2. Holotype of Pterygotrigla gomoni sp. nov. (WAM P 26270 – 004, 156 mm TL, preserved): A, lateral view; B, view of partially expanded inner surface of left pectoral fin showing markings.

FIGURE 6. Map of the Australian region showing the distributions of Pterygotrigla gomoni (blue dot) and P. saumarez (red dots).