Engyprosopon xystrias Hubbs, 1915

Amaoka, Kunio & Ho, Hsuan-Ching, 2018, Review of the genus Engyprosopon Günther, 1862 (Pleuronectiformes: Bothidae) from waters off Taiwan, with descriptions of two new species, Zootaxa 4413 (3), pp. 449-481 : 451-453

Engyprosopon xystrias Hubbs, 1915

Figure 1 ; Table 1

Engyprosopon xystrias Hubbs, 1915: 475 (type locality: Vincennes Strait, Japan, 30°12'N, 130°43'40"E, 83 fathoms [151.8 m]). Norman, 1934:211; Okada & Matsubara, 1938:422; Matsubara, 1955:1259; Amaoka, 1969:87; Amaoka et al., 1993:385.

Material examined. NMMB-P 22216, male, 88.7 mm SL, Ke-tzu-Liao, Kaohsiung, southwestern Taiwan, 9 Mar. 2015. Other localities: FAKU 26177, male, 87.1 mm SL and FAKU 26451, male, 73.0 mm SL, Kagoshima Pref., 9–28 Aug. 1956; HUMZ 124863, male, 67.0 mm SL, 22°38.2'S, 167°34.8'E, New Caledonia, 105–110 m, 9 Sep. 1989; MNHN 1993-0025, male, 60.0 mm SL, 22°31.7'S, 167°32.4'E, New Caledonia, 150–155 m, 9 Sep. 1989; MNHN 1993-0024, male, 52.1 mm SL, and HUMZ 124862, female, 51.5 mm SL, 21°06.00'S, 167°26.20'E, Loyalty Islands, 200–240 m, 20 Feb. 1989; MNHN 1993-0023, 2 males, 47.1–66.8 mm SL, 20°00.20'S, 158°46.60'E, Chesterfield and Bellona Plateaus, 225 m, 27 July 1984.

Diagnosis. Gill rakers 0–6 + 13–18; anterior margin of head anterior to both eyes with about 4–5 pale blotches margined by dark bands; scales on front margin of head more strongly ctenoid and non-deciduous compared to body scales.

Description. Dorsal-fin rays 92 (88–98, from other localities), anal-fin rays 65 (60–77), ocular-side pectoralfin rays 12 (12–13), blind-side pectoral-fin rays 9 (10–12), caudal-fin rays 3 + 11 + 3 (3 + 11 + 3), ocular-side pelvic-fin rays 6 (6), blind-side pelvic-fin rays 6 (6), scales in lateral line 40 (39–50), gill rakers 0 + 13 (0–6 + 13– 18), vertebrae 10 + 26 (10 + 25–27).

In SL (* = mean data not available): HL 3.81 (3.60–4.07, from other localities), body depth 2.03 (1.94–2.10). In HL: snout 4.66 (4.37–5.48), upper eye diameter 2.95 (2.41–3.04), lower eye diameter 2.91 (2.49–2.98), interorbital width 2.65 (2.43–7.88), ocular-side upper jaw 2.95 (2.51–3.00), blind-side upper jaw 2.91 (2.56–3.00), ocular-side lower jaw 2.43 (2.03–2.33), blind-side lower jaw 2.33 (2.03–2.30), caudal peduncle depth 2.40 (2.08– 2.62), ocular-side pectoral fin 1.18 (1.0–1.14), blind-side pectoral fin 2.43 (1.99–2.58), ocular-side pelvic fin 3.07 (2.50–2.95), blind-side pelvic fin 2.43 (2.62–3.32), base of ocular-side pelvic fin 3.53 (2.61–3.00), base of blindside pelvic fin 8.32 (8.20–9.69), longest dorsal-fin ray * (1.71–2.04), longest anal-fin ray * (1.70–2.25), middle caudal-fin ray 1.35 (1.09–1.20).

Body moderately ovate, deepest in anterior 1/3, its depth about 1/2 of body length; dorsal and ventral contours almost symmetrical, with gradual taper posteriorly. Caudal peduncle less than 1/4 of body depth. Head large, its length more than 1/4 of SL; upper profile of head with small concavity anterior to upper margin of lower eye. Snout short, much shorter than eye diameter. Rostral spine present in males (absent in females and juveniles in comparative specimens). Eyes large, lower eye diameter about equal to maxilla length; lower eye in advance of upper eye. No orbital spine in both sexes. Interorbital space widely concave in males (distinct sexual or ontogenetic differences in its width in comparative specimens). Nostrils on ocular side anterior to upper margin of lower eye; anterior nostril a short tube with a small triangular flap posteriorly, posterior nostril not tubular and without flap; nostrils on blind side closely set below origin of dorsal fin, similar in shape to those on ocular side.

Mouth rather large, oblique, maxilla extending to below anterior portion of lower eye; anterior tip of upper jaw extending slightly beyond tip of lower jaw when mouth closed. Teeth on upper jaw biserial, those in outer series larger and more widely spaced than those in inner row, some canine-like teeth anteriorly; lower jaw teeth conical and uniserial, nearly similar in size to anterior teeth of upper inner row. Gill rakers on first arch slender and slightly pointed or rounded at tip, inside edge smooth, no gill rakers on upper limb (0–6 in comparative specimens). Ocularside scales ctenoid with short ctenii, large and deciduous; scales on anterior margin of head more strongly ctenoid than those on body, and not deciduous; tips of both jaws and tip of snout on ocular side naked; cycloid scales on blind side of body.

Dorsal- and anal-fin rays without elongate rays, very easily broken. Ocular-side pectoral-fin rays short in both sexes, equal to or slightly shorter than head length; ocular-side pectoral fin about 2 times length of blind-side pectoral fin. Ocular-side pelvic-fin origin at tip of isthmus, ocular-side fifth fin ray opposite to first ray of blindside fin. Tip of isthmus nearly reaching vertical line through middle of lower eye. Caudal-fin rays branched except for three upper- and three lowermost fin rays.

Coloration in alcohol. Body pale brown; anterior margin of head before both eyes with 4–5 pale blotches margined by dark bands; one obtuse dark spot on middle of straight section of lateral line; ocular-side pectoral fin with some dark bands; middle of caudal fin between third and fifth fin rays counted from uppermost and lowermost fin rays with pair of large jet-black blotches. Blind side of body dark except for head in males (yellowish white in females and juveniles). All fins on both sides dark brown with many dark spots; blind-side paired fins uniformly yellowish white.

Sexual dimorphism. This species shows sexual dimorphism only in interorbital width, presence of a rostral spine, and coloration on the blind side of the body.

Distribution. Widespread in the western Pacific Ocean, from southern Japan, Taiwan, South China Sea to Coral Sea and Saya de Malha Bank in the Western Indian Ocean. Bathymetric range 30–240 m ( Hensley & Amaoka, 2001).

Remarks. This species is characterized in having a pair of black botches on the caudal fin and numerous gill rakers on the lower limb of the first gill arch. This specimen collected off southwestern Taiwan represents the first record from waters off Taiwan, though it was known from off southern Japan and the South China Sea ( Amaoka et al., 1993).

Figures

FIGURE 1. Engyprosopon xystrias Hubbs, 1915. NMMB-P22216, male, 88.7 mm SL. A. ocular side, B. blind side.