Arnoglossus oxyrhynchus Amaoka, 1969

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 161-163

Arnoglossus oxyrhynchus Amaoka, 1969

Sharpsnout lefteye flounder; ṱ9¥6ľ

Figures 1 D–E; Tables 1–2

Arnoglossus oxyrhynchus Amaoka, 1969:135 (Type locality: Mimase, Kochi Prefecture, Japan). Ho et al., 2009:5 (new record).

Specimens examined. NMMB-P23317 (1 male, 1 female, 148.0–171.1), Ke-tzu-liao, 22 Apr. 2016 .

Diagnostic features. D 110–113; A 85–86; P 14; C 3+11+3=17; LLs 82–83; GR 0+8–9=8–9; vert. 11+35– 36=46–47.

Body elongated, greatest depth near anterior 1/3 part of body (36.1–36.7% SL). Head small, its length about 65–70% body depth (24.6–26.2% SL); front of head with shallow concavity in front of upper eye; head profile gentle, same in both sexes. Snout sharply protruding, snout length slightly shorter than eye diameter. Rostral spine absent on tip of snout in both sexes. Eye diameter much shorter than upper-jaw length; upper eye extremely close to dorsal margin of head. No orbital spines in both sexes. Interorbital space high, with narrow bony ridge extending from anterior margin of lower eye to posterior space between both eyes.

Mouth large, upper-jaw length on ocular side 11.0–11.5% SL; anterior tip of upper jaw protruding beyond anterior tip of lower jaw; maxilla extending to slightly behind middle part of lower eye. Teeth on both jaws uniserial except for biserial on posterior half on blind side; 4 enlarged canines on upper jaw anteriorly, protruding beyond anterior tip of lower jaw; lateral teeth of lower jaw canine-like, stronger and more apart than those on upper jaw. Gill rakers only on lower limb, short and strong bearing 3 or 4 sharp spines on inner margin.

Scales small and deciduous, ctenoid on ocular side with row of short ctenii, cycloid on blind side. Anterior 1–3 rays of dorsal fin elongate in males, second ray longest, longer than 1/2 HL; no elongate rays in females. Pectoral fin of ocular-side short, about half of head length (10.7–12.9% SL); that of blind side very short. Caudal fin round, uppermost and lowermost 3 rays simple, and middle rays divided into 2 branches.

Coloration. Ocular side of body uniformly pale brownish without distinct blotches or spots, snout dark; dorsal and anal fins uniformly pale brownish with a row of darkish spots; posterior part of pectoral and pelvic fins on ocular side with dark blotch, darker in males than in females. Blind side of body uniformly milky white.

Size. Reaching 170 mm SL off Taiwan; up to about 194 mm SL in southern Japan ( Amaoka, 1969).

Distribution. Southwestern Taiwan; Western Pacific Ocean ( Amaoka, 2016).

Remarks. Ho et al. (2009) firstly reported 2 specimens from Taiwan. This species belongs to a group of Arnoglossus with many scales on the lateral line and spines on the inner margin of the gill rakers. It resembles A. japonicus in having an elongate second dorsal-fin ray in males and a sharply protruding snout, but differs in having ctenoid scales on the ocular side, more dorsal- and anal- fin rays, more lateral-line scales and vertebrae, and a black blotch on pectoral and pelvic fins.

Figures

FIGURE 1. A–B. Arnoglossus japonicus, NMMB-P23187, male 121.0 mm SL (A) and female, 110.2 mm SL (B). C. A. macrolophus, NMMB-P 23204, male, 81.1 mm SL. D–E. A. oxyrhynchus, NMMB-P23317, male, 148.0 mm SL (D) and female, 171.1 mm SL (E). F. A. polyspilus, NMMB-P29041,164 mm SL. G. A. tenuis, NMMB-P25684, 64.5 mm SL. H. A. yamanakai, NMMB-P25685, 95.0 mm SL.