Arnoglossus tenuis Günther, 1880

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 164

Arnoglossus tenuis Günther, 1880

Dwarf lefteye flounder; AE¥6ľ

Figure 1G ; Tables 1–2

Arnoglossus tenuis Günther, 1880:55 (Type locality: Hong Kong, China). Shen, 1984:450; Chen & Yu, 1986:817; Shen in Shen et al., 1993:567; Shen & Wu, 2012:748.

Arnoglossus aspilos (not of Bleeker, 1851):? Chen & Weng, 1965:41;? Chen, 1969:214;? Chen & Yu, 1986:817;? Shen & Wu, 2012:747.

Arnoglossus thori (not of Kyle, 1913):? Chen & Weng, 1965:40.

Specimens examined. NMMB-P23199 (9, 57.3–62.8), Ke-tzu-liao, 3 Apr. 2016 ; NMMB-P25682 (3, 59.9–65.4), Ke-tzu-liao, 27 Jun. 2016 ; NMMB-P25684 (8, 55.2–64.5), Dong-gang, 11 Oct. 2016 . More specimens deposited in NMMB-P collection.

Diagnostic features. D 89–96; A 68–78; P 10–12; C 2+13+2=17; LLs 51–58; GR 0+5–8=5–8; vert. 10+28– 30=38–40.

Body elongated, greatest depth slightly anterior of middle part of body (38.4–48.0% SL). Head small, its length about half of body depth (22.3–24.3% SL); front of head with distinct concavity in front of upper eye; head profile gentle, same in both sexes. Snout shorter than eye diameter. Rostral spine absent on tip of snout in both sexes. Eye diameter slightly shorter than upper jaw. No orbital spines in both sexes. Interorbital ridge low, extending from anterior margin of lower eye to posterior margin of upper eye.

Mouth very small, upper-jaw length on ocular side 7.3–8.3% SL; maxilla extending to or slightly behind anterior margin of lower eye. Teeth on both jaws uniserial, closely set, not enlarged anteriorly; lower jaw teeth on ocular side curved inward, teeth on blind side slightly longer and stronger than those on ocular side. Gill rakers only on lower limb, long and slender, pointed at tip and not serrate.

Scales large, deciduous, ctenoid with short ctenii on ocular side, cycloid on blind side. Pectoral fin on ocular side much shorter than head length (13.0–15.4% SL); that on blind side very short.

Coloration. Ocular side of body uniformly pale brown without distinct blotches or spots, all fins uniformly pale brownish without spots. Blind side of body uniformly milky white.

Size. Reaching 65 mm SL in Taiwan; up to about 120 mm total length elsewhere ( Hensley & Amaoka, 2001).

Distribution. Northeastern and southwestern Taiwan; Indian and Western Pacific oceans ( Amaoka, 2016).

Remarks. This species resembles A. aspilos in having small a mouth and fewer scales on the lateral line. It differs from the latter in having slightly more dorsal- and anal-fin rays and more lateral-line scales. Shen (1983) pointed out that the specimen identified as A. aspilos by Chen & Weng (1965) is a misidentification (see above). Moreover, A. tenuis resembles A. macrolophus in body shape, small mouth, fewer dorsal- and anal-fin rays, but can be distinguished by lacking elongate anterior dorsal-fin rays and no black spots on the posterior portions of the dorsal- and anal-fin bases.

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.