Engyprosopon brevifrontale, Amaoka & Ho, 2018

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 : 465-468

Engyprosopon brevifrontale sp. nov.

Figures 10–11 ; Table 2

Holotype. NMMB-P 22217, male, 93.5 mm SL, Ke-tzu-liao, Kaohsing, southwestern Taiwan, northern South China Sea, bottom motor trawl, ca. 30–100 m, 28 Mar. 2015.

Paratype. NMMB-P25746 , male, 85.8 mm SL, collected with holotype.

Diagnosis. A species of Engyprosopon with a deep and short body, large eyes situated close to the margin of the head, 0 + 9–10 smooth gill rakers, strong rostral spine on the ocular side, strong upper orbital spines, small rostral spine on the blind side, and with a dark blue peritoneum.

Description. Dorsal-fin rays 83 (85 in paratype), anal-fin rays 64 (67), ocular-side pectoral-fin rays 12 (12), blind-side pectoral-fin rays 9 (9), ocular-side pelvic-fin rays 6 (6), blind-side pelvic-fin rays 6 (6), scales in lateral line 43 (43), gill rakers 0 + 10 (0 + 9), vertebrae 10 + 25 (10 + 25).

In SL: HL 3.77 (3.65), body depth 1.73 (1.67). In HL: snout 4.77 (5.34), upper eye diameter 2.88 (2.73), lower eye diameter 2.82 (3.09), interorbital width 3.18 (2.87) in males, ocular-side upper jaw 2.56 (2.67), blind-side upper jaw 2.58 (2.28), ocular-side lower jaw 2.14 (2.10), blind-side lower jaw 1.92 (2.10), caudal peduncle depth 2.25 (2.24), ocular-side pectoral fin 0.64 (0.48), blind-side pectoral fin 1.77 (1.62), ocular-side pelvic fin damaged, blind-side pelvic fin damaged, base of ocular-side pelvic fin 2.46 (2.45), base of blind-side pelvic fin 8.27 (8.39), longest dorsal fin ray damaged, longest anal fin ray damaged, middle caudal fin ray damaged.

Body deeply ovate, deepest in anterior 1/3 of body, its depth much deeper than 1/2 of SL; dorsal and ventral contours similar, except for head region anterior to eyes. Caudal peduncle about equal to 1/5 of body depth. Head large, its length slightly longer than 1/4 of SL; upper profile steep with a concavity anterior to upper margin of lower eye. Snout very short, much shorter than eye diameter. Strong rostral spine, orientated upward, at snout tip on both sides in males, blind-side spine much shorter than ocular-side spine ( Fig. 11A, B ). Eyes large, eye diameter slightly shorter than maxilla length, lower eye slightly in advance of upper eye. Strong orbital spine orientated upward, before upper eye, bifurcated at tip ( Fig. 11A ). Interorbital space wide, deeply concave. Ocular-side nostrils dorsal to rostral spine and anterior to upper margin of lower eye; anterior nostril a short tube with tiny flap anteriorly and large round flap posteriorly, posterior nostril a short tube; blind-side nostrils very small, closely set below origin of dorsal fin.

Mouth large, oblique; maxilla extending to vertical through middle of lower eye; anterior tip of upper jaw beyond tip of lower jaw when mouth closed. Teeth on ocular-side upper jaw biserial, those in outer series larger, more widely spaced and fewer than those in inner series; some canine-like teeth anteriorly; series of inner teeth small, conical, close-set, angled inwards; teeth on blind-side upper jaw almost uniserial; lower jaw teeth uniserial, conical, similar in size to anterior teeth in upper outer series; anterior teeth of upper jaw protruding outside beyond tip of lower jaw when mouth closed. Gill rakers on first arch long, slender, with smooth edges; no gill rakers on upper limb ( Fig. 11C ). Scales on both sides very deciduous; those on ocular side of body feebly ctenoid with short ctenii; tips of both jaws and snout naked; scales on blind side of body cycloid.

Dorsal-fin origin on blind side below concavity on head margin, without elongate rays. Anal-fin origin ventral to pectoral fin base. Ocular-side pectoral fin with elongate rays, second fin ray longest, 1.6 (2.1 in paratype) times of head length; length of blind-side pectoral fin much less than one-half of ocular-side fin. Ocular-side pelvic-fin origin at tip of isthmus, ocular-side fifth ray opposite to first ray of blind-side fin. Tip of isthmus near vertical line through middle of lower eye. Distal part of caudal-fin rays broken, middle rays branched.

Coloration in alcohol. Ocular side of body light brown with many scale pockets with dark skin; dark blue on peritoneum region; inner sides of surface of both eyes with numerous dark spots; tip of lower jaw with dark spots. On blind side, body dark except for head; tip of lower jaw black.

Sexual dimorphism. No female specimens were available to this study; however, based on other species of this genus with similar features, it is probable that this species likely to be sexually dimorphism in interorbital width, the presence of rostral and orbital spines, length of the ocular-side pectoral fin and in coloration on the blind side of the body.

Distribution. Known from only the type specimens collected from off Ke-tzu-liao, Kaohsiung, southwestern Taiwan at depth around 30– 100 m.

Remarks. This species resembles two congeners, E. xenandrus from Hawaii and E. vanuatsuense from Vanuatu, in having a deep body and large eyes. The new species differs from these others in having a deeper body (1.67–1.73 vs. 1.83–2.04 in SL), smaller head (3.65–3.77 vs. 3.09–3.49 in SL), fewer gill rakers (0 + 9–10 vs. 0–3 + 13–14) and in other counts and proportions ( Table 3). It also resembles E. filimanus and E. maldivense in lacking a pair of black blotches on the caudal fin, in having similar numbers of dorsal- and anal- fin rays, scales in lateral line and several other features, but differs from both in its deeper body (1.67–1.73 vs. 1.82–2.10), larger upper eye (2.73–2.88 vs. 3.12–3.96), narrower caudal peduncle (2.24–2.25 vs. 1.74–2.15) and other differences as shown in Table 3.

Figures

FIGURE10. Engyprosopon brevifrontale sp. nov. NMMB-P22217,holotype,male, 93.5 mm SL. A. ocular side, B.blind side.

FIGURE11. Engyprosopon brevifrontale sp. nov. A.Rostral and orbital spines on ocular side, B. rostralspine on blind side, C. gill rakers on first arch, from NMMB-P25746, paratype.