Rhinogobius phuocbinhensis, Chen & Nguyen & Huynh, 2024

Rhinogobius phuocbinhensis new species

(Cá bống đá Phước Bình, 佛ậ吻ṞẊ)

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined

Holotype.—SIE:Ich:2310131, 38.9 mm SL, a hill stream of Cai Phan Rang River basin, the Phuoc Binh National Park, Ninh Thuan Province, Vietnam, Coll. Q. T. Huynh et al., 13 Oct. 2023.

Paratypes.—NTOUP-2023-10-201, 5 specimens, 34.7–40.9 mm SL, other data same as holotype .

Diagnosis

Rhinogobius phuocbinhensis n. sp. can be well distinguished from other congeners by its specific patterns of coloration and meristic features: (1) fins rays: second dorsal fin rays I/8; anal fin rays I/8; pectoral fin rays modally 19; (2) squamation: longitudinal scale series 26–27 (modally 27); perdorsal scales 9–10 (modally 9); vertebral count 26; and (3) specific colouration pattern: densely-set of small blackish brown spots on cheek and interorbital region to snout in male and many small blackish brown dots in first dorsal fin of both sexes.

Description

Body proportions in Table 1 View TABLE 1 . Body cylindrical anteriorly, compressed posteriorly. Head rather large, somewhat depressed in male. Eye large, dorsolateral. Snout pointed. Cheek somewhat fleshy in male. Lips thick. Mouth oblique, but small, rear edge not yet extending to vertical of anterior margin of eye. Both jaws with 3–4 rows of conical teeth, outer jaws enlarged. Tongue margin rounded. Anterior nostril in short tube and posterior nostril round. Gill opening restricted, extending ventrally near vertical midline of opercle. Vertebral count 10 + 16 = 26 (n=6).

Fins. D1 VI, D2 I/8; A I/8; P 18–19 (modally 19); V I/5+I/5. D1 rounded, 3 rd and 4 th rays longest, with rear tip while depressed extending to vertical of 2 nd branched ray of D2 origin in male, but not reaching the point in female. Origin of A inserted below around first branched ray of D2. The rear tips of D2 and A rays when depressed fall well short of procurrent rays of C. P moderate large and oblong, its rear tip near reaching vertical line through anus. V rounded, spinous rays with somewhat pointed membrane lobe. C elliptical, rear edge rounded.

Scales. Body with moderately large ctenoid scales, anterior region of predorsal area naked; posterior dorsal area and belly cycloid. LR 26–27 (modally 27); TR 9–10 (modally 9); PreD 9–10 (modally 9); and SDP 6–7 (modally 6). Head and prepelvic region naked. Anterior edge of midpredorsal squamation reaching the midline of upper end of gell-opening.

Head lateral-line system ( Fig. 2 View FIGURE 2 )

Canals: Nasal extension of anterior oculoscapular canal with terminal pore σ located in between anterior and posterior nostrils. The gap between two oculoscapular canals is less than the length of posterior oculoscapular canal. Anterior interorbital sections of oculoscapular canal with paired poreλ. A single pore κin near rear of interorbital region. Pore ω present near posterior, dorsal margin of eye. Lateral section of anterior oculoscapular canal with pore α and terminal pore ρ. Posterior oculoscapular canal with two terminal pores θ and τ. Preopercular canal with three pores γ, δ and ε.

Sensory papillae: Row a extending froward beyond vertical of anterior margin of orbit. Row b length less than eye diameter. Rows c, d longer. A single cp papilla. Row f paired. Anterior edge of row oi almost connected to lower region of row ot.

Colouration of fresh preserved ( Figs. 1 View FIGURE 1 , 3–4 View FIGURE 3 View FIGURE 4 )

Body light brown to yellowish brown. Side of body with 6–8 major grayish brown blotches with a median row of blackish brown dots. The blotches with several tiny black to blackish brown spots. Dorsal region of body with 5–6 major grayish blotches. Caudal fin base with a blackish brown crescent range of black dots. Head light brown to yellowish brown. Dorsal side of snout with a pair of blackish brown stripes united to snout tip, but lacking any of infraorbital stripe or bars. Lips and dorsal snout grayish brown to light brown. Cheek light brown with very densely set of blackish brown spots in male but yellow brown spotless in female. Branchiostegal membrane grayish and spotless in both sexes.

First dorsal fin translucent with 5–7 horizontal rows of blackish brown dots. Its membrane with a grayish spot in front of second spines. Second dorsal fin with translucent with 8–10 oblique rows of blackish brown dots with a distal grayish brown margin. Anal fin gray entirely. Pectoral fin translucent with several vertical rows of small brownish black dots from anterior part of fin membrane to the base. Its basal region with a somewhat square mark un upper side. Caudal fin translucent with 7–8 somewhat vertical rows of grayish black curves or waving lines. Lower part of fin membrane with a grayish region. Pelvic fin pale to gray and spotless.

Etymology

The specific name, phuocbinhensis , refers to the collecting type locality: the small tributary in the Cai Phan Rang River basin of Phuoc Binh National Park, Ninh Thuan, Vietnam.

Distribution

This new species is, thus far, only found in the hill-stream of the Cai Phan Rang River, south central Vietnam. However, since it belongs to amphidromous species, is rather possible to find the species inhabiting the nearby river basins.