A new freshwater goby of Rhinogobius Gill, 1859 (Teleostei, Gobiidae) from South Central Vietnam Author Chen, I-Shiung Institute of Marine Biology, National Taiwan Ocean University, Keelung, 202301, Taiwan, R. O. C. & Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung, 202301, Taiwan, R. O. C. Author Nguyen, Anh-Tuan Phuoc Binh National Park, Bac Ai District, Ninh Thuan Province, 59408, Vietnam Author Huynh, Quang-Thien Southern Institute of Ecology, Institute of Applied Materials Science, Vietnam Academy of Science and Technology, Ho Chi Minh City, 71515, Vietnam text Zootaxa 2024 2024-12-10 5550 1 354 361 https://doi.org/10.11646/zootaxa.5550.1.35 journal article 10.11646/zootaxa.5550.1.35 1175-5326 14389415 0274EAC4-EC89-4C10-AC94-584EB3BA4C8F Rhinogobius phuocbinhensis new species (Cá bống đá Phước Bình, 佛ậ吻ṞẊ ) ( Figs. 1–4 ) 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 . 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). TABLE 1. Morphometry of Rhinogobius phuocbinhensis from south central Vietnam.

Type	Holotype	Paratypes
Sex	M	F	F	F
Standard length	38.9	40.8	36.7	36.4
% in SL
Head length	33.7%	29.4%	30.0%	28.1%
Predorsal length	42.3%	39.0%	38.5%	38.2%
Snout to 2nd dorsal fin origin	60.9%	58.2%	59.1%	57.8%
Snout to anal fin origin	62.9%	61.7%	61.0%	62.0%
Snout to anus	59.3%	58.1%	57.2%	58.0%
Prepelvic length	31.7%	29.0%	30.4%	28.7%
Caudel peduncle length	13.7%	12.0%	13.7%	13.0%
Caudal peduncle depth	16.2%	25.8%	32.7%	28.0%
First dorsal fin base	20.5%	19.9%	18.3%	18.1%
Second dorsal fin base	16.8%	17.9%	17.8%	18.9%
Anal fin base	15.1%	14.3%	15.7%	14.8%
Caudal fin length	25.3%	24.8%	22.8%	23.8%
Pectoral fin length	24.4%	23.4%	22.7%	22.7%
Pelvic fin length	16.6%	15.2%	15.3%	15.8%
Body depth of pelvic fin origin	20.8%	19.3%	18.8%	19.5%
Body depth of anal fin origin	23.8%	19.1%	20.0%	19.0%
Body width of anal fin origin	16.9%	13.2%	15.5%	13.7%
Pelvic fin origin to anus	29.4%	28.1%	28.5%	29.8%
% in HL
Snout length	29.8%	34.3%	33.4%	33.0%
Eye diameter	17.9%	25.4%	24.2%	25.4%
Postorbital length	40.8%	48.4%	45.1%	45.5%
Cheek depth	23.4%	28.7%	26.5%	27.1%
Head width in upper gill-opening	34.9%	50.3%	45.1%	52.1%
Head width in maximum	58.8%	74.8%	67.9%	78.8%
Fleshy interorbital width	15.1%	23.1%	19.0%	21.2%
Bony interorbital width	5.7%	8.3%	7.9%	7.2%
Lower jaw length	26.2%	29.3%	28.4%	29.3%

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. FIGURE 1 . Fresh catch of alive Rhinogobius phuocbinhensis n. sp. , Cai Phan Rang River basin, south central Vietnam. (upper one: male; lower one: female). Head lateral-line system ( Fig. 2 ) FIGURE 2 . Head lateral-line system of Rhinogobius phuocbinhensis , holotype, 38.9 mm SL, Cai Phan Rang River basin, south central Vietnam. 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 , 3–4 ) 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. FIGURE 3 . Rhinogobius phuocbinhensis , holotype (upper one), 38.9 mm SL; paratype, 40.9 mm SL, Cai Phan Rang River basin, south central Vietnam. 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 . FIGURE 4 . Head pigmentation pattern of Rhinogobius phuocbinhensis , holotype (upper one), 38.9 mm SL; paratype (lower one), 40.9 mm SL, Cai Phan Rang River basin, south central 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.