Rhinogobius ngutinhoceps, Endruweit, 2018

Endruweit, Marco, 2018, Description of four new species of freshwater gobies from the Black River drainage in China and Vietnam (Teleostei: Gobiidae), Zootaxa 4486 (3), pp. 284-310 : 297-302

Rhinogobius ngutinhoceps , new species

( Figs. 8–10 )

Holotype. ZFMK ICH-104105 , 40.0 mm SL, male; Muong So com., Phong Tho Cty., Lai Chau Prov., Vietnam; Nam So River , Nam Na River; coll. M. Endruweit & S.V. Ngo, 6 July 2015.

Paratype. KIZ 2015005363 , 1 specimen, female, 33.9 mm SL, data as for holotype.

Diagnosis. Rhinogobius ngutinhoceps can be distinguished from its congeners by the following combination of characters: presence of supraotic pore β in anterior oculoscapular canal; cheek and operculum with about 65 dark rounded to vermiform marks and branchiostegal membrane unmarked in males; snout pointed; lower jaw conspicuously protruding; cephalic lateralis pore λ absent; predorsal length to D1 40–41% SL; 12–15 predorsal scales; and 29 vertebrae.

Description. Morphometric proportions given in Table 3. Caudal peduncle short and shallow; depth 2.2 length in male, 2.5 in female. Head long, strongly depressed, wider than deep. Eye small, dorsolateral. Interorbital distance moderate. Cheek not inflated; edge of operculum represents maximum body width. Snout pointed. Mouth terminal, oblique, about 40° to body axis. Lips thick in male, thin in female. Maxilla extending vertical nearly through middle of orbit. Jaws each with 3 alternating rows of small villiform teeth; outer row slightly enlarged, recurved; lower jaw protruding. Mental frenum trapezoid. Gill opening relatively large, dorsally reaching upper origin of pectoral fin, ventrally reaching forward to isthmus. Gill rakers 3 + 7. Genital papilla short, not reaching origin of origin of anal fin. VC 11 + 18 = 29; AP 2; DF 3-22110 (holotype), 3- 122110. Largest known size 40.0 mm SL (holotype, male).

Fins. D 1 VI–VII; D 2 I,8; A I,7–8; P 16–17; C (7–8) + 7. First dorsal fin spine IV longest, non-filamentous, reaching origin of second dorsal fin when adpressed in male, not reaching fin origin in female. Second dorsal fin and anal fin reaching past midway to caudal-fin base in male, reaching midway in female. Pectoral fin oblong, with a pointed rear edge, reaching past anus in male, with rounded rear edge, reaching anus in female. Caudal fin spatulate, oblong with rounded rear edge.

Scales. LL 30–32; TR 10–12; PD 12–15; SDP 7–9; CPS 12. Flank scales arranged in regular rows; anterior margin of predorsal squamation linear to slightly furcate, laterally reaching forward to about preoperculum, medianly with small cycloid scales anterior to first dorsal fin ( Fig. 10 ); anterior margin of abdominal squamation obliquely bridging space between bases of pectoral and pelvic fins. Head, nape, prepectoral, prepelvic areas naked.

Cephalic lateralis system. Canals: Preorbital section of anterior oculoscapular canal reduced; terminal pore σ between nostrils, mesially; pores λ absent; pore κ located centrally at about posterior rim of orbit; postorbital section of oculoscapular canal with pore ω and pores α, β and ρ located laterally in oculoscapular groove; supraotic pore ω located dorsolaterally, slightly posterior to vertical through pore α. Posterior oculoscapular canal with terminal pores Θ and τ. Terminal pores ρ and Θ well separated by distance of about 1/3 eye diameter. Preopercular canal with pores γ, δ and ε along edge of preoperculum. Sensory papillae: Row a long with about 7 papillae slanting downward anteriorly, reaching vertical through mid of orbit. Row b long, with about 15 papillae, nearly horizontal. Row c long, from beneath anterior nostril to vertical through mid of orbit with about 14 prominent papillae. Row d long, with about 23 papillae, running along labial groove to about posterior rim of orbit. Rows c and d nearly parallel. Row cp as single papilla located between the terminals of rows c and d. Opercular rows os, ot and oi present; ot and oi not interconnected. Approximate pathways of canals and papillae rows depicted in Figure 10 .

Coloration of preserved specimens. Head and body light brown, gradually darker dorsally; abdomen beige. Predorsal area and flank with small dark brown spots; spots distinctively smaller than pupil, not coalescent; flank spots concentrated around midline. Scales in longitudinal series light brown with dark brown mark along distal edge. Snout, interorbital and nape dark gray to black; unmarked. Cheek and operculum light brown to gray with about 65 dark gray spots partially coalescent forming vermiform markings in male, light brown with about 55 small dark brown spots in female. Branchiostegal membrane gray, unmarked. Pectoral fin with gray crescentshaped mark along base in male, with four brown spots in female. First dorsal fin with 4 transverse rows of black spots superimposed by black blotch between spines I and III. Second dorsal fin with 5–6 transverse rows of black spots and broad white distal band. Caudal fin with 6–8 transverse rows of poorly marked, gray spots. Pectoral fin light gray to hyaline. Pelvic fin gray with white distal band. Anal fin gray.

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Distribution. Rhinogobius ngutinhoceps is only known from its type locality ( Fig. 4 ).

Etymology. The specific epithet derives from the Vietnamese ‘Ngu Tinh’, a mythical creature with the head of a fish, and from the Greek ‘kephale’ for head; in reference for the species' large gape; a compound noun in apposition.

Figures

FIGURE 4. Map of the Red River and adjacent drainages. Rivers: 1, Mekong; 2, Ma River, 3, Black River; 4, Red River; 5, Nanpanjiang River. Type localities: Ǫ, Rhinogobius coccinella; ●, R. nanophyllum; □, R. ngutinhoceps; ■, R. phuongae.

FIGURE 8. Rhinogobius ngutinhoceps, ZFMK ICH-104105, holotype, 40.0 mm SL, male; Phong Tho, Lai Chau, Vietnam; Nam Na River.

FIGURE 9. Rhinogobius ngutinhoceps, KIZ 2015005363, paratype, 33.9 mm SL, female; Phong Tho, Lai Chau, Vietnam; Nam Na River.

FIGURE 10. Rhinogobius ngutinhoceps, cephalic lateralis system, composite drawing based on holotype and paratype.