Rhinogobius nanophyllum, 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 : 294-297

Rhinogobius nanophyllum , new species

( Figs. 5–7 )

Holotype. ZFMK ICH-104094 , 58.1 mm SL, male; Chahe village , Jiangcheng Cty., Puer Pref., Yunnan Prov., China; Mengyejiang River; coll. M. Endruweit, 28 Dec. 2011 .

Paratypes. ZFMK ICH-104095-4098 , 4 specimens, 48.5–55.4 mm SL, data as for holotype . ZFMK ICH- 104084-4091, 8, 43.2–59.6 mm SL, location as for holotype, coll. M. Endruweit & J. Wang, 30 Dec. 2009 . KIZ 2011002879, 2880, 2884, 2887-2890, 6, 42.8–56.8 mm SL, location and collector as for holotype, 30 Dec. 2011.

Diagnosis. Rhinogobius nanophyllum can be distinguished from its congeners by the following combination of characters: cheek, operculum and pectoral-fin base with about 90 indistinct white rounded to vermiform marks, caudal fin plain-colored, and second dorsal fin with very broad dark gray median band and broad white proximal band reaching procurrent caudal-fin rays in males; predorsal area with a large somewhat squarish black blotch immediately anterior to the dorsal-fin origin in males, blotch absent in females; caudal-peduncle length of 22–25% SL and pectoral-fin length of 21–24% SL in males; head width at tip of operculum of 53–58% HL in males and 58- 61% HL in females; 0 predorsal scales; 8–10 [9] branched rays in second dorsal fin; 7–8 [8] branched anal-fin rays; and 28 vertebrae.

Description. Morphometric proportions given in Table 2. Caudal peduncle short and moderately shallow; depth 1.9–2.4 length in males, 1.9–2.2 in females. Head long, slightly depressed, wider than deep. Eye large, dorsolateral. Interorbital distance short. Cheek inflated in males, moderate in females; representing maximum body width. Snout rounded. Mouth terminal, oblique, about 25° to body axis in males, about 45° in females. Lips thick, fleshy in males, thin in females. Maxilla extending past vertical through anterior rim of orbit. Jaws each with 4 alternating rows of small villiform teeth; outer 2 rows slightly enlarged; upper jaw protruding. Mental frenum fully interrupting lower lip in males larger than about 55 mm SL. Gill opening relatively large, dorsally reaching upper origin of pectoral fin, ventrally reaching forward to isthmus. Gill rakers 4 + 7. Genital papilla long, reaching origin of origin of anal fin in males. VC 11 + 17 = 28; AP 2–3 [3]; DF 3-22110, 3-21210 [3-22110]. Largest known size 59.6 mm SL (ZFMK ICH-104088, paratype, male).

Fins. D 1 VI; D 2 I,8–10 [9]; A I,7–8 [8]; P 15–17 [16]; C 7 + 7. First dorsal fin spine IV longest, nonfilamentous, reaching origin of first branched ray of second dorsal fin when adpressed in males, not reaching fin origin in females. Second dorsal fin reaching procurrent caudal-fin rays in males, not reaching midway to caudalfin base in females. Anal fin reaching past midway to caudal-fin base in males, not reaching midway in females. Pectoral fin oval, long, reaching anus in males; nearly circular, short, not reaching anus in females.

Scales. LL 29–32 [31]; TR 11–12 [11]; PD 0; SDP 9–13 [11]; CPS 12. Flank scales arranged in regular rows; anterior margin of predorsal squamation deeply concave, laterally reaching forward to about pore τ ( Fig. 7 ); anterior margin of abdominal squamation obliquely bridging space between bases of pectoral and pelvic fins. Head, nape, prepectoral, pre- and subpelvic areas and tapering median strip anterior to anus naked.

Cephalic lateralis system. Canals: Preorbital section of anterior oculoscapular canal with terminal pore σ between nostrils, mesially; pore λ and central pore κ located at about vertical through anterior rim of orbit and posterior rim, respectively; postorbital section of oculoscapular canal with pore ω located dorsolaterally, slightly posterior to vertical through pore α; pores α and ρ located laterally in oculoscapular groove. Posterior oculoscapular canal with terminal pores Θ and τ. Terminal pores ρ and Θ separated by distance of about 1/6 eye diameter. Preopercular canal with pores γ, δ and ε along edge of preoperculum. Sensory papillae: Row a long with about 6 papillae slanting downward anteriorly, reaching past vertical through mid of orbit. Row b long, with about 17 papillae slanting downward posteriorly. Row c long, from beneath anterior nostril to vertical through posterior rim of orbit with about 10 prominent papillae. Row d long, with about 25 papillae, running along labial groove to about posterior rim of orbit. Rows c and d nearly diverging. 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 7 .

Coloration of preserved specimens. Head and body brown; dorsum dark brown with reddish brown hue; abdomen beige. Flank with midlateral series of six diffuse dark brown to black blotches interconnected over dorsum; blotches usually thinner than interspaces. Scales in longitudinal series beige with dark brown to black mark along distal edge. Nape gray. Cheek brown with dark reddish brown hue. Operculum light brown. Cheek, operculum and pectoral-fin base with about 90 indistinct white spots in males, spots partially coalescent and smaller than pupil. Predorsal area with black vermiform lines and large somewhat squarish black blotch immediately anterior to the dorsal-fin origin in males, blotch absent in females. Upper half of cheek and operculum and predorsal area with pattern of beige to brown spots on black ground leaving thin borders between spots in females, spots partially coalescent forming vermiform lines and about size of the pupil. Branchiostegal membrane gray, mesially turning beige, unmarked. Pectoral fin with vertical dark brown mark along base; inconspicuous in males, conspicuous in females. First dorsal fin with conspicuous black band over entire length, most intense anterior to spine IV, and broad proximal white band in males, with 3–5 transverse rows of gray spots in females. Second dorsal fin with very broad dark gray median band and broad white distal band in males, with 4–5 transverse rows of gray spots in females. Caudal fin plain beige to gray with white distal band in males, six transverse rows of gray spots in females. Pectoral beige basally to gray distally. Pelvic fin gray with white distal band. Anal fin beige with broad dark brown median band and white distal band in males, plain beige in females.

Distribution. Sympatric with Rhinogobius coccinella , but more abundant; Mengyejiang River, Jiangcheng County, Puer Prefecture, Yunnan Province, China ( Fig. 4 ).

Etymology. A compound of the Greek words ‘nanos’ for minute and ‘phyllon’ for leaf; Latinized. The enlarged second dorsal and anal fins in males of Rhinogobius nanophyllum , which are fully stretched during courtship, somewhat resembling a small leaf floating over the substratum; a 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 5. Rhinogobius nanophyllum, ZFMK ICH-104094, holotype, 58.1 mm SL, male; Jiangcheng, Yunnan, China; Mengyejiang River.

FIGURE 6. Rhinogobius nanophyllum, KIZ 2011002884, paratype, 49.7 mm SL, female; Jiangcheng, Yunnan, China; Mengyejiang River.

FIGURE 7. Rhinogobius nanophyllum, cephalic lateralis system, composite drawing based on holotype and paratypes.