Vietnamophryne aurantifusca, Ninh & Le & Bui & Nguyen & Orlov & Moseyko & Le & Nguyen & Hoang & Ziegler & Nguyen, 2023

Ninh, Hoa Thi, Le, Linh Tu Hoang, Bui, Hai Tuan, Nguyen, Huy Quoc, Orlov, Nikolai, Moseyko, Olga Bezman, Le, Manh Van, Nguyen, Sang Ngoc, Hoang, Chung Van, Ziegler, Thomas & Nguyen, Tao Thien, 2023, A new species of Vietnamophryne (Anura: Microhylidae) from Northeastern Vietnam, Zootaxa 5374 (4), pp. 505-518 : 509-515

Vietnamophryne aurantifusca sp. nov.

( Figure 2 )

Holotype. IEBR A.5242 (Field number NH.2023.214), adult male, collected in the karst forest of Sinh Long Commune , Na Hang District, Tuyen Quang Province, Vietnam (22°31’03.4”N; 105°23’18.6”E, at an elevation of 1.056 m a.s.l.) on 25 May 2023 by Nguyen et al.

Paratype. Adult male IEBR A.5243 (Field number NH.2023.215), the same data as the holotype .

Diagnosis. The new species from Tuyen Quang is distinguished from its congeners on the basis of the following characteristics: (1) Body size small SVL (n= 2 males, 17.6–18.2 mm); (2) Head wider than long, HW/HL 1.17–1.19; (3) snout short, round in dorsal view (SL/ HW 0.33–0.35), snout length greater than eye length (SL/ EL 1.33 – 1.50 ); (4) eye round ( EL / HW 0.23–0.25; (5) tympanum small, round, TYD / SVL 0.04–0.05; (6) first finger (F1) well developed, more than half of second finger (F2) (1 FLO/2 FLO 0.58–0.64), relative finger lengths: I<II<IV<III, relative toe lengths: I<II< V <III<IV; (7) tips of all digits round, not expanded in F1–F4, T1 , T2 , and T5 , weakly expanded in T3 and T4 ; (8) subarticular tubercles under fingers and toes indistinct; (9) outer metatarsal tubercle absent, inner metatarsal tubercle small, flattened; (10) dorsal skin relatively smooth with some rounded nodules, concentrated in the middle of the back, arranged along the length of the back, a prominent ridge along the spine; (11) orangish-brown with a small triangle shape between eyes; venter orange, with grey marbling, most intense on the throat, ventral side of limbs dark grey with some whitish marbling (For the measurement see Table 3 ).

Description of holotype. Habitus stout, body size small (SVL 18.2 mm), head wider than long (HW/HL 1.19), snout short, obtuse, round in dorsal view, truncate in lateral view (SL/HW 0.35) ( Fig. 2 ), snout length greater than eye length (SL/EL 1.50); nostril round, lateral, closer to the tip of snout than to eye (N-EL/SL 0.51); dorsal surface of head slightly convex; canthus rostralis distinct, round; loreal region concave; eyes round medium-sized (EL/HW 0.23); eyes slightly protuberant in dorsal and lateral views; pupil round; tympanum well discernible, circular, small (TYD/SVL 0.04), located distantly from the eye (TED/SVL 0.04), tympanic rim not elevated above skin of the temporal area, supratympanic fold present, distinct, glandular ( Fig. 2 ); vomerine teeth and spikes absent; tongue spatulate and free behind, papillae on tongue absent and vocal sac opening very small and hard to spot, deep in the palate.

Forelimbs. Short, greater than one-fifth of body length (LAL/SVL 0.38); lower arm shorter than hand, almost one-third of forelimb length (FLL/Ua 0.36); fingers short, round in cross-section, first finger well developed, more than half of second finger (1FLO/2FLO 0.64); relative finger lengths: I<II<IV<III ( Fig. 2D ); webbing absent; dermal fringes present, weakly developed. Tip of the first finger rounded, slightly tapered. Tips of fingers II–V rounded, not dilated, finger disks absent, terminal grooves absent; longitudinal furrow on dorsal surface of fingers absent; subarticular tubercles under fingers indistinct; nuptial pad absent; two palmar tubercles: inner palmar tubercle small, rounded; outer palmar tubercle rounded; palmar surface smooth, supernumerary palmar tubercles absent.

Hindlimbs. Short and thick, thigh length less than half of the snout-vent length (FeL/SVL 0.45); tibiotarsal articulation of adpressed limb reaching eye level; femur length nearly equal to tibia length (FeL/TL 0.97); relative toe lengths: I<II<V<III<IV; tarsus smooth, tarsal fold absent; tips of toes rounded, first toe slightly tapered, tips of toes III and IV slightly dilated ( Figure. 2E ), terminal grooves absent; toes rounded in cross-section; webbing absent between all toes; dermal fringes on toes present, weakly developed; subarticular tubercles under toes ovoid, slightly flattened; single metatarsal tubercle: inner metatarsal tubercle rounded, flattened.

Skin texture. Dorsal skin relatively smooth with some rounded nodules, concentrated in the middle of the back, arranged along the length of the back, a prominent ridge along the spine, dorsal surfaces of the forearm, posterior and lateral parts of the dorsum, sacral area, and dorsal surfaces of hindlimbs shagreened; upper eyelids slightly harsh, supratympanic folds with low glandular ridges; ventral sides of the trunk, head and limbs completely smooth; well developed distinct dermal ridge present on midline of head and dorsum, running from between eyes to vent.

Color of holotype in life. Dorsum orangish-brown, posteriorly darker, tubercles dark brown, densely scattered on dorsal surfaces of head, body, and limbs ( Fig. 2A, C ); posterior parts of dorsum of hindlimbs dark brown with black pustules; canthus rostralis ventrally dark brown; loreal region dark with some whitish mottling on lower jaw and mouth; upper eyelids dark brown; dorsal surfaces of forearms orange brown interspersed with greyish brown; supratympanic fold dark-brown with some whitish pustules; ventrally orange, fainter on chest, throat, and ventral surfaces of limbs, and with grey marbling, concentrated on the throat and ventral surfaces of limbs; ventral sides of fingers and toes dark grey with some whitish marbling. Pupil rounded, black, iris uniform dark brown.

Color of holotype in preservative: Dorsal surface changed from brown to grey scattered with dark-brown tubercles and pustules; ventral surface of body faded completely to creamy white with dark-grey marbling denser on the throat, hands, tibia and feet.

Variation. The holotype IEBR A.5242 has more tubercles on dorsum than the paratype IEBR A.5243.

Etymology. Specific epithet is based on the Latin word for orange (aurantium) and brown (fuscus) and refers to the orange brown colouration of the new species. As for the common English name of the new species, we propose Orange-brown Dwarf Frog and the common name in Vietnamese as “Nhái lùn nâu cam”.

Distribution. Vietnamophryne aurantifusca sp. nov. is currently known only from the type locality in Tuyen Quang Province, Vietnam.

Comparisons. Comparative morphological characteristics are given in Table 4 . Vietnamophryne aurantifusca sp. nov. can be distinguished from the other Vietnamophryne species by a combination of the following characteristics: from V. cuongi by having dorsal skin relatively smooth, with some rounded nodules, concentrated in the middle of the back vs. mostly smooth skin on dorsum with somewhat enlarged flat pustules in V. cuongi ; Dorsum orangish-brown with a grey patch in triangle shape between eyes; ventral side orange, with grey marbling in Vietnamophryne aurantifusca sp. nov. vs. dorsally black brown, pustules on lateral dorsum white-brown and ventral side milkywhite with grey marbling in V. cuongi ( Nguyen et al. 2021) .

From V. inexpectata by having a larger size in males (SVL 17.6–18.2 mm vs. 14.2 mm in V. inexpectata ); head wider than long vs head as long as wide (HW/HL 1.17–1.19 vs. 1.01 in V. inexpectata ); snout length greater than eye length (SL/EL 1.35–1.50 vs. 0.95 in V. inexpectata ); a smaller tympanum (TYD/SVL 0.04–0.05 vs. 0.09 in V. inexpectata ); first finger more developed (1FLO/2FLO 0.58–0.64 vs. 0.30 in V. inexpectata ); ventral surface orange (vs. greyish-beige coloration in V. inexpectata ; dorsum relatively smooth with some rounded nodules, arranged along the length of the back, a prominent ridge along the spine (vs. warty skin on posterior and shagreened skin on anterior parts of dorsum in V. inexpectata ) ( Poyarkov et al. 2018).

From V. occidentalis by having a smaller size (SVL 17.6–18.2 mm vs. 20.5 in V. occidentalis ); white spots on dorsolateral region (vs. absent in V. occidentalis ); snout length greater than eye length (SL/EL 1.33–1.42 vs. 0.84 in V. occidentalis ; first finger well developed (1FL/2FL 0.59–0.66 vs 0.43 in V. occidentalis ); ventral surface orange with grey marbling (vs. bright orange-red with sparse dark brown marbling in V. occidentalis ) ( Poyarkov et al. 2018).

From V. orlovi by having a greater size in males (SVL SVL 17.6–18.2 mm vs. 15.4 mm in V. orlovi ); head wider than long vs head longer than wide (HW/HL 1.17–1.19 vs. 0.87 in V. orlovi ); a smaller tympanum (TYD/SVL 0.04–0.05 vs. 0.06 in V. orlovi ); first finger more developed (1FLO/2FLO 0.58–0.64 vs. 0.50 in V. orlovi ); ventral surface orange with grey marbling (vs. bright lemon-yellow with dark brown marbling in V. orlovi ) ( Poyarkov et al. 2018).

From V. vuquangensis by having a greater size (SVL 17.6–18.2 mm vs. 14.1–14.9 mm in V. vuquangensis ); first finger more developed (1FLO/2FLO 0.58–0.64 vs. 0.43–0.49 in vs. V. vuquangensis ); ventral surface orange with grey marbling (vs. ivory-lemon to lemon-yellow with weak dark-brown marbling in V. vuquangensis ). Dorsum orangish-brown, posteriorly darker, tubercles dark brown densely scattered in Vietnamophryne aurantifusca sp. nov. (vs. dorsum reddish-grey on black tone, black markings mixed with small, densely scattered speckles in V. vuquangensis ) ( Hoang et al. 2021).

Figures

FIGURE 2. Dorsal, ventral, and lateral views of the holotype of Vietnamophryne aurantifusca sp. nov (A, B & C). Ventral sides of the right hand and the left foot with scale bar 2 mm (D & E).