A new species of Vietnamophryne (Anura: Microhylidae) from Northeastern Vietnam Author Ninh, Hoa Thi 0009-0002-8133-432X Institute of Genome Research, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi, Vietnam ninhhoa. hnue @ gmail. com; https: // orcid. org / 0009 - 0002 - 8133 - 432 X ninhhoa.hnue@gmail.com Author Le, Linh Tu Hoang 0009-0002-8133-432X Institute of Genome Research, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi, Vietnam ninhhoa. hnue @ gmail. com; https: // orcid. org / 0009 - 0002 - 8133 - 432 X ninhhoa.hnue@gmail.com Author Bui, Hai Tuan 0009-0002-8133-432X Institute of Genome Research, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi, Vietnam ninhhoa. hnue @ gmail. com; https: // orcid. org / 0009 - 0002 - 8133 - 432 X ninhhoa.hnue@gmail.com Author Nguyen, Huy Quoc 0000-0003-3171-1561 Vietnam National Museum of Nature, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi, Vietnam huynguyen 17295 @ gmail. com; https: // orcid. org / 0000 - 0003 - 3171 - 1561 huynguyen17295@gmail.com Author Orlov, Nikolai Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, St. Petersburg, 199034, Russia Author Moseyko, Olga Bezman Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, St. Petersburg, 199034, Russia Author Le, Manh Van 0000-0002-7401-4830 Institute of Tropical Biology, Vietnam Academy of Science and Technology; 9 / 621 Hanoi Highway, Ho Chi Minh City, Vietnam leemanh 94 @ gmail. com; https: // orcid. org / 0000 - 0002 - 7401 - 4830 leemanh94@gmail.com Author Nguyen, Sang Ngoc 0000-0002-7401-4830 Institute of Tropical Biology, Vietnam Academy of Science and Technology; 9 / 621 Hanoi Highway, Ho Chi Minh City, Vietnam leemanh 94 @ gmail. com; https: // orcid. org / 0000 - 0002 - 7401 - 4830 leemanh94@gmail.com Author Hoang, Chung Van Forest Resources and Environment Centre, 300 Ngoc Hoi Road, Thanh Tri, Hanoi, Vietnam Author Ziegler, Thomas AG Zoologischer Garten Köln, Riehler Strasse 173, D- 50735 Cologne, Germany & Institute of Zoology, University of Cologne, Zülpicher Strasse 47 b, D- 50674 Cologne, Germany Author Nguyen, Tao Thien 0009-0002-8133-432X Institute of Genome Research, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi, Vietnam ninhhoa. hnue @ gmail. com; https: // orcid. org / 0009 - 0002 - 8133 - 432 X ninhhoa.hnue@gmail.com text Zootaxa 2023 2023-11-20 5374 4 505 518 https://mapress.com/zt/article/download/zootaxa.5374.4.3/52303 journal article 10.11646/zootaxa.5374.4.3 1175-5326 10158674 5DA74ABE-380E-4CDE-A0F3-5A9A4A2881C8 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 ). TABLE 3. Measurements (in mm) and proportions of the type series of Vietnamophryne aurantifusca sp. nov.

Field no	NH.2023.214/ IEBR A.5242	NH.2024.215/ IEBR A.5243
Holotype	Paratype
Sex	Male	Male
SVL	18.2	17.6
HL	5.8	5.9
SL	2.4	2.3
EL	1.6	1.7
N-EL	1.2	1.1
HW	6.9	6.9
IND	2.0	1.8
IOD	3.0	2.3
UEW	1.1	1.1
FLL	3.6	3.4
LAL	7	7.0
Ua	10.1	10
FeL	8.1	8.2
TL	8.3	8.5
FTL	11.3	11.7
TYD	0.8	0.9
TED	0.8	0.5
1FLO	0.7	0.7
2FLO	1.1	1.2
3FLO	2.1	2.3
4FLO	1.2	1.5
1TOEL	1.7	1.1
2TOEL	3.1	2.6
3TOEL	5.0	5.2
4TOEL	7.5	7.4
5TOEL	4.8	5.0
HW/HL	1.19	1.17
SL/HW	0.35	0.33
SL/EL	1.50	1.35
EL/HW	0.23	0.25
TYD/SVL	0.04	0.05
1FLO/2FLO	0.64	0.58

...Continued on the next page TABLE 3. (Continued)

Field no	NH.2023.214/ IEBR A.5242	NH.2024.215/ IEBR A.5243
N-EL/SL	0.50	0.48
TED/SVL	0.04	0.03
LAL/SVL	0.38	0.40
FLL/Ua	0.36	0.34
FeL/TL	0.98	0.97

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). 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. FIGURE 3. Dorsal view of Vietnamophryne aurantifusca sp. nov. , holotype (NH.2023.214) A and B; paratype (NH.2023.215) C and D after fixation. TABLE 4. Selected diagnostic characteristics for the species in the genus Vietnamophryne . ND = No data.

Species	Sex	SVL	Dorsolateral white spots	Ratio head width and head length	Ratio snout length and eye length	Tympanum length	Finger 1 length	Ventral coloration	Dorsal skin texture
Vietnamophryne aurantifusca sp. nov.	Male	17.55–18.24	Present	Head wider than long (HW/ HL 1.17–1.19)	Snout length greater than eye length (SL/EL 1.33–1.45)	Small tympanum (TYD/SVL 0.04– 0.05)	Well developed, more half of second finger (1FLO/ 2FLO 0.59–0.66)	Ventrally orange coloration with grey marbling concentrate on the throat	Dorsal skin relatively smooth, with some rounded nodules
Female	ND	ND	ND	ND	ND	ND	ND	ND
Male	ND	ND	ND	ND	ND	ND	ND	ND
Vietnamophryne cuongi	Female	16.9–18.1	Present	Head wider than long (HW/ HL 1.10–1.23)	Snout length greater than eye length (SL/EL 1.33–1.42)	Large tympanum (TYD/SVL 0.08– 0.09)	Well developed, about half of second finger (1FLO/2FLO 0.43–0.62)	Ventrally milky-white coloration with gray marbling	Mostly smooth skin on dorsum with somewhat enlarged flat pustules
V. orlovi	Male	15.4	Present	Head longer than wide (HW/ HL 0.87)	Snout length greater than eye length (SL/EL 1.39)	Smaller tympanum (TYD/ SVL 0.06)	Well developed, half of second finger (1FL/2FL 0.50)	Ventrally bright lemon- yellow with dark brown marbling	Smooth anteriorly, somewhat shagreened posteriorly with small flat pustules loosely scattered on posterior dorsum
	Female	17.1	Present	Head longer than wide (HW/ HL 0.98)	Snout length greater than eye length (SL/EL 1.31)	Smaller tympanum (TYD/ SVL 0.07).	Well developed, half of second finger (1FLO/ 2FLO 0.50)	Ventrally bright lemon- yellow with dark brown marbling	Smooth anteriorly, somewhat shagreened posteriorly with small flat pustules loosely scattered on posterior dorsum

...Continued on the next page TABLE 4. (Continued)

Species	Sex	SVL	Dorsolateral white spots	Ratio head width and head length	Ratio snout length and eye length	Tympanum length	Finger 1 length	Ventral coloration	Dorsal skin texture
V. vuquangensis	Male	14.1–14.9	Present	Head wider than long, (HW/HL 1.17– 1.24)	Snout length greater than eye length (SL/EL 1.19–1.28)	Tympanum relatively faint, comparatively small, rounded, 0.05–0.06 of SVL	Well developed, less than half of second finger (1FLO/2FLO 0.43–0.49)	Ventrally ivory-lemon to lemon-yellow with weak dark-brown marbling	Shagreened with small flat pustules loosely scattered on dorsum
Female	15.2–17.3	Present	Head wider than long, (HW/HL 1.10– 1.31)	Snout length greater than eye length (SL/EL 1.03–1.30)	Tympanum comparatively small, rounded, 0.05–0.06 of SVL	Well developed, less than half of second finger (1FLO/2FLO 0.44–0.50)	Ventrally bright lemon- yellow with weak dark- brow marbling	Mostly smooth, slightly shagreened posteriorly, lacking enlarge tubercles
V. inexpectata	Male	14.2	Present	Head as long as wide, (HW/HL 1.01)	Snout length comparable eye length (SL/EL 0.95)	Larger tympanum (TYD/SVL 0.09)	Rudimentary, slightly protuberant as nub (1FLO/ 2FLO 0.30)	Ventrally grayish-beige coloration with gray marbling	Warty skin on posterior and shagreened skin on anterior parts of dorsum
Female	ND	ND	ND	ND	ND	ND	ND	ND
V. occidentalis	Male	20.5	Absent	Head less longer than wide (HW/HL 0.99)	Snout length shorter than eye length (SL/EL 0.84)	Tympanum comparatively small, round, 0.05 of SVL	Well developed, half of F2 length (1FL/2FL 0.43)	Ventrally bright orange-red with sparse dark brown marbling	Completely smooth, posteriorly with loosely scattered small flat tubercles present
Female	ND	ND	ND	ND	ND	ND	ND	ND

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 ).