Microhyla hmongorum, Van Hoang & Nguyen & Phan & Pham & Ninh & Wang & Jiang & Ziegler & Nguyen, 2022

Hoang, Chung Van, Nguyen, Tao Thien, Phan, Tien Quang, Pham, Cuong The, Ninh, Hoa Thi, Wang, Bin, Jiang, Jianping, Ziegler, Thomas & Nguyen, Truong Quang, 2022, Distribution pattern of the Microhyla heymonsi group (Anura, Microhylidae) with descriptions of two new species from Vietnam, European Journal of Taxonomy 846, pp. 1-41 : 18-24

Microhyla hmongorum sp. nov.

urn:lsid:zoobank.org:act:3158A3D2-A0D7-43C5-B7E3-C7247567E1AA

Figs 2–3 , Tables 1–3

Diagnosis

Microhyla hmongorum sp. nov. is distinguished from its congeners by a combination of the following morphological characters: 1) size small (SVL 13.8–17.4 in 5 ♂♂; 19.2–20.3 in 3 ♀♀); 2) snout profile acuminate; 3) dorsal skin smooth with tiny and flat tubercles unevenly scattered, dorsolateral edges not sharp; 4) chest and belly creamy-white fades towards the groin and thighs with indistinct grayish mottling along the thighs and belly edges, chin, throat pinkish white with scattered indistinct grayish mottling; 5) first finger longer than one half of second finger.

Etymology

The specific name is a patronym for the H’Mong people, an ethnic minority people in the northwest montane regions of Vietnam. Their assistance made it possible for us to collect the type specimens of the new species in the montane forest of Lai Chau Province, northwestern Vietnam. We recommend ‘Hmong Narrow-Mouth Frog’ as the common English name and ‘Nhái bầu hmông’ as the Vietnamese name.

Material examined

Holotype VIETNAM • adult ♂; northern Vietnam, Lai Chau Province, Tam Duong District ( Fig. 4 ); 22°21′15.7″ N, 103°36′36.4″ E; 1362 m a.s.l.; 22 May 2020; C.V. Hoang et al. leg.; IEBR A.4905 ( TD-LC2020.121 ).

Paratypes VIETNAM • 4 adult ♂♂; same collection data as for holotype; IEBR A.4906–4907 ( TD-LC2020.122 , TD-LC2020.123 ), IEBR A.4908–4909 ( TD-LC2020.129 , TD-LC2020.130 ) • 3 adult ♀♀; same collection data as for holotype; IEBR A.4910 ( TD-LC2020.124 ), IEBR A.4911–4912 ( TD-LC2020.131 , TD-LC2020.132 ) .

Description of holotype ( Fig. 4 , Table 3 )

Preserved specimens were in good condition.

HABITUS. Stocky, SVL 17.4 mm; body triangular shaped; head as long as wide (HL/ HW 1.00); snout long, abruptly round in dorsal view, projecting beyond margin of lower jaw, equal to diameter of eye (SL/EL 1.02); eyes small, slightly protuberant, pupil round ( Fig. 4F ); dorsal surface of head flat, canthus rostralis round; loreal region steep, weakly concave; nostril round, lateral, below canthus rostralis, nostril-eyelid length (N-EL 1.3 mm) greater than one half of eye length (N-EL/ EL 0.61); interorbital distance (IOD 1.8 mm) greater than internarial distance (IND 1.5 mm) and upper eyelid width (UEW 1.4 mm); pineal spot absent, tympanum hidden, supratympanic fold weak, extending from posterior corner of eye to arm insertion; vomerine teeth absent; tongue without papillae, roundly spatulate and free at the rear half of its length; slit-like openings to a median vocal sac.

FORELIMBS. Short, about two times as long as snout–vent length (FLL/SVL 0.57); hand length two times shorter than forelimb length (HAL/ FLL 0.42); fingers slender, free of webbing, a little flat in cross-section, with skin fringes on fingers present, dorsoventrally flattened; first finger well developed, longer than one-half length of second finger (1FLO/ 2FLO 0.69), second finger slightly longer than fourth (2FLI / 4FLI 1.32) and longer than one-half length of third finger (2FLI / 3FLI 0.68); relative finger lengths: I<IV<II<III ( Fig. 4C ); dorsal surface of fingertip with median longitudinal groove, forming two scutes, grooves present in all fingers; relative finger disk widths: I<IV<II<III; nuptial pad absent; subarticular tubercles on fingers distinct, round, formula: 1:1:2:2 (given for fingers I:II:III:IV, respectively); inner metacarpal tubercle round and prominent (IPTL 0.6 mm); a paired outer metacarpal tubercle divided by a waistline into two unequally sized parts (OPTL 0.5 mm): outer part slightly oval, greater than inner part quite crescent ( Fig. 4C ).

HINDLIMBS. Slender and slightly short (HLL 30.5 mm), tibia length longer than half of snout–vent length (TL/ SVL 0.53); tibiotarsal articulation at straightened limb not reaching snout; foot longer than tibia (FL/TL 1.54); relative toe lengths: I<II<V<III<IV; tarsus smooth, inner tarsal fold absent; tips of all toes distinctly dilated into disks ( Fig. 4D ), wider than those of fingers (3TDW 0.5 mm, 3FDW/ 3TDW 0.69), dorsal surface of all toes with median longitudinal grooves at disks; relative toe disk widths: I<V<II<III <IV; webbing between toes basal and poorly developed, webbing formula: I2–2½II2 –3½III3 –4⅓IV4⅓ –3V ( Fig. 4D ); subarticular tubercles on toes small, prominent, round, formula 1, 1, 2, 3, 2; inner metatarsal tubercle elongated, oval, large and prominent (IMTL 0.4); outer metatarsal tubercle round, elevated and very distinct, slightly greater (OMTL 0.6) than length of inner metatarsal tubercle.

SKIN. Dorsal surface smooth with tiny and flat tubercles unevenly scattered; dorsolateral edges not sharp; upper eyelid without supraciliary spines; flanks of body and lateral sides of head smooth, hindlimb dorsally scattered with some low pustules; ventral side of body and limbs smooth, vent area smooth with several low tubercles in cloacal region ( Fig. 4B ). Cloacal opening unmodified, directed posteriorly, at lower level of thighs.

Coloration of holotype in life

Dorsal surface of head and trunk beige with dark brown dust forming blurred markings; two dark brown tiny spots between eyelids; a small dark brown marking in ‘()’-shape in the center of dorsum; a middorsal line extending from the tip of snout to vent; a dark brown rhombus pattern on dorsum: one side is a small dark marking in ‘()’-shape, one side is a small dark brown blurred marking in ‘()’-shape.

Flanks and lateral side of head dark with a dark lateral stripe running from tip of snout to nostril, fading towards upper jaw ( Fig. 4A ). Chest and belly creamy white fading towards the groin and thighs with indistinct grayish mottling along the thighs and belly edges. Chin, throat pinkish white with scattered indistinct grayish mottling ( Fig. 4B ). Limbs dorsally beige with narrow blurred dark brown crossbars; fingers and toes dorsally brown with scattered dark brown crossbars; limbs ventrally crystal-clear with scattered dark grey and white dust, getting thicker toward shank and foot. Iris bicolored, golden in upper third, dark copper in its lower two thirds; pupil oval, horizontal, black.

Coloration of holotype in preservative

After preservation in ethanol, dorsal coloration changed from beige to greyish beige; ventral surface of chest, belly, and limbs changed from crystal clear to white; dorsal pattern, dark spots on dorsum and stripes on dorsal surfaces of limbs unchanged, dark brown pattern changed to dark grey; iris completely black, pupil round, white.

Variation

The paratypes vary in body size, coloration of dorsal surface, dorsal marking and black scapular spots. Adult males are smaller than adult females. The female’s belly is whiter than that of the male.

Comparisons

Microhyla hmongorum sp. nov. is distinguished from other members of the Microhyla heymonsi group by the following morphological characteristics: 1) body size small (SVL 13.8–17.4 in 5 ♂♂; 19.2–20.3 in 3 ♀♀) versus M. ninhthuanensis (SVL 17.3–18.8 in ♂♂; 21.6–23.6 in ♀♀), M. daklakensis (SVL 17.7– 20.1 in ♂♂; 22.9–26.8 in ♀♀), M. neglecta (SVL 18.7–20.2 in ♂♂; 23.4–26.2 in ♀♀); 2) snout profile acuminate versus M. ninhthuanensis , M. daklakensis (snout profile rounded) and M. heymonsi s. str. (snout profile obtusely pointed); 3) dorsal skin smooth with tiny and flat tubercles unevenly scattered, dorsolateral edges not sharp versus M. ninhthuanensis (smooth, flanks shagreened; dorsolateral edges not sharp), M. daklakensis (smooth, flanks smoothly shagreened; dorsolateral edges not sharp), M. heymonsi s. str. (smooth, dorsolateral edges not sharp), M. pineticola (almost smooth above, with few tiny tubercles scattered in posterior part of dorsum and along the dorsolateral edges; dorsolateral edges sharp), M. neglecta (smooth with evenly scattered small flat tubercles; dorsolateral edges sharp); 4) chest and belly creamy white fades towards the groin and thighs with indistinct grayish mottling along the thighs and belly edges, chin, throat pinkish white with scattered indistinct grayish mottling versus M. ninhthuanensis , M. daklakensis , M. heymonsi s. str. (chest and belly creamy white; chin dark grey; throat white with scattered dark grey dusting), M. pineticola (belly purplish-grey with indistinct whitish mottling; chin dark greyish with orange speckles and a thin light coloured medial stripe continuing to chest and belly), M. neglecta (chest and belly yellowish with indistinct greyish marbling laterally; centre of chin grey, sides dark brown to black with a thin, light-coloured medial stripe not reaching the chest); 5) first finger longer than one half of second finger versus M. ninhthuanensis , M. pineticola , M. heymonsi s. str. (first finger shorter than one half of second finger). Detailed comparisons between Microhyla hmongorum and other species of the M. heymonsi group are shown in Table 5 and of the genus Microhyla in total are shown in Appendix 1.

Natural history

All specimens were collected at night from 19:00 to 23:00 on the forest trails near streams in the evergreen forest at an elevation of 1300 m a.s.l. ( Fig. 7A ). Air temperature was 23°C and relative humidity was 89%. Other anuran species found at the type locality were Leptobrachella ventripunctata (Fei, Ye & Li,

1990) and Limnonectes bannaensis Ye, Fei, Xie & Jiang, 2007 . Larval stages, eggs and advertisement call of the new species are unknown.

Distribution

Microhyla hmongorum sp. nov. is known from Hoang Lien Range, NW Vietnam. Garg et al. (2019) reported this species from Phongsali and Luang Prabang provinces of Laos and Poyarkov et al. (2019) recorded the species from Kachin of Myanmar. It is expected to be found in southwestern Yunnan Province, China as well ( Fig. 5 ).

Figures

Fig. 2. Bayesian inference matrilineal genealogy of the Microhyla heymonsi group derived from the analysis of 12S rRNA–16S rRNA mtDNA sequences. Numbers above and under branches are Bayesian posterior probabilities and ML bootstrap values. The scale bar represents 0.1 nucleotide substitutions per site.

Fig. 3. Bayesian inference matrilineal genealogy of the Microhyla heymonsi group derived from the analysis of 16S rRNA mtDNA sequences. Numbers above and under branches are Bayesian posterior probabilities and ML bootstrap values; the scale bar represents 0.5 nucleotide substitutions per site.

Fig. 4. Microhyla hmongorum sp. nov., ♂, holotype (IEBR A.4905 (TD-LC2020.121)). A. Dorsolateral view in life. B. Ventral view in life. C. Underside of left hand. D. Underside of right foot. E. Lateral view of the head. Scale bars = 1 mm.

Fig. 7. A. Habitat ofMicrohyla hmongorum sp. nov. in Tam Duong District, Lai Chau Province, Vietnam. B. Habitat of Microhyla xodangorum sp. nov. in Kon Plong District, Kon Tum Province, Vietnam. Photos by C.V. Hoang.

Fig. 5. Map showing the distribution pattern of the Microhyla heymonsi group based on available molecular and morphological data collected from East and Southeast Asia (red area: M. heymonsi s. str. Vogt, 1911 and M. cf. heymonsi; yellow area: Microhyla sp1; blue area: Microhyla sp2; green area: M. ninhthuanensis Hoang et al., 2021; pink area: Microhyla hmongorum sp. nov.).