Microhyla xodangorum, 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 : 24-27

Microhyla xodangorum sp. nov.

urn:lsid:zoobank.org:act:2C2DD014-C1A0-439B-8B15-CFB30D715149

Figs 1–3 , 5–6 , 7B , Tables 1–3 , 5

Diagnosis

Microhyla xodangorum sp. nov. is distinguished from its congeners by a combination of the following morphological characteristics: 1) size large (SVL 25.6 in a single ♀); 2) snout profile round; 3) dorsal skin almost smooth with flat tubercles evenly scattered in dorsum; dorsolateral edges sharp; 4) chest and belly yellowish with indistinct greyish mottling laterally; chin grey with thickly greyish mottling and a thin, light-coloured medial stripe not reaching the chest; 5) first finger longer than one half of second finger; 6) disks on distal end of fingers II–IV weak; 7) tibiotarsal articulation at straightened limb well beyond snout.

Etymology

The specific name is a patronym for the Xo Dang people, an ethnic minority people in Kon Tum Province, Vietnam. Their assistance made it possible for us to collect the holotype of the new species in the montane forest of the Kon Tum Plateau, Central Highlands of Vietnam. We recommend ‘Xodang Narrow-mouth Frog’ as the common English name and ‘Nhái bầu xƠ đăng’ as the Vietnamese name.

Material examined

Holotype VIETNAM • adult ♀; Central Vietnam, Kon Tum Province, Kon Plong District, Mang Canh Commune ( Fig. 6 ); 14°38'49.2″ N, 108°15′39.9″ E; ca 1253m a.s.l.; 15 Sep. 2018; C.V. Hoang leg.; IEBR A.4913 (KP-MĐ-2018-21).

Description of holotype ( Fig. 6 )

Preserved specimens were in good condition.

HABITUS. Stocky, size medium (SVL 25.6 mm); head wider than long (HL/ HW 0.83); snout long, abruptly round in dorsal view, projecting beyond margin of lower jaw, longer than diameter of eye (SL / EL 1.29); eyes small, slightly protuberant, pupil round ( Fig. 6A ); nostril oval, lateral, nostril-eyelid length (N-EL 1.4 mm) shorter than eye length (EL 2.2 mm); dorsal surface of head flat, loreal region acute, canthus rostralis round; interorbital distance greater than internarial distance (IOD / IND 1.31) and upper eyelid width (IND/ UEW 1.68); tympanum hidden, supratympanic fold weak, from posterior corner of eye to arm insertion; vomerine teeth absent, tongue without papillae, oval and free at rear half of its length.

FORELIMBS. Short, about one-half of snout-vent length (FLL/ SVL 0.52); hand two times shorter than forelimb length (HAL/ FLL 0.45); fingers slender, free of webbing, round in cross-section, dermal fringes weak; first finger longer than one-half length of second finger (1FLO / 2FLO 0.53); second finger slightly longer than fourth (2FLI / 4FLI 1.35) and shorter than third (2FLI / 3FLI 0.67); relative finger lengths: I<IV<II<III ( Fig. 6C ). All disks bearing narrow peripheral grooves, dorsal surface of each fingertip with median longitudinal groove, forming two scutes; relative finger disk widths: I <IV<II <III; nuptial pad absent; subarticular tubercles on fingers distinct, round, formula: 1:1:2:2; inner metacarpal tubercle (IPTL 0.6) oval, prominent; an outer metacarpal tubercle quite round (OPTL 1.3).

HINDLIMBS. Slender and long (HLL 48.3 mm), tibia length longer than half of snout–vent length (TL/ SVL 0.60); tibiotarsal articulation at straightened limb well beyond snout; foot longer than tibia (FL /TL 1.38); relative toe lengths: I<II=V<III<IV; tarsus smooth, inner tarsal fold absent; tips of all toes distinctly dilated into disks, slightly wider than those of fingers (3TDW 1.0 mm, 3FDW/3TDW 0.78), 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: I1½–2½II1¾ –3III2¾– 3¾IV4 –2½V ( Fig. 6D ); dermal fringe distinct on toes; subarticular tubercles prominent, all present, circular, formula 1, 1, 2, 3, 2; outer metatarsal tubercle oval and distinct (OMTL 0.5) than length of inner metatarsal tubercle elongated, oval and prominent (IMTL 0.6).

SKIN. Dorsal surface of head and body almost smooth with flat tubercles evenly scattered on dorsum; dorsolateral edges sharp; dorsal surface of hind limbs and cloacal region with few low tubercles scattered; ventral surfaces smooth, present few tubercles in belly face of thighs near cloacal region.

Coloration of holotype in life ( Fig. 6A–B )

Dorsal surface of head and trunk beige with dark brown dust, forming the markings; a dark brown marking triangle shape between eyelids, continuing and then extending to the groin as a faint dark brown hourglass shape; the biggest black circle ‘o’ shape between middle of hourglass shape; few tiny black scapular spots and black dots scattered around the hourglass shape. Flanks and lateral head dark brown, supratympanic fold and armpit region beige; upper jaw dark brown with few tiny beige spots below the eye level; dorsal surfaces of limbs beige with dark brown crossbars and few small black spots ( Fig. 6A ). Chest and belly yellowish with indistinct greyish mottling laterally. Chin grey with thickly greyish mottling and a thin, light-coloured medial stripe not reaching the chest ( Fig. 6B ). Iris golden in upper one-third with black reticulation, dark copper in its lower two-third, darkly pigmented at anterior and posterior corners; pupil round, black ( Fig. 6A ).

Coloration of holotype in preservative

After preservation in ethanol, dorsal coloration changed from beige to whitish grey; ventral surface of chest, belly, and limbs changed from dark-beige to dark grey; 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.

Comparisons

Microhyla xodangorum sp. nov. differs from other species of the M. heymonsi group by the following characteristics: 1) size large (SVL 25.6 in a ♀) versus Microhyla hmongorum sp. nov. (SVL 13.8–17.4 in 5 ♂♂; 19.2–20.3 in 3 ♀♀), M. ninhthuanensis (SVL 17.3–18.8 in ♂♂; 21.6–23.6 in ♀♀), versus M. pineticola (SVL 17.2–19.5 in ♂♂; 18.0–23.0 in ♀♀); 2) snout profile round versus Microhyla hmongorum , M. pineticola , M. neglecta , (snout profile acuminate) and M. heymonsi s. str. (snout profile obtusely-pointed); 3) dorsum skin almost smooth with flat tubercles evenly scattered in dorsum; dorsolateral edges sharp versus Microhyla hmongorum (smooth with tiny and flat tubercles unevenly scattered, dorsolateral edges not sharp), 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), M. neglecta (smooth with evenly scattered small flat tubercles); 4) chest and belly yellowish with indistinct greyish mottling laterally; chin grey with thickly greyish mottling and a thin, light-coloured medial stripe not reaching the chest versus Microhyla hmongorum (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), 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, lightcoloured 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. group (first finger shorter than one half of second finger); 6) disks on distal end of fingers II–IV weak versus Microhyla hmongorum , M. daklakensis , M. ninhthuanensis , M. heymonsi s. str. (disks on distal end of all fingers); 7) tibiotarsal articulation at straightened limb well beyond snout versus Microhyla hmongorum , M. daklakensis , M. ninhthuanensis , M. heymonsi s. str. (shorter than snout). Detailed comparisons between Microhyla xodangorum 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 ground near the banks of a small stream in dipterocarp forest ( Fig. 7B ). Air temperatue was 21°C and relative humidity was 97%. Larval stages, eggs and the advertisement call of the new species are unknown.

Distribution

Microhyla xodangorum sp. nov. is currently only known from the type locality in Kon Tum Plateau, Kon Tum Province, Vietnam ( Fig. 7 B ). The species was found at an elevation of ca 1250 m a.s.l. Based on its habitat and altitudinal range, the new species is likely endemic to the Central Highlands of Vietnam. However, the extent of its actual distribution range requires further studies.

Figures

Fig. 1. Plots of the first principal component (PC1) versus the second (PC2) for the males and the females of Microhyla hmongorum sp. nov. (green), Microhyla xodangorum sp. nov. (pink), M. ninhthuanensis Hoang et al., 2021 (red), M. daklakensis Hoang et al., 2021 (blue), and M. cf. heymonsi Vogt, 1911 (black).

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. 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.).

Fig. 6. Microhyla xodangorum sp. nov., ♀, holotype (IEBR A.4913 (KP-MĐ-2018-21)). A. Dorsolateral view in life. B. Ventral view in life. C. Underside of right hand. D. Underside of right foot. 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.