Berdmore’s narrow-mouthed frog.

Engystoma berdmorei Blyth, 1856 “1855”: 720. Type(s): not stated. Type locality: “Schwe Gyen” (now Shwegyin) on the Sitang River, “Pegu” (now Bago Region), Myanmar; Sclater (1892: 23).

Callula natatrix Cope, 1867: 192. Syntypes: MCZ 630 (= MCZ 1587), and MCZ A-153454-57 (apparently renumbered), according to Barbour and Loveridge (1929) and Harvard University, USA data (http://mczbase.mcz.harvard.edu). Type locality: “Near Rangoon, Burmah” (now Yangon Region, Myanmar); Li et al. (2019: 568).

Diplopelma (Engystoma) berdmorei — Günther (1868: 146).

Diplopelma pulchrum Theobald (1868: 83, in part) (non Engystoma pulchrum Hallowell, 1861, now Microhyla pulchra; misidentification).

Diplopelma berdmorei — Theobald (1873: 112).

Microhyla berdmorii — Boulenger (1882: 166). Incorrect subsequent spelling.

Microhyla (Engystoma) berdmorei — Mason (1882: 292).

Microhyla (Engystoma) berdmorei — Boulenger in Mason (1882: 500).

Microhyla berdmorei — Bourret (1942: 509, in part); Frank and Ramus (1995: 90, in part); Dutta (1997: 58–59, in part); Das and Dutta (1998: 64); Chanda (2002: 36-39, in part); Choudhury (2002: 277, in part); Devi and Shamungou (2006: 317–324); Sarkar and Ray (2006: 291, in part); Das and Dutta (2007: 154–181); Wogan et al. (2008: 88, in part); Dinesh et al. (2009: 302: in part); Mahony et al. (2009: 80–94); Mathew and Sen (2010: 65–66); Sengupta et al. (2010: 30); Bjiu et al. (2019: 103); Garg et al. (2019: 15, in part); Li et al. (2019: 566, in part); Nguyen et al. (2019: 549-580, in part); Ahmad and Mim (2020: 36–71); Gorin et al. (2020: 1–47, in part); Hakim et al. (2020: 1239-1268); Poyarkov et al. (2020c: 1525–1558, in part); Gorin et al. (2021: 97, in part); Kundu et al. (2021: 1586–1591, in part); Zug (2022: 30, in part); Raj et al. (2023: 57–61); Dinesh et al. (2023: 7, in part); Frost (2024, page “Microhyla berdmorei” in part).

Microhyla (Microhyla) berdmorei — Dubois (1987: 3).

Microhyla butleri (non Microhyla butleri Boulenger, 1900) — Lalremsanga et al. (2007: 348; misidentification).

Microhyla sp. — Hasan et al. (2012: 162–172).

Not stated in the original publication; ZSIC 9718–20 (not examined by us) were listed as syntypes by Sclater (1892), although Blyth (1856) provided measurements for a single specimen. Garg et al. (2019) discussed the confusing status of the type specimens; see discussion below.

Microhyla berdmorei sensu stricto is characterized by a combination of the following morphological features: (1) large body size (SVL 33.0 mm in a male, 36.3−38.1 mm in females), with moderately slender and triangular body habitus; (2) head wider than long; (3) dorsal skin shagreened with occasional small tubercles; (4) snout rounded in dorsal and ventral views, obtusely pointed in lateral view; (5) first finger shorter than half of the second finger length; (6) finger tips with weak disks bearing wide and shallow dorsomedial grooves; (7) toes with distinct disks, each bearing a narrow and deep dorsomedial groove; (8) tibiotarsal articulation of the adpressed limb extending far beyond snout; (9) toe webbing reaching disks on all toes except toe IV; webbing formula: i1-1ii1-2iii1-2iv2-1v; (10) throat and chin dusty gray to almost black in breeding males; belly yellowish-white; (11) dorsal surfaces of forelimbs and hindlimbs with narrow prominent crossbars, up to 5–6 crossbars on thighs; (12) dark-brown patch above cloacal opening inverted-U-shaped or crescent-shaped; dark blotches on both sides of cloaca; (13) dorsum generally with distinct olive-brown “teddy-bear”-pattern edged with light brown; dark dorsal markings may be indistinct or completely absent; (14) body flanks with black irregular spots and blotches; (15) broad olive-gray lateral band extending from armpit to middle of trunk; (16) light postocular stripe yellowish-beige with no dark edging; (17) reddish spots on dorsum and dorsal surfaces of hindlimbs absent; (18) iris with black stripe below the pupil.

In this study, we used morphological data from five specimens of M. berdmorei sensu stricto from India (see Table S2 for details).

An adult female in a good state of preservation. Body size large (SVL 36.4 mm; other measurements are presented in Table S2). Body habitus slender, triangular, and dorsoventrally flattened (Fig. 9). Head triangular in dorsal view; wider than long (HW/HL ratio 1.19). Snout comparatively short and protruding (SL/HL ratio 0.46), rounded in dorsal view (Fig. 9A), obtusely pointed in profile, noticeably extending beyond the edge of the lower jaw (Fig. 9E). Eyes large, protruding in dorsal and lateral views, significantly shorter than the snout (EL/SL ratio 0.71), slightly longer than interorbital distance (IOD/EL ratio 0.90). Canthus rostralis distinct, rounded; loreal area slightly concave. Nostrils oval-shaped, with lateral orientation, situated below the canthus rostralis, slightly closer to tip of snout than to eye. Interorbital distance greater than internarial distance (IND/IOD ratio 0.86). Upper eyelid length less than the interorbital distance (UEW/IOD ratio 0.79). Tympanum concealed, supratympanic fold indistinct, marked by a series of low tubercles (Fig. 9E). Tongue slender, rounded, free for the posterior four-fifths of its length; vomerine teeth absent. Eggs seen through the incision on the left lateral side of belly; eggs small, rounded, ca. 1.3–1.5 mm in diameter, pigmented (Fig. 9B).

Forelimbs short and slender (Fig. 9A, B); lower arm elongated and thin (LAL/FLL ratio 0.85), hand less than half of forelimb length (HAL/FLL ratio 0.48). Fingers slender and elongated; finger webbing or skin fringes absent. First finger well-developed, notably less than half of the second finger length (Fig. 9D); the relative finger length formula: I < II ≤ IV < III. Fingertips rounded, slightly expanded into disks notably narrower than the basal phalanges of the respective fingers. Finger tips lacking peripheral grooves bearing a wide and shallow median notch on the dorsal surface of each finger (Fig. 6B). Finger tips almost equal in width, with the first finger tip slightly narrower. Subarticular tubercles on fingers distinct, large, rounded, and protruding; the distal subarticular tubercle on the fourth finger less distinct. The subarticular tubercle formula: 1, 1, 2, 2 (Fig. 9D). Two metacarpal tubercles: inner metacarpal tubercle distinct, protruding, rounded in shape; outer metacarpal tubercle rounded and flattened, its diameter subequal to the diameter of inner metacarpal tubercle (OPTL/IPTL ratio 0.89).

Hindlimbs long, slender, almost four times longer than the forelimbs (HLL/FLL ratio 3.85). Thighs muscular, massive (Fig. 9B), shanks elongated and slender, comprising approximately one-third of the hindlimb length (TL/HLL ratio 0.35). When the limbs are positioned at the right angle to the body, the heels significantly overlap. Tibiotarsal articulation of the adpressed limb extends well beyond the tip of the snout. Foot length comprises more than one-third of the hindlimb length, being significantly shorter than the tibia (FL/HLL ratio 0.31, TL/FL ratio 1.16). The relative toe lengths: I < II < V ≤ III < IV. Shanks smooth, inner tarsal fold absent. Tips of all toes distinctly widened into round disks, notably wider than the finger tips (4FDD/3FDD ratio 1.75). Toe webbing fully developed, reaching the disks on all toes except the toe IV; webbing formula: i1-1ii1-2iii1-2iv2-1v (Fig. 6A). Subarticular tubercles on toes distinct, rounded, slightly protruding, subarticular tubercle formula: 1, 1, 2, 3, 2 (Fig. 9D). Internal metatarsal tubercle of moderate size, slightly elongated, with indistinct margins, comprising less than half the length of the first toe (IMTL/1TOEL ratio 0.36, Fig. 9C). Outer metatarsal tubercle small but distinct, rounded, prominent with well-defined margins, subequal to the length of inner metatarsal tubercle (OMTL/IMTL ratio 0.94, Fig. 9C).

Skin on dorsum shagreened, with rare small tubercles getting denser laterally (Fig. 7A). Dorsal surfaces of forelimbs almost smooth, with the exception of tiny tubercles present on forearms. Dorsal surface of hindlimbs with small tubercles sparsely scattered on thighs and shanks (Fig. 9A). Upper eyelid smooth. Body flanks smooth, numerous small warts around the tympanal region. Ventral sides of body and limbs completely smooth (Fig. 9B). Cloacal opening unmodified, with posterior orientation.

Dorsum in life olive-brown with a bronze tint laterally with a dark-brown “teddy-bear” pattern (see Rakotoarison et al. 2017) with irregular borders (Fig. 7A). Dark-brown triangular interorbital bar located between the posterior parts of upper eyelids continues posteriorly, sharply narrowing at the level of head base and broadening at the scapular area. A pair of dark-brown blotches edged with beige form a trapezoidal dark marking around the cloacal opening. A yellowish-beige light postocular stripe running from the posterior corner of the eye to the axilla (Fig. 7A).

Body and head flanks slightly darker than the lateral sides of the dorsum. Snout olive-brown lacking dark markings. Broad dark olive-gray band running posteriorly from the eye. Upper jaw dark-brown with a few irregular light-brown or cream spots below the eye. Narrow cream stripe running from the posterior corner of the eye to the axilla. Except for the upper arm, limbs dorsally with indistinct brownish crossbars and spots: two crossbars visible on lower arms, three crossbars on thighs and shanks. Fingers and toes with brown transverse dorsal bars.

Belly and chest yellowish-white, with a few irregular grayish spots in chest area (Fig. 7A). Throat and chin with dense dark-gray mottling, which gets darker along the edges of mandible and mouth corners. Ventral surfaces of limbs beige to bluish-gray lacking dark markings (Fig. 9C,D); feet ventrally with dark-brown marking extending from the tibiotarsal joint to the ventral surfaces of toes and toe webbing (Fig. 9C). Iris bronze with a distinct vertical dark stripe ventrally. Pupil round, black, outlined with a thin golden circle.

After two years in preservative, the pattern described above generally remains unchanged (Fig. 9). Dorsal background color faded to light-gray, and the dark dorsal markings became less discernible. The characteristic dark spot above the cloacal opening, the “teddy-bear” pattern, and other dark markings remain visible. Limbs fade to yellowish-gray, but the dark crossbars on the limbs remain visible. Ventral surfaces fade to light-beige; however, the dark markings on the chin still remain notable as brownish-gray mottling.

The examined individuals are overall quite similar in appearance. Differences in size and body proportions are provided in Tables 4 and 5. In females, the body length (SVL) ranges from 36.3 to 38.1 mm (n = 3); the single examined male had a smaller body size (SVL 33.0 mm). Dorsal background coloration of the examined specimens varied from olive-brown to yellowish-brown. The male specimen had a notably darker chin than the examined females (Fig. 7A).

The species name “­berdmorei” was given in honor of Captain Major Thomas Matthew Berdmore (1811–1859), a British officer and naturalist who was stationed in Myanmar during the mid-19^th century. M. T. M. Berdmore was famous for the collection of numerous animal specimens, including this particular species of frog. Recommended common names: “Berdmore’s narrow-mouthed frog” (English); “Nhái bầu Béc-mơ” (Vietnamese); “uzkorot Berdmora” (узкорот Бердмора, Russian); “Changpîng” (Mizo; literally meaning “spindle frog”); “Eung mae nao Pama” (อึ่งแม่หนาวพม่า, Thai).

Based on our definition of M. berdmorei sensu stricto, the actual range of this taxon (Fig. 1) is restricted to: India (northeastern part of the country: Meghalaya, Assam, Tripura, and Mizoram states), Bangladesh (central, northeastern, and southeastern parts of the country), and Myanmar (northwestern and central parts of the country). The earlier records of the occurrence of M. berdmorei in Indochina, Malaysia, and Indonesia refer to other species of the M. berdmorei complex described below.

Microhyla berdmorei sensu stricto inhabits various types of moist evergreen forests, including monsoon and perennial rainforest types. It is generally associated with hilly regions and is often found near streams; it also occurs in secondary forests. Specimens of this species are active day and night, often hiding in the leaf litter on the forest floor. When disturbed, they make extraordinary long and vigorous jumps to escape. In Assam State, India, breeding activity typically occurs in still pools between October and November (Garg et al. 2019; IUCN 2022). The noisy rasping call of M. berdmorei sensu stricto can be heard at night from beside forest pools; we have observed specimens of this species displaying cephalic amplexus (Fig. 7A). In India, Garg et al. (2019) recorded specimens from thickly vegetated swampy areas near the water bodies, either inside secondary forests or adjacent to human settlements. In Lawachara N. P., Bangladesh, Hakim et al. (2020) found M. berdmorei on trails, roads, and leaf litter in mature forests, degraded forests, tea plantations, and village habitats. Microhyla berdmorei coexists with M. mymensinghensis Hasan et al., 2014 in the northeastern (Dinajpur, Parbatipur) region of Bangladesh (Hasan et al. 2014). This species was found either in the grass below large trees, referred to as “Lendi Korui” by the locals, or in expansive fields with some vegetation and somewhat damp and loose soil. Indigenous to the region, this species is commonly referred to as “Boro Laubichi Bang”, and its diet mostly includes ants and other small insects (Hasan et al. 2014). In Mizoram, India, the species prefers waterbodies with sandy to gravel bottoms for breeding (Raj et al. 2023).

Raj et al. (2023) presented a detailed description of the larval morphology of M. berdmorei from Aizawl, Mizoram, India. Tadpoles at Gosner stage 34 reach 20–21 mm in length; at Gosner stage 39 they reach 27–28 mm in length. At Gosner stage 37, body large, oval-shaped in dorsal view; body length comprises 37% of total length; snout broad and truncate in dorsal view, acutely rounded in lateral view; eyes with lateral orientation; eye-nostril distance comprises 69% of eye-snout distance; interorbital distance ca. three times greater than internarial distance; spiracle large, medial, located on ventral surface; spiracle-snout distance comprises 83% of body length; vent tube opening medial, reaching ventral fin edge; ventral tail fin deeper than dorsal tail fin, reaching its maximal height at tail mid-length; caudal musculature comprises 40% of tail height; tail tip sharply pointed, flagellated. Oral disc terminal, comprising a half of interorbital distance in width; lacking papillae or keratinized structures; a U-shaped medial notch protrudes from the mouth between the two semicircular labial flaps (Lalremsanga and Muansanga 2022; Raj et al. 2023). In life, head, body, and caudal musculature translucent and white with numerous tiny melanophores; posterior parts of body darker due to pigmentation of inner integument; ventrally milky white and transparent with gut coils visible; few large melanophores present on both tail fins; smaller melanophores present on tail musculature. Tadpoles of M. berdmorei are lentic suspension feeders.

The male advertisement call of M. berdmorei represents a series of short rasping sounds resembling the sound of a ratchet. In an unpublished doctoral thesis, Lalremsanga (2011: 102) provided a description of the advertisement call for the M. berdmorei population from Mizoram, Northeast India. The call series consisted of one to seven calls emitted at a 3 s interval; a single call series lasted for 1.4–1.6 s. Each call consisted of 7–12 pulses and lasted for 0.2 s at an interval of 0.06 s. The amplitude of the call increased slowly and reached a peak in the middle, which then decreased slowly until the end. The frequency spectra ranged between 1484 and 2046 Hz, with the dominant frequency being 1677 Hz.

Our recording of male advertisement call series of M. berdmorei from Aizawl, Mizoram State, India, consisted of several calls (2–5; average 3.6±1.2) emitted at a 2.5±0.2 s (1.47–3.20 s) interval. A single call lasted for 0.20±0.07 s (0.12–0.33) on average. Each call consisted of 11±2.0 (9–13) pulses emitted at an interval of 0.06 s. The call’s amplitude increased slowly and reached a peak in the middle of the call, after which it gradually decreased; thus, each call’s relative amplitude profile has a symmetrical shape (Fig. 10A). The peak frequency of a call comprised 1892±82 Hz (1781–1969 Hz), which is notably higher than the earlier estimates of Lalremsanga (2011).

Microhyla berdmorei sensu stricto can be distinguished from all other known Microhyla species currently known from South and Southeast Asia by its complete foot webbing, extending well beyond the first subarticular tubercle on either sides of toe IV and reaching up to the disks on the remaining toes (vs. rudimentary to medium foot webbing in all other species); by terminal phalanges of toes Y-shaped (vs. simple, knobbed, or T-shaped in all other species; see Garg et al. 2019); and by toe tips enlarged into disks with dorso-terminal grooves (vs. almost absent). This species can be differentiated from its close genetic congener M. darevskii by finger I length less than half of finger II length (F1 < ½F2 vs. F1 > ½F2); by weak disks present on fingers (vs. finger disks totally absent); by ventral color lightly colored, yellowish-white with irregular grayish spots (vs. no yellow color on groin and belly); by pattern on flanks and shanks consisting of brown or black irregular spots and blotches (vs. absent); by iris coloration bronze with a distinct dark vertical stripe below the pupil (vs. golden with black reticulation); and by foot webbing reaching to disks except toe IV (vs. reaching to disks on all toes) (see Blyth 1856; Poyarkov et al. 2014; Garg et al. 2019; our data).

For comparisons of M. berdmorei sensu stricto with other closely related members of the M. berdmorei species complex, see below.

Malcolm’s narrow-mouthed frog.

Synonymy and chresonymy.

Microhyla malcolmi Cochran, 1927: 182. Holotype: USNM 72172 (Fig. 11). Type locality: “Pak Jong, Siam”, now Pak Chong District, Nakhon Ratchasima Province, Thailand — Parker (1928: 473–499); Barbour and Loveridge (1929: 235); Bourret (1942: 509); Li et al. (2019: 568).

Microhyla fowleri Taylor, 1934: 284. Holotype: ANSP 19903 (Fig. 12). Type locality: “Chieng Mai, Siam”, now Chiang Mai Province, Thailand — Dubois (1987: 3); Bourret (1942: 509); Taylor (1962: 560); Fei (1999: 292–293); Yang and Rao (2008: 124); Fei et al. (2009: 890–894); Fei et al. (2010: 481); Matsui (2011: 33–49); Matsui et al. (2011: 168, 171, 174, in part); Fei et al. (2012: 567); Poyarkov et al. (2014: 89–148); Pradana et al. (2017: 70-90); Li et al. (2019: 568).

Microhyla (Microhyla) fowleri — Dubois (1987: 3).

Microhyla berdmorei — Bourret (1942: 509, in part); Parker (1928: 473–499, in part); Barbour and Loveridge (1929: 235); Parker (1934: 127, in part); Taylor (1962: 560, in part); Heyer (1971: 64–66, in part); Berry (1975: 118–119, in part); Dubois (1987: 3, in part); Stuart (1999: 49, in part); Orlov et al. (2002: 99, in part); Ohler et al. (2002: 465–481, in part); Chan-ard (2003: 102, in part); Teynié et al. (2004: 35, in part); Nguyen et al. (2005: 44, in part); Stuart (2005: 35); Devi and Shamungou (2006: 317–324, in part); Grismer et al. (2006: 63, in part); Stuart and Emmett (2006: 6); Das and Yaakob (2007: 68, in part); Grismer and Aun (2008: 277, in part); Neang and Holden, (2008: 63, in part); Wogan et al. (2008: 88, in part); Chan et al. (2009: 278, in part); Nguyen et al. (2009: 97, in part); Chan-ard et al. (2011: 131, in part); Thong-aree et al. (2011: 99–106, in part); Grismer et al. (2004: 18, in part); Manthey and Denzer (2014: 3–21, in part); Poyarkov et al. (2014: 89–148, in part); Sumarli et al. (2015: 8, in part); Vassilieva et al. (2016: 72–73, in part); Do et al. (2017: 88–89, in part); Mulcahy et al. (2018: 95, in part); Nguyen et al. (2019: 549-580, in part); Geissler et al. (2019: 40–63); Niyomwan et al. (2019: 222–223, in part); Garg et al. (2019: 15, in part); Poyarkov et al. (2020b: 136–163, in part); Gorin et al. (2020: 1–47, in part); Makchai et al. (2020: 116, in part); Poyarkov et al. (2021: 40, in part); Gorin et al. (2021: 97, in part); Zug (2022: 30, in part); Hoang et al. (2022: 35, in part); Frost (2024: page “Microhyla berdmorei” in part).

USNM 72172 (adult female), by original designation (not physically examined by us, but see Fig. 11). Type locality: “Pak Jong, Siam”, now Pak Chong District, Nakhon Ratchasima Province, Thailand (see Fig. 9).

Microhyla malcolmi is characterized by the following combination of morphological attributes: (1) large body size (SVL 33.2−41.8 mm in males, 36.0−­43.8 mm in females), with slender and triangular body habitus; (2) head longer than wide; (3) skin on dorsum slightly shagreened, laterally with sparse tiny tubercles; (4) snout obtusely pointed in dorsal, ventral, and lateral views; (5) first finger shorter than half of second finger length; (6) finger tips with weak disks lacking dorsomedial grooves; (7) toes with well-developed disks lacking or bearing rudimentary dorsomedial grooves; (8) tibiotarsal articulation of an adpressed limb extends far beyond snout; (9) toe webbing complete, reaching disks on all toes; webbing formula: i1-1ii1-1iii1-1iv1-1v; (10) throat and chin dark-gray to almost black in males; belly bluish-gray anteriorly, yellowish posteriorly; (11) dorsal surfaces of fore- and hind limbs with wide dark crossbars, up to 3–4 crossbars on thighs; (12) brown patch above cloacal opening of variable shape and indistinct edges; (13) dark-brown dorsal “teddy-bear”-pattern distinct, usually edged with light-brown or beige anteriorly; (14) black spots and blotches of irregular shape on body flanks; (15) broad grayish-brown lateral band lateral stripe extending from armpit to groin; (16) light postocular stripe beige with black edging; (17) reddish spots on dorsum and dorsal surfaces of hindlimbs absent; (18) iris with black stripe below the pupil.

In this study, we used morphological data from 52 specimens of M. malcolmi from Thailand, Laos, and Vietnam (see Table S2 for details).

An adult male specimen in a very good state of preservation. Body size large (SVL 37.1 mm; other measurements are presented in Table S2). Body habitus slender, triangular, dorsoventrally flattened (Fig. 13E). Head triangular in dorsal view; longer than wide (HW/HL ratio 0.94). Snout comparatively long and protruding (SL/HL ratio 0.34), obtusely pointed in dorsal view (Fig. 13A), gently obtusely pointed in profile, and noticeably extending beyond the edge of the lower jaw (Fig. 13E). Eyes large, protruding in dorsal and lateral views, significantly shorter than the snout (EL/SL ratio 0.75), and longer than the interorbital distance (IOD/EL ratio 0.88). Canthus rostralis distinct, rounded; loreal area notably concave, smooth. Nostrils oval-shaped, with lateral orientation, located below the canthus rostralis; closer to eye than to the tip of snout. Interorbital distance broader than internarial distance (IND/IOD ratio 0.72). Upper eyelid smaller than interorbital distance (UEW/IOD ratio 0.69). Tympanum concealed, faintly developed glandular supratympanic fold extending from the posterior corner of eye to axilla (Fig. 13E). At the level of mouth corner, supratympanic fold bends posteriorly and extends to the forelimb insertion. Tongue slender, rounded, free behind for half of its length; vomerine teeth absent; gular vocal sac present, single.

Forelimbs short and slender (Fig. 13A); lower arm elongated and thin (LAL/FLL ratio 0.75), hand less than half of forelimb length (HAL/FLL ratio 0.42). Fingers slender and elongated, webbing or skin fringes on fingers absent. First finger well-developed, subequal to half of the second finger length (Fig. 13D); the relative finger length formula: I < II ≤ IV < III. Fingertips rounded, slightly expanded, noticeably narrower than the basal phalanges of the respective fingers. Finger tips lacking peripheral grooves, dorsomedial grooves absent, or present as a very shallow rudimentary medial notch (Fig. 6D). Finger tips almost uniform in width, with the tip of the first finger being slightly narrower. Subarticular tubercles on fingers distinct, large, rounded, and protruding, with the distal subarticular tubercle on the fourth finger being less distinct. Subarticular tubercle formula: 1, 1, 2, 2. Nuptial pad absent (Fig. 13D). Two metacarpal tubercles: inner metacarpal tubercle distinct, protruding, rounded in shape; outer metacarpal tubercle rounded, flattened, its diameter equal to the diameter of inner metacarpal tubercle (OPTL/IPTL ratio 1.0).

Hindlimbs long and strong, slender, almost four times longer than the forelimbs (HLL/FLL ratio 3.66). Thighs robust and muscular (Fig. 13B), shanks elongated and slender, comprising approximately one-third of the hindlimb length (TL/HLL ratio 0.37). When the limbs are held at the right angle to the body, the heels significantly overlap. Tibiotarsal articulation of the adpressed limb extends well beyond the tip of the snout. Foot length comprises more than one-third of the hindlimb length, being significantly shorter than tibia (FL/HLL ratio 0.27; TL/FL ratio 1.36). The relative toe lengths: I < II < V ≤ III < IV. Shanks smooth, inner tarsal fold absent. Tips of all toes distinctly widened into small round disks wider than finger tips (4FDD/3FDD ratio 2.05). Dorsomedial longitudinal grooves absent on all toes or present as rudimentary median notch at the medial edge of toe disk (Fig. 6C). The relative width of toes disks: I < V < II < III ≤ IV. Toe webbing fully developed, web reaching disks on all toes; webbing formula: i1-1ii1-1iii1-1iv1-1v (Fig. 6C). Subarticular tubercles on toes distinct, rounded, slightly protruding, subarticular tubercle formula: 1, 1, 2, 3, 2. Internal metatarsal tubercle of moderate size, oval, slightly elongated, with indistinct margins, less than half the length of the first toe (IMTL/1TOEL ratio 0.45). Outer metatarsal tubercle small but very distinct, rounded, prominent with well-defined margins, slightly longer than inner metatarsal tubercle (OMTL/IMTL ratio 1.12, Fig. 13C).

Skin texture is generally similar to that described for M. berdmorei (see above, Fig. 7A,B). Skin on dorsum slightly shagreened, with sparse small tubercles getting denser on the lateral sides of dorsum (Fig. 7B). Dorsal surfaces of forelimbs almost smooth, few tiny tubercles present on forearms. Dorsal surfaces of hindlimbs with sparse tubercles scattered across thighs and shanks; these tubercles are noticeably smaller than those on dorsum (Fig. 13A). Upper eyelid smooth. Body flanks smooth, numerous small warts present around the tympanal region. Ventral surfaces of body and limbs completely smooth (Fig. 13B). Cloacal opening unmodified, with posterior orientation.

Dorsal background coloration gray-brown with a bronze tinge on the sides of the back, with a faint brown “teddy-bear” pattern medially (Fig. 7B). “Teddy-bear” marking with more distinct borders and beige edging anteriorly; the pattern becoming less distinct posteriorly, beige edging not discernible posteriorly. Interorbital dark bar incomplete, present as two indistinct dark-brown blotches between posterior parts of upper eyelids. Indistinct gray-brown marking in the shape of an inverted triangle between interorbital blotches and the “teddy-bear” pattern on dorsum (Fig. 13A). Posterior part of dorsum brownish with indistinct gray blotches. A wide beige light postocular stripe running under the supratympanic fold from the posterior corner of eye to axilla, dorsally edged with black (Fig. 7B).

The lateral surfaces of the body and head slightly lighter than the dorsum. Snout, canthus rostralis and loreal area uniformly light olive-brown; dark-gray mottling present on the upper jaw; a few irregular black or brownish spots present below the eye. A broad grayish-brown band running from the posterior margin of the eye along the supratympanic fold. A narrow blackish-brown interrupted stripe running from the posterior corner of the eye to the axilla. A series of irregular black blotches and spots on body flanks between the axilla and groin. Except for the upper arm, limbs dorsally bearing indistinct dark-gray crossbars with indistinct edges; two crossbars visible on the lower arms; three crossbars present on each thigh and shank. Fingers and toes dorsally with narrow blackish transverse crossbars.

Belly lightly colored; anterior part of the belly bluish-gray, posterior portion of the belly, groin, ventral surfaces of upper arms, and thighs yellow to yellowish-gray with indistinct gray mottling on thighs (Fig. 7B). Gular area dark-gray; chin covered with dense gray mottling which gets darker at the edges of the mandible, mouth corners and gradually fades to bluish-gray towards the chest. Shanks ventrally light yellowish-gray, small black spots present on the ventral surfaces of the limbs. Fore- and hindlimbs ventrally grayish-yellow to yellowish. Ventral surfaces of hands (Fig. 13D) show no distinct pattern; feet ventrally with dark blackish-brown marking extending from the tibiotarsal joint to the ventral surfaces of toes and toe webbing (Fig. 13C). Iris bronze with black reticulations and a distinct black vertical stripe ventrally (Fig. 7B). Pupil round, black, outlined with a thin golden circle.

After two years in preservative, the pattern described above generally remains unchanged, though light colors, like the yellowish coloration of the ventral surfaces and the olive-bronze coloration of dorsum faded to off-white and light gray, respectively. The dark dorsal pattern have become slightly less discernible. The characteristic dark spot above the cloacal opening, black spots and blotches on flanks, and dark markings on feet remain visible, they have turned dark grayish-brown. The limbs have turned yellowish-gray, and the dark crossbars still visible as indistinct dark-gray patterns. The ventral surfaces have faded to light beige; however, the dark markings on the chin have turned dark-gray but are still well discernible.

The examined individuals are overall quite similar in appearance. Differences in size and body proportions of the examined specimens are provided in Tables 4 and 5. In females, the body length (SVL) ranges from 33.1 to 43.8 mm (n = 17); in males, the SVL ranges 25.4–41.8 mm (n = 35). The dorsal background coloration varies from gray-brown to gray. Some male specimens demonstrate a darker and more contrasting dorsal “teddy-bear”-pattern (ZMMU A-5073, ZMMU A-4710). Breeding males have a darker-colored chin (dark-gray to blackish) than females (gray).

The species was named after Dr. Malcolm Arthur Smith (1875–1958), a famous British herpetologist and physician, who collected many specimens in the early 20^th century across Thailand, Vietnam and Malaysia. Recommended common names: “Malcolm’s narrow-mouthed frog” (English); “Nhái bầu Mao-com” (Vietnamese); “uzkorot Malkolma” (узкорот Малькольма, Russian); “Eung mae nao” (อึ่งแม่หนาว, Thai).

Based on our revalidation and definition of M. malcolmi, we define the range of this species as follows (Fig. 1): China (extreme south of Yunnan Province: Jinghong, Mengla, and Mengyang counties), Vietnam (northwestern, central, and southern parts of the country), Laos (entire country), Cambodia (entire country), and Thailand (entire country). The southernmost record is known from Perlis State in Peninsular Malaysia (Fig. 1, locality 32). Microhyla malcolmi is also expected to occur in eastern Myanmar, though further studies are needed to clarify the extent of its distribution.

Microhyla malcolmi inhabits various habitats, including primary and secondary forests as well as human-modified rural landscapes in lowland and hilly areas at elevations up to 2200 m a.s.l. In the lowland monsoon forests of southern Vietnam, this species appears to be associated with bamboo tangles (Vassilieva et al. 2016) and is also often recorded along forest streams. Microhyla malcolmi is active both day and night; according to Vassilieva et al. (2016), its diet consists mainly of ants. Breeding was observed in Vietnam and Cambodia and usually had two peaks of reproductive activity: in May-June and October-December (Neang and Holden 2008; Vassilieva et al. 2016). The noisy rasping call of breeding males can be heard at night from beside forest pools (Neang and Holden 2008). Breeding mainly takes place in slowly-flowing forest streams, ponds, rain pools, puddles and other similar still waterbodies; the reproductive activity usually starts after heavy rains. Clutches include hundreds of small (1.6–1.7 mm) pigmented floating eggs. In Thailand, the species prefers waterbodies with dead leaves and branches on silty bottoms for breeding (Meewattana 2022).

A detailed description of the larval morphology of M. malcolmi from Thailand was presented by Meewattana (2022) (referred to as M. berdmorei in his work). Tadpoles at late developmental stages reach 20–30 mm in length with large body, oval-shaped in dorsal view; interorbital distance ca. five times greater than internarial distance; mouth-snout distance equal to snout-eye distance; anal tube with vertical orientation reaching the edge of ventral fin; ventral tail fin less than twice as deep as dorsal tail fin; both fins deeper than tail musculature at the level of fourth proximal segment; tail tip tapering (Meewattana 2022). Oral disc terminal, comprising a half of interorbital distance in width; lacking papillae, jaw sheaths, or labial teeth (Meewattana 2022). In life, head, body, and caudal musculature pale grayish; posterior part of body dark-gray or black; dorsally with a weak dark marking between the eyes; tail fins transparent. Tadpoles of M. malcolmi are lentic suspension feeders.

The male advertisement call of M. malcolmi represents a series of noisy rasping sounds that resemble the sound of a ratchet to the human ear. Heyer (1971) provided a brief description of an advertisement call for a M. malcolmi population from Sakaerat Experimental Station, Nakhon Ratchasima Prov., Thailand (referred to as M. berdmorei in his work). The duration of the call was 0.09–0.26 s, with each call consisting of 3–9 pulses at a pulse rate of 33–35 pulses per second, and the peak frequency of the call estimated at 1500–1800 Hz.

Our recording of M. malcolmi advertisement calls taken in Song Hinh Forest Reserve, Phu Yen Province, Vietnam, included call series, each of them consisting of several calls (4–6; average 5.2±1.4) emitted at a 2.3±1.5 s (0.97–3.79 s) interval; a single call lasted for 0.22±0.04 s (0.16–0.31) on average. Each call consisted of 9±1.1 (8–10) pulses. The call’s amplitude increased sharply, reached its peak in the first 0.05–0.10 s of call duration, and then gradually decreased towards the call’s end; the last half of the call duration had a notably lower amplitude (491±57 Hz) than the first half (Fig. 10B). We estimated the call peak frequency to be 1631±93 Hz (1507–1809 Hz), which agrees well with the estimates of Heyer (1971).

Microhyla malcolmi was previously considered as a junior synonym of M. berdmorei, but this species can be differentiated from M. berdmorei sensu stricto by having: fully-developed foot webbing (I1-1II1-1III1-1IV1-1V vs. I1-1II1-2III1-2IV2-1V); supratympanic fold distinct (vs. indistinct); comparativey shorter snout (SL/HL ratio 0.31−0.39 [avg. 0.34, n = 21] in males, 0.32−0.37 [avg. 0.35, n = 9] in females of M. malcolmi vs. 0.46 in male [n = 1], 0.45−0.46 [avg. 0.45, n = 3] in females of M. berdmorei sensu stricto); snout shape in dorsal and ventral views (obtusely pointed vs. rounded); crossbars on thighs wide, 3–4 crossbars on each thigh (vs. crossbars narrow, up to 5–6 crossbars on each thigh); background color of dorsum grayish-brown (vs. olive-brown with a bronze tinge); head longer than wide (vs. head wider than long); finger tips with weak disks lacking dorsomedial grooves (vs. finger tips with weak disks bearing wide and shallow dorsomedial grooves); and toes with well-developed disks lacking or bearing rudimentary dorsomedial grooves (vs. toes with distinct disks, each bearing narrow and deep dorsomedial groove).

For comparisons of M. malcolmi with other members of the M. berdmorei species complex, see below.

Sundaic narrow-mouthed frog.

Microhyla berdmorei — Inger (1966: 149–151, in part); Grandison (1972: 59, in part); Dring (1979: 194, in part); Malkmus et al. (2002: 130–131, in part); Grismer et al. (2004: 18, in part); Das and Yaakob (2007: 68, in part); Grismer and Aun (2008: 277, in part); Chan et al. (2010: 203, in part); Teynié et al. (2010: 8); Matsui (2011: 35, 39); Matsui et al. (2011: 168, 171, 174, in part); Pradana et al. (2017: 70–90, in part); Firdaus et al. (2018: 1–6, in part); Haas et al. (2018: 89–114); Chan et al. (2019: 1057, in part); Nguyen et al. (2019: 549–580, in part); Gorin et al. (2020: 1–47, in part); Gorin et al. (2021: 97, in part); Poyarkov et al. (2021: 40, in part); Haas et al. (2022: 304–305); Badli-Sham et a l. (2023: 49, 82, in part); Frost (2024: page “Microhyla berdmorei” in part).

ZMMU A-8011, adult female from environs of Sungai Tua Recreational Forest, Selangor State, Malaysia (approximate coordinates: 3.32°N, 101.70°E), collected on January 27, 2003, by A. T. Aful.

Two adult males: ZMMU A-8012 and ZMMU A-8014 and two adult females: ZMMU A-8010, ZMMU A-8013, all collection data are the same as for the holotype. One adult male: ZMMU A-6158 from Kuala Tahan District, Pahang State, Malaysia (approximate coordinates: 3.96°N, 102.44°E) collected on January 18, 2003, by A. T. Aful.

Microhyla sundaica sp. nov. is characterized by a combination of the following morphological features: (1) medium body size (27.5−27.9 mm in males, 28.3−31.4 mm in females), with moderately stocky and triangular body habitus; (2) head wider than long; (3) dorsal skin shagreened with numerous small tubercles; (4) snout pointed in dorsal and ventral views, bluntly rounded in lateral view; (5) first finger notably longer than half the length of second finger; (6) finger tips with well-developed disks bearing wide and deep dorsomedial grooves; (7) toes dilated in wide disks, each with complete and deep dorsomedial groove, separating the toe disk into a pair of scale-like pads; (8) tibiotarsal articulation of the adpressed limb extending far beyond the snout tip; (9) toe webbing reaching to the disks on all toes; webbing formula: i1-1ii1-2iii1-1iv1-1v; (10) throat and chin dark-gray in males, beige in females; belly bright yellow in life; (11) dorsal surfaces of forelimbs without prominent crossbars, hindlimbs with 2–3 dark-brown crossbars on thighs and shanks; (12) two black blotches above cloacal opening edged with beige; (13) gray-brown dorsal “teddy-bear”-pattern distinct, edged with beige or white, anteriorly connecting with the dark interorbital bar; (13) dark spots and blotches on body flanks absent or scarce; (15) grayish lateral band with irregular edges extending from armpit to groin; (16) light postocular stripe absent; (17) reddish spots on dorsum and dorsal surfaces of hindlimbs absent; (18) iris uniform grayish-bronze, no black stripe below the pupil.

An adult female specimen in a very good state of preservation. Body size medium (SVL 31.4 mm; other measurements are presented in Table 2). Body habitus stocky, triangular, and significantly dorsoventrally flattened (Fig. 14E). Head triangular in dorsal view; wider than long (HW/HL ratio 1.16). Snout comparatively short and protruding (SL/HL ratio 0.45), appearing pointed in dorsal and ventral views (Fig. 14E), smoothly rounded in profile, and slightly extending beyond the edge of the lower jaw (Fig. 14E). Eyes comparatively small, slightly protruding in lateral view, not protruding in dorsal view, significantly shorter than the snout (EL/SL ratio 0.76), and slightly shorter than the interorbital distance (IOD/EL ratio 1.03). Canthus rostralis distinct, rounded; loreal area slightly concave. Nostrils oval-shaped, with dorso-lateral orientation, situated almost on the canthus rostralis, closer to tip of snout than to eye. Interorbital distance broader than the internarial distance (IND/IOD ratio 0.77). Upper eyelid length narrower than the interorbital distance (UEW/IOD ratio 0.66). Tympanum concealed, supratympanic fold absent (Fig. 14E). Tongue slender, rounded, free for the posterior four-fifths of its length; vomerine teeth absent. Eggs seen through the incision on the left lateral side of belly small, rounded, ca. 1.0–1.1 mm in diameter, pigmented.

Forelimbs short and slender (Fig. 14A); lower arm elongated and thin (LAL/FLL ratio 0.83), hand less than half of forelimb length (HAL/FLL ratio 0.47). Fingers slender and elongated, webbing or skin fringes on fingers absent. First finger well-developed, notably longer than half of the second finger length (Fig. 14D); the relative finger lengths as follows: I < II < IV < III. Fingertips rounded, expanded into well-developed disks narrower than the basal phalanges of the respective fingers. Finger tips with peripheral grooves, dorsally with a wide and deep dorsomedial notch (Fig. 6F). Finger tips almost equal in width, with the first fingertip slightly narrower. Subarticular tubercles on fingers distinct, large, rounded, and protruding; edges of the distal subarticular tubercle on the fourth finger less distinct. Subarticular tubercle formula: 1, 1, 2, 2 (Fig. 14D). Two metacarpal tubercles: inner metacarpal tubercle distinct, protruding, rounded in shape; outer metacarpal tubercle rounded, flattened, its diameter much less than the diameter of inner metacarpal tubercle (OPTL/IPTL ratio 1.40).

Hindlimbs long, slender, almost four times longer than the forelimbs (HLL/FLL ratio 3.96). Thighs robust and muscular (Fig. 14B), shanks notably elongated and slender, comprising approximately one-third the length of the hindlimb (TL/HLL ratio 0.35). When the limbs are held the right angle to the body, the heels significantly overlap. Tibiotarsal articulation of the adpressed limb extends well beyond the tip of the snout. The foot length is more than one-third of the hindlimb length and significantly shorter than shanks (FL/HLL ratio 0.29; TL/FL ratio 1.21). The relative toe lengths as follows: I < II < V ≤ III < IV. Shanks smooth, with the inner tarsal fold absent. The tips of all toes distinctly widened into wide heart-shaped disks, almost twice as wide as finger disks (4TDD/3FDD ratio 1.77). Toe webbing fully developed, reaching the disks of all toes; webbing formula: i1-1ii1-2iii1-1iv1-1v (Figs 6E, 14C). Toe subarticular tubercles distinct, rounded, slightly protruding, subarticular tubercle formula: 1, 1, 2, 3, 2. The internal metatarsal tubercle of moderate size, oval, slightly elongated, with indistinct margins, less than half the length of the first toe (IMTL/1TOEL ratio 0.31). Outer metatarsal tubercle small but distinct, rounded, prominent with well-defined margins, slightly larger than the inner metatarsal tubercle (OMTL/IMTL ratio 1.45).

Skin on the dorsum slightly tuberculated with numerous small tubercles covering both the middle and the lateral parts of the dorsum (Fig. 7C). Dorsal surfaces of forelimbs smooth. Dorsal surface of hindlimbs with numerous sparse tubercles scattered across thighs and shanks; the tubercles on the hindlimbs notably smaller than those on dorsum (Fig. 14A). Upper eyelid smooth. Body flanks smooth. Numerous small warts present around the tympanal region. Ventral surfaces of body and limbs smooth (Fig. 14B). Cloacal opening unmodified, directed posteriorly.

The dorsal background coloration in life was gray-bronze with a light-gray tint on the sides of the dorsum, with a faint gray-brown “teddy-bear”-pattern in the middle of the dorsum (Fig. 7C). The “teddy-bear”-pattern has regular light edging, which becomes less distinct posteriorly. A pronounced gray-brown interorbital band in the shape of an inverted triangle with irregular borders runs across the head between the posterior parts of the upper eyelids, and is posteriorly connected with the “teddy-bear”-pattern on the dorsum. The lateral sides of the dorsum are lighter and have a light grayish-brown tint. A pair of black spots, edged with beige, located above the cloacal opening.

Body flanks and head lateral sides slightly lighter than the dorsum. Bronze blotches on both sides of the head on canthus rostralis; snout uniformly dark olive-brown. Upper jaw bronze-brown with a few irregular gray or white spots below the eye. Light postocular stripe or other markings in tympanal area or around axilla absent. On forelimbs, no conspicuous stripes or spots; two grayish-brown crossbars with indistinct border present on thighs and shanks. Dorsal surfaces of fingers and toes uniformly gray, lacking transverse stripes or dark spots.

Belly and chest bright yellow, with a few irregular grayish spots on throat and chin, covered with sparse dark-gray spotting (Fig. 7C). This coloration becomes notably darker along the edges of the mandible and the mouth corners. Ventral surfaces of the limbs yellow to grayish-yellow with rare gray spots and mottling. Ventral surfaces of arms (Fig. 14D) and feet (Fig. 14C) with irregular brownish-black blotches. Iris light grayish-bronze without dark reticulations and lacking the dark vertical stripe below the pupil. Pupil round, black, outlined with a thin bronze circle.

After 21 years in preservative, the pattern described above generally remained unchanged, but bright yellow and light-brown colors faded to off-white and gray. The dorsal pattern became less prominent, but all the dark markings on dorsum remain discernible. The dark transverse crossbands and spots on fore- and hindlimbs became less distinct. The gray markings on the chin were still visible as faint gray mottling.

The examined members of the type series are overall quite similar in appearance. Differences in size and body proportions are presented in Tables 4 and 5. We observed sexual differences in body length, with males (SVL 27.5−27.9 mm, n = 3) having significantly smaller SVL than females (SVL 28.3−31.4 mm, n = 3). No differences in coloration between males and females were observed except for the darker coloration of throat and chin in males; the dorsal coloration varies from gray-bronze to light-brown. The dorsal “teddy-bear”-pattern has a darker coloration; in some individuals (ZMMU A-8012 and ZMMU A-8014), the dorsal pattern was more contrasting and had more clear edges. In other individuals, the dorsal pattern was duller with less distinct borders. Two females (ZMMU A-8010 and ZMMU A-8013) had somewhat brighter light-brown coloration of the hindlimbs different from that of the dorsum. In all examined individuals, there were no signs of the presence of a vertical brown stripe on iris except ZMMU A-6158, which showed a rudimentary dark stripe below the pupil that did not reach the ventral edge of the iris.

The species epithet “sundaica” is a latinized adjective in nominative singular, adjusted to the feminine gender of the genus name “Microhyla”, and is given in reference to the distribution of the new species, which inhabits the three major landmasses of the Sundaland, or Sundaic Region, namely: Peninsular Malaysia, Sumatra, and Borneo. “Sundaica” is the Latin name for Sundaland. Recommended common names: “Sundaic narrow-mouthed frog” (English); “Nhái bầu Sunda” (Vietnamese); “Zondskiy uzkorot” (Зондский узкорот, Russian); “Eung mae nao Malayu” (อึ่งแม่หนาวมลายู, Thai); “Katak mulut sempit Sunda” (Malay).

According to our data, M. sundaica sp. nov. inhabits Malaysia (the continental part of the country, and Sabah State on the island of Borneo), Indonesia (on the islands of Borneo (South Kalimantan Province) and Sumatra (Bengkulu and Sumatera Selatan provinces) (Fig. 1). It is likely that the actual distribution of M. sundaica sp. nov. is wider, and it can be found in other parts of Sundaland, including Sarawak State of Malaysia, and other provinces of Sumatra. Despite our repeated efforts, we failed to record M. sundaica sp. nov. in southern Thailand, though the possibility that this species occurs in the southernmost provinces of the country (Narathiwat and Yala provinces) cannot be ruled out completely.

The new species is often recorded while calling from the banks or in shallow rain puddles or swamps (Fig. 15A–B). Although most of the M. sundaica sp. nov. records came from recreational forest areas, this species is also likely to inhabit pristine forests, being especially abundant along the streams or near shallow intermittent pools. Inger et al. (2017) reported that in Borneo male individuals of this species (which he referred to as M. berdmorei) were encountered during vocalization activity while they were hiding in burrows or under dead leaves in the leaf litter; usually males call from ca. 1–5 meters from waterpools or stream banks. In Borneo, this species prefers stagnant temporary waterbodies for reproduction (Inger et al. 2017). Microhyla sundaica sp. nov. has mostly crepuscular activity and is often observed at night actively foraging after heavy rains, usually from 19:00 to 23:00 h. The diet and predators of the new species remain unknown. At the type locality in environs of Sungai Tua Recreational Forest, Selangor State, Malaysia (Fig. 15A), M. sundaica sp. nov. was recorded in sympatry with Ingerophrynus parvus (Boulenger, 1887), Kalophrynus kiewi Matsui, Eto, Belabut & Nishikawa, 2017 and M. butleri Boulenger, 1900. Inger et al. (2017) noted that the new species occurs in mature and secondary forests, mostly at low elevations. Sumarli et al. (2015) reported that male specimens of this species were recorded at night while calling from the top of a boulder at the water’s edge within small puddles; while some specimens were found sitting on mud or in flooded ruts, most were hiding in vegetation along the forest trails. In Peninsular Malaysia, the new species was recorded in sympatry with M. heymonsi Vogt, 1911, and with M. butleri (Sumarli et al. 2015). Dring (1979) reported that in Borneo, M. sundaica sp. nov. males were calling in one chorus with M. borneensis Parker, 1928. In Selangor and Kedah State, Peninsular Malaysia, the species prefers temporary, stagnant pools of water for breeding, with rich leaf litter around (Leong 2004; our observations); males usually call from small holes in the ground on the bank ca. 15–25 cm from the wateredge, or while floating on the water surface (Fig. 15C–D).

A detailed description of the larval morphology of M. sundaica sp. nov. from Selangor, Peninsular Malaysia, was presented by Leong (2004); additional information was provided by Haas et al. (2022). Tadpole total length not exceeding 23 mm. At late development stages, body large, elliptial in dorsal view, body length comprises 162%–168% of body width; dorsum flattened; venter rounded; at Gosner stage 37, body length comprises 39% of total length; snout rounded in dorsal and lateral views; eyes with lateral orientation; nostril located closer to snout tip than to eye; interorbital distance ca. five times greater than internarial distance; spiracle medial with a smooth convex margin, located on ventral surface; spiracle-snout distance comprises 83%–88% of body length; vent tube opening medial, directed ventrally, continuous with ventral fin; ventral tail fin deeper than dorsal tail fin for proximal half; tail gradually tapering towards a narrowly pointed tip lacking terminal filament. Oral disc terminal, lacking papillae or keratinized structures; lower labium not expanded, with distinct median ‘U’-shaped arch. In life, dorsal and lateral surfaces of head and body yellowish; body wall translucent, and caudal musculature whitish; posterior parts of body darker; tail fins clear or have very light pigmentation (Leong 2004). Tadpoles of M. sundaica sp. nov. are lentic suspension feeders.

We recorded the advertisement call of the new species in Gunung Jerai Mt., Kedah, Peninsular Malaysia. The male advertisement call of M. sundaica sp. nov. consists of a series of short nasal rasping squeaks. Each call series consisted of usually seven calls (6–8) emitted at a 1.8±0.3 s (1.34–2.30 s) interval; a single call series lasted for 3.8±2.3 s (2.5–6.7). Individual calls lasted for 0.16±0.03 s (0.12–0.21), and each call consisted of 13±2.3 (8–16) pulses. Each call consisted of two syllables: the introductory note and the main call; the frequency of the introductory note was much lower (739±112 Hz) than that of the main call; the relative amplitude sharply increased in the middle of the call, reaching its maximum in the second half of its duration, and then slowly decreased towards the call end (Fig. 10C). The call’s peak frequency was 2029±106 Hz (1898–2203 Hz).

We here compare M. sundaica sp. nov. with the six other species of the M. berdmorei group species (M. berdmorei sensu stricto, M. malcolmi, M. peninsularis sp. nov. (described below), M. darevskii, M. picta, and Mi. pulchra). The main diagnostic characters separating the new species from these congeners are summarized in Table 5.

Microhyla sundaica sp. nov. is distinguished from M. berdmorei sensu stricto by having: smaller body size in both sexes (SVL 27.5−27.9 mm in males, 28.3−31.4 mm in females vs. 33.0 mm in male, 36.3−38.1 mm in females); finger I length greater than half of finger II length (F1 > ½F2 vs. F1 < ½F2); body habitus stocky (vs. slender); toe webbing complete, webbing formula: i1-1ii1-2iii1-1iv1-1v (vs. webbing formula: i1-1ii1-2iii1-2iv2-1v); dorsomedial grooves on finger and toe disks present (vs. weak or rudimentary); snout in lateral profile bluntly rounded (vs. obtusely pointed); dorsal color gray-bronze with a grayish tint (vs. olive-brown); interorbital markings gray-brown (vs. dark-brown or black); limbs lacking transverse dark crossbars (vs. up to 5–6 narrow prominent crossbars on thighs); iris coloration gray-bronze lacking reticulation and dark vertical stripe (vs. bronze with a black reticulation and a dark vertical stripe below the pupil).

Microhyla sundaica sp. nov. is further distinguished from M. malcolmi by having: small body size in both sexes (SVL 27.5−27.9 mm in males, 28.3−31.4 mm in females vs. 33.2−41.8 mm in males, 36.0−43.8 mm in females); body habitus stocky (vs. slender); finger I length greater than half of finger II length (F1 > ½F2 vs. F1 < ½F2); snout in lateral profile rounded (vs. obtusely pointed); dorsomedial grooves on finger and toe disks present (vs. absent); dorsal color gray-bronze with a grayish tint (vs. gray-brown); limbs with faint gray spots or stripes lacking transverse crossbars (vs. up to 3–4 dark transverse crossbars); iris coloration gray-bronze lacking reticulation and dark vertical stripe (vs. bronze with a black reticulation and a dark vertical stripe below the pupil).

Microhyla sundaica sp. nov. is distinguished from M. darevskii by having: finger disks present (vs. absent); dorsomedial grooves on toe disks present (vs. absent); slightly less developed foot webbing (I1-1II1-2III1-1IV1-1V vs. I1-1II1-1III1-1IV1-1V); dorsal color gray-bronze with grayish tint (vs. brown); interorbital markings gray-brown blotches (vs. dark-brown band); belly color in life bright yellow with irregular grayish spots (vs. no yellow color on belly); limbs with faint gray spots or stripes (vs. absent); iris coloration gray-bronze without reticulation (vs. golden with a black reticulation).

Microhyla sundaica sp. nov. further differs from M. picta by having: body habitus stocky (vs. stout); dorsum slighthly tuberculated with small tubercles (vs. strongly tubercular with large warts); finger I length greater than half of finger II length (F1 > ½F2 vs. F1 < ½F2); finger disks present (vs. absent); toe disks present (vs. absent); dorsomedial grooves on toe disks present (vs. absent); tibiotarsal articulation of an adpressed limb reaching well beyond snout (vs. eye level); better development of foot webbing (I1-1II1-2III1-1IV1-1V vs. I2-2¾II1¾-2¾III2¾-3¾IV4-2½V); dorsal color gray-bronze with grayish tint (vs. brown to sandy); interorbital markings gray-brown blotches (vs. dark-brown band); belly color bright yellow with irregular grayish spots (vs. no yellow color on belly); limbs with faint gray spots or stripes (vs. brown transverse crossbars); iris coloration gray-bronze without reticulation (vs. golden with a black reticulation and with a distinct vertical dark stripe).

Microhyla sundaica sp. nov. can be further differentiated from M. pulchra by having: skin on dorsum shagreened with numerous small tubercles (vs. completely smooth); finger I length greater than half of finger II length (F1 > ½F2 vs. F1 < ½F2); finger disks present (vs. absent); toe disks present (vs. absent); dorsomedial grooves on toe disks present (vs. absent); tibiotarsal articulation of an adpressed limb reaching well beyond snout (vs. to snout or just beyond); better developed foot webbing (I1-1II1-2III1-1IV1-1V vs. I1½-2II1-3III2-3¼IV3½-2V); dorsal color gray-bronze with grayish tint (vs. characteristic agate pattern consisting of numerous light and dark brown lines); interorbital markings as gray-brown blotches (vs. brown transverse band); limbs with faint gray spots or stripes (vs. dark-brown to olive-brown transverse crossbars); iris coloration gray-bronze without reticulation (vs. gray with black reticulation and with a distinct vertical dark stripe).

For comparisons of the new species with M. peninsularis sp. nov., see below.

Peninsular narrow-mouthed frog.

Microhyla berdmorei — Berry (1975: 118–119, in part); Dring (1979: 194, in part); Manthey and Grossmann (1997: 60, in part); Das and Yaakob (2007: 68, in part); Grismer and Aun (2008: 277, in part); Chan et al. (2010: 203, in part); Matsui et al. (2011: 168, 171, 174, in part), Thong-aree et al. (2011: 99–106, in part); Sumarli et al. (2015: 8, in part); Firdaus et al (2018: 1–6, in part); Nguyen et al. (2019: 549–580, in part); Niyomwan et al. (2019: 222–223, in part); Gorin et al. (2020: 1–47, in part); Makchai et al. (2020: 116, in part); Eprilurahman et al. (2021: 456); Gorin et al. (2021: 97, in part); Poyarkov et al. (2021: 40, in part); Frost (2024, page “Microhyla berdmorei” in part).

ZMMU A-8016 (field number NAP-12747), an adult female from the Lam Plok Waterfall, Trang Province, Thailand (7.584°N, 99.799°E; elevation 200 m a.s.l.), collected on August 20, 2022, by

One adult female ZMMU A-8015 (field number NAP-12746), with collection data the same as for the holotype. Two adult males, ZMMU A-8017 (field number NAP-13182) and ZMMU A-8018 (field number NAP-13183), from Namtok Khao Chong, Trang Province, Thailand (7.649°N, 99.739°E; elevation 92 m a.s.l.) collected on August 24, 2021, by P. Pawangkhanant.

Microhyla peninsularis sp. nov. is characterized by the following combination of morphological features: (1) medium body size (SVL 22.1−22.2 mm in males, 30.9–33.2 mm in females), with moderately stocky and triangular body habitus; (2) head wider than long; (2) dorsal skin almost smooth; (3) snout short and bluntly rounded in dorsal, ventral, and lateral views; (4) first finger longer than half of the length of second finger; (5) finger tips weakly expanded into small disks with wide and deep dorsomedial grooves; (6) toes with distinct disks, each with wide and shallow dorsomedial groove separating the disk into a pair of scale-like pads; (7) tibiotarsal articulation of an adpressed limb extending far beyond the snout tip; (8) toe webbing reaching toe disks on all toes except the fourth and third toes; webbing formula: i1-1ii1-2iii1-1iv2-1v; (9) throat and chin gray in females, with dark-gray mottling in males; belly in life yellowish-white lacking dark markings; (10) dorsal surfaces of forelimbs without prominent dark crossbars, hindlimbs with 1–3 weak and indistinct brownish crossbars; (11) two dark-brown blotches above cloacal opening; (12) dorsum rusty-bronze with indistinct darker “teddy-bear”-pattern lacking clear borders and light edging; (13) dark spots and blotches on body flanks absent or scarce; (14) grayish-bronze lateral band with irregular edges extending from armpit to groin; (16) light postocular stripe absent; (17) reddish spots on dorsum and dorsal surfaces of hindlimbs absent; (18) iris with short black stripe below the pupil.

An adult male specimen in a very good state of preservation. Body size medium (SVL 30.9 mm; other measurements are presented in Table 2). Body habitus stocky, triangular, and slightly dorsoventrally flattened (Figs 7D, 16E). Head short, triangular in dorsal view; wider than long (HW/HL ratio 1.23). Snout very short (SL/HL ratio 0.43) and slightly protruding, bluntly rounded in dorsal and ventral views (Fig. 16A,B), bluntly rounded in profile, and only slightly extending beyond the edge of the lower jaw (Fig. 16E). Eyes comparatively small, slightly protruding in lateral view, not protruding in dorsal view (Fig. 16A), eye length subequal to snout length (EL/SL ratio 0.99), and significantly larger than interorbital distance (IOD/EL ratio 0.74). Canthus rostralis indistinct; loreal area slightly concave. Nostrils oval-shaped, with lateral orientation, located closer to tip of snout than to eye. Interorbital distance slightly wider than internarial distance (IND/IOD ratio 0.95). Upper eyelid length less than interorbital distance (UEW/IOD ratio 0.86). Tympanum concealed, supratympanic fold indistinct (Fig. 16E). Tongue slender, rounded, free for the posterior four-fifths of its length; vomerine teeth absent.

Forelimbs short and slender (Fig. 16A); lower arm elongated and thin (LAL/FLL 0.79), hand less than half of forelimb length (HAL/FLL 0.46). Fingers slender and elongated, webbing or skin fringes on fingers absent. First finger well-developed, notably longer than half of the second finger length (Fig. 16D); the relative finger lengths as follows: I < II < IV < III. Fingertips rounded, weakly expanded into small disks, noticeably narrower than the basal phalanges of the respective fingers. Finger tips with peripheral grooves and a wide and deep dorsomedial notch present on the dorsal surface of each finger disk (Fig. 6H). Finger disks almost equal in width, with the first finger disk being slightly narrower. Subarticular tubercles on fingers distinct, large, rounded, and protruding; edges of the distal subarticular tubercle on the fourth finger less distinct. The subarticular tubercle formula: 1, 1, 2, 2; nuptial pad absent (Fig. 16D). Two metacarpal tubercles: inner metacarpal tubercle distinct, protruding, rounded in shape; outer metacarpal tubercle rounded, flattened, its diameter slightly exceeding the diameter of inner metacarpal tubercle (OPTL/IPTL ratio 1.18).

Hindlimbs long, slender, almost four times longer than forelimbs (HLL/FLL ratio 4.21). Thighs robust and muscular (Fig. 16B), shanks moderately elongated and slender, comprising approximately one-third the length of the hindlimb (TL/HLL ratio 0.36). When the limbs are held at the right angle to the body, the heels significantly overlap. Tibiotarsal articulation of the adpressed limb extends well beyond the tip of the snout. Foot length comprises more than one-third of the hindlimb length (FL/HLL ratio 0.23), being significantly shorter than the tibia (TL/FL ratio 1.34). The relative toe lengths as follows: I < II < V ≤ III < IV. Shanks smooth, inner tarsal fold absent. Tips of all toes distinctly widened into oval-shaped disks, toe disks twice as wide as finger disks (4FDD/3FDD ratio 1.97) and the proximal phalnges of respective toes. Toes webbing complete fully developed, reaching toe disks on all toes except fourth and third toes; webbing formula: i1-1ii1-2iii1-1iv2-1v (Figs 6G, 16C). Toe subarticular tubercles distinct, rounded, slightly protruding, subarticular tubercle formula: 1, 1, 2, 3, 2. The internal metatarsal tubercle oval, slightly elongated, with indistinct margins, comprising less than half the length of the first toe (IMTL/1TOEL ratio 0.32). The outer metatarsal tubercle small but distinct, rounded, prominent with well-defined margins, almost twice as long as the inner metatarsal tubercle (OMTL/IMTL ratio 1.90).

Skin on dorsum smooth skin with few tiny tubercles at head base and on lateral sides of the dorsum (Fig. 7D). Dorsal surfaces of forelimbs smooth. Dorsal surfaces of hindlimbs with sparse tiny tubercles scattered on thighs and shanks (Fig. 16A). Upper eyelid smooth. Body flanks smooth, few tiny tubercles in tympanal region. Ventral surfaces of body and limbs completely smooth (Fig. 16B). Cloacal opening unmodified, directed posteriorly.

Dorsal background coloration in life rusty-bronze with indistinct grayish-brown blotch corresponding to the “teddy-bear”-pattern in the middle of the dorsum (Fig. 7D). Dorsal “teddy-bear”-pattern is thus almost indistinct and has faint and irregular borders. Tiny rusty-red spots scattered across the dorsum and the dorsal surfaces of the hindlimbs (Fig. 7D). An indistinct rusty-brown interorbital band in the shape of an irregular blotch with indistinct borders runs across the head between the posterior parts of the upper eyelids. Light postocular stripe or other markings in tympanal area or around axilla absent. A dark blotch at the head base connects the interorbital bar with the dark marking in the middle of the dorsum. Dark markings on dorsum have no light edging. The lateral sides of dorsum slightly lighter, grayish-bronze. A pair of black spots edged with light-brown located above the cloacal opening.

Body and head flanks slightly lighter than the dorsum. Loreal area grayish-bronze lacking dark markings, the upper jaw bronze with indistinct off-white and grayish mottling below the eye, snout uniformly dark olive-brown. Light postocular stripe or dark markings in the tympanal region absent. On forelimbs, there are no conspicuous stripes or spots; hindlimbs with 1–3 weak and indistinct brownish crossbars. Transverse crossbars on fingers and toes absent.

Ventral surfaces lightly colored; belly and chest dull yellowish-white, with a few irregular grayish spots and mottling on throat and along the jaw margins. Rare gray spots and mottling on the ventral surfaces of the limbs. Ventral surfaces of forelimbs yellowish-gray, and the ventral surfaces of hindlimbs greenish-yellow. Ventral surfaces of hands with brown mottling (Fig. 16D), feet with brownish blotches running from the tibiotarsal articulation to the web (Fig. 16C). Iris light-bronze with indictinct brown reticulation; a short black stripe below the pupil not reaching the ventral edge of the iris (Fig. 7D). Pupil round, black, outlined with a thin bronze circle.

After two years in preservative, the coloration pattern described above did not fade, and dark markings on dorsal surfaces of body and limbs became more prominent, especially the brown transverse crossbars on the hindlimbs (Fig. 16). The dorsal background color faded to brown. Traces of rusty-brown markings were observed as faded patterns; rusty-red spots on dorsum and dorsal surfaces of hindlimbs faded completely. The characteristic dark blotches above the cloacal opening remain unchanged. The bright-yellow coloration of the ventral surfaces faded completely; the ventral surface turned light-beige, but the gray markings on the chin are still visible as a light-gray mottling.

The individuals in the type series are all very similar in appearance. Individual differences in size and body proportions are presented in Tables 4 and 5. In two females, the body length (SVL) ranges from 30.93 to 33.23 mm (n = 2); in two males, the SVL was much smaller, 22.05–22.18 mm (n = 2). There were no significant differences in the coloration of male paratypes and females, except that males had a darker throat coloration. The background coloration of the dorsum varied from rusty-bronze to yellowish-bronze. There is a certain variation in the degree of development of dark dorsal markings among the individuals; the male paratypes ZMMU A-8017 and ZMMU A-8018 had somewhat darker and more contrasting dorsal patterns. In females, the dorsal pattern is generally duller with faint borders.

The species epithet “peninsularis” is a Latin adjective in nominative singular, meaning “peninsular”, and is given in reference to the distribution of the new species, which is presently only known from the southern part of the Thai-Malay Peninsula in Trang Province of Thailand and Terengganu State of Malaysia. Recommended common names: “Peninsular narrow-mouthed frog” (English); “Nhái bầu bán đảo Mã Lai” (Vietnamese); “Malayskiy uzkorot” (Малайский узкорот, Russian); “Eung mae nao pak sun” (อึ่งแม่หนาวปากสั้น, Thai); “Katak mulut sempit semenanjung” (Malay).

Currently, M. peninsularis sp. nov. is known only from two localities in the Thai-Malay Peninsula (Fig. 1): Trang Province of Thailand and ­Terengganu State of northern Peninsular Malaysia. However, the ac­tual extent of distribution of the new species remains unknown, and though it is unlikely that M. peninsularis sp. nov. is widely distributed, the discovery of additional populations of this species from southernmost Thailand and Peninsular Malaysia is anticipated.

Microhyla peninsularis sp. nov. inhabits lowland dipterocarp forest habitats, where it was recorded at elevations of 80–200 m a.s.l. (Fig. 17). The lowland dipterocarp forest at the type locality (at Pa Lean District, Trang Province, Thailand) was dominated by trees of the families Dipterocarpaceae (Anisoptera costata Korth., Hopea odorata Roxb., Dipterocarpus gracilis Blume, and Parashorea stellata Kurz), Dilleniaceae (Dillenia indica L., D. pentagyna Roxb.), and Moraceae (Artocarpus chama Buch.). All type specimens were collected at night from 19:00 to 23:00 h after heavy rains and were mostly recorded while sitting in leaf litter or on rotten logs nearby sandy, slow-moving streams. The diet and predators of the new species are unknown. At the type locality, M. peninsularis sp. nov. was found in sympatry with M. heymonsi, M. mantheyi Das, Yaakob & Sukumaran, 2007, Kaloula latidisca Chan, Grismer & Brown, 2014, Micryletta cf. lineata (Taylor, 1962) (Microhylidae), Humerana miopus (Boulenger, 1918), Sylvirana cf. malayana Sheridan & Stuart, 2018 (Ranidae), and Polypedates discantus Rujirawan, Stuart & Aowphol, 2013 (Rhacophoridae).

Larval morphology and biology of the new species are unknown.

The male advertisement call of the new species represents a series of rasping sounds resembling the sound of a ratchet; it was not recorded, and the call parameters remain unknown.

We here compare M. peninsularis sp. nov. with the six other members of the M. berdmorei species group (M. berdmorei sensu stricto, M. malcolmi, M. sundaica sp. nov. (described above), M. darevskii, M. picta, and M. pulchra). The main diagnostic characters separating the new species from its congeners are summarized in Table 5.

Microhyla peninsularis sp. nov. is distinguished from M. berdmorei sensu stricto by having: smaller body size in both sexes (SVL 22.1−22.2 mm in males, 30.9–33.2 mm in females vs. 33 mm in male, 36.3−38.1 mm in females); finger I length greater than half of finger II length (F1 > ½F2 vs. F1 < ½F2); body habitus stocky (vs. slender); dorsomedial grooves on toe disks present (vs. weak); dorsal color rusty-bronze (vs. olive-brown); dark markings on the dorsum and dorsal surfaces of the head indistinct with faint borders (vs. dorsal “teddy-bear”-pattern and interorbital bar dark, contrasting, with light edging); limbs generally have no dark transverse crossbars, or have 1–3 weak crossbars on thighs and shanks (vs. up to 5–6 dark crossbars on thighs); iris coloration bright bronze with brown reticulum and short vertical stripe down from the pupil not reaching the ventral edge of the iris (vs. bronze with a black reticulation and a distinct black stripe below the pupil reaching the ventral edge of the iris).

Microhyla peninsularis sp. nov. is distinguished from M. malcolmi by having: smaller body size in both sexes (SVL 22.1−22.2 mm in males, 30.9–33.2 mm in females vs. 33.2−41.8 mm in males, 36.0−43.8 mm in females); finger I length greater than half of finger II length (F1 > ½F2 vs. F1 < ½F2); body habitus stocky (vs. slender); dorsomedial grooves on toe disks present (vs. absent); slightly less developed foot webbing (webbing formulae: i1-1ii1-2iii1-1iv2-1v vs. i1-1ii1-1iii1-1iv1-1v); dorsal color rusty-bronze (vs. gray-brown); dark markings on the dorsum and dorsal surfaces of the head indistinct with faint borders (vs. dorsal “teddy-bear”-pattern and interorbital bar dark, contrasting, with light edging); limbs generally have no dark transverse crossbars, or have 1–3 weak crossbars on thighs and shanks (vs. up to 3–4 dark crossbars on thighs); iris coloration bright bronze with brown reticulum and short vertical stripe down from the pupil not reaching the ventral edge of the iris (vs. bronze with black reticulation and a distinct black stripe below the pupil reaching the ventral edge of the iris).

Microhyla peninsularis sp. nov. is distinguished from M. sundaica sp. nov. (described above) by having: smaller body size in males (SVL 22.1−22.2 mm vs. 27.5−­27.9 mm); dorsal color rusty-bronze (vs. gray-bronze with grayish tint); dark markings on the dorsum and dorsal surfaces of the head indistinct with faint borders (vs. gray-brown dorsal “teddy-bear”-pattern distinct, edged with beige or white, anteriorly connecting with the dark interorbital bar); limbs generally have no dark transverse crossbars, or have 1–3 weak crossbars on thighs and shanks being more notable in preservation (vs. dorsal surfaces of forelimbs without prominent crossbars, hindlimbs with 2–3 dark-brown crossbars on thighs and shanks); iris coloration bright bronze with brown reticulum and short vertical stripe down from the pupil not reaching the ventral edge of the iris (vs. gray-bronze without reticulation or dark stripe below the pupil).

Microhyla peninsularis sp. nov. is further distinguished from M. darevskii by having: smaller body size in males (SVL 22.1−22.2 mm vs. 27.0–32.6 mm); by finger disks present (vs. absent); by slightly less developed foot webbing (webbing formulae: i1-1ii1-2iii1-1iv2-1v vs. i1-1ii1-1iii1-1iv1-1v); by dorsal color rusty-bronze (vs. brown); by having bright yellow coloration of belly with irregular grayish spots (vs. no yellow color on belly); iris coloration bright bronze with brown reticulum and short vertical stripe down from the pupil not reaching the ventral edge of the iris (vs. golden with a black reticulation and a distinct black stripe below the pupil reaching the ventral edge of the iris).

Microhyla peninsularis sp. nov. further differs from M. picta by having: smaller body size in males (SVL 22.1−22.2 mm vs. 25.2–30.1 mm); body habitus stocky with comparatively longer legs; tibiotarsal articulation of adpressed limb reaches well beyond snout (vs. stout with shorter legs; tibiotarsal articulation of the adpressed limb reaches the eye-snout level); finger I length greater than half of finger II length (F1 > ½F2 vs. F1 < ½F2); finger disks present (vs. absent); toe disks present and dorsomedial grooves on toes (vs. absent); tibiotarsal articulation reaching well beyond snout (vs. to the eye level); by greater development of foot webbing (webbing formulae: i1-1ii1-2iii1-1iv2-1v vs. i2-2¾ii1¾-2¾iii2¾-3¾iv4-2½v); dorsal coloration rusty-bronze (vs. sandy-brown); by having bright yellow coloration of belly with irregular grayish spots (vs. no yellow color on belly); limbs generally have no dark transverse crossbars, or have 1–3 weak crossbars on thighs and shanks being more notable in preservation (vs. brown transverse bars); iris coloration bright bronze with brown reticulum and with short vertical stripe down from the pupil (vs. golden with a black reticulation and with a distinct vertical dark stripe).

Microhyla peninsularis sp. nov. can be further differentiated from M. pulchra by having: skin on dorsum smooth with tiny scarce tubercles (vs. completely smooth); finger I length greater than half of finger II length (F1 > ½F2 vs. F1 < ½F2); finger disks present (vs. absent); toe disks and dorsomedial grooves on toe disks present (vs. absent); tibiotarsal articulation reaching well beyond snout (vs. to snout or just beyond); greater development of foot webbing (webbing formulae: i1-1ii1-2iii1-1iv2-1v vs. i1½-2ii1-3iii2-3¼iv3½-2v), numerous undulating bands and lines on dorsum absent (vs. present); belly color yellowish with irregular grayish spots (vs. greenish-yellow lacking grayish spots); limbs generally have no dark transverse crossbars, or have 1–3 weak crossbars on thighs and shanks being more notable in preservation (vs. numerous brownish transverse crossbars); iris coloration bright bronze with brown reticulum and with short vertical stripe down from the pupil (vs. grayish with a black reticulation and with a distinct vertical dark stripe).