Microhyla sundaica Trofimets, Dufresnes, Pawangkhanant, Bragin, Gorin, Hasan, Lalremsanga, Muin, Le, Nguyen, Suwannapoom & Poyarkov, 2024, sp. nov.
Creators: name: Trofimets, Alexei V.
name: Dufresnes, Christophe
name: Pawangkhanant, Parinya
name: Bragin, Andrey M.
name: Gorin, Vladislav A.
name: Hasan, Mahmudul
name: Lalremsanga, Hmar Tlawmte
name: Muin, Mohd Abdul
name: Le, Dac Xuan
name: Nguyen, Tan Van
name: Suwannapoom, Chatmongkon
name: Poyarkov, Nikolay A.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Amphibia
Anura
Microhylidae
Microhyla
Microhyla sundaica

description: Microhyla sundaica sp. nov.
Figures 6 E – F, 7 C, 10 C, 14, 15 C – D; Tables 2, 3, 6
Suggested common name.
Sundaic narrow-mouthed frog.
Chresonymy.
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).
Holotype.
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.
Paratypes (n = 5).
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.
Diagnosis.
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: i 1-1 ii 1 - 2 iii 1 - 1 iv 1 - 1 v; (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.
Description of the holotype (Fig. 14).
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. 14 E). 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. 14 E), smoothly rounded in profile, and slightly extending beyond the edge of the lower jaw (Fig. 14 E). 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. 14 E). 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. 14 A); 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. 14 D); 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. 6 F). 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. 14 D). 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. 14 B), 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 (4 TDD / 3 FDD ratio 1.77). Toe webbing fully developed, reaching the disks of all toes; webbing formula: i 1-1 ii 1 - 2 iii 1 - 1 iv 1 - 1 v (Figs 6 E, 14 C). 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 / 1 TOEL 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. 7 C). 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. 14 A). Upper eyelid smooth. Body flanks smooth. Numerous small warts present around the tympanal region. Ventral surfaces of body and limbs smooth (Fig. 14 B). Cloacal opening unmodified, directed posteriorly.
Coloration in life.
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. 7 C). 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. 7 C). 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. 14 D) and feet (Fig. 14 C) 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.
Coloration in preservative.
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.
Variation.
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.
Etymology.
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 b ầu Sunda ” (Vietnamese); “ Zondskiy uzkorot ” (Зондский узкорот, Russian); “ Eung mae nao Malayu ” (อ ึ ่ งแม ่ หนาวมลาย ู, Thai); “ Katak mulut sempit Sunda ” (Malay).
Distribution.
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.
Natural history notes.
The new species is often recorded while calling from the banks or in shallow rain puddles or swamps (Fig. 15 A – 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. 15 A), 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. 15 C – D).
Tadpole.
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.
Advertisement call.
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. 10 C). The call’s peak frequency was 2029 ± 106 Hz (1898–2203 Hz).
Comparisons.
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 (F 1> ½ F 2 vs. F 1 <½ F 2); body habitus stocky (vs. slender); toe webbing complete, webbing formula: i 1-1 ii 1 - 2 iii 1 - 1 iv 1 - 1 v (vs. webbing formula: i 1-1 ii 1 - 2 iii 1 - 2 iv 2 - 1 v); 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 (F 1> ½ F 2 vs. F 1 <½ F 2); 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 (I 1-1 II 1 - 2 III 1 - 1 IV 1 - 1 V vs. I 1-1 II 1 - 1 III 1 - 1 IV 1 - 1 V); 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 (F 1> ½ F 2 vs. F 1 <½ F 2); 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 (I 1-1 II 1 - 2 III 1 - 1 IV 1 - 1 V vs. I 2-2 ¾ II 1 ¾ - 2 ¾ III 2 ¾ - 3 ¾ IV 4 - 2 ½ V); 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 (F 1> ½ F 2 vs. F 1 <½ F 2); 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 (I 1-1 II 1 - 2 III 1 - 1 IV 1 - 1 V vs. I 1 ½ - 2 II 1-3 III 2 - 3 ¼ IV 3 ½ - 2 V); 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.
description: Published as part of Trofimets, Alexei V., Dufresnes, Christophe, Pawangkhanant, Parinya, Bragin, Andrey M., Gorin, Vladislav A., Hasan, Mahmudul, Lalremsanga, Hmar Tlawmte, Muin, Mohd Abdul, Le, Dac Xuan, Nguyen, Tan Van, Suwannapoom, Chatmongkon & Poyarkov, Nikolay A., 2024, Four in one: An integrative taxonomic revision of the Microhyla berdmorei complex (Amphibia: Anura: Microhylidae) illustrates the tremendous amphibian diversity of Southeast Asia, pp. 595-641 in Vertebrate Zoology 74 on pages 595-641, DOI: 10.3897/vz.74.e127937