Microhyla peninsularis, Trofimets & Dufresnes & Pawangkhanant & Bragin & Gorin & Hasan & Lalremsanga & Muin & Le & Nguyen & Suwannapoom & Poyarkov, 2024

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, Vertebrate Zoology 74, pp. 595-641 : 595-641

Microhyla peninsularis sp. nov.

Figures 6 G, H , 7 D , 16; Tables 2, 3, 6

Suggested common name.

Peninsular narrow-mouthed frog.

Chresonymy.

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).

Holotype.

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

Paratypes (n = 3).

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 .

Diagnosis.

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: i 1-1 ii 1 - 2 iii 1 - 1 iv 2 - 1 v; (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.

Description of the holotype (Fig. 16 ).

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 7 D , 16 E ). 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. 16 A, B ), bluntly rounded in profile, and only slightly extending beyond the edge of the lower jaw (Fig. 16 E ). Eyes comparatively small, slightly protruding in lateral view, not protruding in dorsal view (Fig. 16 A ), 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. 16 E ). Tongue slender, rounded, free for the posterior four-fifths of its length; vomerine teeth absent.

Forelimbs short and slender (Fig. 16 A ); 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. 16 D ); 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. 6 H ). 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. 16 D ). 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. 16 B ), 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 (4 FDD / 3 FDD 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: i 1-1 ii 1 - 2 iii 1 - 1 iv 2 - 1 v (Figs 6 G , 16 C ). 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 / 1 TOEL 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. 7 D ). Dorsal surfaces of forelimbs smooth. Dorsal surfaces of hindlimbs with sparse tiny tubercles scattered on thighs and shanks (Fig. 16 A ). Upper eyelid smooth. Body flanks smooth, few tiny tubercles in tympanal region. Ventral surfaces of body and limbs completely smooth (Fig. 16 B ). Cloacal opening unmodified, directed posteriorly.

Coloration in life.

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. 7 D ). 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. 7 D ). 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. 16 D ), feet with brownish blotches running from the tibiotarsal articulation to the web (Fig. 16 C ). Iris light-bronze with indictinct brown reticulation; a short black stripe below the pupil not reaching the ventral edge of the iris (Fig. 7 D ). Pupil round, black, outlined with a thin bronze circle.

Coloration in preservative.

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.

Variation.

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.

Etymology.

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 b ầu bán đ ảo Mã Lai ” (Vietnamese); “ Malayskiy uzkorot ” (Малайский узкорот, Russian); “ Eung mae nao pak sun ” (อ ึ ่ งแม ่ หนาวปากส ั ้ น, Thai); “ Katak mulut sempit semenanjung ” (Malay).

Distribution.

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.

Natural history notes.

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 ).

Tadpole.

Larval morphology and biology of the new species are unknown.

Advertisement call.

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.

Comparisons.

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 (F 1> ½ F 2 vs. F 1 <½ F 2); 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 (F 1> ½ F 2 vs. F 1 <½ F 2); body habitus stocky (vs. slender); dorsomedial grooves on toe disks present (vs. absent); slightly less developed foot webbing (webbing formulae: i 1-1 ii 1 - 2 iii 1 - 1 iv 2 - 1 v vs. i 1-1 ii 1 - 1 iii 1 - 1 iv 1 - 1 v); 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: i 1-1 ii 1 - 2 iii 1 - 1 iv 2 - 1 v vs. i 1-1 ii 1 - 1 iii 1 - 1 iv 1 - 1 v); 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 (F 1> ½ F 2 vs. F 1 <½ F 2); 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: i 1-1 ii 1 - 2 iii 1 - 1 iv 2 - 1 v vs. i 2-2 ¾ ii 1 ¾ - 2 ¾ iii 2 ¾ - 3 ¾ iv 4 - 2 ½ v); 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 (F 1> ½ F 2 vs. F 1 <½ F 2); 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: i 1-1 ii 1 - 2 iii 1 - 1 iv 2 - 1 v vs. i 1 ½ - 2 ii 1-3 iii 2 - 3 ¼ iv 3 ½ - 2 v), 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).

Figures

Figure 1. Distribution of the species lineages of the Microhyla berdmorei species complex as identified in the phylogenetic analyses. Star denotes type localities, with their corresponding taxon names in colored clouds; synonyms are shown in quotes; colors correspond to those used in Figures 2–5; symbol shapes denote mtDNA lineages shown in Figure 2. Base map created using simplemappr. net. For locality information see Table S 1. Photos by A. V. Trofimets, A. M. Bragin, P. Pawangkhanant and N. A. Poyarkov.

Figure 6. Dorsal aspects of fourth toes (A, C, E, G) and third fingers (B, D, F, H) of the Microhyla berdmorei species complex members. А, B M. berdmorei sensu stricto, MZMU A- 8005; C, D M. malcolmi, ZMMU A- 7973; E, F M. sundaica sp. nov., ZMMU A- 8011, holotype; G, H M. peninsularis sp. nov., ZMMU A- 8016, holotype. Scale bar equals to 1 mm. Drawings by A. M. Bragin.

Figure 7. Members of the Microhyla berdmorei species complex in life. А M. berdmorei sensu stricto, MZMU A- 8005 and MZMU A- 8003 (a couple showing cephalic amplexus) from Aizawl, Mizoram State, India; B M. malcolmi, ZMMU A- 7973 from Than To, Yala Province, Thailand; C M. sundaica sp. nov., ZMMU A- 8011 (holotype) from environs of Sungai Tua Recreational Forest, Selangor State, Malaysia; D M. peninsularis sp. nov., ZMMU A- 8016 (holotype) from Lam Plok Waterfall, Trang Province, Thailand. Photographs by: A. M. Bragin (A), N. A. Poyarkov (B), A. T. Aful (C), P. Pawangkhanant (D).

Figure 16. Microhyla peninsularis sp. nov. in preservative – Specimen ZMMU A- 8016 (holotype, adult female) from Lam Plok Waterfall, Trang Province, Thailand: A Dorsal aspect; B ventral aspect; C plantar view of the right foot; D volar view of the left hand; E lateral view of head. Scale bar equals 3 mm. Photographs by A. V. Trofimets.

Figure 17. Natural habitat of Microhyla peninsularis sp. nov. at Pa Lean District, Trang Province, Thailand, the lowland dipterocarp forest at the type locality. Photograph by P. Pawangkhanant.