Raorchestes mawsynramensis, Boruah & Deepak & Das, 2025

Boruah, Bitupan, Deepak, V. & Das, Abhijit, 2025, Revision of bush frogs, Raorchestes and Philautus (Amphibia: Anura: Rhacophoridae) from the northeast Indian biodiversity hotspot with description of thirteen new species, Vertebrate Zoology 75, pp. 517-625 : 517-625

Raorchestes mawsynramensis sp. nov.

Figure 26; Tables 1, 2, S 12

Holotype.

An adult male ( WII-ADA 1531 ) collected by BB on 1 June 2022 near Mawrapat ( 25.26144°N, 91.53468°E, elevation 1140 m a. s. l.), East Khasi Hills, Meghalaya, India .

Paratypes.

Six adult males ( WII-ADA 1533 – WII-ADA 1538 ), and an adult female ( WII-ADA 1530 ). Collection details are the same as for the holotype .

Diagnosis.

Small sized Raorchestes, SVL 16–18.7 mm in adult male, SVL in adult female at least 20.0 mm; head length equal to slightly less than width ( HL / HW = 0.92–1.0); vomerine teeth absent; snout rounded on dorsal view; snout length equal to or slightly less than eye length ( SL / EL = 0.87–1.0); nostril equidistant between eye and snout tip; dense spinules on dorsal aspect of head, dorsum and limb, intermixed with scattered bluntly conical tubercles; dorsally pale brown to dark brown; dark brown “) - (“ mark on dorsum; indistinct or distinct dark brown crossbars on forelimb and hindlimb; yellow bar on inter-upper eyelid space may be present; tips of bluntly conical tubercles white; irregular sized white flecks on flank, lateral aspect of head, and on abdomen; supratympanic fold and lower arm pale yellow.

Description of the holotype.

Holotype in good condition except for an incision on ventral side of right thigh; SVL 17.8 mm, dorsoventrally flattened; head slightly wider than long ( HL / HW = 0.92); snout rounded in dorsal view and nearly truncated in lateral view, slightly protruding in ventral view; snout length slightly less than eye length ( SL / EL = 0.88); canthus rostralis distinct, rounded and nearly vertical; loreal region concave; tympanum indistinct, rounded, less than one third of eye length ( HTYD / ED = 0.28); supratympanic fold distinct; internarial distance smaller than inter-upper eyelid width (INS/ IUE = 0.9) and slightly greater than upper eyelid width ( UEW / IUE = 0.89); nostril oval, obliquely oriented, equidistant between eye and snout tip, narial region slightly protruding, internarial space slightly concave on dorsal aspect; inter-upper eyelid space flat; vomerine teeth absent; choanae round; tongue notched posteriorly; trunk dorsoventrally flattened, less than half of snout-vent length ( AG / SVL = 0.47).

Forelimbs slender, forearm shorter than hand length ( FAL / HAL = 0.75); digits with rounded disc, circum-marginal groove present on each disc; metacarpal tubercles indistinct; disc widths of third and fourth finger greater than tympanic diameter; distinct, large and finely granular nuptial pad present on first finger, covering ventrolateral and dorsolateral aspect; subarticular tubercles round, proximal ones on third and fourth fingers smaller and indistinct than distal ones and indistinct, SAT = 1: 1: 2: 2; webbing among fingers absent; relative length of fingers = I <II <IV <III.

Hind limbs slender; thigh length half of snout-vent length ( TL / SVL = 0.49), slightly greater than tibia length ( TBL / TL = 0.95), and greater than foot length ( FOL / TL = 0.77); heels slightly overlapping when tibia folded perpendicular to body axis; relative length of toes = I <II <II <V <IV; toes with rounded disc, width of toe disc equal to those on finger, fourth toe disc largest, disc on fourth and fifth toes wider than tympanic diameter; circum-marginal groove present on each disc; narrow inner metatarsal tubercle present, outer one absent; subarticular tubercles round, proximal ones on TIII-TV indistinct; supernumerary tubercles absent; webbing among the toes slight, between TI and TII rudimentary, webbing not reaching second subarticular tubercle of fourth toe.

Skin on dorsal aspect of snout and head shagreen, spinules not visible as in life condition; indistinct tubercles on inter-upper eyelid space and on upper eyelid; bluntly conical tubercles on head and upper eyelid distinctly visible in life; few distinct tubercles behind angle of jaw; dorsum shagreen with dense spinules, posteriorly spinules not as dense as anterior part; spinules more distinct dorsal to supratympanic fold and dorsum; flank with dense spinules; forelimb and hindlimb smooth in preserved condition, but spinules and blunt tubercles distinctly visible in life; indistinct flat tubercles present around vent; throat and chest smooth; abdomen and ventral aspect of thigh granular; tibia smooth; flat tubercle along outer dorsoventral aspect of tarsus; small granules scattered on dorsal surface of tongue.

Colouration in life.

Dorsal aspect of head and dorsum dark brown; lateral aspect of head whitish with tiny brown speckle, irregular white patches and tiny dots on upper and lower jaw; tip of tubercles and spinules white; supratympanic fold orange yellow; flank whitish with pale brown tinge and brown speckle; lower arm orange yellow; upper arm pale brown with two indistinct and slightly dark brown crossbars; finger disc with dense brown speckle, orange yellow patch on some of finger discs; thigh dorsally pale brown with slightly dark brown speckle on it, knee slightly darker; lateral aspect of thigh pale brown, towards vent whitish with brown speckle, enlarge dark brown patch around vent; tibia pale brown with indistinct slightly darker crossbar and whitish speckle; tibia and foot pale brown with darker brown and white speckles; toe disc with dense brown speckle; tip of tubercles on hindlimb white; tubercles along tarsus white; throat, abdomen and ventral aspect of limb whitish with brown mottling; small white spots irregularly placed on gular region; white spots of irregular size on abdomen, ventrolateral aspect of flank, upper arm, thigh, and tarsus.

Colouration in preservative.

Head dorsally pale brown, upper eyelid dark grey; inverted triangular dark grey mark on parietal region; loreal region slightly darker, lateral aspect of head pale yellowish with brown speckle; dorsum greyish brown, paler towards lateral side; a slightly dark brown “) - (“ mark on dorsum of which anterior ends starts from upper eyelid and posterior ends extends to groin; in life condition this marking was not visible; forelimb and hindlimb pale yellowish with brown mottling; indistinct brown crossbars visible on forearm, thigh, and tibia; ventrally uniform pale-yellowish with brown mottling.

Sexual dimorphism and morphological variation.

Snout-vent length of the collected males (N = 7) smaller than that of the single female. In males, a pair of internal slits present on the lower jaw; an external large subgular vocal sac present in male; enlarged nuptial pad present on the first finger of males. Live colouration varies among individuals, paratype ( WII-ADA 1531 ) had an orange-yellow bar on inter-upper eyelid space followed by a pair of short orange yellow stripe which are joint posteriorly; in WII-ADA 1530 reddish brown hourglass shaped mark on dark brown present on dorsum. In addition to these variation, intensity of dorsal spinules and tubercles varies among individuals, WII-ADA 1530 and WII-ADA 1537 has comparatively fewer scattered spinules on dorsum unlike other individuals; marking on dorsum and crossbars on limbs faint in WII-ADA 1537 and WII-ADA 1538 ; crossbars on limbs of WII-ADA 1536 narrow and more distinct than that of other individuals; dorsal skin on head nearly smooth in WII-ADA 1530 , WII-ADA 1536 and WII-ADA 1538 ; other morphometric variations are given in Table S 12.

Morphological comparison.

Raorchestes mawsynramensis sp. nov. differs from R. andersoni , R. leiktho and R. malipoensis by the position of nostril equidistant between eye and snout tip (vs. nostril closer to snout tip than eye); it differs from R. annandalii by presence of dense spinules on dorsum (vs. skin on dorsum smooth); it differs from R. garo by smaller body size, SVL 16.0– 18.7 mm in adult males (vs. SVL 19.9–26.9 mm in adult males); it differs from R. cinerascens nov. comb. and R. rezakhani by presence of dense spinules on dorsum (vs. scattered tubercles on dorsum); it differs from R. dulongensis by head length being equal to or less than width (vs. head longer than wide), position of nostril equidistant between eye and snout tip (vs. nostril closer to snout tip than eye); it differs from R. hekouensis by presence of nuptial pad only on first finger (vs. nuptial pad present on first and second fingers); it differs from R. hillisi and R. huanglianshan by snout length less than eye length (vs. snout length snout length greater than eye length), position of nostril equidistant between eye and snout tip (vs. nostril closer to snout tip than eye); it differs from R. jadoh by larger body size in adult males, SVL 16.0– 18.7 mm (vs. SVL 13.6–14.0 mm); it differs from R. jadoh and R. jakoid by snout length being less than or equal to eye length (vs. snout length greater than eye length), and thigh length being greater than or equal to tibia length (vs. thigh length less than tibia length); it differs from R. kempiae by presence of dark brown “) - (“ mark on dorsum (vs. concave stripes on dorsum absent or faint); it differs from R. longchuanensis by inter-upper eyelid width being less than or equal to eye length (vs. inter-upper eyelid width greater than eye length); it differs from R. menglaensis by snout length being smaller than eye length (vs. snout length snout length longer than eye length), head length being equal to or less than width (vs. head longer than wide); it differs from R. mindat by presence of dark patches on groin (vs. enlarged black and white patches present on groin), absence of white patches on lateral aspect of thigh (vs. enlarged white patches on lateral aspect of thigh); it differs from R. parvulus by presence of dense spinules on dorsum (vs. scattered spinules on dorsum); it differs from R. orientalis sp. nov. by presence of comparatively dense spinules on head and dorsum (vs. comparatively less spinules on head and dorsum), distinct enlarged tubercles absent on dorsal aspect of head absent (vs. enlarged bluntly conical tubercles on dorsal aspect of head present), three crossbars on thigh and tibia (vs. two to four crossbars on thigh and tibia); it differs from R. shillongensis presence of spinules on dorsum (vs. small blunt tubercles on dorsum); it differs from R. tytthus nov. comb. by snout length being less than or equal to eye length (vs. snout length greater than eye length); it differs from R. yadongensis by inter-upper eyelid width being less than or equal to eye length (vs. inter-upper eyelid width greater than eye length. Morphological comparisons of R. mawsynramensis sp. nov. with our newly described species in this study are provided in respective sections and in Table 1.

Acoustics.

The calls of R. mawsynramensis sp. nov. were recorded at its type locality on 1 June 2022 between 18: 30–19: 15 hrs at an ambient temperature of 24.4 ° C – 26.0 ° C. The call description is based on 40 calls including those from two individuals ( WII-ADA 1531 and WII-ADA 1534 ). The calls are single type, non-pulsatile, emitted as a single call at regular intervals, not in groups (Fig. 24 ). The mean call duration is 16.2 ± 1.99 ms (13–20 ms) with a rise time of 1 ms and a fall time of 15.48 ± 2.09 ms (12–19 ms). The mean interval between calls is 1418.5 ± 264.94 ms (1127–2133 ms). The dominant frequency is 4403.55 ± 74.74 Hz (4263.6–4608.1 Hz). A detailed comparison of the advertisement calls with those of other congeners is presented in Table 2.

Phylogenetic relationship and genetic divergence.

Raorchestes mawsynramensis sp. nov. is sister to R. boulengeri sp. nov. ( UFB 100 , PP 1.0; Figs 2 , 3 ) with genetic divergence of 2.5–2.9 % in the 16 S, 3.9–4.4 % in the cyt b and 3.6–3.9 % in the COI genes. The genetic divergences with other congeners included in this study are 3.2–9.8 % in the 16 S, 9.3–18.2 % in the cyt b and 3.6–15.6 % in the COI genes (Table S 7 A – C).

Etymology.

This specific epithet is a toponym derived from the name “ Mawsynram ” in Meghalaya State which is the wettest place on earth.

Suggested common name.

Mawsynram bush frog.

Distribution and natural history.

Raorchestes mawsynramensis sp. nov. is known only from the type locality around Mawrapat, approximately 5 km southwest of Mawsynram, Meghalaya (Fig. 25 A ). Calling males were found about 1–1.5 m above ground on a slope in the forest; the area was covered by mostly bamboo species and a few palm trees, ferns and shrubs with thick leaf litters; there was a small stream at this site and a road through the forest connecting Mawrapat and Mawsynram (Fig. 20 E ). We found the single female individual among leaf litter. Other sympatric anuran species found at this locality include Rhacophorus bipunctatus Ahl, 1927 , Kurixalus sp. Xenophrys sp. and Amolops sp.

Figures

Figure 2. A, B Maximum likelihood tree inferred from the concatenated data set (16 S, cyt b, COI and RHO) for Raorchestes species from northeast India, Indo-Burma and Indo-China. Outgroups are not shown in this tree. Numbers at the internal branches represent ultrafast bootstrap values (UFB). Values below 50 are not shown. Scale bar: substitutions per site.

Figure 3. A, B Bayesian tree inferred from the concatenated data set (16 S, cyt b, COI and RHO) for Raorchestes species from northeast India, Indo-Burma and Indochina. Outgroups are not shown in the tree. Numbers at the nodes represent posterior probability (PP) value. Values <0.5 are not shown. Scale bar: substitutions per site.

Figure 20. Habitat at the type localities of Raorchestes species of northeast India. A Forest trail at Tura Peak, the type locality of R. garo and R. kempiae; B forest cover and adjacent lowlands of Garo Hills, from Daribokgre; C a landscape view of forest covers and D a forest trail at Namdapha TR, type localities of R. orientalis sp. nov. and R. nasuta sp. nov.; E hills at Mawsynram, near the type locality of R. mawsynramensis sp. nov.; F Nohkalikai Waterfall and forest cover at the type locality of R. boulengeri sp. nov. in Cherrapunji; G dry stream bed and vegetation in Maruwacherra, near Barail WLS, the type locality of R. barakensis sp. nov. and H forest around Jaintia Hills in Narpuh WLS, at the type locality of R. narpuhensis sp. nov.

Figure 24. Comparative spectrograms and oscillograms illustrating representative calls of four species of Raorchestes described in this study. A, B Oscillograms, C spectrogram, D power spectrum. The call marked with an arrow on top in A is expanded in B.

Figure 25. Distribution of Raorchestes species in northeast India. A Raorchestes rezakhani and four other closely related species; B Raorchestes annandalii and three new species. Type localities are denoted by stars, and other localities are denoted by circles.

Figure 26. Raorchestes mawsynramensis sp. nov. A – C Holotype (WII-ADA 1531) in preserved condition, A dorsal view (inset image showing dorsal spinules on dorsum), B ventral view, C lateral view of head. D – G paratype (WII-ADA 1530) in preserved condition. D Dorsal view, E ventral view (inset image showing granular abdomen skin), F ventral view of left hand, G ventral view of left foot. H Holotype in life, I paratype (WII-ADA 1538) in life; J paratype (WII-ADA 1534) in life; K paratype (WII-ADA 1530) in life. Scale bar = 10 mm.