Raorchestes nasuta, 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 nasuta sp. nov.

Figure 34; Tables 1, 2, S 12

Holotype.

An adult male ( WII-ADA 3388 ) collected by RNV on 12 June 2023 from Ranijheel ( 27.53903°N, 96.4888°E, elevation 910 m a. s. l.), Namdapha Tiger Reserve, Changlang District, Arunachal Pradesh, India .

Paratypes.

Two adult males ( WII-ADA 3398 and WII-ADA 3399 ) collected by RNV on 13 June 2023 from Bulbulia ( 27.53872N, 96.4763E, elevation 880 m a. s. l.), Namdapha Tiger Reserve, Changlang District, Arunachal Pradesh .

Referred Material.

Two adult males ( WII-ADA 3216 and WII-ADA 3218 ) collected by RNV and SD on 10 May 2023 from Hornbill ( 27.53810°N, 96.44037°E, elevation 660 m a. s. l.), Namdapha Tiger Reserve, Changlang District, Arunachal Pradesh .

Diagnosis.

A small sized Raorchestes, SVL 17.0– 19.9 mm in adult males, female unknown; head longer than wide; snout acute with dermal projection on snout tip; snout length equal to eye length; inter-upper eyelid width less than or equal to eye length ( IUE / EL = 0.88–0.96); nostril equidistant between eye and snout tip; horn like dermal projection on edge of upper eyelid; an hour-glass shaped dark brown mark starting on inter-upper eyelid space and extending to dorsum; bright yellow patches on groin and thigh; finger and toe disc yellow.

Description of the holotype.

Holotype well preserved except for an incision on the ventral side of right thigh. Adult male, SVL 17.9 mm; head longer than wide ( HW / HL = 0.9); snout acute in dorsal and lateral view as a dermal projection present on snout tip, protruding beyond lower jaw in ventral view; snout length equal to eye length and slightly greater than inter-upper eyelid width ( IUE / SL = 0.85); symphysial knob present on lower jaw; narial region protruding; nostril oval, laterally positioned and obliquely oriented, equidistant between eye and snout tip; slightly concave on dorsal aspect of snout; canthus rostralis rounded, vertical; loreal concave; eye moderate in size ( EL / HL = 0.37); internarial distance nearly equal to inter-upper eyelid width ( IN / IUE = 0.91) and greater than upper eyelid width ( UEW / IN = 0.86); tympanum indistinct, round, one third of eye length ( HTYD / EL = 0.31); supratympanic fold distinct; vomerine teeth absent; choanae round; tongue posteriorly deeply notched and the two lobes are acute; pair of internal vocal sac openings on lower jaw; habitus less than half of snout-vent length ( AG / SVL = 0.46).

Forelimbs slender; forearm nearly equal to hand length ( FAL / HL = 0.96); relative length of fingers = FI <FII <FIV <FIII; rounded disc on finger, disc on finger III and IV wider than tympanic diameter; circum-marginal groove on each disc; rudimentary webbing present between fingers; palmar tubercles indistinct; subarticular tubercles round, lower subarticular tubercle on finger III and IV small and indistinct; enlarged, fine granular nuptial pad on first finger.

Hindlimbs slender; thigh longer than tibia ( TBL / TL = 0.89) and half of snout-vent length ( TL / SVL = 0.5); relative length of toes = TI <TII <TIII <TV <TIV; rounded disc on toe, smaller than those of fingers; circum-marginal groove present each disc; subarticular tubercles distinct in live condition, proximal subarticular on fourth and fifth toes indistinct; inner metatarsal tubercle present, its length equal to width of discs of toes II – V; very thin dermal fringe along fifth toe; webbing moderate, reaching beyond second subarticular tubercle on fourth toe.

Skin on dorsal aspect of snout and head smooth (shagreen in live condition); indistinct tubercles on upper eyelid, a horn like tubercle on edge of each upper eyelid; tubercles on angle of jaw; skin on dorsum (shagreen in live condition) with spinules, scattered on middle and dense towards dorsolateral aspect; a weak mid-dorsal dermal ridge visible in live condition starting from snout and becoming diffused posteriorly; flank smooth; dorsal aspect of forelimb and hindlimb smooth; throat and chest smooth; abdomen and thigh granular; tibia and tarsus smooth.

Colouration in life.

Dorsal aspect of snout and top of head, dorsum brown; an hourglass shaped dark brown marking starting at inter-upper eyelid space and covering posterior half of upper eyelid extending to dorsum, becoming diffused posteriorly; a diffused dark brown broad stripe along supratympanic fold; another similar stripe on loreal region reaching snout tip; irregular pale cream coloured white spots on upper jaw; two yellow spots on groin on each side and inner lateral aspect of thigh; on outer lateral aspect of thigh yellow patches barely visible; a broad cross bar on each thigh and tibia barely visible; disc on digits yellow; ventral aspect of head, chest, abdomen and thigh brown, paler than dorsal aspect; dense dark brown mottling on chin, throat with few white flecks on anterior part of the jaw; brown mottling on ventral aspect of forelimb chest, abdomen and thigh not dense; irregular white flecks on forearm, thigh, tarsus and foot; granules on anterior to middle of the abdomen with white flecks; brown mottling on foot dense;

Colouration in preservative.

Colouration darker than in life; marking on head and dorsum visible; mandibular region dark brown; dorsal aspect of distal half of forearm and hand dark brown; knee dark brown; crossbars on thigh and tibia distinctly visible; one broad cross bar on each thigh and two on each tibia; disc on digits pale cream coloured with brown mottling; dark brown patch around vent; chin and throat brown; chest, abdomen and ventral aspect of thigh pale cream coloured with brown flecks; forearm, tibia, tarsus, and feet brown; yellow spots on groin and thigh and white flecks on abdomen not visible.

Morphological variation.

Detailed morphometric variations are given in Table S 12. Additionally, yellow spots on groin and thighs vary among individuals (Fig. 34 ). For example, WII-ADA 3216 has yellow patches on base of lower arm, ventral aspect of thigh and tibia; distinct enlarged yellow patches on outer lateral aspect of thigh; yellow patches on groin much enlarged unlike holotype; a tubercle on inter-upper eyelid space. Dorsal marking on head and dorsum in WII-ADA 3216 distinct in preserved condition and barely visible in WII-ADA 3218 , WII-ADA 3398 and WII-ADA 3399 . Brown mottling on the ventral side in paratypes is not as dense as in holotype.

Morphological comparison.

Raorchestes nasuta sp. nov. differs from its congeners by its acute snout shape; further it differs from R. andersoni by position of nostril equidistant between eye and snout tip (vs. nostril closer to snout tip than eye); it differs from R. annandalii , R. boulengeri sp. nov., and R. kempiae by presence of enlarged yellow patches on groin and thigh (vs. absent); it differs from R. barakensis sp. nov. by head being longer than wide (vs. head length less than or equal to width), enlarged yellow patches present on groin (vs. enlarged brown patch present on groin), by presence of dark brown hourglass shaped pattern on dorsum (vs. pair of concave dark brown stripes present on dorsum); it differs from R. cinerascens nov. comb. by snout length being equal to eye length and longer than inter-upper eyelid width (vs. snout length less than eye length and equal than inter-upper eyelid width); it differs from R. dulongensis by position of nostril equidistant between eye and snout tip (vs. nostril closer to snout tip than eye), enlarged yellow spots present on groin and thigh (vs. absent); it differs from R. garo by presence of enlarged yellow patches on groin and thigh (vs. dark brown patches with or without yellow spots present); it differs from R. hekouensis by head being longer than wide (vs. head wider than long), snout being longer than inter-upper eyelid width (vs. snout length less than or equal to inter-upper eyelid width), nuptial pad present only on first finger (vs. nuptial pad present on first and second finger); it differs from R. hillisi and R. menglaensis by position of nostril equidistant between eye and snout tip (vs. nostril closer to snout tip than eye), snout length being equal to eye length (vs. snout length greater than eye length); it differs from R. huanglianshan by head being longer than wide (vs. head length less than or equal to width), by snout length being equal to eye length (vs. snout length greater than eye length); it differs from R. jadoh by larger body size in adult males, SVL 17.0–19.9 (vs. SVL 13.6–14.0 mm); itr differs from R. jadoh and R. jakoid snout acute (vs. snout rounded), by position of nostril equidistant between eye and snout tip (vs. nostril closer to snout tip than eye), and enlarged yellow patches present on groin and thigh (vs. absent); it differs from R. lawngtlaiensis sp. nov. by head being longer than wide (vs. head length equal to or smaller than width), by snout length being equal to eye length (vs. snout length less than eye length); it differs from R. leiktho by larger body size in adult males, SVL 17.0– 19.9 mm (vs. SVL 15.7–15.8 mm), an hourglass shaped pattern present on dorsum (vs. absent); 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. malipoensis by head being longer than wide (vs. head wider than long), by snout being longer than inter-upper eyelid width (vs. snout length less than or equal to inter-upper eyelid width); it differs from R. mawsynramensis sp. nov. and R. shillongensis by head being longer than wide (vs. head length less than or equal to width), enlarged yellow patches present on groin and thigh (vs. absent); it differs from R. mindat by presence of yellow patches on groin and thigh (vs. enlarged black and white patches present on groin and thigh), an hourglass shaped pattern present on dorsum (vs. absent); it differs from R. narpuhensis sp. nov. by head being longer than wide (vs. head length less than or equal to width), by position of nostril equidistant between eye and snout tip (vs. nostril closer to snout tip than eye); it differs from R. parvulus by thigh being longer than tibia (vs. thigh length smaller than or equal to tibia length); it differs from R. rezakhani by snout length being equal to eye length (vs. snout length greater than eye length), by head being longer than wide (vs. head wider than long); it differs from R. tytthus nov. comb. by head being longer than wide (vs. head length equal to width), snout length being equal to eye length (vs. snout length greater than eye length); it differs from R. yadongensis by head being longer than wide (vs. head wider than long), inter-upper eyelid width being less than or equal to eye length (vs. inter-upper eyelid width greater than eye length). A detailed morphological comparison is provided in Table 1.

Phylogenetic relationship and genetic divergence.

Raorchestes nasuta sp. nov. is sister to an undescribed species from Tibet and Adi hills, Arunachal Pradesh ( UFB 100 , PP 1.0; Figs 2 , 3 ). These two lineages have a shallow genetic divergence of 1.5–2.0 % in the 16 S gene. The genetic divergence of R. nasuta sp. nov. with other congeners included in this study are 3.1–8.9 % in the 16 S, 9.1–19.2 % in the cyt b and 3.2–14.8 % in the COI genes (Table S 7 A – C).

Etymology.

The specific epithet is derived from the Latin word nose “Nasuta”, in reference to the prominent acute snout of this species.

Suggested common name.

Pointy-nosed bush frog.

Distribution and natural history.

Raorchestes nasuta sp. nov. is currently distributed within Namdapha Tiger Reserve in Ranijheel, Bulbulia and Hornbill on the northern bank of the Noa-Dihing River, Arunachal Pradesh, India between 600–1000 m a. s. l. elevation (Fig. 20 A ). Calling aggregation of the species was recorded between 18: 00–22: 00 hrs on vegetation along streams and forest trails.

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 34. Raorchestes nasuta sp. nov. A – D Holotype (WII-ADA 3388) in preservative, A Dorsal view, B ventral view, C lateral view, D ventral view of right hand. E, F Paratype (WII-ADA 3216) in preservative. G – J Holotype in life, G dorsolateral view, H ventral view, I dorsal view, J groin. K – O paratype (WII-ADA 3216) in life, K dorsolateral view, L dorsal view of head, M ventral view, N groin, O posterior view of thighs. Scale bar = 10 mm. Photos (G – O) by Rajiv N. V.