Raorchestes magnus, 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 magnus sp. nov.

Figure 42; Tables 1, 2, S 12

Holotype.

An adult male ( WII-ADA 1667 ) collected by BB on 4 August 2022 from Tiwarigaon ( 28.22049°N, 95.83799°E, elevation 800 m a. s. l.), Lower Dibang Valley District, Arunachal Pradesh, India .

Paratypes.

Two adult males ( WII-ADA 1666 and WII-ADA 1668 ) collected along with the holotype from same locality .

Referred material.

One adult female ( WII-ADA 1748 ) and two subadult males ( WII-ADA 1739 and WII-ADA 1749 ) collected by BB on 21 August 2022 from Punli ( 28.6327°N, 95.9430°E, elevation 920 m a. s. l.), Dibang Valley District, Arunachal Pradesh ; one subadult ( WII-ADA 1190 ) collected by BB on 26 October 2021 near Jengging ( 28.53543°N, 95.03106°E, elevation 940 m a. s. l.), Mouling National Park, Upper Siang District, Arunachal Pradesh ; one subadult ( WII-ADA 1202 ) collected by BB on 27 October 2021 from Ramsing ( 28.65631°N, 94.97951°E, elevation 620 m a. s. l.), Mouling National Park, Upper Siang, Arunachal Pradesh ; one adult female ( WII-ADA 402 ) and one adult male ( WII-ADA 448 ) collected by AD on 16 October 2018 from Mouling National Park ( 28.47821°N, 94.85392°E, elevation 1520 m a. s. l.), Upper Siang, Arunachal Pradesh ; one juvenile ( WII-ADA 3035 ) collected by BB and AD on 3 September 2022 near Glaw lake ( 27.69583°N, 96.44585°E, elevation 1200 m a. s. l.), Kamlang Tiger Reserve, Lohit District, Arunachal Pradesh ; one adult male ( WII-ADA 3435 ) collected by AD, RNV and JDG on 19 July 2023 near Glaw lake , Kamlang Tiger Reserve, Lohit District, Arunachal Pradesh ; one adult male ( WII-ADA 3424 ) collected by AD, RNV and JDG on 17 July 2023 from Kalai ( 27.72294°N, 96.4346°E, elevation 1110 m a. s. l.), Kamlang Tiger Reserve, Lohit District, Arunachal Pradesh .

Diagnosis.

Medium sized Raorchestes, SVL 22.5–27.4 mm in adult males and SVL 25.5–28.4 mm in adult females; Vomerine teeth absent; head length slightly less than or equal to width ( HL / HW = 0.96–1.03); snout length slightly smaller than eye length ( SL / EL = 0.86–0.97); snout length greater than inter-upper eyelid width ( IUE / SL = 1.03–1.24); nostrils closer to snout tip; internarial distance smaller than inter upper-eyelid width; eye length greater than inter-upper eyelid width (0.77–0.91); numerous spinules on back; bluntly conical tubercles on upper eyelids and limbs; a pair of broad dark concave stripes on back; broad dark crossbars on limbs; dorsally greyish-brown in life; a distinct or faint white bar on interorbital space; three broad crossbars on thigh and tibia.

Description of the holotype.

Holotype is in good preserved condition except for an incision under right thigh. Adult male with vocal sacs, 24.3 mm in SVL; head moderate in size ( HL / SVL = 0.39), slightly wider than long ( HL / HW = 0.98); snout rounded in dorsal view, slightly protruding beyond lower jaw; slight depression on internarial region; outline between snout tip and nostrils concave; narial region slightly protruding; canthus rostralis distinct and rounded, vertical; loreal concave; nostril oval, laterally positioned and obliquely oriented, closer to snout tip than eye ( NS / EN = 0.76); internasal distance equal to upper eyelid width ( UEW / IN = 1.0) and smaller than inter-upper eyelid width ( IN / IUE = 0.87); eyes moderate in size ( EL / HL = 0.4), ele length greater than snout length ( SL / EL = 0.89), protruding in life; tympanum distinct, rounded and one third of the eye length ( HTYD / EL = 0.3); supratympanic fold distinct; choanae rounded; no vomerine teeth; tongue posteriorly wide and notched; pair of slit like openings present on lower jaw; trunk slender, half of snout-vent length (TRL/ SVL = 0.49).

Forelimbs slender; forearm length less than hand length ( FAL / HAL = 0.78); palmar tubercles barely visible; relative length of fingers = I <II <IV <III; finger with rounded disc; disc on third and fourth finger wider than tympanic diameter; circum-marginal groove present each on disc; subarticular tubercles enlarged, rounded except the proximal ones on third and fourth fingers, which are smaller and indistinct; fine granular nuptial pad present on base of first fingers; rudimentary web present between third and fourth fingers.

Hindlimbs slender; thigh length slightly greater than half of snout-vent length ( TL / SVL = 0.53) and slightly greater than tibia length ( TBL / TL = 0.96); tibia length greater than foot length ( FOL / TBL = 0.83); relative length of toes = I <II <III <IV <V; toe with rounded disc; disc width equal to those of fingers; circum-marginal groove present on each disc; subarticular tubercles enlarged and rounded, proximal subarticular tubercles on fourth and fifth toes smaller than distal ones; inner metatarsal tubercle present and outer one absent; supernumerary tubercles absent; webbing moderate, reaching distal to second subarticular tubercle on fourth finger.

Skin on dorsal aspect of snout, inter-upper eyelid space and upper eyelid shagreened; three tubercular projections on top of the head in a straight line, one anterior to inter-upper eyelid space, one on inter-upper eyelid space and one posterior to it; tubercles on upper eyelid barely visible; enlarged tubercles posterior to angle of jaw, one is prominent; indistinct tubercles above supratympanic fold; dense spinules on middle of dorsum and towards dorsolateral aspect, few spinules scattered on anterior part of dorsum, posterior part of dorsum smooth; flank granular, ventro-laterally distinct; forelimbs smooth on dorsal aspect; thighs smooth on dorsal aspect; tibia with few indistinct scattered tubercles; blunt tubercular projections along ventro-lateral side of tarsus; two tubercles below vent, one on each side; on ventrum, throat, chest and abdomen granular; lower arms granular; thighs granular towards its base; tibia smooth.

Colouration in life.

Dorsal aspect of head, dorsum and limbs on top pale brown; markings on head, dorsum and crossbars on limbs faint, not distinct as in preserved condition; irregular shaped and sized dark brown spots on flank, near groin, on supratympanic fold, tibia and discs of outer two digits; enlarged dark brown patch present on groin; enlarged dark brown patches on lateral aspect of the thigh; disc of inner two fingers and inner three toes pale yellow; on ventral aspect, head, chest, abdomen, and limb flesh coloured; irregular brown patches on thigh and tibia.

Colouration in preservative.

Snout on dorsal aspect brown; upper eyelid dark grey; pale cream coloured bar on inter-upper eyelid space and an inverted triangular brown marking posterior to it; a small brown patch behind the upper eyelid; loreal region dark brown; brown streak ventral to eye; brown stripe along lower border of supratympanic fold; back pale greyish brown with an enlarged slightly dark brown patch which anteriorly connected with head marking and posteriorly bifurcated, posterior ends reaching anterior to groin; forelimbs pale cream coloured with brown mottling; broad dark brown band on dorsal aspect of forearm and another one on base of the hand; brown patch on both third and fourth finger; hindlimbs pale cream coloured with brown mottling; distal end of thigh and proximal end of tibia heavily mottled; a brown patch on inner lateral aspect of thigh near groin; single broad dark brown bar on thigh, tibia, tarsus and base of the foot; irregular brown patches on fourth and fifth toes and webbing between them; dark brown patch around the vent; on ventrum, head, trunk, limbs pale cream coloured with irregular brown mottling; brown and light patches on ventral aspect of thigh and tibia.

Sexual dimorphism and morphological variation.

Males have a pair of internal vocal sac openings on the lower jaw, an external subgular vocal sac and a nuptial pad on the first finger. Other morphometric variations among individuals are provided in Table S 12. Dorsal colouration among the individuals varies in life as greyish brown, brown or pale yellowish brown; dorsal concave stripes may be distinct or faint; number of dark brown or black spots on flank, abdomen, and thighs varies among individuals.

Morphological comparison.

Raorchestes magnus sp. nov. differs from its congeners by large body size in adult males, SVL 22.5–27.4 mm (vs. SVL 17.3–19.6 mm in R. annandalii , 16.7–21.0 mm in R. barakensis sp. nov., 17.5–19.1 mm in R. boulengeri sp. nov., 19.6–21.8 mm in R. dibangensis sp. nov., 15.0–19.0 mm in R. dulongensis , 16.1–17.5 mm in R. hekouensis , 15.9–17.7 mm in R. hillisi , 17.0– 19.6 mm in R. huanglianshan , 13.6–14.0 mm in R. jadoh , 18.4–21.6 mm in R. jakoid , 18.1–19.7 mm in R. lawngtlaiensis sp. nov., 15.7–15.8 mm in R. leiktho , 14.6–17.7 mm in R. malipoensis , 16.0– 18.7 mm in R. mawsynramensis sp. nov., 16.6–21.6 mm in R. menglaensis , 16.7–18.3 mm in R. mindat , 17.9–20.6 mm in R. monolithus sp. nov., 17.0– 19.9 mm in R. nasuta sp. nov., 18.0– 21.1 mm in R. narpuhensis sp. nov., 14.6–20.8 mm in R. orientalis sp. nov., 17.0– 18.6 mm in R. parvulus , 18.85–20.90 mm in R. rezakhani , 13.9–20.4 mm in R. shillongensis ); further it differs from R. andersoni by presence of three broad dark crossbars on thigh and tibia (vs. single crossbar on thigh and tibia); it differs from R. annandalii by presence of enlarged black or dark brown patch on groin (vs. no marking present on groin); it differs from R. dulongensis by snout length being smaller than eye length (vs. snout length equal to eye length); it differs from R. eaglenestensis sp. nov. by presence of enlarged black or dark brown patch on groin (vs. no marking present on groin); it differs from R. hekouensis by presence of nuptial pad only on first finger (vs. nuptial pad present on first and second finger); it differs from R. hillisi and R. huanglianshan by snout length being less than eye length (vs. snout length greater than eye length); it differs from R. jadoh by inter-upper eyelid width being less than eye length (vs. inter-upper eyelid width greater than eye length); it differs from R. jakoid by snout length being less than eye length (vs. snout length greater than eye length); it differs from R. kempiae by presence of enlarged black or dark brown patch on the groin (vs. short brown stripe present on groin); it differs from R. khonoma sp. nov. by snout length being greater than inter-upper eyelid length (vs. snout length less than or equal to inter-upper eyelid width), and eye length being greater than inter-upper eyelid width (vs. eye length equal to inter-upper eyelid width); it differs from R. longchuanensis by inter-upper eyelid width being less than eye length (vs. inter-upper eyelid width greater than eye length); it differs from R. malipoensis by snout length being greater than inter-upper eyelid width (vs. snout length less than or equal to inter-upper eyelid width); it differs from R. menglaensis by head length being equal to or less than width (vs. head longer than width); it differs from R. yadongensis by eye length being greater than snout length and inter upper eyelid width (vs. eye length equal to snout length and inter-upper eyelid width); it differs from R. cinerascens nov. comb. by snout length being greater than inter-upper eyelid width (vs. snout length equal to inter upper eyelid width); it differs from R. tytthus nov. comb. by snout length being less than eye length (vs. snout longer than eye length). A detailed morphological comparison with its congeners is given in Table 1. Morphologically R. magnus sp. nov. is close to R. arunachalensis sp. nov. and R. garo .

Phylogenetic position and genetic divergence.

Raorchestes magnus sp. nov. is sister to R. arunachalensis sp. nov. ( UFB 99, PP 1.0; Figs 2 , 3 ). The genetic divergence of R. magnus sp. nov. with other congeners included in this study is 2.8–8.4 % in the 16 S, 12.5–18.4 % in the cyt b and 7.5–14.1 % in the COI genes (Table S 7 A – C).

Etymology.

The specific epithet is derived from the Latin word “Magna” meaning large, as this species is the largest (maximum SVL 28.4 mm) of all Raorchestes species found in northeast India.

Suggested common name.

Large bush frog.

Distribution and natural history.

Currently Raorchestes magnus sp. nov. has been recorded from Mouling National Park, Kamlang Tiger Reserve and Dibang Valley in Arunachal Pradesh (Fig. 25 B ). Individuals of this species were observed on leaves up to one metre above ground on roadsides near Punli in Dibang valley in August 2022. Calling individuals were observed on leaves about three metres above ground in Tiwarigaon during the same month. Juveniles were along forest trails streams in October 2021; individuals were recorded on leaves near Glaw Lake and in Kalai camp, Kamlang Tiger Reserve in September 2022 and July 2023. Other amphibian species recorded in the same habitat as R. magnus sp. nov. are Xenophrys ancrae , Nasutixalus sp. Amolops cf. adicola , Amolops beibengensis Jiang et al., 2020 , Rhacophorus tuberculatus ( Anderson, 1871) , Zhangixalus smaragdinus (Blyth, 1852) , Theloderma moloch ( Annandale, 1912) in Dibang Valley and Amolops gerbillus ( Annandale, 1912) , Ingerana borealis , Xenophrys sp. in Mouling National Park.

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 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 42. Raorchestes magnus sp. nov. A – F Holotype (WII-ADA 1667), A dorsal view, B ventral view in preserved condition, C dorsolateral view, D ventral view, E groin, F posterior view of thigh. G WII-ADA 448 in life from Mouling NP. H – M WII-ADA 402 from Mouling NP, H dorsal view, I ventral view in preserved condition, J dorsolateral view, K ventral view, L groin, M posterior view of thigh in life. N Paratype (WII-ADA 1668) in life. O WII-ADA 1739 in life from Punli. P WII-ADA 1190 in life from Jengging. Scale bar = 10 mm.