Raorchestes barakensis, 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 barakensis sp. nov.

Figure 28; Tables 1, 2, S 12

Holotype.

An adult male ( WII-ADA 612 ) collected by BB on 18 April 2019 from Maruwacherra ( 24.973744°N, 92.768593°E, elevation 50 m a. s. l.), Cachar District, Assam, India .

Paratypes.

Six adult males ( WII-ADA 611 , WII-ADA 613 – WII-ADA 617 ). Collection details are same as for the holotype .

Referred material.

Three adult males ( WII-ADA 862 , WII-ADA 863 and WII-ADA 865 ) collected by BB and AD on 2 August 2021 from Aramsangram ( 25.8312°N, 94.8731°E, elevation 1460 m a. s. l.), approximately 1.6 km (aerial distance) northeast to Pungro, Kiphire District, Nagaland ; one adult male ( WII-ADA 942 ) collected by BB, NGP and AD on 4 September 2021 from Hmuifang ( 23.45357°N, 92.75236°E, elevation 1500 m a. s. l.), Aizawl District, Mizoram ; one adult male ( WII-ADA 1050 ) collected by BB, NGP and AD on 13 September 2021 from Phuldungsei ( 23.53537°N, 92.41584°E, elevation 780 m a. s. l.), Dampa Tiger Reserve, Mamit District, Mizoram ; seven adult males ( WII-ADA 1335 , WII-ADA 1340 , WII-ADA 1346 – WII-ADA 1350 ) collected by BB and AD on 13 May 2022 from Motijheel Trail ( 27.49963°N, 96.33256°E, elevation 370 m a. s. l.), Namdapha Tiger Reserve, Changlang District, Arunachal Pradesh ; three adult males ( WII-ADA 1451 – WII-ADA 1453 ) collected by BB, VJ and AD on 20 May 2022 from Gibbons Land ( 27.50168°N, 96.33169°E, elevation 350 m a. s. l.), Namdapha Tiger Reserve, Changlang District, Arunachal Pradesh ; two adult males ( WII-ADA 1643 and WII-ADA 1644 ) collected by BB on 25 July 2022 from Lamdan ( 24.5954°N, 93.70851°E, elevation 1270 m a. s. l.), Churachandpur District, Manipur ; one adult male ( WII-ADA 3207 ) collected by RNV and SD on 5 May 2023 near M’Pen village ( 27.50166°N, 96.32147°E, elevation 370 m a. s. l.), Changlang District, Arunachal Pradesh .

Diagnosis.

Small sized Raorchestes, SVL 16.7–21.0 mm in adult males; head length equal to or less than width ( HL / HW = 0.89–1.01); snout length less than or equal to eye length ( SL / EL = 0.82–1.03); nostril equidistant between eye and snout tip or slightly closer to snout tip; internarial distance less than or equal to inter-upper eyelid width ( IN / IUE = 0.74–1.0) and greater than upper eyelid width ( UEW / IN = 0.7–0.91); inter-upper eyelid width smaller than eye length ( IUE / EL = 0.72–0.96); vomerine teeth absent; nuptial pad present on first finger in males; blunt tubercles on head, upper eyelid, behind upper eyelid, forearm, thigh, tiba, and tarsus; spinules on dorsum intermixed with blunt tubercles; a brown “) - (“ marking on dorsum; brown crossbars on forearm, thigh and tibia; disc on inner two fingers yellow; bony projection on humerus on ventral aspect.

Description of the holotype.

Holotype in good condition except for an incision on abdomen towards left side and another incision on ventral side of right thigh. Adult male with vocal sac, 20.4 mm in SVL; head length equal to width; snout rounded in dorsal view, truncated in lateral view and slightly protruding beyond lower jaw; canthus rostralis smooth, obliqued; loreal region concave; snout length equal to eye length; nostril oval, laterally positioned, obliquely oriented, slightly closer to snout tip than eye ( NS / EN = 0.86); internarial distance slightly smaller than inter-upper eyelid width ( IN / IUE = 0.88) and greater than upper eyelid width ( UEW / IN = 0.86); internarial region slightly concave; area between nostril and snout tip slightly concave; tympanum distinct, round, its diameter less than one third of eye length; tongue posteriorly wide and deeply notched; vomerine teeth absent; choanae round; pair of internal slit like openings present on lower jaw towards edges; symphysial knob present on lower jaw; habitus stout, half of the snout-vent length.

Forelimbs slender, hand length slightly less than forearm length ( HAL / FAL = 0.94), digit with rounded disc; circum-marginal groove present on each disc; third finger longest, relative length of fingers = I <II <IV <III; disc on third finger largest and slightly wider than tympanic diameter ( HTYD /FIIID = 0.73); webbing on hand absent; subarticular tubercles distinct, enlarged and round except proximal ones on third and fourth fingers which are indistinct and smaller; subarticular tubercle formula on fingers I – IV = 1: 1: 2: 2; palmar tubercles indistinct; bony projection on humerus directed ventrally (Fig. 25 )

Hindlimbs slender; thigh length half of snout-vent length ( TL / SVL = 0.51); tibia length nearly equal to thigh length ( TBL / TL = 0.97) and longer than foot length ( FOL / TBL = 0.78); foot length greater than tarsus length ( TarL / FOL = 0.70); fourth toe longest, relative length of toes = I <II <III <V <IV; toe with rounded disc; circum-marginal groove present on each disc, disc on fourth toe as wide as that of third finger; small inner metatarsal tubercle present and outer one absent; subarticular tubercles enlarged and round except proximal subarticular tubercles of toes III – V which are indistinct and smaller, proximal one on fourth toe barely visible; SAT on toe I – V = 1: 1: 2: 3: 2; webbing among toes small, reaching proximal to second subarticular tubercle of fourth toe.

Skin on dorsal aspect of snout, head and upper eyelid shagreen; few indistinct, flat and rounded tubercles on upper eyelid; loreal region shagreen and ventral to eye smooth; supratympanic fold distinct; two rounded tubercles on mandibular region on each side behind angle of jaw; skin on dorsum shagreen with numerus spinules and intermixed with scattered small blunt tubercles, spinules dense on middle of dorsum and towards the dorsolateral aspect, scattered on anterior part of dorsum and absent towards the posterior part; few small blunt tubercles scattered behind upper eyelid and above supratympanic fold; flank ventro-laterally granular, but indistinct; limbs dorsally smooth with scattered small blunt tubercles on forearm and tibia; area of forelimb insertion granular; on ventral aspect, head smooth; skin on gular region loose; chest smooth; underside of lower arm granular; indistinct, flat and enlarged tubercles along ventral aspect of forearm and continuing to palm proximal to fourth finger; few indistinct flat tubercles on palm; finely granular nuptial pad on first finger; abdomen granular; thigh granular towards base; tibia and tarsus smooth; few flat indistinct tubercles scattered along ventro-lateral aspect of tarsus and base of foot proximal to fifth toe; numerous granular tubercles on ventral aspect of foot.

Colouration in preservatives.

Snout and inter-upper eyelid space greyish brown on dorsal aspect; upper eyelid dark grey; posterior part of head slightly paler in middle; loreal region slightly darker brown; dorsum brown, paler towards flank; dark brown “) - (“ mark on dorsum, anterior ends of this marking starts from posterior corner of upper eyelid and above supratympanic fold, posterior ends directing towards groin; forelimb brown dorsally, one dark brown cross bar on forearm and another short one on hand proximal to fourth finger; disc of the two inner fingers are cream coloured dorsally while the disc of the two outer fingers with brown patch or marbling; dorsal aspect of thigh pale yellowish brown with three dark brown crossbars, outer two bars indistinct and incomplete; tibia on dorsal aspect brown with three dark brown crossbars; tarsus and foot slightly paler than tibia; dark brown crossbar on tarsus and another short one on base of foot proximal to fifth toe; two or three indistinct crossbars on fourth and fifth toe; area around vent dark brown; ventrum pale cream coloured, mottled with brown; mottling heavy on chin region and along lower jaw border, less dense on chest, abdomen and lower arm; forearm, palm and fingers heavily mottled with brown; mottling absent on tubercles of hand, forearm, finger and on granules of abdomen; brown mottling darker on tarsus and foot than thigh and tibia and mottling absent on tubercles on tarsus and foot.

Colouration in life.

Head, dorsum and limbs brown dorsally with scattered tiny dark brown spots; slightly darker patch on inter-upper eyelid space; irregular dark brown patches on both upper and lower jaw and below supratympanic fold; “) - (“ marking on dorsum not visible as on preserved condition which is broken into irregular dark brown patches in life condition; flank slightly paler than dorsum; dark brown crossbars on forelimb and hindlimb distinct; outer crossbars on thigh and shank incomplete; irregular dark brown mottling on hand, finger, foot and toe; disc of first and second finger yellow while disc of the two outer fingers yellow with brown mottling; toe discs pale yellowish brown with dark brown mottling; ventrally flesh coloured with irregular brown mottling; tubercles on forelimb and granules on abdomen pale yellowish; tibia, tarsus, and foot dark brown; irregular pale yellowish patches on thigh and tarsus; flank near groin slightly darker brown; lateral aspect of thigh dark brown.

Morphological variation.

Morphometric variations among individuals of the species are provided in Table S 12. Dorsal colouration varies greyish brown to pale brown; concave stripes on dorsum and crossbars on limb may be indistinct; intensity of tubercles and spinules on head and dorsum varies among individuals (Fig. 28 ).

Morphological comparison.

Raorchestes barakensis sp. nov. can be distinguished from its congeners included in this study except R. rezakhani by the presence of bony projection on humerus which is absent in other congeners from the region. Detailed comparisons are given in Table 1. Further the new species differs from R. dulongensis by head length being equal to or smaller than width (vs. head longer than wide; 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. huanglianshan and R. tytthus nov. comb. by snout length being equal to or less than eye length (vs. snout length greater than eye length); it differs from R. jadoh by larger body size in adult males, SVL 16.7–21.0 mm (vs. 13.6–14.0 mm), and 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 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. leiktho by larger body size in adult males, SVL 16.7–21 mm (vs. SVL 15.7–15.8 mm); it differs from R. longchuanensis , R. yadongensis and R. malipoensis by inter-upper eyelid width being less than eye length (vs. inter-upper eyelid width greater than eye length); R. malipoensis by inter-upper eyelid width being less than eye length (vs. inter-upper eyelid width greater than or equal to eye length); it further differs from R. mindat by presence of an enlarged brown patch on the groin (vs. enlarged black and white patches present on groin); it differs from R. rezakhani by the presence of dense spinules on dorsum (vs. scattered tubercles on dorsum).

Acoustics.

The calls of Raorchestes barakensis sp. nov. were recorded in its type locality Maruwacherra, Assam on 18 April 2019 at an ambient temperature of 28.5 ° C between 19: 00 hrs and 19: 30 hrs; at Motijheel Trail, Namdapha Tiger Reserve on 13 May 2022 at 18: 30 hrs and an ambient temperature of 23.6 ° C; at Lamdan, Manipur on 25 July 2022 at an ambient temperature of 21.6 ° C at 19: 00 hrs. Call description is based on analyses of 35 calls from three individuals ( WII-ADA 613 , WII-ADA 1335 and WII-ADA 1643 ). The calls are single type, pulsatile and mostly emitted at regular intervals rather than in groups (Fig. 24 ). The mean call duration is 714.0 ± 909.05 ms (91–4464 ms) with 9.05 ± 12.46 pulses per call (2–59 pulses per call) and at pulse rate of 13.15 ± 0.62 pulses / sec (11.73–14.08 pulses / sec). The mean call rise time is 405.14 ± 404.02 ms (72–2327 ms) and the mean fall time is 306.4 ± 594.49 ms (19–2137 ms). The mean pulse duration is 19.69 ± 9.14 ms (10–34 ms) and the mean pulse period is 77.82 ± 39.44 ms (30–92 ms). The mean interval between calls is 1094.44 ± 638.54 ms (534–2281 ms). The mean dominant frequency is 3718.47 ± 119.97 Hz (3445.3–3832.9 Hz). A detailed comparison of the advertisement calls with those of the congeners is presented in Table 2.

Phylogenetic relationship and genetic divergence.

Raorchestes barakensis sp. nov. is sister to R. jakoid ( UFB 100 , PP 0.99; Figs 2 , 3 ) with genetic divergence of 4.5–5.9 % in the 16 S. The genetic divergence with other congeners included in this study is 3.6–7.6 % in the 16 S, 13.8–21.2 % in the cyt b and 10.1–16.8 % in the COI genes (Table S 7 A – C).

Etymology.

The specific epithet is a toponym derived from the name of the river “Barak” in Assam. The type locality of this species lies in Barak valley.

Suggested common name.

Barak Valley bush frog.

Distribution and natural history.

The new species is widely distributed in the hills ranging south of Brahmaputra valley within an elevation range 50–1500 m a. s. l. (Fig. 25 A ). Currently this species is recorded from in and around Barail Wildlife Sanctuary, Assam; Aramsangram in the state of Nagaland; Hmuifang and Dampa Tiger Reserve in Mizoram; Lamdan in Manipur to Namdapha Tiger Reserve in Arunachal Pradesh. We found individuals of this species calling from shrubs, and bamboo thickets at lower perch heights of approximately one metre above ground.

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 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 28. Raorchestes barakensis sp. nov. A – J Holotype (WII-ADA 612), A dorsal view, B ventral view, C lateral view of head, D ventral view of right hand, E ventral view of left foot in preserved condition, F dorsolateral view, G dorsal view, H ventral view, I groin, J posterior view of thighs in life. K WII-ADA 942 in life. L WII-ADA 1335 in life. M WII-ADA 1050 in life. N WII-ADA 862 in life. O WII-ADA 1644 showing dorsal spinules. P WII-ADA 1340 in preserved condition. Q an uncollected calling male from the type locality Maruwacherra, Assam. R WII-ADA 1644 in life. Inset images showing bony projection on humerus in K, L, N. Scale bar = 10 mm.