Raorchestes lawngtlaiensis, 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 lawngtlaiensis sp. nov.

Figure 32; Tables 1, 2, S 12

Holotype.

WII-ADA 947 , an adult male collected by AD, BB and NGP on 6 September 2021 from Ngengpui Wildlife Sanctuary ( 22.48498°N, 92.75653°E, elevation 210 m a. s. l.), Lawngtlai District, Mizoram, India .

Paratype.

An adult male ( WII-ADA 946 ) collected by AD, BB and NGP on 6 September 2021 from Ngengpui Wildlife Sanctuary ( 22.48906°N, 92.75678°E, elevation 210 m a. s. l.), Lawngtlai District, Mizoram .

Diagnosis.

A small sized Raorchestes, SVL = 18.1–19.7 mm in males, female unknown; snout rounded, slightly less than eye length; nostril closer to snout tip than eye; head slightly wider than long or equal proportions; inter-upper eyelid width less than eye length; vomerine teeth absent; nuptial pad present on first finger in males; dorsal aspect pale yellowish brown; “) (“ shaped broad dark brown marking on dorsum, posterior ends of this marking bordered by irregular white spots; an oblique dark brown stripe bordered with white spots on flank; dark crossbars bordered with white spots on forelimb and on hindlimb; irregular small white spots on dorsal aspect of head; dorsum and limb; tympanic region dark brown; a dark brown streak ventral to eye bordered with white streak; groin, axilla, hind arm, lateral side of thigh, finger and toe discs yellow; irregular white flecks on chest and abdomen; forelimb and hindlimb dark brown; gular region yellowish brown.

Description of the holotype.

Adult male, SVL 18.1 mm; head wider than long ( HL / HW = 0.95); snout rounded with a blunt tubercular projection at tip, truncated in lateral view, snout length less than eye length ( SL / EL = 0.83); nostril oval, equidistant between eyes and snout tip; inter-upper eyelid width greater than inter narial distance ( IN / IUE = 0.76); internarial distance equal to upper eyelid width; eye length nearly half of head length ( EL / HL = 0.46); canthal ridge distinct, oblique; loreal slightly concave; tympanum rounded, distinct; tympanic diameter one fifth of eye length; supratympanic fold distinct; vomerine teeth absent; choanae round; tongue notched medially at posterior end and with sparsely distributed flat granules.

Forelimbs slender, forearm shorter than hand length ( FAL / HAL = 0.86); third finger longest, relative length of fingers = I <II <IV <III; finger with rounded disc, disc with circum-marginal groove; disc on second, third and fourth finger wider than horizontal tympanic diameter; subarticular tubercles round and distinct except proximal ones on third and fourth fingers; palmar tubercles indistinct; nuptial pad present on first finger.

Hindlimbs slender, thigh length longer than shank length ( TBL / TL = 0.92) and foot length ( FOL / TL = 0.85); shank longer than foot length ( FOL / TBL = 0.92); fourth finger longest toes, relative length of toes = I <II <III <V <IV; toe with rounded disc, disc with circum-marginal groove, disc width of fourth toe slightly less than that of third toe; subarticular tubercles round and distinct except proximal ones on fourth and fifth toes; inner metatarsal tubercle present, longer than horizontal tympanic diameter, outer metatarsal tubercle absent.

Skin on dorsal aspect of head smooth with scattered spinules; distinct spinules on upper eyelid; few granular tubercles behind angle of jaw; numerous spinules on dorsum, above supratympanic fold and flank; limb smooth dorsally; throat, chest, abdomen and ventral aspect of thigh granular; tibia and tarsus smooth.

Colouration in life.

Dorsal aspect of head and dorsum pale yellowish brown; slightly dark brown patch on snout and posterior part of head; tubercles on snout, upper eyelid and posterior part of head white; lateral aspect of head pale yellowish brown; narial region dark brown; alternative dark brown and white bands on upper jaw; white speckles on angle of jaw and mandibular region; tympanic region dark brown; few irregular sized white spots on dorsum; a pair of concave dark brown stripes on dorsum, posteriorly prominent and edged with white speckles; another similar short stripe on flank; white flecks on axilla; irregular white spots on forelimb; finger discs yellow; white spots of irregular size and shape on hindlimb; an indistinct broad crossbar on thigh and tibia; groin and lateral aspect of thigh pale yellow; ventral aspect of head yellowish with dense brown and white marbling, few small white patches along lower jaw; irregular white flecks on chest, abdomen, forelimb and hind limb; finger and disc pale yellow; yellow tinge on toe, first toe on left side yellow.

Colouration in preservative.

Dorsal and ventral colouration similar with that of colouration in life except that white spots visible in life are not visible in preserved condition; brown reticulation on pale-cream coloured background on chest and abdomen.

Morphological comparison.

Raorchestes lawngtlaiensis sp. nov. 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 by internarial distance being equal to upper eyelid width (vs. internarial distance greater than upper eyelid width), snout length being less than eye length (vs. snout length equal to or greater than eye length); it differs from R. barakensis sp. nov. by absence of bony projection on humerus (vs. bony projection on humerus present); it differs from R. boulengeri , R. kempiae , R. orientalis sp. nov., and R. shillongensis sp. nov. by internarial distance being equal to upper eyelid width (vs. internarial distance being greater than upper eyelid width); it differs from R. cinerascens nov. comb. by presence of a single broad crossbar on thigh and tibia (vs. three crossbars on thigh and tibia); it differs from R. dulongensis by snout length being less than eye length (vs. snout length equal to eye length); it differs from R. garo by smaller body size, SVL 18.1–19.7 mm in adult males (vs. SVL 19.9–26.9 in adult males); it differs from R. hekouensis , R. hillisi and R. malipoensis by larger body size, SVL 18.1–19.7 mm in adult males (vs. SVL 16.1–17.5 mm in R. hekouensis , 15.9–17.7 mm in R. hillisi and 14.6–17.7 in R. malipoensis ); it differs from R. hillisi by snout length being less than eye length (vs. snout length greater than eye length); it differs from R. huanglianshan by snout length being less than eye length (vs. snout length greater than eye length); it differs from R. jadoh by larger body size in adult males, SVL 18.1–19.7 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 eye length (vs. snout length greater than eye length), inter-upper eyelid width being less than eye length (vs. inter-upper eyelid width greater than or equal to 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 18.1–19.7 mm (vs. SVL 15.7–15.8 mm); 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 inter-upper eyelid width being less than eye length (vs. inter-upper eyelid width greater than or equal to eye length); it differs from R. mawsynramensis sp. nov. by presence of moderately dense spinules on dorsum (vs. comparatively denser spinules on dorsum), presence of dark brown stripe edged with white spots on flank (vs. absent); it differs from R. menglaensis by snout length being smaller than eye length (vs. snout length longer than eye length), head length being equal to or slightly smaller than its width (vs. head longer than its width); it differs from R. mindat by presence of dark brown band bordered with white spots on groin (vs. enlarged black and white patches present on groin), by absence of white patches on lateral aspect of thigh (vs. enlarged white patches on the lateral aspect of thigh); it differs from R. narpuhensis sp. nov. by internarial distance being equal to upper eyelid width (vs. internarial distance greater than upper eyelid width), presence of dark brown stripe edged with white spots on groin (vs. no pattern on groin); it differs from R. parvulus by thigh being longer than tibia (vs. thigh shorter than or equal to tibia length); it differs from R. rezakhani by presence of dark brown stripe edged with white spots on flank (vs. no brown stripe on flank); it differs from R. tytthus nov. comb. by snout length being less than eye length (vs. snout length greater than eye length); it differs from R. yadongensis by inter-upper eyelid width being less than eye length (vs. inter-upper eyelid width greater than eye length), by snout length being less than eye length (vs. snout length equal to eye length). A detailed morphological comparison is given in Table 1.

Phylogenetic relationship and genetic divergence.

Raorchestes lawngtlaiensis sp. nov. is sister to R. narpuhensis sp. nov. (Figs 2 , 3 ). The genetic divergence with other congeners included in this study is 2.3 – 9.3 % in the 16 S, 13.9 – 21.0 % in the cyt b and 13.9 – 21.0 % in the COI genes (Table S 7 A – C).

Etymology.

The specific epithet is a toponym derived from the name “ Lawngtlai ” District in Mizoram State where the type locality of this species lies.

Suggested common name.

Lawngtlai bush frog.

Distribution and natural history.

Raorchestes lawngtlaiensis sp. nov. is currently known from its type locality in Ngengpui Wildlife Sanctuary, Lawngtlai, Mizoram (Fig. 19 A ). The holotype was found calling on a leaf approximately at one metre height above ground along a forest trail at around 23: 00 hrs. The paratype was recorded while it was calling from a bamboo branch approximately 1.5 m above ground at around 20: 15 hrs at the edge of a small stream of approximately two meters in width (Fig. 33 A ).

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 19. Distribution of Raorchestes species in northeast India. A Raorchestes garo and three others closely related new species; B Raorchestes kempiae, R. shillongensis, R. mindat and three new species. Type localities are denoted with stars.

Figure 32. Raorchestes lawngtlaiensis sp. nov. A – E Holotype (WII – ADA 947) in preservative and F, G holotype in life; A dorsal view, B ventral view, C lateral view of head, D ventral view of right hand, E ventral view of right foot; F dorsolateral view, G ventral view. H, I Paratype (WII-ADA 946) in preservative and J – M in life; H dorsal view, I ventral view, J, K dorsolateral view, L ventral view, M groin. Scale bar = 10 mm.

Figure 33. Habitat at the type localities of Raorchestes species in northeast India. A Lowland forest stream at the type locality of R. lawngtlaiensis sp. nov. in Ngengpui WLS; B landscape view of Mehao WLS from Abango, type locality of R. dibangensis sp. nov. in Abango; C. hill stream and riparian habitat at the type locality of R. shillongensis in Malki, Shillong; D landscape view of the hills at Pumdunlong, the type locality of R. monolithus sp. nov. at Willong Khullen Village; E landscape view of hills and lowland areas at Khonoma, the type locality of R. khonoma sp. nov.; F forest cover at Bompu, Eaglenest WLS at the type locality of R. eaglenestensis sp. nov.; G hill stream and forest cover at Abor hills, habitat of R. magnus sp. nov.; H landscape view of Abor hills and adjacent lowland areas, habitat of R. arunachalensis sp. nov.