Raorchestes garo ( Boulenger, 1919 ) Naveen, Chandramouli & Babu, 2024

Naveen, R. S., Chandramouli, S. R., Babu, S., Ryndongsngi, A. M., Karunakaran, P. V. & Kumara, Honnavalli N., 2024, Rediscovery and redescription of Ixalus garo Boulenger, 1919, and Ixalus kempiae Boulenger, 1919, with a reassessment of the taxonomic status of Raorchestes cangyuanensis Wu, Suwannapoom, Xu, Murphy & Che, 2019 and the description of a new species from the Garo Hills of Meghalaya, Herpetozoa 37, pp. 359-372 : 359-372

Raorchestes garo ( Boulenger, 1919) comb. nov.

Ixalus garo Boulenger 1919

Rhacophorus (Philautus) garo – Ahl 1931

Philautus garo – Bourret (1942)

Material studied.

Holotype: ZSI 19187 (Fig. 2 above) sub adult, collected by S. W. Kemp, from “ Above Tura ” .

Topotypes: SACON VA 809 (Fig. 2 below), 163, 305, 306, 308 adult males, collected by RSN on April 26 th, 2022 from (25.51 ° N, 90.38 ° E, 895 m) , and SACON VA 129 , an adult female, on June 23 rd, 2020 from Daribokgre Community Reserve (25.47297 ° N, 90.3148 ° E, 1200 m), East Garo Hills, Meghalaya, India .

Diagnosis.

Raorchestes garo comb nov. is placed in the genus Raorchestes due to the combination of following characters: small body size, vomerine teeth absent, single translucent external subgular vocal sac present, and tips of all fingers and toes expanded into discs with circum-marginal grooves (see Biju et al. 2010). The species can be distinguished from congeners in the Indo-China region by the following combination of characters: A medium-sized (mean SVL 20.92 mm) arboreal species with a truncated snout scarcely projecting beyond the mandible; tympanum small, fairly distinct, ovoid, and supra-tympanic fold evident; tongue without papilla; ventral aspect of the hind limb dark orange in color; finger and toe discs well developed; tips of all fingers and toes brown to yellowish orange; toe webbing I 1-1 II 1 - 1 III 3 - 3 IV 3 - 2.5 V. Phylogenetically, R. garo clusters with R. shillongensis with a low bootstrap support (ML BS: 51) and shows the lowest genetic divergence from R. longchuanensis (4.28 %).

Description of a topotype.

SACON VA 809 Medium-sized adult male (SVL 23.8 mm), dorsal skin mostly smooth with a few irregularly scattered spinules and lateral skin completely smooth, ventral skin slightly granulose, increasingly granulose towards the lower body. Head large (HL: SVL 0.30), wider than long (HL: HW 0.86). A short snout (ED: ES 0.95), sharply pointed in dorsal view. Canthus rostralis evident and rounded; loreal region slightly concave. Trunk short (AG: SVL 0.54) and stout (AG: BW 1.20); eyes large (ED: HL 0.43); nostrils, rounded, with no visible rim, situated almost midway between the snout and the eye (EN: ES 0.58), directed laterally; with a weakly developed rim around them. Tympanum distinct, ovoid (TYD 1.36). Inter-orbital space broader than inter-narial space (IO: IN 1.59). Upper arms short (UAL: SVL 0.20), shorter than lower arms (UAL: LAL 0.75); palm shorter than the upper arms (UAL: PAL 0.74); relative finger lengths III> IV> II> I. Subarticular tubercles distinct in both palmar and plantar surfaces, rounded; no webbing between fingers; fingers with well-developed ovoid-shaped discs. Thighs short, nearly half as long as the body (FEL: SVL 0.46), nearly as long as the tibia (FEL: TBL 0.97). Foot slightly shorter than the thigh (FEL: FOL 1.29), toes short, toe discs well developed and ovoid, smaller than finger discs, toes with partial webbing, webbing formula I 1-1 II 1 - 1 III 3 - 3 IV 3 - 2.5 V. Dorsum uniformly brown with yellowish white spinules; loreal region dark brown; iris golden brown. Venter white, speckled with black and gray spots, and lower trunk grayish brown. Groin orange (bordered by golden yellow) turning red as it reaches the thighs (Fig. 3 ).

Variation.

Morphometric measurements of the holotypes and other preserved topotypes examined are presented in Table 2 . Variations noted during examination of preserved specimens and live individuals observed in the field. The single female specimen collected during this study is larger (SVL 26.1 mm) than all the males (range 15.58–23.8 mm; mean SVL 20.92 mm). Dorsal coloration variable from light to reddish or dark brown. Some individuals with an hourglass pattern, intensity of the dorsal hourglass pattern variable from feeble to bold and black (usually absent in males during the breeding season). Some individuals with a darker hourglass pattern and light background (in VA 305), and some with lighter hourglass pattern and darker background (in VA 308). Bands on the limbs feeble to bold. Ventral coloration uniform in all individuals.

Comparisons.

Raorchestes garo is genetically divergent (4.28–8.34 % on the 16 S rRNA gene) from congeners; the least divergent species is R. longchuanensis , with a divergence of 4.28 %. However, on the phylogenetic tree, it clusters with R. shillongensis , with a low node support (51). From congeners in the Indo-China region, it can be easily distinguished by: having an externally visible tympanum (absent in R. kempiae , R. shillongensis , R. menglaensis and R. rezakhani ); ventral aspect of the hind limb dark orange in color (vs. uniform creamy white in R. kempiae and dark gray in R. rezakhani ); toe webbing I 1-1 II 1 - 1 III 3 - 3 IV 3 - 2.5 V in R. garo (vs. I 1-2 II 2 - 1 III 1 - 1 IV 1 - 2 V in R. kempiae , I 2–2 II 2–2 III 2–3 IV 3–2 V in R. malipoensis, II 1–2 III 1–2.5 IV 2.5–1 V in R. menglaensis, II 1–2 III 1–2.5 IV 2.5–1 V in R. hillisi, II 1–2 III 1–2 – IV 2–1 V in R. huanglianshan and I 2–2 II 1.75–2 III 1.5–3 IV 2.75–2 V in R. rezakhani ); snout short and truncate in R. garo (vs. rounded in R. kempiae , R. menglaensis , R. hillisi , R. hekouensis , R. malipoensis , R. longchuanensis and R. huanglianshan and sharply projecting in R. annandalii and R. yadongensis ).

Natural history and distribution.

These frogs can be heard calling at dusk. Males were seen to be actively vocalizing from April to September. Most individuals recorded during this study were observed to be calling from shrubs (usually higher> 2.5 m above the ground). The species was infrequently encountered and was only recorded from areas above 800 m asl during this study. This species was recorded from three different localities in and around the West Garo Hills region: Sakalgre (25.51 ° N, 90.38 ° E; 895 m); Daribokgre (25.47 ° N, 90.31 ° E; 1200 m); and Mandalgre (25.48 ° N, 90.41 ° E; 1081 m). Based on the locations from the study, we calculated the extent of occurrence of this species with the current data from this study, and it was estimated to be 11.46 km 2. However, further surveys are required to robustly estimate the distribution range of this species.

Remarks.

Boulenger (1919) described this species from the Garo Hills along with Bufoides kempi and R. kempiae . Our topotypical specimens are in agreement with the holotype and with Boulenger’s description in most characters. Kharkongor et al. (2016) reported a population of Raorchestes from Upper Shillong with detailed morphological description as Philautus garo . Although their descriptions of these specimens closely match the description of R. garo , since these are not topotypical populations, i. e., the collection locations occur almost 200 km (aerial distance) from the type locality and from a different elevational range, further studies based on molecular analysis are required to see if this population is conspecific with Raorchestes garo .

Figures

Figure 2. The holotype of Ixalus garo (ZSI 19187) (above) (not to scale); SACON VA 809 in preservation (below); A. Dorsal view; and B. Ventral view. Scale bars: 10 mm.

Figure 3. Raorchestes garo (dorsolateral view of SACON VA 809, on top and dorsal view of SACON VA 809, bottom left and dorsal view of VA 305, adult male bottom right, showing hourglass pattern) from Garo Hills in life.