Rohanixalus shyamrupus Biju & Garg & Gokulakrishnan & Chandrakasan & Thammachoti & Ren & Gopika & Bisht & Hamidy & Shouche 2020, comb. nov.

Rohanixalus shyamrupus (Chanda and Ghosh, 1989) comb. nov.

Shyamrup’s Bubble-nest Frog

(Figs. 1–2, 4, 7, 18–19; Tables 1, 3, 4)

Original name and description. Philautus shyamrupus Chanda and Ghosh, 1989. Chanda S. K. and Ghosh A. K. 1989. A new frog of the genus Philautus Gistel, from the proposed Namdapha Biosphere Reserve, Arunachal Pradesh, northeast India. Journal of the Bombay Natural History Society, 86: 215–217. Type. Holotype, ZSIC A 7944 (formerly ZSI-KZ 313), by original designation. Type locality. “Hornbill, Namdapha Tiger Reserve”, Arunachal Pradesh, India. Current status of specific name. Valid name as Rohanixalus shyamrupus (Chanda and Ghosh, 1989) comb. nov.

Taxonomic remarks. Chanda & Ghosh (1989) originally placed this species in the genus Philautus. The original description, as well as Chanda & Sarkar (1997), did not compare this taxon with any known Philautus species from Eastern Himalayas or neighbouring regions, other than with unrelated ranid species (Dubois 1999; Bossuyt & Dubois 2001). Based on the description and available photograph (Chanda & Sarkar 1997), Bossuyt & Dubois (2001) suggested that the species is not a member of Philautus due to characters such as longitudinal bands or lines on the body or flanks, smooth chest and belly, extensive webbing, and lack of inner and outer metatarsal tubercles. They provisionally transferred it to the genus Chirixalus, without stating any potentially close taxa. We examined the holotype of Philautus shyamrupus and found that it represents a member of the genus Rohanixalus due to characters such as the presence of dorsolateral stripes and dorsal spots. We have further confirmed the identity and generic placement of Rohanixalus shyamrupus (Chanda and Ghosh, 1989) comb. nov., both morphologically and phylogenetically, based on new topotypic and additional collections from Northeast India (Figs. 1, 2; Table 1).

Diagnosis. Small-sized adults (male SVL 18–21 mm, female SVL 24–25 mm) with a slender body; snout nearly pointed in dorsal view; dorsal colouration light to dark brown with a reddish tinge; the entire dorsum, lateral surfaces, and dorsal surfaces of limbs covered with fine dark brown speckles, some speckles clumping together to form dark and irregular blotches on the dorsum; a dark and continuous dorsolateral stripe starts from the tip of the snout, extends through the eyes, and reaches close to the vent on either side; lateral surfaces of the head, including tympanic region, darker than dorsum; foot webbing moderate, just above the second subarticular tubercle on either side of toe IV. Further, the eggs are light green in colour and laid in bubble nests.

Genetic divergence. For the mitochondrial 16S gene, Rohanixalus shyamrupus differs from other genetically known congeners (Fig. 1) by average uncorrected genetic distance of: 9.4–10.1% from R. baladika, 8.2–10.2% from R. hansenae, 3.0–3.4% from R. senapatiensis, and 8.6–10.1% from R. vittatus. Some previously sampled populations from the geographically close Putao district in Kachin state of Myanmar (‘ Feihyla vittata ’ Group I of Aowphol et al. 2013; R. cf. shyamrupus in the present study, Fig. 1) are related to R. shyamrupus by 2.8% divergence. Further studies are required to ascertain the identity of Putao populations, as well as two additional unidentified lineages (Rohanixalus sp. 1 and Rohanixalus sp. 2). For detailed intra-generic comparisons see Table 3.

Distribution. Rohanixalus shyamrupus was originally described from Changlang district in the state of Arunachal Pradesh, India. In the present study, we genetically confirm the identity and phylogenetic relationship of the species based on topotypes from Namdapha Tiger Reserve, Changlang district. Additionally, this species is known from West Kameng district in Arunachal Pradesh; and Kohima and Peren districts of Nagaland. Previous reports of R. vittatus from Nagaland (Romer 1951 “1949”; Kiyasetuo & Khare 1986) are likely to refer to this species.