Arunachal Rain Snake

description

(Figs. 1 – 7; Tables 1 & 3) urn: lsid: zoobank. org: act: 0393 FC 04 - EAA 6 - 477 C-AC 31 - BCDB 78 A 2 AFC 9

Description of a new species of Smithophis Giri et al. 2019 (Serpentes: Colubridae Natricinae) from Arunachal Pradesh, India

description

Description of holotype. See Table 1 for morphometric and meristic data. Specimen in good condition, although slightly dehydrated; two constrictions on anterior half of body caused by tight tag string; outer edge of head shields missing in parts. Body subcylindrical, slightly flattened ventrally (1.3 times as wide (10.9 mm) as high (8.5 mm) at midbody), widest at midbody, tapering posteriorly and more substantially anteriorly. Head broader than tall, barely wider than anterior of body. In dorsal view head slightly ovate, sides very slightly convex, gently converging anteriorly; front of snout not pointed, truncated. In lateral view, head tapers gently from back to prefrontal, more strongly tapered in front of prefrontal. Paired shields on top of head (= parietals only) abutting along midline rather than imbricate / overlapping. In dorsal view, rostral much broader than long, substantially shorter than distance between it and prefrontal; projects beyond tip of lower jaw; ventrally with transverse concavity, notched (C-shaped) at margin of mouth. Frontal subpentagonal, lateral edges anteriorly diverging; substantially shorter and smaller than each parietal, shorter than distance betw

Description of a new species of Smithophis Giri et al. 2019 (Serpentes: Colubridae Natricinae) from Arunachal Pradesh, India

diagnosis

Diagnosis and identification. Smithophis arunachalensis sp. nov. is referred to the genus Smithophis based on the presence of single internasal and single prefrontal shields (a unique condition within Natricinae: see Giri et al. 2017; Vogel et al. 2020). The new species is distinguished from congeners as follows: S. arunachalensis sp. nov. differs from S. atemporalis by the presence of temporal shields (versus absence) and by having bright yellow venter in life (versus whitish); from S. bicolor in colour pattern, by having a sharply zigzag border between the darker dorsum and paler venter, along the entire lateral surface of the body and tail (versus absence of zigzag border), and in having (versus lacking) and a dark midventral line on the underside of the tail (see Figs. 1 – 2,4,6,8 – 9; Table 2 & 3). The new species differs from S. linearis by having fewer than six circumorbital scales (excluding the supralabials: versus more than 5) and by lacking (versus having) narrow dark and pale longitudinal lines on upper surface of body and tail.

Description of a new species of Smithophis Giri et al. 2019 (Serpentes: Colubridae Natricinae) from Arunachal Pradesh, India

distribution

Distribution, natural history and conservation. Smithophis arunachalensis sp. nov. is known from six localities from eastern Arunachal Pradesh, including Roing and Koronu in Lower Dibang Valley District, Dening in Lohit District and three localities in Namdapha Tiger Reserve in Changlang District of Arunachal Pradesh. The elevation ranges from 310 m in the foothills of Mishmi Hills to 580 m at Namdapha Forest Camp. The holotype was caught while it was moving on the side of a stream in moist evergreen forest. The area was characterised by degraded forest with extensive bamboo regeneration along both sides of the stream. The stream section where the snake was found had large, bryophyte covered boulders and bedrock near a pool and riffle section (Fig. 7). The snake was caught in dim light during heavy rain, near dawn at 05: 00. Smithophis arunachalensis sp. nov. seems to be a rarely encountered snake. Since its first collection around the year 1935, only five other specimens have been collected, and multiple surveys in Lower Dibang Valley in Arunachal Pradesh by A. D. between 2005 and 2012 yielded only a single sighting. Although some localities where S. arunachalensis sp. nov. occurs

Description of a new species of Smithophis Giri et al. 2019 (Serpentes: Colubridae Natricinae) from Arunachal Pradesh, India