Smithophis arunachalensis, Das & Deepak & Captain & Wade & Gower, 2020

Das, Abhijit, Deepak, V., Captain, Ashok, Wade, Edward O. Z. & Gower, David J., 2020, Description of a new species of Smithophis Giri et al. 2019 (Serpentes: Colubridae Natricinae) from Arunachal Pradesh, India, Zootaxa 4860 (2), pp. 267-283 : 268-278

publication ID	https://doi.org/ 10.11646/zootaxa.4860.2.8
publication LSID	lsid:zoobank.org:pub:9BA7720C-C00F-4953-B480-CD8960C0CA6E
DOI	https://doi.org/10.5281/zenodo.4537892
persistent identifier	https://treatment.plazi.org/id/0393FC04-EAA6-477C-AC31-BCDB78A2AFC9
taxon LSID	lsid:zoobank.org:act:0393FC04-EAA6-477C-AC31-BCDB78A2AFC9
treatment provided by	Plazi
scientific name	Smithophis arunachalensis
status	sp. nov.

Treatment

Smithophis arunachalensis sp. nov.

( Figs. 1–7 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 ; Tables 1 View TABLE 1 & 3 View TABLE 3 )

urn:lsid:zoobank.org:act:0393FC04-EAA6-477C-AC31-BCDB78A2AFC9

Rhabdops bicolor (Blyth, 1854) : Smith (1943: 329, in part); Sanyal & Gayen (1985: 301, in part); Captain & Patel (1997: 14, in part); Pawar & Birand (2001: 77, in part); Bhatt (2004: 196); Borang et al. (2005: 23); Sanyal & Gayen (2006: 273, in part); Sharma (2007: 238, in part); Ahmed et al. (2009: 159, in part); Das (2010: 261–265, in part)

Rhabdops bicolour [sic]: Sanyal & Gayen (2006: 248, in part)

Smithophis bicolor (Blyth, 1854) : Giri et al. (2019: 245 View Cited Treatment , 255, in part); Vogel et al. (2020: 51, 52, 54, 64)

Holotype. BNHS 3650 View Materials ( Figs. 1–2 View FIGURE 1 View FIGURE 2 ), female, collected from Koronu , Lower Dibang Valley District, Arunachal Pradesh, India ( Fig. 4 View FIGURE 4 : 28.101333° N, 95.908111° E, 310 m elevation) by Abhijit Das on 21 April 2005. GoogleMaps

Paratypes (n = 2). BMNH 1935.10.12. 10 ( Figs. 4a View FIGURE 4 , 5 View FIGURE 5 ), male, collected from Dening , Mishmi Hills, “ Assam ” (28.019225° N, 96.227778° E, 650 m elevation, currently in Lohit District, Arunachal Pradesh, India), collected by D.K. Barnah, donated by M. Steele GoogleMaps ; ZSIK 23875 ( Fig. 4b View FIGURE 4 ), male, collected from Namdapha Camp , 58 km east of Miao, Changlang District, Arunachal Pradesh, India (27.492361°N, 96.381666°E, 580 m elevation) 23 April 1981, by S. Biswas GoogleMaps .

Referred specimens (n = 3). Roing Forest Department collection, uncatalogued ( Fig. 6a View FIGURE 6 ), male, collected from Roing , Lower Dibang Valley District , Arunachal Pradesh, India (28.157000° N, 95.854483° E, 312 m elevation). Miao Museum, Namdapha Tiger Reserve , Changlang, Arunachal Pradesh, India, two uncatalogued specimens, collected by P.K. Biswas on 4 October 1991 from 14 th mile, Miao-Vijoynagar Road, Changlang District, Arunachal Pradesh, India (27.500183°N, 96.386472°E, 330 m elevation), and by P.K. Biswas on 8 September 1995 from Deban ( Fig. 6b View FIGURE 6 ), Changlang District, Arunachal Pradesh (27.487872°N, 96.344 244 °E, 560 m elevation) GoogleMaps .

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 View FIGURE 1 –2,4,6,8–9; Table 2 View TABLE 2 & 3 View TABLE 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 holotype. See Table 1 View 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 between it and snout tip. Internasal single, smaller than single prefrontal. Nasals subrectangular, larger than trapezoid loreal. Single supraocular, two preoculars and two postoculars each side; supraocular largest of these scales, longer than wide. Upper pre- and post-oculars much larger than lower pre- and postoculars; lower pre- and postocular not in contact due to intervening SL3.

External naris on dorsolateral-facing surface, seen as C-shaped slit in front of flap, in broad, shallow depression slightly posterodorsal of centre of nasal. External naris visible anteriorly as well as dorsally and primarily laterally. Five supralabials (SLs) on each side; SL5 largest, longest; SL1 smallest and shortest; SL1 contacts rostral and nasal (and, perhaps, loreal), SL2 contacts loreal (and, perhaps, nasal) and lower preocular, SL3 contacts lower pre- and postoculars and eye, SL4 contacts lower postocular and anterior temporal, SL 5 contacts anterior and posterior lower temporal. Eye contacts third supralabial in addition to supra-, pre- and postoculars. Eye lateral; pupil subcircular. Temporals 1+2 on left and 1+1 on right. Parietals longer than wide, larger than other head scales. Midline interparietal suture more than three quarters length of each parietal; parietals barely projecting posterior to suture; each parietal approximately twice as long as frontal; each parietal contacts frontal, supraocular, upper postocular, anterior and upper posterior temporals, and three (right) or four (left) other scales. Posterior margin of each parietal somewhat scalloped.

Mental small, subtriangular, wider than long. Infralabials 7,7; first pair in midline contact; second pair smallest; fourth largest and longest. Two pairs of genials; first pair largest, longer than broad, in long midline contact; second pair not in contact, separated by one small, midline scale. Anterior genials contact infralabials (ILs) 1–4; posterior genials contact IL 4. Anteriormost ventral separated from each posterior genial by four scales, separated from each posteriormost infralabial by six scales. Teeth largely obscured by gingivae, but estimated as 8 marginals on each side of upper jaw.

Macroscopically and under low magnification (using a light dissecting microscope) body scales smooth. No keels or apical pits. Vertebral scale row not different from adjacent dorsal scale row. Exposed parts of dorsal body scales generally evenly sized on dorsum and along body except for those involved in dorsal scale row reductions and for lowest dorsal scales level with first few ventrals which are lower, more elongate. Dorsal scales closer to vent slightly smaller than at midbody; those at anterior of body smallest. Dorsal scale rows 17 at level of first ventral, maintained to vent.

Posteriormost ventral with slight posteromedial extension. Anals paired (right overlapping left), each slightly larger than posteriormost ventral. Each anal overlaps 6,7 small scales in addition to first subcaudal. Tail subcircular in cross section, slightly flattened ventrally. Dorsal tail scales more heterogenous in size than on body, without clear patterns. Subcaudals paired/divided throughout, terminal scale (scute) conical, approximately as wide as long, pointed.

Macroscopically bicoloured, darker black-brown above, whitish ochre below. Body scales iridescent. Alternating (at least asymmetric) longer dark and shorter pale, typically V-shaped (when viewed laterally) or to trapezoid markings (when viewed from above) along body and tail. On body 37, 38 dark ‘bands’, on tail 12,12. Ventrally projecting dark trapezoid shapes (from level with approximately 24th ventral) extend onto lateral edges of ventrals leaving broad, entirely pale band along most of venter. Anteriormost dark trapezoid (less than one head length behind head) with gently rounded ventral margin, extends onto third dorsal scale row. Whitish inverted V-shaped markings (“Vs”) extend dorsally between each dark trapezoid up to the sixth (rarely seventh) dorsal scale row. Along the first quarter of body the border between pale-dark markings wavy, rapidly becoming increasingly sharply zigzag towards the posterior. Ventrally projecting dark marks extend as far as midventer on tail from behind vent, forming alternating (dark and pale) transverse bands; where pale bands approach midventer (only on anterior half of tail, where they are longer) they remain separated by narrow midventral dark line. Whitish ventrals with fine pale grey speckles on posterior half of body. Anals each with pale grey blotches as well as speckles.

Head dark dorsally, brown-grey, slightly paler than body dorsum, generally uniform, rostral slightly paler. Dark of dorsum extends onto upper margins of SLs, SLs otherwise pale (whitish, as body venter) with very few (more on SL1) pale grey specks. Dark scales on dorsum (including head) are mottled under low power dissecting microscope. First pair of ILs and anterior genials with pale grey speckles (fewer on mental). Underside of head otherwise pale, whitish. Inside of mouth pale with two dark spots on either side of the anterior of pterygoid part of palate.

Variation among paratypes. Paratypes do not differ substantially from the holotype ( Fig. 4a,b View FIGURE 4 , Table 1 View TABLE 1 ). Paratypes are generally in moderate condition, with following exceptions: the front of head of BMNH 1935.10.12. 10 is not attached to its body, and is kept in a small container within the same jar; and the head and approximately four head lengths behind head of ZSIK 23875 is unnaturally flattened, it also has a constriction behind the head possibly due to the knot for tag. Both BMNH 1935.10.12. 10 and ZSIK 23875 have darker Vs on body and tail. ZSIK 23875 has 6 IL on either side, otherwise scalation is very similar to that of the holotype.

Colour in life. Based on holotype ( Fig. 2 View FIGURE 2 ). Dorsum (head, body and tail) predominantly black above, including downward pointing triangles on flanks; venter and upward pointing triangles of body and tail bright yellow. Most head scales uniformly black; rostral predominantly black. Supralabials black above, cream-yellow below; border between the two colours indistinct. Iris black. Mental and tip of first pair of chin shields black mottled. Dark parts of venter and underside of tail blackish. The venter of ZSIK was recorded as yellowish-white by Sanyal & Gayen (1985, 2006) but it is not clear whether that was in life or preservation. A photograph of an individual from Deban (Namdapha Tiger Reserve, Changlang District, Arunachal Pradesh, India) seen by one of us (A.C.) had a bright yellow venter in life.

Etymology. Named after Arunachal Pradesh, India, an Indian state that has yielded many notable herpetological discoveries. The type and all other currently known localities of the new species are in Arunachal Pradesh. This is the second snake to be named after the state, after Trimeresurus arunachalensis Captain, Deepak, Pandit, Bhatt & Athreya, 2019 .

Suggested common names. Arunachal Rain Snake or Black and Yellow Smithophis .

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 View FIGURE 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 are in areas that are under some protection (Namdapha Tiger Reserve and on the fringes of Mehao Wildlife Sanctuary), so little is known of the distribution and natural history of this species that it is currently likely to qualify as Data Deficient based on criteria for the Red List of Threatened Species ( IUCN Standards and Petitions Committee 2019).