Smithophis atemporalis, Giri & Gower & Das & Lalremsanga & Lalronunga & Captain & Deepak, 2019

Giri, Varad B., Gower, David J., Das, Abhijit, Lalremsanga, H. T., Lalronunga, Samuel, Captain, Ashok & Deepak, V., 2019, A new genus and species of natricine snake from northeast India, Zootaxa 4603 (2), pp. 241-264 : 246-251

Smithophis atemporalis gen. et. sp. nov.

( Figs. 1–7 ; Table 2 )

Rhabdops bicolor (Blyth, 1854) : Das (2015: photograph on p. 65), Laltanpuia et al. (2008: 119, in part; fig. 16).

Diagnosis. A Smithophis lacking temporal shields.

Holotype. BNHS 3523 ( Figs. 2 , 3 ), male, collected from Mizoram University Campus , Aizawl, India (23.76338°N, 93.09916°E, 833 m elevation) by H.T. Lalremsanga on 10 July 2014. See map in Fig. 4 .

Paratypes (n = 6). BNHS 3524 — BNHS 3527 , BNHS 3529 , males and BNHS 3528 , female, collected from Mizoram University Campus, Aizawl on 14 August 2014 by H.T. Lalremsanga .

Referred specimens. BNHS 3530 male, collected from Model Veng , Aizawl, India (23.71083°N, 92.93194°E, 1014 m elevation) on 18 September 2015 and BNHS 3531 male, collected from Luangmual , Aizawl, India (24.45750°N, 92.69953°E, 1025 m elevation) on 20 October 2014 by S. Lalrounga. These are referred rather than paratypic material because we have not generated detailed morphometric and meristic data .

Description of holotype. See Table 2 for morphometric and meristic data. Good condition, slightly dehydrated; ca. 20 mm longitudinal ventral incision into ventral surface of base of tail (through which hemipenis observed).

Body somewhat laterally compressed (1.5 times as high as wide at midbody) with flattened venter and arched dorsum, widest at midbody, tapering posteriorly and more substantially anteriorly. Head elongate, broader than tall, slightly 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 very 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 approximately three times broader than long, substantially shorter than distance between it and frontal; projects beyond tip of lower jaw; ventrally with transverse concavity, notched (C-shaped) at margin of mouth. Frontal subpentagonal, lateral edges anteriorly diverging; shorter and smaller than each parietal, shorter than distance between it and snout tip. Internasal single, smaller than single prefrontal. Nasals subquadrangular, squarish, notably larger than squarish loreal. Single supraocular, preocular and postocular each side; supraocular slightly larger than preocular, itself slightly larger than postocular. Pre- and postocular each kidney shaped; supraocular elongate, longer than wide.

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 (mostly) laterally. Five supralabials (SLs) on each side; SL 5 largest, longest; SLs 1 and 4 subequal, smallest; SLs 2 and 3 subequal. SL 1 contacts rostral and nasal, SL 2 contacts loreal, SL3 contacts preocular and eye, SL 4 contacts postocular and parietal, SL 5 contacts parietal). Eye contacts third supralabial only. Eye lateral; pupil subcircular, very slightly elliptical (long axis vertical). No temporal shields. Parietals longer than wide, larger than other head scales. Midline interparietal suture a little more than two thirds length of each parietal; parietals barely projecting posterior to suture; each parietal more than twice as long as frontal; each parietal contacts frontal, supraocular, postocular, and fourth and fifth supralabial, plus five other scales. Posterior margin of each parietal rounded, somewhat scalloped.

Mental small, subtriangular, wider than long. Infralabials 7,7; first pair in midline contact; second pair smallest; fourth largest. On right, fourth infralabial longest, on left seventh as long.

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 and 5 (left) or 4 only (right). 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 10 or 11 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 except for loss of third dorsal scale row on left, six ventrals anterior to vent.

First ventral divided/paired. 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 subtriangular in cross section, 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-grey above, whitish below. Body scales iridescent. Dorsum dark. Alternating (at least asymmetric) longer dark and shorter pale markings along body and tail. On body 36, 35 dark ‘bands’, on tail 20, 16. On last three quarters of body, ventrally projecting dark trapezoids extend onto lateral edges of ventrals (leaving broad, entirely pale band along most of venter), these dark trapezoids anteriorly steadily less ventrally extensive. Anteriormost dark trapezoid (two head lengths behind head) extends onto second dorsal scale row. Whitish inverted-Vs extend dorsally between each dark trapezoid up to the fourth dorsal scale row, though partly continues as mottled pale grey scales up to vertebral scale or even one scale row onto opposite side and often (mostly on posterior half of body) connecting with grey dorsal part of inverted pale Vs from opposite side. Along the first quarter of body the border between pale-dark markings wavy, rapidly becoming increasingly sharply zigzag. Ventrally projecting dark marks extend as far as midventer on tail from behind vent, forming alternating (dark-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.

Variation among paratypes. The heads of the paratypes are illustrated in Fig. 5 . See Table 2 for variation in meristic and morphometric features. Paratypes generally in moderate to good condition, with following exceptions. BNHS 3524 dehydrated, contorted, yellowed ventrally with dorsolateral longitudinal incision on posterior half; BNHS 3525 soft posterior half, with 10 mm tail incision and missing terminal scute of tail; BNHS 3526 with couple of breaks along body, distorted mouth, marginal and palatal tooth-bearing bones removed from upper jaw, long tail incision with both hemipenes removed; BNHS 3527 a little dehydrated with two ventral longitudinal incisions on body, ventral tail incision with one hemipenis removed; BNHS 3528 dehydrated in small parts, soft in others, ventral incision in tail; BNHS 3529 a little dehydrated with ventral incision on anterior of tail .

Paratypes typically match holotype description except where noted here. Notch on ventral surface of rostral shield very shallow in BNHS 3524 , more U- than C-shaped in BNHS 3526 . Posterior margins of parietals not scalloped in BNHS 3524 , 3525 , 3526 and 3527, and more pointed than rounded in BNHS 3526 , 3527 , 3528 and 3529. Supraocular and postocular ‘fused’ on left of BNHS 3524 ; left pro- and postocular subequal in size in BNHS 3529 ; six infralabials on left of BNHS 3524 ; two postoculars on left of BNHS 3524 . Each parietal contacts four rather than five scales in addition to head shields in all paratypes except for six on left of BNHS 3526 , five on left of BNHS 3527 and 3529. Only first (not first and second) SLs contact nasal shield on each side in BNHS 3524 . Fourth IL invariably longest and largest. Only IL 4 contacts posterior genial in BNHS 3527 , 3528 and 3529, otherwise IL 5 also makes contact on one side only. Anterior and posterior genials subequal in BNHS 3524 , 3526 and 3528; posterior genials slightly larger in BNHS 3529 . First ventral entire rather than divided in all paratypes except BNHS 3529 . Three rather than four scales between posterior genials and first ventral in BNHS 3526 (and on right of BNHS 3528 and 3529). Upper jaw marginal tooth counts approximately 10 or 11 on each side in all paratypes. Eighteen (rather than 17) dorsal scale rows at level of first ventral in BNHS 3526 , though reducing to 17 by fourth ventral; 17 rows maintained to vent in BNHS 3524 , 3526 , 3527 , 3528 and 3529; only BNHS 3525 with reduction to 16 rows (like holotype) shortly anterior to vent (level with third ventral anterior to vent). Each anal overlaps 4–7 small scales in addition to anteriormost subcaudals. Tail with subcircular rather than subtriangular cross section posteriorly in all paratypes except BNHS 3524 and 3528. Terminal scute slightly upturned in BNHS 3527 and 3528 .

Dark bands on dorsum of body 27–37, on tail 13–18 ( Table 2 ). Whitish part of inverted Vs on body extend dorsally to third (rather than fourth) dorsal scale row in all paratypes except BNHS 3525 where some reach the fourth. Few of the grey speckled apices of inverted Vs extend beyond midvertebral row or connect with opposite inverted Vs in most paratypes; where they occur, connections typically confined to midbody ( BNHS 3528 ) or posteriorly ( BNHS 3524 , 3525 , 3529 ). Grey speckles on ventrals sparsely on anterior as well as posterior of BNHS 3525 ; only at midbody and some of last few ventrals on BNHS 3528 ; concentrated into very narrow, broken midventral line (as far forwards as second ventral) in BNHS 3529 ; absent except for single posterior speck in BNHS 3527 . Anals variably without grey blotches ( BNHS 3527 ) or speckles (left of BNHS 3526 ) or both ( BNHS 3524 ). Midventral darker line on posterior of tail absent in BNHS 3526 , thick but mostly broken in BNHS 3528 , well developed in BNHS 3525 and 3529. Dark bands do not meet midventrally on anterior two thirds of tail in BNHS 3527 .

Head blackish dorsally, not paler than anterior of body in BNHS 3525. In addition to rostral, internasal (and to a lesser degree prefrontal, frontal) and anterior half of nasal and internasal paler than rest of head shields dorsally in BNHS 3524 and 3527, respectively. First SL no more speckled than other SLs in BNHS 3525, 3526, 3527 and 3528. Speckles extending beyond first ILs to second (BNHS 3524), fourth (BNHS 3526, 3527) or sixth (BNHS 3525); no speckles on left first IL of BNHS 3529. Mouth with tiny specks of pigment under tongue and posterolaterally in BNHS 3526.

Colour in life. Based on uncollected specimens ( Fig. 6 ). Head, body and tail predominantly glossy black above, creamish-white below. More precisely: upper scales of head (frontal, prefrontal, internasal, nasals, loreals, preoculars, oculars, supraoculars, postoculars, parietals and all scales bordering posterior margin of parietals) uniform glossy black. Rostral predominantly black, creamish-white on lower portion. Supralabials black above, creamish-white below; the proportions between the two shades vary from about half and half, to almost entirely creamish-white; the border between the two is indistinct and either heavily mottled, or speckled with black. Eye with round pupil; pupil and iris black. Venter creamish-white. Under the head and neck and to approximately three head-lengths behind head, the creamish-white is tinted with yellow (less markedly posteriorly) and this pale region forms an undulating line where it meets the glossy black dorsum on the lower lateral edges of the snake. After approximately three head-lengths, the pale venter colour forms upward-pointing triangles. From approximately midbody the triangles become narrower and taller, sometimes even reaching the uppermost dorsal scale row and forming, or giving the appearance of faint bands.

Etymology. The specific epithet is in reference to the lack of temporal shields, a diagnostic feature of the new species. For nomenclatural purposes, the species epithet is considered a noun in apposition.

Suggested common name. Mizo rain snake or Narrow-headed smithophis (English). Mizo Ruahrul (Mizo).

Distribution, natural history and conservation. Smithophis atemporalis gen. et. sp. nov. is presently known with certainty only from in and around the type locality of the campus of Mizoram University and some nearby localities. The precise limits of this species’ distribution are unclear, partly because the species has sometimes previously been confused with S. bicolor , such that anecdotal reports need reassessment. Reassessment of distribution is one of the issues that need to be dealt with before the conservation assessment of this species can be adequately assessed. In Aizawl, S. atemporalis gen. et. sp. nov. is commonly seen during the monsoons, especially in, or close to streams and other wet places, close to human habitation and after rain showers. Locally this species is called ‘ ruahlawmrul ’, a rain-loving snake. Smithophis atemporalis gen. et. sp. nov. appears to have a tolerance for human dominated landscapes, though traffic is likely a threat given that these snakes have been seen on paved roads ( Fig. 7 ). Few sightings have been made in forest habitats, though systematic survey data are not available. Smithophis atemporalis gen. et. sp. nov. have been seen in the wild feeding on earthworms and juvenile skinks, and one individual was observed in captivity eating the eggs of the frog Fejervarya asmati (HTL, SL pers. obs.). One other S. atemporalis gen. et. sp. nov. individual laid three eggs in captivity (HTL, SL pers. obs.).

Figures

FIGURE 1. Bayesian tree showing phylogenetic relationships of Smithophis gen. nov. and Rhabdops within Natricinae snakes. Bayesian posterior probability and Maximum Likelihood bootstrap support are shown at each internal branch. PP below 0.60 and BS below 60 are not shown.

FIGURE 2. Holotype of Smithophis atemporalis gen. et. sp. nov. (BNHS 3523) whole preserved specimen in A) dorsal and B) ventral views. Scale bars 10 mm.

FIGURE 3. Holotype of Smithophis atemporalis gen. et. sp. nov. (BNHS 3523) head of preserved specimen in A) dorsal, B) ventral, C) right lateral and D) left lateral views. Scale bars 10 mm.

FIGURE 4. Map showing the position (white star) of the type locality of Smithophis atemporalis gen. et. sp. nov. in Mizoram, India. Examined comparative materials of the only known congener, S. bicolor comb. nov. (including the type), are from the Khasia (or Khassia or Khasi) Hills, Shillong, Tura or Aizawl, or from unspecified localities in northeast India. See Appendix 3 for locality details.

FIGURE 5. Paratypes of Smithophis atemporalis gen. et. sp. nov. (specimen numbers given in first row). Heads of preserved specimens in A) dorsal, B) ventral, C) right lateral and D) left lateral views. Scale bars 10 mm.

FIGURE 6. Smithophis atemporalis gen. et. sp. nov. Colouration in life of: A) specimen from Aizawl, and B) topotypic specimen from Mizoram University Campus, Aizawl. Specimens not collected.

FIGURE 7. Habitat of Smithophis atemporalis gen. et. sp. nov. A) Stream in Mizoram University Campus, B) Stream in Aizawl, note water pipelines indicating human activity, C) Road near Chawlhhmun, Aizawl, Mizoram,, and D) Road at Tuivamit, Aizawl.

Tables

TABLE 2. Meristic and morphometric (in millimetres) data for examined specimens of Smithophis atemporalis gen. et. sp. nov. Head length = distance between snout tip and back of lower jaw; bilateral structures given in left, right order; ventral count recorded using Dowling method; subcaudal counts exclude terminal scute; small scales overlapped by anals excludes anteriormost subcaudals. * indicates measure/count incomplete because end of tail missing. The format ‘X-Y’ is used to denote the shortest distance between features X and Y.

Museum prefix and tag number	BNHS 3523	BNHS 3524	BNHS 3525	BNHS 3526	BNHS 3527	BNHS 3528	BNHS 3529
Sex	M	M	M	M	M	F	M
Tail length	119	145	80*	170	135	135	115
Snout-vent length	321	355	400	455	430	390	330
Total length	440	500	480*	625	565	525	445
Head length	9.3	11.8	10.6	11.5	10	10.8	10
Head width (maximum)	5.3	5.7	5	6.7	5.7	5.2	5.4
Midbody circumference	28	35	32	40	30	32	30
Nostril-nostril	2.5	3.2	2.8	3	2.9	2.9	2.6
Eye-eye	3.8	4.5	4	5	4.3	4	4.3
Eye-snout tip	3.8	4.6	4	4.9	4.1	4.2	4.3
Eye diameter	1.2	1.5	1.5	1.5	1.4	1.3	1.4
Maximum width of rostral	2.6	3.4	3	3.5	3.4	3.1	2.9
Max. length frontal shield	2.8	3.3	2.9	3.5	3.1	3.1	3.1
Max. width frontal shield	3	3.4	3.1	3.5	3.3	3.2	3.1
Max. length parietal	5.8	6.6	6.2	7.2	6.4	6.4	6.1
Ventral scales	199	203	192	201	198	187	197
Subcaudal scales	82, 82	77, 76	51,52*	83, 84	75,75	74,75	77, 77
Small scales overlapped by anals 6,7		5,5	6,6	6,7	7,?	4,5	6,7
Dark Vs on body	36,35	37,36	39,42	36,35	37,36	31,33	32,27
Dark bands on tail	20,16	17,18	13,14	16,18	14,15	13,14	13,13