Amphiesma clerki ( Wall, 1925 )

David, Patrick, Agarwal, Ishan, Athreya, Ramana, Mathew, Rosamma, Vogel, Gernot & Mistry, Viral K., 2015, Revalidation of Natrix clerki Wall, 1925, an overlooked species in the genus Amphiesma Duméril, Bibron & Duméril, 1854 (Squamata: Natricidae), Zootaxa 3919 (2), pp. 375-395 : 377-385

Amphiesma clerki ( Wall, 1925)

( Fig. 1–6 )

Natrix clerki Wall, 1925: 809 . Type locality. “Sinlum Kaba, Kachin Hills”, now Sinlumkaba (24°16'N – 97°31'E), Kachin State, Myanmar. Holotype. BMNH 1946.1.13.50, adult male; collected by Mr. Clerk, 1924.

Material (n = 10 preserved specimens + 5 unpreserved, living specimens). Nepal (?). BMNH 58.6.24.5, “ Nepal ”.— India. Sikkim. BMNH 60.3.19.1359, NMW 22383:2, “Sikkim”, no precise locality.—West Bengal. BMNH 80.11.10.153, “Darjeeling”; BMNH 1923.10.13.38, “Darjeeling District”.—Arunachal Pradesh. IISER RS09, Talle Valley.— Nagaland. KSC 414, Sechu, 1000 m. — Myanmar. Kachin State. BMNH 1946.1.13.50 (Holotype), “Sinlum Kaba, Kachin Hills”, now Sinlumkaba; BMNH 1940.6.4.29, “Pangnamdim, The Triangle, Upper Burma ”, a village about 24 km northeast of Watamkawng (27°43'N- 97°52'E).— People’s Republic of China. Yunnan Province. CAS 215036, Nu Jiang Nature Reserve, near Pianma (26°00' 10.3 N- 98°39' 31.7 E), Nu Jiang County.

Systematics. This species has seemingly been mentioned in the literature only by Wall (1925, 1926). Subsequently, it was placed in the synonymy of Natrix parallela (now Amphiesma parallelum ) by Smith (1943: 288). It is here resurrected with full species status. This species is monotypic.

Diagnosis. A species of Amphiesma characterized by (1) a dark dorsal background, dark brown, dark greyishbrown or dark brownish-grey (same in life), becoming more or less distinctly darker on the back than on sides; (2) laterally, a series of pale yellow, pale yellowish-brown or brownish-yellow spots (reddish-brown or rusty red in life), distinctly larger and conspicuous on the neck and forepart of the body, connected along the hinder half of the body by a pale dorsolateral stripe extending on the 5th–7th dorsal scale rows; (3) scales broadly edged with dark brown on the lower part of the sides, producing irregular blotches; (4) faint, irregular and short blackish-brown streaks on the 1st dorsal scale row, producing a very discontinuous zigzag ventrolateral stripe; (5) a conspicuous, broad, blackish-brown postocular streak extending from behind the eye to the corner of the mouth then extending, usually without gap (rarely discontinuous) on the side of the neck; (6) a conspicuous, pale (cream or pale yellow), V or Y-shaped chevron starting on each side from behind the last supralabial and reaching the upper surface of the neck, pointing backwards; (7) supralabials dotted with brown to black dots or even nearly brown, edged with dark brown and with usually a conspicuous streak on the hinder margin of the 6th SL; (8) venter creamy yellow (bright reddish-brown, rusty red or crimson in life), with outer tips of ventral scales light brown (dark purplish-red in life); (9) 18–22 maxillary teeth, the last two strongly enlarged, either without diastema or barely separated from anterior teeth by a short diastema; (10) 19–19–17 dorsal scale rows; (11) dorsal scales strongly keeled on all dorsal scale rows, including 1st row; (12) tail long, ratio tail length / total length 0.262–0.325 (0.280–0.325 in males, 0.262–0.273 in females); (13) 162–173 ventrals; (14) 85–108 subcaudals; (15) anal plate divided; (16) usually 1 preocular; (17) usually 2 anterior temporals.

Redescription of the holotype of Natrix clerki , BMNH 1946.1.13.50 ( Fig. 1–2 )

Habitus. Body elongate, cylindrical; head elongate, rather narrow, distinct from the neck; snout average, accounting for 26.3 % of HL, 1.3 times as long as eye diameter, slightly flattened, narrowing anteriorly, blunt when seen from above, rounded seen in profile, with no defined canthus rostralis; nostril piercing laterally; eye large, its diameter 2.2 times the distance between its inferior margin and upper lip edge; pupil round; tail long, cylindrical and progressively tapering.

SVL 384 mm; TaL 170 mm; TL 554 mm. Ratio TaL / TL: 0.307.

Dentition. Maxillary teeth: 21 subequal + 3 strongly and abruptly enlarged teeth, about twice as large as anterior teeth, without diastema.

Body scalation. Dorsal scales: 19-19-17 rows; scales very strongly keeled on the upper part of the back, a little bit less strongly keeled on the sides and the 1st dorsal scale rows; all scales strongly and deeply notched at their apical part, especially on the posterior part of the body; apical pit present on each scale; scales of 1st dorsal scale row slightly enlarged.

Ventrals: 171 (+ 2 preventrals); subcaudals: 108, all paired; anal divided.

Head scalation. Rostral 1.6 times as wide as high; nasal rectangular, longer than high, with a lateral nostril piercing in the middle of the scale; internasals subtriangular, slightly (1.1 times) longer than wide, anteriorly narrowed but truncated, with the fore width about 0.6 times as great as the hind width; prefrontals barely longer than internasals; one large, longer than wide undivided supraocular on each side; frontal bell-shaped, 1.7 times as long as wide; parietals large, in contact along a suture about 0.9 times as long as frontal; one subrectangular loreal on each side, 1.1 times longer than high; 8 / 8 supralabials, 1st and 2nd supralabials in contact with nasal, 2nd and 3rd supralabials in contact with loreal, 3rd–5th supralabials entering orbit, 7th supralabial largest; 1 / 1 tall, narrow preocular; no subocular; 3 / 3 small postoculars; 1 anterior temporal, temporals with the formula 1+2 on each side; 9 / 9 infralabials, 1st pair in contact, 1st–4th infralabials in contact with anterior chin shields, 4th and 5th infralabials largest.

Coloration and pattern. Body dark greyish-brown on the back, brown or tan on its sides but with a distinctly darker, blackish-brown area on the neck sides and extreme forepart of the body; on the sides of the body, most scales of the 1st to 4th dorsal scale rows broadly edged with blackish-brown, producing reticulations and blackishbrown, irregular, oblique blotches on the sides; dorsum irregularly marked with small, black spots more or less arranged as one or two vertebral series and two irregular series on each outer side of the dorsum just above each dorsolateral stripe; on each side, a series of large, rounded, irregular but conspicuous pale yellow blotches on the neck and fore part of body, extending on 4th–7th or 5th–7th dorsal scale rows, not connected by a dorsolateral stripe, progressively turning into smaller, pale yellowish-brown blotches aligned on the upper half of 5th, 6th and lower half of 7th DSR, rounded on the fore quarter to third of the body, more elongate, faint and reduced to the 5th and 6th rows posteriorly, connected from the first quarter to third of the body by an indistinct pale yellowish-brown dorsolateral stripe extending along on the 5th DSR from the second quarter of the body to the vent, more conspicuous posteriorly; another series of 7 or 8 vertical, yellow streaks interrupting the dark brown dorsal colour of the sides of the first quarter of the body, originating from the ventral colour and reaching the levels of the 5th or 6th DSR, alternating or in contact with the dorsolateral blotches; scales of the 1st DSR marked with faint and irregular blackish-brown short streaks, producing a very discontinuous, zigzag-like ventrolateral stripe, more conspicuous from the level of the second quarter of the body. Upper tail surface as the body, with scales strongly edged with dark brown. The dorsolateral stripes vanish progressively a short distance posterior to vent.

The head is greyish-brown above with brown vermiculation; upper sides of snout and rostral yellowish-brown, paler than upper surface; a narrow, dark streak in front of the eye, extending from the nasal to the upper part of the preocular; supralabials bright ivory; 1st–5th SL dotted with minute black dots; 2nd–5th SL narrowly edged with dark brown, more broadly on hinder margin of 6th SL; a conspicuous, broad, blackish-brown postocular streak extends from behind the eye to the corner of the mouth on the 2 lower postoculars, anterior temporals, upper part of 6th SL, much of 7th SL and the whole of 8th SL, this latter scale with an elongate bright ivory blotch in its upper middle; behind the lower half of the 8th SL, the blackish-brown postocular streak extends slightly downwards, without interruption on the neck, and widens on the side of neck, producing the darker colour of the side of the neck, blotched with the first dorsolateral blotches, before fading out into the greyish-brown colour of the body sides; on each side, behind the upper half of the 8th SL, a bright, conspicuous, oblique ivory streak, reaching the vertebral row and producing a bright chevron-like marking on the neck, its apex directed backwards and reaching the first dorsolateral blotch; a short, pale yellow occipital streak; eyes black. The chin and throat are uniformly creamishyellow, with a few faint, diffuse greyish-brown spots on the infralabials.

The venter is uniformly creamish-yellow, with outer tips of ventral scales brown and a few medial brown spots. The subcaudal surface is uniformly creamish-yellow with outer margins of subcaudals narrowly edged with dark brown; tip of the tail with dark brown spots.

According to Wall (1925), the freshly killed specimen was “blackish-olivaceous dorsally to the edges of the ventrals. A series of ill-defined light roundish spots on the 5th row above the ventrals and the adjacent halves of the 4th and 6th rows, continued to the base of the tail. Belly yellowish anteriorly, merging to pale salmon posteriorly, suffused more deeply laterally; with an occasional small dark round spot on the edges of the ventrals. Head blackish-olivaceous. A short mesial light streak just behind the parietals. A light well-defined V on the nape beginning behind the gape. First 5 supralabials with black posterior borders. A black postocular stripe to the sides of the neck. Chin immaculate.”

Variation (based on 10 preserved and 5 living specimens). Habitus. Body elongate, cylindrical; head ovoid, elongate, distinct from neck; snout average, accounting for 22.7–28.5 % of HL or 1.0–1.3 times as long as eye diameter, slightly flattened, narrowing anteriorly, blunt when seen from above, rounded seen in profile, with no defined canthus rostralis; nostril laterally positioned; eye large, its diameter 2.0–2.6 times the distance between its inferior margin and upper lip edge; pupil round; tail long, cylindrical and progressively tapering.

The maximal total length known is 770 mm (SVL: 520 mm, TaL: 250 mm; male; specimen not preserved from Arunachal Pradesh). The longest known female is 725 mm long (SVL 531 mm, TaL 194 mm; CAS 215036). Ratio TaL / TL: 0.262–0.325, with a clear sexual dimorphism (see below).

Dentition. Maxillary teeth: 18–22, with 16–20 subequal teeth + 2 strongly and abruptly enlarged teeth, about 2.0–2.2 times larger than anterior teeth, either without diastema (see Fig. 10 ) or with a short diastema.

Body scalation. Dorsal scales in 19-19-17 rows, all scales strongly keeled, including those of the 1st dorsal scale row, more strongly keeled on the upper part of the dorsum; all scales strongly and deeply notched apically, especially on the posterior part of the body; 2 apical pits present. VEN: 158–173 (plus 1 or 2 preventrals); SC: 85–108, all paired; anal plate divided.

Head scalation. Rostral about 1.5–1.6 times as wide as high; nasal rectangular, longer than high, with a lateral nostril piercing in the middle of the scale; internasals subtriangular, as long as wide or barely longer than wide, anteriorly narrowed but truncated, with the fore width about 0.45–0.6 times as great as the hind width; prefrontals about 1.0–1.3 times as long as internasals; one large, longer than wide, undivided supraocular on each side; frontal bell-shaped, elongate, 1.4–1.7 times as long as wide, 2.2–2.7 times longer than prefrontals; parietals large, in contact along a suture about 0.9–1.1 times as long as frontal; one subrectangular loreal on each side, 1.1–1.2 times longer than high; 8 (rarely 9, in 3 / 28 occurrences) supralabials, 1st and 2nd SL in contact with nasal, 2nd and 3rd SL in contact with loreal, 3rd–5th (rarely 4th–6th) SL entering orbit, 7th SL largest; no subocular; on each side 1 (rarely 2) preoculars, tall and narrow; 3 small postoculars in all examined specimens; 1 (in 10/28 occurrences) or 2 (in 14/28) anterior temporals with the formulae 1+2 or 2+2; 9 or 10 (8 and 11 in 1/28 occurrences) infralabials, 1st pair in contact, 1st–4th or 1st–5th infralabials in contact with anterior chin shields, 4th and 5th infralabials largest.

Colour and pattern. In preservative ( Fig. 1–2 ), the upper body is rather dull, dark greyish-brown, dark brownish grey, brownish-lead grey, dark grey or dark olivaceous brown, darker than sides of the body at midbody; body sides are tan, pale brown, chestnut-brown or dark brown but are usually darker on the sides of the neck and extreme forepart of the body, such as dark chestnut-brown or blackish-brown, distinctly darker than the remaining part of body sides; this darker lateral colour gradually merges with the lateral colouration but extends over the entire lateral surface in some very dark specimens; scales of the 1st to 4th or 5th dorsal scale rows broadly edged with blackish-brown or black, producing dark reticulations and conspicuous irregular, oblique blotches on the sides arranged in a complex and irregular pattern; dorsum nearly uniform or usually irregularly marked with small, black spots more or less arranged as series; laterally, a series of distinctly enlarged and conspicuous, irregular, ivory, pale yellow or pale yellowish-brown blotches on the neck and fore part of body, extending on 4th–7th or 5th–7th DSR, progressively turning into smaller and darker, yellowish-brown or pale brown blotches on the upper half of 5th, 6th and lower half of 7th DSR, rounded and enlarged on the fore quarter to third of the body, more elongate, faint and reduced to the 5th and 6th rows posteriorly, connected from the first quarter to third of the body by a more or less distinct pale or dark yellowish-brown or rusty brown dorsolateral stripe extending along on the 6th, more conspicuous on the hind part of the body; in some specimens, the brown colour on the lateral aspect of the neck and first quarter of the body is interrupted by pale yellow vertical bars originating from the ventral colour and reaching up to the levels of the 6th or 7th DSR, usually much shorter, often reduced to paler areas or absent in most specimens; scales of the 1st dorsal scale row marked with short, irregular blackish-brown streaks, producing a very discontinuous, zigzag-like ventrolateral stripe, sometimes present only in the hind part of the body. Upper tail surface as the body, with scales strongly edged with dark brown; dorsolateral stripes vanishes progressively a short distance posterior to vent.

The head is greyish-brown, brown, brownish-grey above, usually with dark brown vermiculation; upper sides of snout and rostral paler than upper surface and rather pale brown or dark yellowish-brown; narrow, dark streak in front of the eye from the nasal to the upper part of the preocular; supralabials ivory, creamish-yellow, yellowishbrown or pale creamish-brown; 1st–3rd to 1st–5th SL dotted with minute brown to black dots or even nearly brown; 2nd–5th SL narrowly edged with dark brown, with usually a broader, more conspicuous streak on the hinder margin of the 6th SL; a conspicuous, broad, blackish-brown or black postocular streak extends from behind the eye to the corner of the mouth, covering lower postocular, anterior and part of posterior temporals, upper part of 6th SL, at least the upper half of 7th SL and the whole of 8th SL; 8th SL uniformly dark or with a pale (ivory or pale yellow) blotch or irregular in its middle; posterior to the lower half of the 8th SL, the blackish-brown postocular streak extends without interruption or, in a few occurrences, with a short, heavily dark spotted gap, onto the lateral surface of neck before fading into the paler background colour of the lateral aspect of the body; posterior to the upper half of the 8th SL, on each side, a bright, conspicuous, oblique ivory, yellow or yellowish-brown streak, reaching the vertebral row where each branch merges and produces a bright V or Y-shaped chevron-like marking on the neck, its apex directed backwards and reaching the first dorsolateral blotch; a short, pale yellow occipital streak usually present. The chin and throat are uniformly ivory, creamish-yellow or pale yellow, with a few faint, diffuse greyishbrown spots on the infralabials.

The venter is uniformly ivory or creamish-yellow, with outer tips of ventral scales brown or dark greyishbrown, and a few brown spots on outer parts of some ventrals. The subcaudal surface is as the venter with outer dark margins of subcaudals narrowly edged with dark brown or black; tip of the tail with dark brown spots or greyish-brown.

In life ( Fig. 3–6 ), the upper body is dark olive green to dark greyish-brown with faint black transverse markings, reticulations and conspicuous irregular, oblique blotches, especially on the forepart of the body; the dorsal colour pattern is more or less uniform throughout, except in one specimen it is interrupted by reticulation on the forepart just posterior to the chevron pattern on the nape; the transverse markings are formed by alternate scales irregularly black edged on the same row; some of the scales along the black transverse marking are bright red; the black transverse markings continue on the tail with the marking on the first scale row forming a continuous transverse line or band which extends onto the tail; interstitial skin white; on each side, a bright red, faint dorsolateral line extends along the length of the body on both sides on the 6th and 7th DSR.

Dorsal sides of the head are dark olive green to greyish brown; a faint pale brown streak on the centre of the nape and occiput; a black or blackish-brown preocular and postocular streak extends from the tip of the anterior nasal scale through the eye and, posteriorly, towards the extremity of the nape where it fades into the paler body colour; supraoculars with a cream or yellow streak that extends on the top of the nape as a distinct line and merges with each other forming a Y- or V-shaped chevron marking on the nape; supralabials bright yellow or sometimes white, speckled with black. Chin and throat are bright yellow or sometimes white. The iris is dark brown or black with a bright red ring around it; other parts of the eye dark olive green to dark grey.

The venter is bright yellow to white; outer margins of ventral scales bright red with black markings; the bright red blotches continuing to the tip of the tail.

Sexual dimorphism. It is marked in two characters: (1) ratio tail / total length: males: 0.280–0.325 vs. females: 0.262–0.273; and (2) the number of subcaudals: males: 87–108 vs. females: 84–85. Quite interestingly, the small diastema of maxillary teeth was seen only in females.

Distribution ( Fig. 7 ; numbers refer to the circles on the map). This species is known only from the eastern part of the Himalaya Range and adjacent ranges. Nepal (?). BMNH 58.6.24.5, “ Nepal ” (1). India. Sikkim. No precise locality (2). West Bengal. Darjeeling (3). Arunachal Pradesh. West Kameng District. Eaglenest Wildlife Sanctuary (4); Lower Subansiri District. Talle Valley, near Hapoli (5); Changlang District. Outskirts of Shidi (Gandhigram) (6). Nagaland. Kohima District. Sechu (7). Myanmar. Kachin State. Vicinity of Watamkawng (8); Sinlumkaba (9). People’s Republic of China. Yunnan Province. Nu Jiang Nature Reserve, near Pianma, Nu Jiang County (10).

The locality of specimen BMNH 58.6.4.25 is given as “ Nepal ”, without precision. It was deposited by B. H. Hodgson, who collected in Nepal but also in Sikkim. Additional specimens from Nepal are necessary to confirm the occurrence of A. clerki in that country; see also the discussion given below under the account of Amphiesma parallelum and the discussion given in Vogel & Hauser (2006) on the Nepalese locality of Ptyas nigromarginata (Blyth, 1854) .

Comments. This species shows consistent morphological differences with Amphiesma parallelum ( Boulenger, 1890) that are detailed below in the Discussion.

Figures

FIGURE 1. Amphiesma clerki (Wall, 1925), holotype, BMNH 1946.1. 13.50. General dorsal view, ventral view and dorsal and lateral head view. Photographs by Patrick David.

FIGURE 2. Amphiesma clerki (Wall, 1925), holotype, BMNH 1946.1. 13.50 (left) compared to Amphiesma parallelum (Boulenger, 1890), specimen BMNH 1946.1. 13.53 (lectotype). Photographs by Patrick David.

FIGURE 3. Amphiesma clerki (Wall, 1925), live specimen AP 1. Photograph by Viral Mistry.

FIGURE 4. Amphiesma clerki (Wall, 1925), live specimen AP 2. Photograph by Ishan Agarwal.

FIGURE 5. Amphiesma clerki (Wall, 1925), live specimen AP 3. Photograph by Ashok Captain.

FIGURE 6. Amphiesma clerki (Wall, 1925), live specimen RS 09. Photograph by Rohan Pandit.

FIGURE 7. Map showing the known distributions of A. parallelum (triangles) and A. clerki (dots).

FIGURE 10. Maxilla of specimen RS 09, Amphiesma clerki (Wall, 1925). Note the absence of diastema between anterior teeth and the strongly and abruptly enlarged posterior teeth. Photograph by Viral Mistry.