Amphiesma inas (Laidlaw, 1901)

David, Patrick, Vogel, Gernot & Rooijen, Johan Van, 2013, On some taxonomically confused species of the genus Amphiesma Duméril, Bibron & Duméril, 1854 related to Amphiesma khasiense (Boulenger, 1890) (Squamata, Natricidae), Zootaxa 3694 (4), pp. 301-335 : 318-321

Amphiesma inas (Laidlaw, 1901)

( Fig. 6 )

Tropidonotus inas Laidlaw, 1901: 576 , Pl. 35: Fig. 3 & 4 . – Type locality. “Gunong Inas ”, now Gunung Inas [Mt. Inas ], near Lawin, State of Perak, West Malaysia, Federation of Malaysia. – Holotype. A juvenile, currently not traced (not in BMNH or ZRC collections); collected by Messrs. Laidlaw and Yapp, Skeat Expedition, 1899–1900.

Tropidonotus inas .—Boulenger 1912: 123 & 125—Smith 1916: 159—Werner 1929: 25

Natrix inas .—Smith 1930: 43; 1943: 291 (specimens from “Pen. Siam and Malay Peninsula”)—Smedley 1932: 115—Pope 1935: 90—Bourret 1936a: 103, 113 & 132.—Tweedie 1953: 70, 71: Fig. 17a-b, 65, 123; 1957: 72, 73: Fig. 18a-b, 67, 127.

Amphiesma inas .—Malnate 1960: 50, 52 & 57—Taylor 1965: 821, 829 & 830: Fig. 54—Tweedie 1983: 86, 93 & 94: Fig. 22ab, 156—Welch 1988: 30—Cox 1991: 235, 236: Fig. 21—Manthey & Grossmann 1997: 304 & 313—Cox et al. 1998: 44— Chan-ard et al. 1999: 30 & 153 (center and bottom)—Chanhome et al. 2001: 58.—Inger & Voris 2001: 887—Iskandar & Colijn 2001: 96 (in part)—David & Das 2003: 416, 417 & 418—Leong & Lim 2003: 132—Nabhitabhata et al. 2004: 124 (in part: mentions of Khao Luang, Nakhon Si Thammarat Province, and of Prachuap Khiri Khan)—Pauwels et al. 2009: 77—Das 2010: 150: Pl. 67, 332.

Material examined (10 specimens). Thailand. Nakhon Si Thammarat Province. BMNH 1916.3.27.31, Khao Wang Hip (upper camp).— Federation of Malaysia. West Malaysia. State of Pahang. MNHN 1999.9092, Cameron Highlands.—ZRC 2.4055, Cameron Highlands, 4,500′; ZRC 2.4056–4058′, Cameron Highlands, 4–5,000′.—ZRC 2.4059, Fraser’s Hill.—ZRC 2.5920, Gunung Brinchang.—BMNH 1938.8.7.13–14, Bukit Fraser (or Fraser’s Hills).

Taxonomic comments. Amphiesma inas was described from a juvenile specimen which cannot be currently traced. In contrast to the statement of Iskandar & Colijn (2001), this type is not in the collections of the Natural History Museum of London. As defined here, A. inas is endemic to Peninsular Thailand and West Malaysia. This species is monotypic.

Diagnosis. A species of the genus Amphiesma characterized by the combination of (1) a moderately elongate body; (2) nostrils directed laterally; (3) 19–21 maxillary teeth, gradually enlarged, the last 2 teeth distinctly enlarged; (4) 19 dorsal scale rows at midbody, strongly keeled on upper rows, moderately but distinctly keeled on 1st scale row; (5) dorsal pattern made of a series of yellow or ochre (cream in preservative) dorsolateral spots on a faint dorsolateral stripe (or absent), the first two or three enlarged and connected by a yellow stripe, other also enlarged on the anterior part of the body; (6) each posterior supralabial with a large, elongate, straight or oblique, cream blotch, or scale largely cream; (7) pattern of the neck made of a conspicuous, pale stripe extending from the corner of the mouth to the first enlarged dorsolateral spot; (8) venter ivory or cream, with the outer quarter or third of each ventral dark reddish-brown, in contact with the dorsal colour; (9) eye large, 1.9–2.0 times the distance between the lower margins of eye and of lip; (10) 141–151 VEN, 93–109 SC; (11) internasals abruptly truncated anteriorly, (12) 9 supralabials; and (13) 1 anterior temporal.

Amphiesma inas is easily distinguished from A. boulengeri by (1) 2nd to 9th DSR more keeled in A. inas , (2) scales of 1st DSR keeled (vs. smooth in A. boulengeri ), and (3) a distinct pattern on posterior supralabials. In contrast, A. inas and A. khasiense are very similar. The most obvious characters for separating these two species are the dorsolateral spots, yellow and conspicuous in A. inas , the first two or three distinctly enlarged and connected by a wavy stripe, small and rather reddish-brown in A. khasiense , and the stripe on the neck, broad in A. inas and connected to the first enlarged dorsal spot, short, narrow or often broken into spots in A. khasiense . Characters of use for separating these taxa are given below in the Discussion.

Variation (based Smedley 1932, Taylor 1965, Tweedy 1983 and on 8 examined specimens). Body cylindrical, elongate, rather slender in males, slightly more robust in old females, slightly laterally compressed; head rather elongate, oval, depressed in front of the eye, distinct from neck; snout rather short, blunt, amounting for 25.0–27.5 % of HL or 1.30–1.55 times as long as diameter of eye; nostrils large, crescentic, directed laterally and piercing in the middle of the nasal; eye large, 1.90–2.05 times the distance between the lower margin of eye and the lower edge of lip, with a round pupil; tail long, thin and tapering.

The maximal total length known is 634 mm (SVL 428 mm; TaL 206 mm; specimen ZRC 2.5920; male). The SVL of the longest known female is equal to 549 mm, which would give a TL of about 670 mm. Ratio TaL / TL: 0.321–0.342, without sexual dimorphism.

Dentition. Maxillary teeth 19–21, gradually enlarged, the last 2 teeth distinctly enlarged.

Body scalation. DSR: 19–19–17 scale rows; dorsal scales rhomboedric, normal or notched at their posterior extremity, distinctly keeled, more strongly in the posterior half of the body on all rows; scales of 1st DSR more or less strongly keeled, never smooth.

Scale row reductions: first reduction (19→17) at VEN 85 (at left) and second reduction (17→15) at VEN 87 (at left) in a single specimen.

VEN: 141–151 (plus 1 preventral in all examined specimens); SC: 93–109, all paired, without sexual dimorphism; ratio VEN / SC: 1.35–1.50; anal plate divided.

Position of the reduction to 6 scale rows around the tail: 11th–21st SC, with a sexual dimorphism (see dimorphism). Ratio length of the portion of tail with 4 dorsal scale rows / length of the portion of tail with 6 dorsal scale rows: 1.20–1.50.

Head scalation. Rostral trapezoidal wider than high, barely visible from above; nasals subrectangular, elongate, vertically divided on their lower half, with the posterior part larger and higher than anterior one; internasals subtriangular, rather small, in broad contact, about 1.1–1.2 times as long as wide, abruptly truncated anteriorly with anterior margin about 0.45–0.60 times the width of the posterior margin; 2 wide, subrectangular prefrontals, 1.3–1.5 times as long as internasals; frontal hexagonal, shield-like with apex directed posteriorly, rather small, 1.35–1.55 longer than wide, 1.8–1.9 times as long as prefrontal; 1 supraocular on each side, longer than wide, about as wide as internasals; two large parietals, 1.2–1.4 times longer than frontal; 1 small, rectangular loreal scale, 0.8–1.3 times as high as long, in broad contact with the nasal; 9 SL, 3rd–9th longer than high; 1st and 2nd SL small and short, in contact with nasal; 2nd and 3rd SL in contact with the loreal; 4th–6th SL entering orbit; 7th and 8th SL largest; 1 relatively large or 2 small preoculars on each side; 2 or 3 small postoculars; 1 anterior temporal, narrow and elongate, with complete temporal formulas as 1 + 2 + 2; 10 infralabials (9 in 1 / 16 occurrences), first pair in contact each with other, 1st–4th IL in contact with anterior chin shields, 6th IL largest.

Coloration and pattern in alcohol. The upper surface of body is dark reddish-olive brown, dark greyish-brown, dark reddish-brown or blackish-brown, variegated with darker pigmentation producing 2 or 3 rows of faint, irregular blotches on the upper scale rows and on the sides; a well defined pale yellow or pale grey dorsolateral stripe, wavy or broken by two or three large yellow blotches, extends on 5th and 6th DSR from the neck and foremost part of the body, turning into a pale, irregular, creamish-brown or rusty brown stripe extending on upper half of 5th and the whole of 6th dorsal scale rows, sometimes also on lower edge of 7th DSR, progressively fainter, usually not visible after midbody; on this dorsolateral stripe or on the background colour, a series of cream or yellow (coral, orange or red in life) spots, about 1 scale long and at 2–4 scales from each other, rather large and conspicuous on the anterior quarter or third or body, becoming smaller posteriorly; some very narrow cream dashes between dorsolateral spots on the anterior third of the body; a short, narrow ventrolateral stripe extending on the lower edge of scales of 1st DSR up to about the level of 12th to 30th VEN. The tail is as the body, with minute dorsolateral cream or yellow (coral, orange or red in life) spots, vanishing progressively and disappearing completely at mid-length of the tail; posterior half of tail uniformly dark, variegated with irregular and faint darker pigmentation.

The head is dark greyish-brown or reddish brown, paler than the background colour of the body, with irregular dark brown vermiculations; upper head surface with irregular paler areas, speckled with minute blackish-brown dots; usually a small, yellow spot on the each parietal; a short cream streak just behind parietals present or absent; anterior six supralabials dark with an irregular cream spot, larger on 5th and 6th supralabials reducing the dark colour to the posterior edge of the scale; 7th, 8th and 9th supralabials blackish-brown, darker than upper head surface, with either a large blotch in their middle, pure white or cream (same in life), slightly oblique, horizontally elongate, or with a triangular blotch covering the lower part and middle of the supralabial, in both cases not in contact with each other, contrasting sharply with the dark colour of the head; blotch more irregular in 9th SL; no postocular streak; on each side of the neck, either a conspicuous series of rounded or elongate cream, yellow or pale grey blotches, or a rather wide but continuous, oblique, cream, yellow or pale grey stripe extends obliquely from the corner of the mouth to the anterior part of the dorsolateral stripe or to the first dorsolateral spot. The throat and chin are cream or ivory; infralabials and mental usually heavily spotted with small, irregular dark reddish-brown spots; usually minute dots on the preventral area.

The venter is uniformly ivory or cream (yellow in life), with about 1/4 to 1/3 of the outer part of each scale very dark brown, in contact without discontinuity with the background colour of the body except for a short distance on the anterior body; sometimes a minute, elongate cream spot on the outer, posterior edge of each ventral just at the level of the base of ventral tips, producing a narrow, discontinuous ventral stripe separating the dark tip from the dark ventral blotch. The tail is ivory or cream below, with outer edges of subcaudals very dark brown; posteriorly, the tail becomes darker.

Hemipenis. In situ, it is short and stout as in other species of the group, undivided but with two short extensions at its tip, reaching in situ the 6th or 7th SC; sulcus spermaticus simple, S-shaped, reaching the top of the hemipenis, with prominent lips. The organ is entirely covered with short but dense spines, at the exception of the base which is covered with large calyces; lips of the sulcus also densely covered with short, thick spines; both extensions densely covered with rather numerous thin spines; 3 large, thick spines on the internal side of the organ at 90° of the sulcus; a very large spine at the base of the organ, on the side opposite to the sulcus.

Sexual dimorphism. In our limited sample, we could find a sexual difference only in the position (counted in number of subcaudals) of the reduction from 6 to 4 scale rows around the tail of subcaudals, with males: 19th–21st SC vs. females: 11th–15st SC.

Distribution.—According to the definition of Amphiesma inas given here and authors cited above: Thailand. Prachuap Khiri Kahn Province. Huay Tam Phra (after Taylor 1965; specimen not seen). Nakhon Si Thammarat Province. Khao Wang Hip; San Yen, Khao Nan National Park, 08° 46' N 099° 31' E, ca. 1,300 m a.s.l.; Fig. 6 ).— Federation of Malaysia. West Malaysia. State of Perak. Gunung Inas . State of Pahang. Cameron Highlands; Bukit Fraser (Fraser’s Hills); Genting Highlands; Gunung Brinchang. This species should be searched in other mountain ranges of West Malaysia.

In the literature, Amphiesma inas has also been cited from the island of Sumatra in Indonesia (Mumpuni 2001). We have examined the specimen from Sumatra (MZB 2186). It proved to be the second known specimen of Amphiesma kerinciense David & Das, 2003 (see below). Lastly, Das (2010) mentioned Amphiesma inas from several Thai provinces as far north as Loei Province. All specimens of this group recorded from Thailand north of the Isthus of Kra and seen by us are referable to Amphiesma khasiense or A. boulengeri .

Biology. A. inas has been recorded only from forested areas at high elevations between 1,000 and 1,500 m a.s.l. According to Das (2010), it is nocturnal and terrestrial, active on the forest litter and among buttresses. Little else is known about the biology of this seemingly rare species.

Figures

FIGURE 3. One of the syntypes of Tropidonotus khasiensis, BMNH 1946.1. 12.81, Khasi Hills, India. Photos Gernot Vogel.

FIGURE 4. Comparison of the pattern of the upper labials of three species of the Amphiesma khasiense group. A. A. boulengeri, BMNH 1969.1710, Kampot Province, Cambodia. B. A. boulengeri, FMNH 180153, Nakhon Ratchasima Province, Thailand. C. A. modestum, BMNH 1925.9. 17.2, Kachin Hills, Myanmar. D. A. khasiense, BMNH 1946.1. 12.82, syntype, State of Meghalaya, India. E. A. khasiense, BMNH 1946.1. 13.63, holotype of Natrix gilhodesi, Kachin State, Myanmar. F. A. khasiense, BMNH 1925.4. 2.13, Kachin State, Myanmar. Photos Gernot Vogel.

FIGURE 6. Living specimen of Amphiesma inas (Laidlaw, 1901), San Yen, Khao Nan National Park, Nakhon Si Thammarat Province, Thailand. Photo Michael Cota.