Hebius venningi ( Wall, 1910 )

David, Patrick, Vogel, Gernot, Nguyen, Truong Quang, Orlov, Nikolai L., Pauwels, Olivier S. G., Teynié, Alexandre & Ziegler, Thomas, 2021, A revision of the dark-bellied, stream-dwelling snakes of the genus Hebius (Reptilia: Squamata: Natricidae) with the description of a new species from China, Vietnam and Thailand, Zootaxa 4911 (1), pp. 1-61 : 7-13

1. Hebius venningi ( Wall, 1910)

( Figs. 1–2 )

Tropidonotus venningi Wall, 1910: 345 .—

Type locality. “Haka Chin Hills”, now Hakha , Hakha District, Chin State, Myanmar.— Holotype. BMNH 1946.1.21.86 (formerly BM 1910.1.4.6), adult male; collected by F. E. W. Venning, September or October 1908.

Tropidonotus venningi . — Venning 1911: 773; Werner 1929: 15 & 24 (in part).

Natrix venningi .— Wall 1923: 601; Wall 1925c: 921; Wall 1926: 560 (in part); Bourret 1936b: 55 (in part: only the mention of “ Birmanie ”); Smith 1943: 285 & 286 (in part).

Amphiesma venningi .— Malnate 1960: 51, 52 & 57; Dowling & Jenner 1988: 9 (in part); Welch 1988: 34; Zhao & Adler 1993: 228 (in part; only for the record from “ Burma ”); Iskandar & Colijn 2001: 98 (in part: except the mention from China); Captain & Bhatt 2002: 354, 355, 356: Fig. 1–4 ; Das 2002: 19 (text: in part; figure: genuine H. venningi depicted); Mathew & Meetei 2004: 135; Whitaker & Captain 2004: 214 (in part), 215–217 (figures); Whitaker 2006: 112; Zhao 2006: 174 & 175 (in part; only for the record of Myanmar); David et al. 2007: 54 (in part) & 60 (in part: specimens from Chin State, Myanmar); Sharma 2007: 206 & 207 (in part); Das 2010: 152: Pl. 68: Fig. 7 (genuine H. venningi depicted) & 335 (in part: at the exception of the mention of China, Yunnan Province); Das 2012: 118 (text: in part; figure: genuine H. venningi depicted) & 151; Wallach et al. 2014: 33 (in part: only mentions from Arunachal Pradesh, India, and Chin State, Myanmar).

Paranatrix venningi .— Mahendra 1984: 245.

Hebius venningi .— Guo et al. 2014: 431 & 438 (citations on pages 428 and 429 refer to other species; see below); Das & Das 2017: 126 (text: in part; figure: genuine H. venningi depicted) & 168; Boundy 2020: 92.

Amphiesma vinningi [sic]).— Ahmed et al. 2009: 155.

Natrix venningi venningi . — Smith 1940: 483 [as “the typical form”]; Smith 1943: 286 (in part: at the exception of specimens from “Nam-ti Valley”).

Amphiesma venningi venningi .— Welch 1988: 34; Zhao et al. 1998: 90 (in part); Captain & Bhatt 2002: 354 & 355; Zhao 2006: 175 (in part); Sharma 2007: 207 (in part: mention from Chin State).

Paranatrix venningi venningi .— Mahendra 1984: 245.

Amphiesma cf. modestum (nec Tropidonotus modestus G̹nther, 1875).— Ahmed et al. 2009: 155.

Specimens examined (14).— Myanmar. Chin State. BMNH 1946.1.21.86 (ex BM 1910.1.4.6; holotype of Tropidonotus venningi ); BMNH 1946.1.13.42 (ex BM 1910.12.9.1); BMNH 1946.1.13.49, BNHS 1316–1320, “Haka, Chin Hills”, now Hakha, 22°38’60”N, 93°37’00”E, Hakha District; CAS 235175, Shawn Khyak stream, near Ahone village , Mindat Township , Mindat District , 21°18’40.3”N, 93°45’31.9”E, 3,255 ft; CAS 233206, Chun Kyone, Hakha Township , Hakha District , 22°46’38.5”N, 93°33’55.7”E, 5,360 ft; CAS 234777, a small stream, Kanpetlet town , northern Kanpetlet Township , Mindat District , 21°11’55.7”N, 94°03’34.0”E, 4,062 ft; CAS 235376–235377, Maw stream, near Myin village , Mindat Township , Mindat District , 21°36’34.8”N, 93°53’07.3”E, 3,040 ft. Naga Self-Administered Zone (or Sagaing Region) . CAS 245379, Laung Nguk village, Lahe Township , 26 090’17.8”N, 95 31’17.3”E, 2,857 ft.

Taxonomic comments.—This species was first mentioned in the literature by Venning (1910: 340) on the basis of two specimens, “Nos XXXV and XXXVI”, referred to the genus Tropidonotus but which Venning did not formally name. It was then formally described in a subsequent paper of the same volume by Wall (1910: 345). Although this species was described on the basis of two specimens, Wall (1910) considered the specimen deposited in London (specimen BMNH 1946.1.21.86; formerly BM 1910.1.4.6) to be the holotype (“the type”, according to Wall) whereas the second specimen, considered to be a paratype (the “cotype”) was reported by Wall (1910) to be deposited in collections of the Bombay Natural History Society. In contrast, Wallach et al. (2014: 34) recognized three syntypes: (1) BMNH 1946.1.21.86, considered to be the holotype by Wall (1910), (2) BMNH 1946.1.13.49, a juvenile, considered to be the “co-type” by Wall (1910), previously deposited in the collections of the Bombay Natural History Society ( Mumbai, India), and (3) BMNH 1946.1.13.60. This latter specimen is in fact the holotype of Natrix nigriventer Wall, 1925 , here recognized as a valid species; it has been collected in June 1924 and cannot belong to the type series of a species described in 1910.

Hebius venningi has long been divided into two subspecies, the nominative one and Natrix venningi taronensis Smith, 1940 . On the basis of the differences in morphology of these two taxa discussed below and of their allopatric distributions, we consider them to be distinct at the specific level (see below). This position had been previously adopted in 2009 in the list of snakes of Myanmar provided on the website of the California Academy of Sciences:

(http://researcharchive.calacademy.org/research/herpetology/myanmar/project.html; accessed on July 20 th 2014). The validity of Hebius taronensis at full species status was eventually accepted by Das (2010: 335; as Amphiesma taronense ). Hebius venningi is thus a monotypic species.

Furthermore, Wall (1925: 588) described Natrix nigriventer from the vicinity of Bhamo, in Kachin State, Myanmar, but Wall (1926) synonymized it with Natrix venningi . This position was followed by Smith (1943). On the basis of our specimens at hand, we consider this taxon to be distinct from both H. venningi and H. taronensis and we resurrect it below at full species status.

There has been some confusion about the distribution of this species, especially in India. Gayen (2002) recorded a specimen from the Jaintia (or Jayanyia) Hills, State of Meghalaya, in Northeast India, a record mentioned by Whitaker & Captain (2004: 214), but Mathew & Meetei (2004) showed that the specimen was misidentified and should be referred to Hebius xenura (Wall) . Captain & Bhatt (2002) published the first authenticated record of Hebius venningi from India, on the basis of five specimens collected near Gandhigram (also called Shidi), Changlang District, State of Arunachal Pradesh. These authors noted that four of these specimens (specimens #2–5) could be referred to “ Amphiesma venningi venningi ” as defined by Smith (1940; 1943) whereas specimen #1, with 104 subcaudals only, agreed with the description of “ Amphiesma venningi taronense ( Smith, 1940) ”. Nevertheless, Captain & Bhatt (2002) considered all the specimens to be “the same kind of animal” and referred them to as Amphiesma venningi venningi .

This mix of specimens of two “subspecies” in a single locality and a comparison of their subcaudal counts with those of specimens of “ A. venningi ” from Yunnan led Captain & Bhatt (2002) to consider that the number of subcaudals was not a reliable character and that the validity of the subspecies taronensis was doubtful. In fact, these authors were not aware of the description of Hebius nigriventer (Wall, 1925) , a species resurrected below after having long been confused with H. taronensis and which occurs in Yunnan. While females of H. nigriventer may have the same number of subcaudals than H. taronensis , these species clearly differ from each other by several characters detailed below. On the basis of data and pictures published by Captain & Bhatt (2002) and Whitaker & Captain (2004), we agree with these authors in referring four of their five specimens to Hebius venningi sensu stricto as defined here. Although the ventrolateral blotches depicted in Whitaker & Captain (2004: 356, Fig. 4 ) and the venter largely pale (orange in life) along much of its length are not present in the holotype and several other examined specimens, these characters also appear in specimens from Myanmar, for example, CAS 245379. Furthermore, the dorsal pattern (including head), the dorsal scalation, the numbers of ventrals, and the number of subcaudals of two specimens with a complete tail are typical of H. venningi . In contrast, we here refer specimen #1, with 104 subcaudals, to Hebius taronensis on the basis that (1) its number of subcaudals does not agree with that of H. venningi but perfectly fits that of H. taronensis , (2) Captain & Bhatt (2002) would have noticed the peculiar dorsal and ventral patterns of H. nigriventer , and (3) Changlang District is less than 50 kilometres from the region of Putao, type locality of Hebius taronensis .

Thanks to the courtesy of A. Das, who communicated us additional unpublished pictures and data (pers. comm., August 2019), we identify as Hebius venningi the specimen from Mizoram ( India) depicted by Ahmed et al. (2009: 154) as Amphiesma cf. modestum . These authors thus published the first record of H. venningi from the State of Mizoram in Northeast India. Subsequently, Lalbiakzuala & Lalremsanga (2019) also published a record of “ H. venningi ” from the State of Mizoram. However, this specimen is referable to another species, the status of which will be discussed elsewhere.

H. venningi has also been recorded from Bangladesh by Reza (2010). However, pictures and morphological data of their specimen make clear that it is a Hebius xenura . So there is currently no record of this species from Bangladesh. Lastly, other records from Yunnan, China ( Kou 1985; Zhao & Adler 1993; Zhao et al. 1998; Zhao 2006), not cited above in the chresonymy, should now be referred to Hebius nigriventer (Wall, 1925) , a species that is resurrected below from its synonymy with H. venningi . Lastly, the locality cited by Smith (1943) as Bhamo Valley, in Kachin State, northern Myanmar, now also refers to Hebius nigriventer . As a consequence, H. venningi is currently restricted to extreme north-eastern India and western and north-western Myanmar.

Diagnosis.—A moderately to large sized species of the genus Hebius characterized by the combination of (1) 17–18-17-16–17 dorsal scale rows, moderately keeled at midbody, strongly keeled posteriorly but 1 st DSR smooth; (2) scales around the base of the tail strongly keeled; (3) head moderately distinct from the neck; (4) eye rather large; (5) maxillary teeth 28–30, the last two moderately enlarged; (6) tail long, with a ratio TaL/TL usually> 0.30; (7) VEN 155–172; (8) SC 115–129; (9) prefrontal scales 2; (10) anterior temporal rectangular, narrowing anteriorly; (11) venter never entirely dark along the whole length of the body: venter pale yellowish-grey or pale yellowishbrown (usually pink or coral-red in life, sometimes dark yellow) mesially, at least on the anterior part of the body, with outer parts of ventrals heavily and broadly clouded with darker hues of brown or dark brown; these dark areas extend progressively more widely inwards giving a dark, clouded venter posteriorly; (12) dorsum and sides olivebrown, olive-grey, dark grey, brown to dark brown or sometimes blackish-brown (same in preservative and in life); (13) dorsal surface distinctly chequered by the presence on sides and upper part of the body of diffuse, elongate or rectangular blackish-brown or very dark grey blotches; (14) a dorsolateral series of irregular blotches, yellow-ochre or yellowish-brown (brighter yellow-ochre or yellowish-brown in life), enlarged and forming a chain on the first quarter to third of the body, progressively smaller, usually vanishing after midbody; (15) a dark postocular streak usually present; and (16) an ochre-yellow or yellowish-brown streak on each side of the neck and nape forming an incomplete collar.

Description.—Body rather slender, stouter in large females, cylindrical; the head is somewhat elongate, subrectangular, moderately distinct from the thick neck, flattened anteriorly; snout elongate, obtuse as seen from above, oblique seen in profile, flat, 19.5–20.5 % of HL, or 1.6–2.0 times longer than diameter of eye; nostrils placed dorsolaterally on the snout and directed slightly dorsolaterally, small, round, piercing in the middle of the nasal; eye rather large, about 1.2–1.8 times greater than the distance between its lower margin and the margin of the lip, with a round pupil; tail long and tapering.

The maximal known total length is 780 mm (SVL 550 mm; TaL 230 mm; specimen #1 of Captain & Bhatt [2002], probably a female). The longest known male is 658 mm long (SVL 430 mm, TaL 228 mm long; BMNH 1946.1.21.86, holotype).

Ratio TaL/TL: 0.295 –0.347, without sexual dimorphism.

Dentition. 28–30 maxillary teeth gradually enlarging, the last 2 moderately enlarged, without diastema.

Body scalation. DSR: 17–18-17-16–17 rows; scales rhomboedric, moderately keeled at midbody, more strongly keeled posteriorly; scales of 1 st DSR smooth; dorsal scales around the base of the tail strongly keeled.

In our sample of 14 specimens, two have 18 scale rows around the neck; two others have 16 scale rows before vent; all others have 17–17–17 dorsal scale rows throughout the body.

VEN: 155–172 (plus 1 or 2 preventrals); SC: 115–129, all paired, without sexual dimorphism; cloacal plate divided.

Ratio VEN/SC 1.24–1.54.

Position of the reduction to 6 scale rows around the tail: SC 6–24, with a strong sexual dimorphism (see below); ratio: length of the portion of tail with 6 dorsal scale rows/length of the portion of tail with 4 dorsal scale rows: 1.0–2.5 with a sexual dimorphism.

Head scalation. Arrangement of upper head scales complete including 2 internasals, 2 prefrontals, 2 supraoculars, 1 frontal, and 2 parietals. Rostral wider than high, barely visible from above; nasals subrectangular, elongate, about 1.4–1.6 times longer than high, vertically divided above and below the nostril, with the posterior part equal to anterior one; internasals subtriangular, in broad contact with each other, about 0.9–1.2 times longer than wide, moderately narrowing anteriorly with an anterior margin about 0.5–0.6 times the width of the posterior margin; 2 prefrontals, rather small, short but wide, distinctly broader than long, 1.1–1.2 times longer than internasals; frontal large, shield-like, 1.2–1.3 times longer than wide and 2.0–2.4 times longer than prefrontal; 1 supraocular on each side, subtriangular, 2.0–2.4 longer than wide, about as wide as internasals; parietals large and broad, 1.4–1.6 times longer than the frontal, or suture between parietals 1.1–1.2 times longer than frontal; 1/1 loreal, pentagonal, elongate, 1.3–1.5 times longer than high, in broad contact with the nasal; 1 or more commonly 2 preoculars, upper one larger than lower one; 3 small postoculars in all examined specimens; 9/9 SL (8/ 8 in one specimen only), the first five as long as high or longer than high, 1 st and 2 nd SL small and short, in contact with the nasal, 2 nd– 3 rd SL or 2 nd– 4 th SL in contact with the loreal, 4 th– 6 th or 5 th– 6 th SL entering orbit, 7 th and 8 th SL largest; 1 anterior temporal, rectangular, elongate, narrowing anteriorly, followed by 1 or 1+1/1 posterior temporals, the most common formula being 1+1 temporals; 9 or 10 (11 in only 1/18 occurrences, namely in adding the values met on each side) infralabials, first pair in contact, 1 st– 5 th IL in contact with anterior chin shields, 5 th and 6 th IL largest; posterior chin shields longer than anterior ones.

Coloration and pattern. The dorsal surface and sides are olive-grey, olive-brown, greyish-brown, dark grey, brown, dark brown or sometimes blackish-brown, darker on the top than on the sides of the body, with scales indistinctly edged or speckled with very dark brown; dorsum with a chequered pattern, more distinct on the anterior half of the body, by the presence on the 2 nd to 8 th dorsal scale rows and vertebral scale rows of 4 to 5 series of irregular, diffuse elongate or rectangular blotches, blackish-brown or very dark grey blotches, often fuzzy, larger at the bottom of the sides and on 6 th– 8 th dorsal rows, covering a length of 1.5 to 2.5 dorsal scales; on each side of the body, a dorsolateral series of irregular blotches, yellow-ochre or yellowish-brown on the 4 th– 6 th or 5 th– 6 th DSR, enlarged, and forming a chain on the first quarter to third of the body, progressively smaller, vanishing after midbody or remaining as very faint pale spots throughout the body. The tail is as the body surface, chequered with small dark blotches and spots.

The head is olive-brown, greyish-brown, brown to dark brown, paler on the rostral and sides of the snout; cephalic scales scattered with pale brown, yellowish-brown or dark yellow-ochre vermiculations, sometimes producing short, irregular, parallel streaks or elongate areas on prefrontals and frontal and an oblique streak on the outer edge of each parietal; often the presence of twin parietal pale spots; anterior supralabials greyish-yellow, pale brown or ochre yellow, especially on their lower half, more or less strongly powdered with olive-brown or dark brown on their upper part, and more or less broadly edged with dark or blackish-brown; a broader, dark brown or blackishbrown, oblique streak on the posterior edge of 6 th and 7 th SL; 8 th or 9 th SL, or both, mostly dark brown, with only the lower part pale; often a faint, poorly-defined, paler area on temporals; usually a dark, oblique postocular streak extending from eye to the corner of the mouth on the top of the 9 th SL and temporals, sometimes poorly defined if the background colour is dark; an irregular yellow-ochre or brownish-yellow, oblique streak directed upwards and backwards extending from the corner of the mouth to the nape, forming a short chevron, sometimes faint or nearly absent; a thin streak of same colour extends from the interparietal suture to the apex of the chevron. Infralabials, chin and throat yellowish-cream or pale yellow-ochre, often nearly uniform with a few dark brown spots on chin shields and throat, sometimes heavily spotted with dark brown spots and flecks; infralabials each edged with dark brown on both edges, sometimes strongly speckled with dark brown.

The venter is never entirely dark along the whole length of the body, i.e., always pale mesially at least on the anterior fifth, quarter, third or half of the body, sometimes only on the first 20 ventrals, depending on specimens. This pale colour may be beige, pinkish-brown, yellowish-cream, pale yellowish-ochre or pale brownish-grey in preservative on the inner half to two-thirds of ventral width, with tips and outer parts of ventrals heavily and broadly clouded with darker hues, such as dark greyish-brown, brown or dark brown; this dark, clouded area progressively extends inwards, reducing the pale coloration to a narrow mesial part of ventrals then making the venter entirely clouded with dark hues on the posterior part of the body; tips of ventrals often with a large black blotch. Tail dark greyish-brown, dark brown or blackish-brown, uniform or with the edges of subcaudals pale grey or brown.

In life, the dorsal surface and sides are olive-grey, olive-brown, greyish-brown, dark grey, brown, dark brown or sometimes blackish-brown; the dark dorsal blotches forming the chequered pattern are blackish-brown or very dark grey blotches; the pale irregular blotches on each side of the body are usually bright and conspicuous, greyish-yellow, yellow-ochre or yellowish-brown, sometimes dark greyish-yellow. Pale markings on the head, such as vermiculations and streaks, and supralabials are also bright yellow-ochre or yellowish-brown. The pale area of the venter is pink or bright coral red, sometimes yellow ( Fig. 2 ).

Hemipenes.—In situ, it is single, short and thin, reaching the 8–9 th SC, proximal part covered with short spines, 2 or 3 spines much larger and hooked; distal part covered with small, dense spines; sulcus spermaticus short and with poorly visible lips.

Sexual dimorphism. — It is expressed in the following characters:

(1) Weakly by the difference in the number of ventral scales: males: 164–167 (mean = 165.5, SD (standard deviation) = 1.7); females: 157–165 (mean = 160.0, SD = 4.4).

(2) Strongly by the difference in the position of the reduction from 8 to 6 scale rows around the tail (counted in number of subcaudals): males: SC 19–24; females: SC 4–9.

(3) Strongly by the difference in length of the portion of tail with 6 dorsal scale rows/length of the portion of tail with 4 dorsal scale rows: 2.1–2.5 in 4 males, 1.0– 1.4 in 2 females.

Distribution ( Fig. 3 ).— India. State of Arunachal Pradesh. Patkai Hills, Changlang District; Tirap District ( Borang et al. 2005). State of Nagaland. Khonoma, Kohima District; Dzulake (or Dzuleke, Kohima District ( Ahmed et al. 2009; M. F. Ahmed, pers. comm., May 2018; A. Das, pers. comm., August 2019). State of Mizoram. Vicinity of Tamdil Lake, Saitual Sub-Division, Aizawl District, 900 m. a.s.l.— Myanmar. Known only from the west of the country. Chin State. Chin Hills, near Hakha, Hakha District; Mindat Township and Kanpetlet Township, Mindat District. Sagaing Region (or Naga Self-Administered Zone). Lahe Township.

Biology.—The specimens for which data are available were collected in pristine or disturbed evergreen or semievergreen submontane forest and mixed or deciduous moist montane forest, between 870 and 1,635 metres a.s.l. Most snakes were found near hills or montane streams. According to Whitaker & Captain (2004), Hebius venningi feeds on tadpoles and frogs.

This species seems to be common in some places ( Borang et al. 2005). It is inoffensive and does not attempt to bite when handled.

Figures

FIGURE 1. Hebius venningi Wall, holotype (BMNH 1946.1.21.86)—A: dorsal view; B: ventral view; C: lateral view of the head, right side; D: close-up dorsal view of the head. Photographs: Gernot Vogel.

FIGURE 2. Hebius venningi Wall, alive—A & C: specimen from Changlang District, Arunachal Pradesh, India. Photographs: Ashok Captain.—B: specimen CAS 233206, Chun Kyone, Hakha Township, Hakha District, Chin State, Myanmar. Photograph: Hla Tun.

FIGURE 3. Distribution map of species with 15 or 17 dorsal scale rows at midbody. Circles: Hebius annamensis Bourret. Diamonds: Hebius venningi Wall. Inverted triangles: Hebius taronensis Smith. Squares: Hebius nigriventer Wall. Triangles: Hebius chapaensis Bourret.

FIGURE 4. Hebius nigriventer Wall, holotype (BMNH 1946.1.13.60)—A: dorsal view; B: ventral view; C: lateral view of the head, right side; D: close-up dorsal view of the head. Photographs: Gernot Vogel.

FIGURE 7. Hebius taronensis Smith, alive—Specimen from Lake Indawgyi, Mohnyin Township, Kachin State, Myanmar. Photograph: Nikolay Poyarkov.