Hebius igneus, David & Vogel & Nguyen & Orlov & Pauwels & Teynié & Ziegler, 2021

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 : 44-52

8. Hebius igneus spec. nov.

( Figs. 15–16 )

Tropidonotus modestus (nec Tropidonotus modestus G̹nther, 1875).— Bourret 1927: 237 (?).

Natrix modesta (nec Tropidonotus modestus G̹nther, 1875).— Bourret 1936b: 72 (in part), 73 (in part: mention from “ Tonkin ” and description of the venter as “Dessous ... presque entièrement noirâtre”); Bourret 1939a: 42 (by inference); Bourret 1939b (in part: mention from Tam Dao, by inference): 53; Tran et al. 1981: 380 (?; tentatively but this mention does not refer to Hebius boulengeri ).

Amphiesma modesta .— Dao 1981: 7; Dao 1982: 8 (species with 19 DSR); Nguyen et al. 1995: 32; Zhao et al. 1998: 66 (in part: only specimens of Table 14 listed below in the non-type specimens); Orlov et al. 2000: 71 (in part: mention of Tam Dao); Le et al. 2001: 27; Bain & Nguyen 2004: 7; Ho et al. 2005: 99 (?); Nguyen et al. 2005a: 75 (in part: mentions from Vietnam except that from Gia Lai); Nguyen et al. 2005b: 120; Orlov 2005: 33 (in part).

Amphiesma modestum .— Ziegler & Le 2006: 40, 41 & 49; Nguyen et al. 2009: 354 (in part: probably the mentions from the provinces of Cao Bang and Ha Giang); Ziegler et al. 2007: 20, 22 & 23.

Natrix modesta modesta (nec Tropidonotus modestus G̹nther, 1875).— Bourret 1935b: 259 & 261 (Reprint p. 1 & 3); Bourret 1936b: 73 & 74 (in part: mention from “ Tonkin ” and description of the venter as “Dessous ... presque entièrement noirâtre], 74: Fig. 30 (specimen from Tam Dao); Bourret 1937: 27 & 29; Bourret 1939b (in part: mention from Tam Dao, by inference): 53.

Amphiesma deschauenseei (nec Natrix deschauenseei Taylor, 1934 ).— Nguyen et al. 2009: 354 (in part); Bain & Hurley 2011: 104 & 128; Guo et al. 2014: 428: Table 1 , 434: Fig. 2A , 435: Fig. 2 B–C (specimen AMNH 148575 from Vietnam).

Holotype.— IEBR 2295 , an adult female, from Ban Cai, 21°51’714N, 106°58’063E, elevation: 350–450m, Duc Xuan , Na Hang District, Tuyen Quang Province, Vietnam. Collected by Truong Quang Nguyen, Kien Van Doan and Cuc Thu Ho, 21 May 2004.

Paratypes (8 specimens).— VIETNAM. IEBR A.2018.2 (Field number ROM 28638), a stream on the east side of the village of Tam Dao (21°27’31”N, 105°38′61”E), elevation 925 m, Tam Dao Hill Station; collected by Cuc Thu Ho, Sergei A. Ryabov and Nikolai L. Orlov, July 2001. Lào Cai Province. IEBR A.2018.3 (Field number ROM 03474), Fan Si Pan mountain range (22°19’N, 103°47’ E), elevation 1,900 m, Sa Pa District ; collected by Cuc Thu Ho, Sergei A. Ryabov and Eugenyi Rybaltovsky, July 2001.— PEOPLE’ S REPUBLIC OF CHINA. Yunnan Province. CIB R579003 (Nr 8278), Xishuangbanna, Xishuangbanna Dai Autonomous Prefecture. - KIZ 75I324, Lafu , Menglian , Pu’er Prefecture ; KIZ 75I423, Menglian , Menglian Dai , Lahu and Va Autonomous County, Pu’er Prefecture; KIZ 79I195, KIZ 79I300, Manlai, Daxueshan, Yongde County , Lincang Prefecture .

Additional specimens (2).— VIETNAM. Ha Giang Province. AMNH 148575, Mt. Tay Con Linh II, Cao Bao Commune, Vi Xuyen County; collected by Raoul Bain & Truong Quang Nguyen, May 2000. Vinh Phuc Province . THAILAND. Nan Province. FMNH 271591, Amphoe Pua (i.e, Pua District) .

Taxonomic note. This species has long been known in the literature, at least since Bourret (1935b: 259 & 261 [Reprint p. 1 & 3]), under the combination Natrix modesta modesta , and appeared again in Bourret (1936b: 73–74 [in part], 74: Fig. 30), Bourret (1937: 27 & 29) and Bourret (1939b: 53, by inference) under the same combination. Hebius igneus spec. nov. was even depicted by Bourret (1936b: 74: Fig. 30). Subsequently, this species has been identified as Amphiesma deschauenseei or A. modesta , now Hebius deschauenseei and Hebius modestus , respectively; see the chresonymy given above.

Diagnosis.—A moderately to large sized species of the genus Hebius , defined by the combination of the following characters: (1) 19-19-17 dorsal scale rows, feebly or moderately keeled at midbody, more strongly keeled posteriorly at the exception of the scales of the 1 st DSR, all smooth; (2) dorsal scales around the base of the tail strongly keeled; (3) head moderately distinct from the neck; (4) eye rather large; (5) maxillary teeth 29–30, the last two moderately enlarged; (6) tail long, with a ratio TaL/TL at least equal to 0.295; (7) VEN 159–169; (8) SC 115–129; (9) prefrontals 2; (10) one anterior temporal; (11) venter overall dark, i.e., dark brown, blackish-brown or black, with either pale irregular streaks or with several parallel, connected rows of dark blotches separated from each other by a narrow, irregular pale area; (12) dorsal surface and sides dark brown, dark chestnut-brown or blackish-brown, irregularly spotted by the presence of blackish-brown or black scales, darker than the background colour; (13) a dorsolateral series of bright orange, coral or rusty red blotches (yellow in preservative), distinctly enlarged behind the neck and at least on the anterior half of the body, then progressively smaller but always visible; these blotches may be connected and form a distinct dorsolateral line; (14) a dark postocular streak present; and (15) an ochre-yellow or yellowish-brown streak on each side of the neck and nape forming an incomplete collar.

Morphological comparisons of Hebius igneus spec. nov. with other species.—Because of its peculiar dorsal pattern made of distinct, aligned bright dorsolateral blotches combined with an overall dark venter, we here put emphasis on the colour and patterns in comparing the new species with other species.

Hebius igneus spec. nov. differs from H. annamensis (Bourret) , H. atemporalis (Bourret) , H. chapaensis (Bourret) , H. groundwateri (Smith) , H. nigriventer (Wall) new. comb., H. sauteri (Boulenger) (including the subspecies H. s. bourreti and H. s. maximus), H. taronensis (Smith) , and H. venningi (Wall) , as well as three species present in Borneo, i.e., H. arquus (David & Vogel) , H. frenatus (Dunn) and H. sarawacensis (G̹nther), in having 19 DSR vs. 17 rows in all these species and sometimes 15 in H. annamensis . Furthermore, by its largely black venter, Hebius igneus spec. nov. further differs from the mainland species H. annamensis , H. atemporalis , H. groundwateri , H. sauteri , and H. venningi which have a large part of the venter pale.

Among the numerous species with 19 dorsal scale rows, Hebius igneus spec. nov. differs by its dorsal pattern from a number of distinctly striped species such as Amphiesma stolatum (Linnaeus) , and Hebius bitaeniatus (Wall) , H. clerki (Wall) , H. metusia (Inger, Zhao, Shaffer & Wu) , H. octolineatus (Boulenger) and H. parallelus (Boulenger) (see David et al. 2005) which display pale and dark dorsal stripes. Furthermore, these species have a pale venter and a lower number of subcaudals.

Also by its dorsal and ventral patterns, Hebius igneus spec. nov. differs from species with 19 DSR of the Hebius khasiensis -group, hence containing H. khasiensis (Boulenger) , H. boulengeri (Gressitt) , H. craspedogaster (Boulenger) , H. inas (Laidlaw) , H. johannis (Boulenger) , H. kerinciensis (David & Das) , and H. leucomystax (David, Bain, Nguyen, Orlov, Vogel, Vu & Ziegler) . All these species have dorsolateral spots and stripes but the blotches are smaller and all these species have a pale venter at the exception of the tips of ventrals. Furthermore, both H. khasiensis and H. inas differ from Hebius igneus spec. nov. by the pattern of their supralabials, composed of distinct, pale blotches in H. khasiensis and H. inas , at least on the posterior supralabials. Furthermore, Hebius igneus spec. nov. differs from H. leucomystax (David, Bain, Nguyen, Orlov, Vogel, Vu & Ziegler) and H. lacrima Purkayastha & David by its overall dark supralabials vs. supralabials largely white in these two latter species, plus by its venter largely dark, and its different dorsal pattern.

In the same way, Hebius igneus spec. nov. differs from H. optatus (Hu & Zhao) and H. andreae (Ziegler & Le) by its dorsal pattern made of conspicuous dorsolateral blotches vs. patterns made of vertical, narrow or wide crossbars, without longitudinal dorsolateral stripes or series of dots in these two latter species. Malnate (1962) referred Hebius craspedogaster , H. popei , H. pryeri , H. sauteri and H. vibakari in a distinct species group, named as the “ Amphiesma vibakari -group”. Besides H. sauteri , which has 17 DSR at midbody, Hebius igneus spec. nov. differs from these species by its dorsal and ventral patterns and by its higher number of subcaudals.

Hebius igneus spec. nov. obviously shares one or more characters with other species of “dark-bellied” Hebius , as treated here. However, for summarizing, Hebius igneus spec. nov. differs from H. annamensis , H. chapaensis , H. deschauenseei , H. modestus , H. nigriventer , H. taronensis and H. venningi by the combination of the following characters: (1) 19 DSR at midbody, (2) scales near vent and the base of the tail strongly keeled, (3) at least 159 ventrals, (4) a dorsolateral series of bright orange, coral or rusty red elongate blotches, larger anteriorly but extending behind half of the body, and (5) several parallel series of dark blotches on the venter more or less separated by narrow pale stripes. Tentatively included in this group but not addressed here, Hebius xenura (Wall) , which has also 19 DSR at midbody and dorsal blotches, differs from Hebius igneus spec. nov. by (1) its undivided subcaudals (vs. divided in H. igneus ), (2) fewer subcaudals, i.e., 92–105 vs. 115–129, and (3) its ventral pattern, pale with tips of ventrals dark vs. venter overall dark.

As shown above, Hebius annamensis , H. chapaensis , H. nigriventer , H. venningi , and H. taronensis have 17 DSR at midbody (or 15 in H. annamensis ) vs. 19 in Hebius igneus spec. nov. Furthermore, H. annamensis and H. venningi have a venter largely pale mesially or, in H. venningi , pale mesially on the anterior part of the body, clouded with darker hues of brown on the outer parts of ventrals and entirely clouded posteriorly.

Among the other two species of this group with 19 DSR at midbody, Hebius igneus spec. nov. differs from H. modestus by (1) dorsal scales before the base of the tail and supracaudal scales just after strongly keeled vs. weakly keeled in H. modestus , (2) slightly more ventrals, 159–169 VEN vs. 143–163, (3) venter overall dark brown, blackish-brown or black, with either pale irregular streaks or with several parallel, connected rows of dark blotches separated from each other by a narrow, irregular pale area vs. venter pale ochre-brown or pale brown on a wide central area, broadly edged with dark brown or blackish-brown on the outer quarter of ventrals, rarely nearly overally dark except on its anterior part, (4) a dorsolateral series of bright orange, coral or rusty red blotches, distinctly enlarged behind the neck and at least on the anterior half of the body, then progressively smaller but always visible vs. a more or less conspicuous, ochre-yellow, ochre-red, orange-brown or reddish-brown stripe, often reduced to a succession of elongate blotches on the anterior part of the body, and (5) a dark postocular streak present vs. no such streak.

Lastly, Hebius igneus spec. nov. is more similar to H. deschauenseei , from which it differs as follows: (1) supracaudal scales around the base of the tail strongly keeled vs. weakly keeled in H. deschauenseei , (2) Ratio TaL/TL, 0.30–0.33 vs. 0.33–0.38, (3) venter overally dark after the 5 th– 8 th ventrals, i.e., dark brown, blackish-brown or black, with 4 or 5 parallel, connected rows of dark blotches separated from each other by a narrow, irregular pale area vs. venter never entirely dark along its whole length, creamish-yellow or pale yellowish-grey with three parallel stripes of aligned dark blotches separated from each other by a pale area in H. deschauenseei , (4) dorsal surface and sides dark brown, dark chestnut-brown or blackish-brown vs. olive-brown, olive-grey or greyish-brown, (5) dorsolateral blotches, distinctly enlarged behind the neck and at least on the anterior half of the body, then progressively smaller but always distinct vs. dorsolateral blotches not as enlarged anteriorly and progressively smaller and united, forming a dorsolateral stripe, and (6) a dark postocular streak present vs. postocular streak absent or barely visible.

Although it is a juvenile with a rather pale venter anteriorly, specimen FMNH 271591 from Nan Province, Thailand, is here referred to Hebius igneus spec. nov., and not to H. deschauenseei . Its strongly keeled scales in the region of the base of the tail (vs. weakly keeled), its ventral pattern, overally black, and its dorsal pattern are typical of H. igneus spec. nov.

Etymology.—The specific nomen is the Latin adjective igneus (a, um) which means “in fire”. This specific name was coined by analogy to the large bright orange dorsolateral blotches on the forepart of the body.

We suggest the following common names: Fire-back Keelback (English), Hébius igné (French), Feuerfleckige Wassernatter (German), Huo Wen Fu Lian She (ẊỠẘdzdz) (Chinese), Ngu Lai-sab Fai (Thai) and Rắn sãi lửa (Vietnamese).

Description of the holotype ( Fig. 15 ).— General morphology. Body rather robust but elongate; head moderately elongate (4.0% of SVL), moderately distinct from the thick neck, flattened anteriorly in front of the eyes; snout elongate, subrectangular as seen from above, oblique seen in profile, 30.4% of HL, or 2.2 times as long as horizontal diameter of the eye; nostrils distinctly placed dorsolaterally on the snout and directed slightly dorsolaterally, round, quite large, piercing the middle of nasal; eye rather large, diameter 1.4 times as large as the distance between its lower margin and the margin of the lip, with a round pupil; tail cylindrical, long and tapering.

Size. - SVL: 534 mm; TaL: truncated; HL: 21.4 mm; ratio TaL/TL: not available.

Dentition. - Maxillary teeth: 28 gradually increasing in size + 2 distinctly enlarged teeth, without diastema.

Body scalation. - DSR: 19-19-17 scales, scales rhomboedric, not notched at their distal end, weakly keeled at midbody, more strongly keeled posteriorly at the exception of the scales of the 1 st DSR, all smooth; scales before vent and around the base of the tail strongly keeled.

Dorsal scale row reduction:

4+5 + 4 (9) 4+5 + 4 (98)

21 ——————— 19 ——————— 17

4+5 + 4 (10) 4+5 + 4 (101)

165 VEN (+ 2 preventrals);> 50 SC (incomplete tail), all paired. Cloacal plate divided.

Position of the reduction to 6 scale rows around the tail: 13 th SC. Length, in number of subcaudals spanned, of the portion of tail with 6 caudal scale rows (see Malnate & Underwood 1988): 26; length of tail with 4 caudal scale rows: unavailable, tail truncated; ratio: length with 6 dorsal scale rows/length of the portion of tail with 4 dorsal scale rows: unavailable.

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, nearly pentagonal, distinctly elongate, about 2.0 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 1.0–1.2 times longer than wide, distinctly narrowing anteriorly, the width of the anterior margin about 0.5 times of the posterior margin; 2 prefrontals, rather small, short but wide, distinctly broader than long, 1.1 times longer than internasals; frontal large and elongate, shield-like, 1.45 times longer than wide and 2.0 times longer than prefrontal; 1/1 supraocular, subtriangular and elongate, 2.0/1.8 times longer than wide, about as wide as internasals; parietals large and broad, 1.9 times longer than the frontal, or suture between parietals 1.3 times longer than frontal; 1/1 loreal, pentagonal, moderately elongate, 1.4 times longer than high, in broad contact with the nasal; 2/2 preoculars, upper one larger than lower one; 2/2 small postoculars; 9/9 SL, 1 st longer than high, 2 nd– 6 th slightly higher than long, 7 th– 9 th large and longer than high, 1 st and 2 nd SL in contact with the nasal, 2 nd– 4 th SL in contact with the loreal, 4 th– 6 th (left) and 5 th– 6 th (right) SL entering orbit, 7 th and 8 th SL largest, 9 th rather short; 1/1 anterior temporal, rectangular, elongate, slightly narrowing anteriorly, followed by 1+1/1 (left) and 1+1 (right) posterior temporals; 10/10 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 in alcohol. - Body blackish-brown, slightly darker on the top of the body than on its sides; many scales of the sides edged with blackish-brown or black and, also, somewhat paler in their middle; some scales of the sides of the body darker than the dorsal background colour, producing darker spots; a series of conspicuous, elongate dorsolateral, yellow blotches on 6 th and 7 th dorsal scale rows (66 at left, 68 at right), 2 to 2.5 DSR long and 1.5 to 2 scales high on the neck, distinctly enlarged, then 1 to 1.5 scale long and 1.5 to 2 scale high, often irregularly split into two parts on fore third of the body, progressively smaller, irregularly split after midbody and reduced to a spot posteriorly but always visible; no dorsolateral stripe.

The tail is of the same background colour than the body but without any spot or other mark on its top and sides.

Head blackish-brown above with some scattered beige dots on internasals, prefrontals and cephalic region; a short, faint, cream sagittal line just behind the suture between parietals; rostral and nasals slightly paler than upper head surface; a very thin and faint (barely visible at right), yellowish-brown, postocular streak extending obliquely downwards from the upper postocular along the anterior outer edge of each parietal then across upper temporals up to the upper edge of the 9 th SL; supralabials with a blackish-brown background colour; 1 st to 6 th supralabials somewhat paler near their anterior suture, more conspicuous on the edge of 6 th SL; 7 th SL yellowish-cream on a large oblique part of its central area with only the top and bottom of the scale blackish-brown; a small area near the lower anterior margin of 8 th SL also yellowish-cream, forming with the central area of 7 th SL a conspicuous, elongate and oblique marking; posterior part of 9 th SL pale yellowish-brown; in contrast, the upper parts of 7 th, 8 th and 9 th SL, and anterior temporal uniformly black, forming a large, oblique postocular streak extending from behind the eye to the corner of the mouth and slightly beyond; sides of the neck yellowish-cream, strongly spotted with blackish-brown, from which extends a yellowish-cream, oblique streak directed upwards and backwards at left, and two connected blotches at right, forming an irregular, yellowish-brown V-like mark just behind the head with its branches not in contact on the neck.

Infralabials blackish-brown with lower parts of posterior infralabials irregularly marked with yellowish-cream; mental scale dark brown; chin and throat yellowish-cream with dark brown spots on anterior chin shields and a few other scattered spots on the back of the throat; lower sides of the neck yellowish-cream with four irregular dark brown streaks on each side.

Venter overall dark due to numerous blackish-brown, connected blotches on a yellowish-cream background colour arranged as follows: venter yellowish-cream on the first seven ventrals, with a mesial row of dark blotches and tips of ventrals dark, then, on the next three or four ventrals, 3 or 4 rows of dark blotches, one or two mesially plus one on the tip of each ventral, separated by pale background colour, then 4 or 5 parallel, elongate blotches (not three as in H. deschauenseei ), extending from the anterior margin of the ventral and not or barely reaching its posterior margin, these blotches becoming progressively wider and connected, reducing the background colour to short, pale irregular streaks separating the rows of dark blotches; after the first third of the body, the blotches are entirely connected, forming dark transversal blotches on much of each ventral, leaving a narrow, pale area along the posterior edge of each ventral.

Tail blackish-brown below, with only the posterior edge of each subcaudal narrowly edged with beige brown.

The coloration in life was rather similar, but more bright, at the exception of the dorsolateral spots which were orange and the apex of the chevron on the neck that was bright yellow.

Description of the paratypes and variation.—A summary of morphological and meristic data of the paratypes is given in Table 1 . Other important characters agree with features of the holotype and are mentioned below in the variation.

General morphology. The maximal known total length is 602 mm long (SVL 409 mm, TaL 193 mm; specimen IEBR A.2018.2, female). Specimen KIZ 75I324 (male), with an incomplete tail, has a SVL = 595 mm, a value which would give a total length of ca. 860 mm.

Body relatively slender in males, more robust but elongate in females. Head both moderately elongate and distinct from the neck, amounting (in adults above SVL 300 mm) for 3.7–4.3 % of SVL (x = 4.0 %); snout elongate, rather flat, subrectangular as seen from above, oblique seen in profile, amounting (in adults) for 27.6–30.4 % (x = 29.0 %) of HL in both sexes, or 2.1–2.7 (x = 2.4) times as long as diameter of eye; eye large, amounting for 1.4–1.7 (x = 1.5) times the distance eye–lip. Tail progressively tapering. Ratio TaL/TL: 0.297 –0.331, without sexual dimorphism, but this ratio is based on only three values as most specimens have truncated tails.

Body scalation. DSR: 19–21-19-17, feebly or moderately keeled at midbody, more strongly keeled posteriorly, always smooth on 1 st DSR; dorsal scales immediately before vent and around the base of the tail strongly keeled.

In our sample of 11 specimens, only one has 21 DSR behind neck while another has 20 DSR.

The reduction 19 + 17 DSR, as DSR 4 + 5 + 4, appears at VEN 85–98 at left, at VEN 100–103 at right.

VEN: 159–169 (plus 1–2 preventrals); SC: 115–129, all paired; cloacal plate divided.

Length in number of subcaudals spanned, of 6 caudal scale rows (see Malnate & Underwood 1988): 13–30 (in females); length in number of subcaudals spanned, of 4 caudal scale rows: 38–68. Ratio: length 4 rows/length 6 rows: 1.86–2.92 (in females).

Dentition: 29–30 maxillary teeth in a continuous series, gradually enlarged with posterior two teeth slightly enlarged, without diastema.

Head scalation. It is as described for the holotype and paratypes, with the following variation: internasals subtriangular and narrowing forward, 1.1–1.4 times as long as wide and 0.35–0.45 times as wide anteriorly than posteriorly; prefrontals subrectangular, broader than long; frontal hexagonal, large and elongate, 1.15–1.45 times as long as wide, 1.6–2.0 times longer than the prefrontals; parietals long and wide, in contact for a length 1.2–1.3 times as great as the frontal length; 1/1 pentagonal loreal, horizontally elongate, 0.6–0.7 times as high as long, in broad contact with the nasal; 2/2 preoculars in all examined specimens; 2 or 3 postoculars (2/ 2 in 7/ 11 specimens, 3/ 3 in 4/11), the upper one larger than the two lower ones; 9/9 supralabials in all examined specimens, 1 st– 2 nd SL (in 7/ 11 specimens) or 1 st– 3 rd SL (in 4/11) in contact with the nasal, 2 nd– 3 rd SL (in 6/22 occurrences), 2 nd– 4 th SL (12/22) or 3 rd– 4 th SL (4/22) in contact with the loreal, usually 5 th– 6 th SL entering orbit (14/22 occurrences), or 4 th– 6 th SL (7/22), rarely 4 th– 5 th SL (1/22); 7 th– 8 th SL largest ones, much enlarged; 1/1 anterior temporal in all examined specimens, followed by 1, 1/1+1 or 2 posterior temporals; usually 10 infralabials (in 17/22 occurrences), also 9 IL (in 4/22) or 11 IL (1/22), first pair in contact behind the mental, 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. Dorsal surface and sides dark or very dark brown, even blackish-brown or deep black, more rarely dark chestnut-brown, nearly uniform or irregularly spotted by the presence of blackish-brown or black scales, darker than the background colour; in some specimens, many scales of the sides edged with blackish-brown or black and also somewhat paler in their middle; in all examined specimens, a series of 65 to 75 conspicuous, elongate dorsolateral blotches on 5 th and 6 th or 6 th and 7 th dorsal scale rows, yellow, pale yellowish-brown or pale reddish-brown in preservative, distinctly enlarged on the neck where they are about 2 to 2.5 DSR long and 1.5 to 2 scales high, then progressively smaller, often split into two parts on fore third of the body, irregularly split after midbody and reduced to a spot or a dash posteriorly but always visible; dorsolateral stripe usually absent but a faint, ochre-brown or reddish-brown stripe, may be present between the blotches along the posterior part of the body. The upper surface of tail is dark coloured as the body, either with a dorsolateral series of horizontally elongate pale spots in preservative or uniformly dark.

Head as described for the holotype: upper surface, parietal region and background colour of supralabials dark brown or blackish-brown, with scattered beige or pale brown dots on internasals, prefrontals and cephalic region; a short, cream sagittal line just behind the suture between parietals present but more or less faint; rostral and sides of the snout slightly paler than upper head surface; a yellowish-brown or yellowish-ochre line on the outer edge of each parietal and onto upper temporals very thin or often absent; usually (rarely completely absent) a yellowish-brown or yellowish-ochre postocular streak, varying from barely visible or even reduced to a few dots, to quite broad and distinct, extending from upper postocular downwards to 9 th SL and the corner of the mouth; 1 st to 6 th supralabials more or less distinctly paler, i.e., dark brown or dark ochre-brown, near their anterior edge, also often in their central part or even the anterior half of the scale; 6 th SL usually more distinctly paler in its anterior half; 7 th SL yellowishcream or ochre-brown on a large part, either as a triangular pale area, wider at its base on its anterior half or on its central area with only the top and bottom of the scale blackish-brown; 8 th SL also yellowish-cream or ochre-brown on its lower anterior part, sometimes forming with the central area of 7 th SL a conspicuous, elongate and oblique marking, or when the paler areas of the 7 th and 8 th are disjunct, forming two pale, parallel triangles; posterior part of 9 th SL creamish-yellow or pale yellowish-brown; upper parts of 7 th, 8 th and anterior part or middle of 9 th SL, and anterior temporal uniformly black or very dark blackish-brown, forming a large, irregular, oblique postocular streak extending from behind the eye to the corner of the mouth and slightly beyond in some specimens; sides of the neck yellowish-cream, strongly spotted with blackish-brown, from which extends a yellowish-cream, more or less wide oblique streak directed upwards and backwards, forming an irregular, yellowish-brown V-like mark just behind the head with its branches not in contact on the neck.

Venter overall dark as in the holotype, with numerous dark greyish-brown, dark brown or blackish-brown blotches on a yellowish-cream background colour; venter largely yellowish-cream anteriorly on the first 5 to 8 ventrals, with a mesial row of dark blotches or a solid streak and tips of ventrals dark, then, from 3 to 5 rows of parallel, elongate dark blotches, one to three mesially plus one on the tip of each ventral, separated by pale background colour, extending from the anterior margin of the ventral and not or barely reaching its posterior margin, these blotches becoming progressively wider and connected, reducing the background colour to short, pale irregular streaks separating the rows of dark blotches; after the first third to half of the body, depending on specimens, the blotches are entirely united and form dark, transversal blotches on much of each ventral, leaving a narrow, pale area along the posterior edge of each ventral.

Tail blackish-brown below, with only the posterior edge of each subcaudal narrowly edged with beige brown or yellowish-ochre.

In life, the coloration and pattern are quite similar to the conditions in preservative but more bright; the dorsal background coloration is chestnut-brown, dark brown, blackish-brown or even deep black, more or less iridescent; many scales of the sides are marked with yellow or yellowish-ochre; the dorsolateral blotches are conspicuous, bright yellow, orange, rusty red or bright reddish-ochre. Pale markings and vermiculations on the head are more conspicuous, more bright yellow, golden yellow or yellowish-ochre; when present, the large blotch on the 7 th supralabial is cream, yellowish-ochre or ochre-brown; the elongate blotch on the temporal region and on the hind part of the head is pale yellow, golden yellow, or yellowish-ochre, the branch obliquely directed upwards and backwards on the neck being often more orange colored; the background colour of the venter between dark blotches is cream or pale yellowish-grey.

Sexual dimorphism. According to our sample of 11 specimens, it is only weakly expressed in a single character:

Position of the reduction to 6 scale rows around the tail, expressed in the number of subcaudals: males: 14–21 vs. females 8–15.

Our limited sample does not show any difference in the numbers of ventrals and subcaudals or in the ratio TaL/TL.

Hemipenes.—The everted hemipenis (AMNH 148575) is short, single, cylindrical, reaching only the 7 th SC. It is entirely covered with spines, of which a few are largest at the base of the organ near the sulcus spermaticus; a few isolated large spines at the distal end of the organ.

Distribution (Map 12).— Hebius igneus spec. nov. occurs over the eastern part of the range of the informal group of the “dark-bellied” Hebius species.

People’s Republic of China. Yunnan Province. Baoshan Prefecture; Pu’er Prefecture; Xishuangbanna Dai Autonomous Prefecture.— Vietnam. North of the country: Ha Giang Province. Vi Xuyen District . Lao Cai Province. Sa Pa, Van Ban. Tuyen Quang Province. Na Hang District . Vinh Phuc Province. Tam Dao National Park . – Thailand. Nan Province. Pua District .

Based on its currently known distribution, Hebius igneus spec. nov. may obviously be expected in northern and north-western Laos. It may also be expected from other parts of north-eastern Thailand such as Loei Province.

Biology.—This species inhabits regions covered with tropical evergreen forest and subtropical montane evergreen and deciduous forests between 300 and 1,900 m a.s.l. All specimens were collected in close association with rocky, fast-moving mountain streams in forested areas. This species is crepuscular and nocturnal. It feeds on frogs of the families Megophryidae and Ranidae .

Figures

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 15. Hebius igneus spec. nov., holotype (IEBR 2295)—A: dorsal view; B: ventral view; C: lateral view of the head, right side. Photographs: Patrick David.

FIGURE 16. Hebius igneus spec. nov., alive—A: specimen from Yen Bai Province, Vietnam. Photograph: Nikolai Orlov. B: specimen from Ha Giang Province. Photograph: Truong Quang Nguyen. C: specimen from Lao Cai Province. Photograph: Truong Quang Nguyen.