Hebius deschauenseei ( Taylor, 1934 )

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 : 40-44

publication ID	https://doi.org/ 10.11646/zootaxa.4911.1.1
publication LSID	lsid:zoobank.org:pub:361E198B-5F04-4E5F-824A-73F488AB4A8B
persistent identifier	https://treatment.plazi.org/id/383AEC41-FFA8-FFC1-FF6A-F989FD72CDCE
treatment provided by	Plazi
scientific name	Hebius deschauenseei ( Taylor, 1934 )
status

Treatment

7. Hebius deschauenseei ( Taylor, 1934) View in CoL

( Fig. 14 View FIGURE 14 )

Natrix deschauenseei Taylor, 1934: 300 , 301: Figs. 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 , Pl. 17: Fig. 5 View FIGURE 5 .—

Type locality. “Chieng Mai, North Siam”, now Chiang Mai, Chiang Mai Province, Thailand.— Holotype. ANSP 19927 , adult male; collected by R. M. de Schauensee, Janu-ary–March 1933.

Natrix deschauenseei .— Bourret 1936a 103 (in part; the wide range given for this species is obviously erroneous); Taylor & Elbel 1958: 1151; Taylor 1965: 825, 826: Fig. 52.

Macropophis deschauenseei . — Bourret 1936b: 105.

Amphiesma deschauenseei .— Malnate 1960: 50, 52 & 56; Welch 1988: 30; Cox 1991: 234, 268: Pl. 76; Chan-ard et al. 1999: 30; Chanhome et al. 2001: 58; Nabhitabhata et al. 2004: 124; David et al. 2007: 41, 54, 56 & 59 (in part: specimens from Thailand only); Pauwels et al. 2009: 77 & 78; Das 2010: 331 (in part: mention of Thailand only); Bain & Hurley 2011 (in part): 104 & 128; Iskandar & Colijn 2001: 95; Cox et al. 2012: 365 & 366, 367 (in part: mentions of Thailand only); Das 2012: 113 (in part: mention of Thailand only); Chan-ard et al. 2015: 230.

Hebius deschauenseei . — Guo et al. 2014: 438 (implicitely); Boundy 2020: 92.

Natrix modesta (nec Tropidonotus modestus G̹nther, 1875).— Mell 1929: 5, 16, 145 (in part: mention from “Nordsiam” only), 147 (in part: mention from “Nordsiam” only) & 157; Smith 1943: 285, 290 & 291.

Amphiesma modesta .— Nabhitabhata 1987: 42.

Specimens examined (17).— Thailand. Chiang Mai Province. BMNH 1969.1721–1725, “Pa Meang, Me Nga, N. Siam”, BMNH 1974.5193, “Pa Meang, Me Nga, N. Thailand”, now in the vicinity of Pa Muang (or Pamuang); CUB MZ(R)5, Forestry Station, Doi Suthep, 3,000 ft; CUB MZ(R)36118, Doi Suthep; FMNH 178396–178398, Chiang Mai. Chiang Rai Province. BMNH 1969.1719, “Doi Chang”, now Doi Chang (Mt. Chang), Chiang Rai District. Unspecified locality. BMNH 1921.4.1.6–9, “Hills of North Siam”; CUB MZ(R)1999.63, “Thailand”.

Taxonomic comments.—This species was recognized as valid in the genus Natrix by Bourret (1936a) but Bourret (1936b) placed it in the genus Macropophis Boulenger, 1893 , a genus that was considered a synonym of Tropidonophis Jan, 1863 which includes natricid species of the Philippines, eastern Indonesia and Australasia ( Malnate & Underwood 1988). Subsequently Natrix deschauenseei was synonymized with N. modesta (G̹nther, 1875) by Smith (1943: 290), along with three other species now considered to be valid (see above under the account of Hebius modestus ). Subsequently, the validity of Natrix deschauenseei was recognized by Taylor & Elbel (1958) and Taylor (1965), and accepted by all subsequent authors, although H. deschauenseei has not always been correctly identified, for example by Nabhitabhata (1987) who confused it with H. modestus (see above). Hebius deschauenseei is monotypic.

Diagnosis.—A moderately to large sized species of the genus Hebius characterized by the combination of (1) 19-19-17 dorsal scale rows, moderately or weakly keeled at midbody, more strongly keeled posteriorly excepted scales of the 1 st DSR, all smooth; (2) dorsal scales around the base of the tail weakly keeled; (3) head moderately distinct from the neck; (4) eye rather large; (5) 29–30 maxillary teeth, the last two moderately enlarged; (6) tail long and tapering, with a ratio TaL/TL at least equal to 0.33; (7) VEN 149–168; (8) SC 115–141; (9) prefrontal 2; (10) usually 5 th– 6 th SL entering orbit; (11) 1 anterior temporal; (12) venter never entirely dark: along its whole length, creamish-yellow or pale yellowish-grey with three parallel rows of dark blotches, one on the outer part of each ventral, and one on the central part of the venter producing three irregular, parallel stripes separated from each other by a narrow, pale area; (13) dorsum and sides olive-brown, olive-grey or greyish-brown, sometimes dark brown; (14) dorsal surface with irregular, blackish-brown or very dark grey blotches, not producing a chequered pattern; (15) a dorsolateral series of large, elongate blotches, yellow-ochre, rusty red or yellowish-brown, enlarged on the first quarter to third of the body, progressively smaller and united, forming a dorsolateral stripe, usually extending along the whole of the body on the 4 th– 5 th or 5 th– 6 th dorsal scale rows; (16) postocular streak present, not visible in dark specimens; and (17) 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; head moderately elongate, triangular, moderately distinct from the thick neck, flattened anteriorly; snout elongate, obtuse or squarish as seen from above, oblique seen in profile, flat, 25.9–31.3 % of HL, or 1.7–2.1 times as long as diameter of eye; nostrils small, round, placed dorsolaterally on the snout and directed slightly dorsolaterally; eye rather large, about 1.5–1.8 times as large as 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 553 mm (SVL 368 mm; TaL 185 mm; specimen BMNH 1969.1721, female) but specimen BMNH 1969.1719, with an incomplete tail and a SVL 556 mm long, should have reached a total length of ca. 850 mm. The longest known male is 484 mm long (SVL 312 mm, TaL 172 mm long; CUB MZ(R) 36118).

Ratio TaL/TL: 0.327 –0.378, without sexual dimorphism.

Dentition. 29–36 maxillary teeth gradually enlarging, the last 2 to 4 moderately enlarged, without diastema.

Body scalation. DSR: 19-19-17 rows; scales rhomboedric, weakly or moderately keeled; scales of 1 st DSR smooth; dorsal scales around the base of the tail not strongly keeled.

VEN: 149–168 (plus 2 or 3 preventrals); SC: 115–141, all paired, with a weak sexual dimorphism; cloacal plate divided.

Ratio VEN/SC 1.11–1.32.

Position of the reduction to 6 scale rows around the tail: SC 5–22, 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: 1.2–2.4 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 1.0–1.2 times longer than wide, distinctly narrowing anteriorly with an anterior margin about 0.4–0.5 times the width of the posterior margin; 2 prefrontals, rather small, short but wide, distinctly broader than long, 1.0–1.3 times longer than internasals; frontal large and elongate, shield-like, 1.2–1.6 longer than wide and 1.8–2.4 times longer than prefrontal; 1 supraocular on each side, subtriangular, 2.0–2.2 times longer than wide, about as wide as internasals; parietals large and broad, 1.8–2.2 times longer than the frontal, or suture between parietals 1.2–1.4 times longer than frontal; 1/1 loreal, pentagonal with its apex directed backwards, distinctly elongate, 1.4–1.8 times longer than high, in broad contact with the nasal; 2/2 preoculars in all examined specimens, upper one larger than lower one; 2/2 or more rarely 3/3 small postoculars; usually 9/9 SL (8/ 9 in 1/ 18 specimens, 10/ 9 in 1/18 and 10/ 10 in 2/18), 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– 4 th SL or 3 rd– 4 th SL (2 nd– 3 rd SL in 1/ 18 specimens) in contact with the loreal, mostly 5 th– 6 th SL entering orbit (in 29/36 occurrences), also 4 th– 6 th SL (3/36), 5 th– 7 th or 6 th– 7 th (in 2/36 occurrences each), 7 th and 8 th SL largest; 1 anterior temporal, rectangular, elongate, narrowing anteriorly, followed by 2 or 1+1/1 posterior temporals, the most common formula being 1+2 temporals; 10/10 (in 17/18 occurrences) or 9/10 (1/18) 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. This species is quite variable. The dorsal surface and sides are pale olive-brown, olivegrey, pale greyish-brown, bronze-brown, dark reddish-brown or dark brown; scale rows of the upper dorsal surface distinctly darker, up to blackish-brown; on the sides, scales may be pale centered and indistinctly edged with minute dark brown blotches; two or three series of small, irregular dark blotches on the sides; dorsal surface with usually two or three series of irregular, elongate, blackish-brown or very dark grey blotches, rather faint in darker specimens but conspicuous in paler ones, the series just above the dorsolateral stripe more conspicuous; another series of dark, elongate blotches just below the dorsolateral stripe; a faint dorsolateral stripe, reddish-brown or brown, extending from the neck to the base of the tail barely visible, on which is superposed a conspicuous series of dorsolateral bright yellow, yellow-ochre, rusty red or yellowish-brown blotches on the 4 th– 6 th then 5 th– 6 th DSR, much enlarged, distinctly elongate or X-shaped, or as high as long on the first fifth to quarter of the body, 2 to 2.5 scales high and long, progressively smaller and more elongate, forming a chain, then united and forming a narrow, dorsolateral stripe posteriorly, 1.5 to 2 scales high; lower part of scales of the 1 st dorsal row largely dark brown or blackish-brown, forming an irregular, ventrolateral dark stripe. The tail is as the body surface, speckled with small dark blotches and spots and with a yellow-ochre, rusty red or yellowish-brown narrow, irregular dorsolateral stripe, no more than 1 scale high, progressively vanishing around the posterior half of the tail.

The head is olive-brown, olive-grey or brown, upper head surface with irregular darker vermiculations or irregular areas; rostral and sides of the snout paler; an oblique streak on the outer edge of each parietal present or absent; 4 or 5 anterior supralabials strongly powdered with olive-brown, greyish-brown or pale brown, edged with dark brown or blackish-brown; a broader suture, dark brown or blackish-brown, on the posterior edge of 6 th and 7 th SL; 7 th, 8 th and 9 th SL (when present) pale yellowish-brown or yellowish-grey, also edged with blackish-brown; a dark postocular streak, oblique or Z-like, i.e., straight, then strongly oblique then straight, extends from behind the eye or from postoculars to the corner of the mouth on the top of the 8 th and 9 th SL and temporals; a poorly-defined, paler area on temporals above the dark postocular streak; an irregular yellow-ochre or brownish-yellow, oblique streak directed upwards and backwards, extending from the corner of the mouth and the pale area on the temporals to the nape, forming a short chevron, sometimes faint or nearly absent; a thin streak of same colour extending from the interparietal suture to the apex of the chevron. Infralabials, chin and throat yellowish-cream or pale yellowishbrown, often nearly uniform with a few dark brown spots on chin shields and throat, sometimes heavily spotted with dark brown spots; infralabials more or less broadly and distinctly edged with dark brown on both their anterior and posterior edges.

The venter is never entirely dark but contains dark blotches in its middle: background colour creamish-yellow, yellowish-brown, beige ochre-brown, or olive-grey, darker posteriorly; tips and extreme outer part of ventrals dark brown; 3 parallel series of blotches or spots, olive-grey, dark grey, brown, dark brown or blackish-brown, extending from the neck to the vent: one located on the mesial part of the ventrals, the two outer ones located at the level of the outer third of each ventral, not in contact with the dark hues of the ventral tip; usually only the two outer series begin at the neck, the central one beginning at level of the 10 th– 15 th ventral, or, in an opposite way, the central stripe begins first, the two lateral ones farther back; these blotches are more or less enlarged, those of the outer series triangular with their apex directed posteriorly, those of the central one wider, looking as a flat, irregular triangle or more irregular; the three series may be close but never united, or even distinctly separated when they are made of rather small spots, widening posteriorly; sometimes, these series are barely visible in specimens with a rather dark venter. Tail dark greyish-brown, dark brown or blackish-brown, covered with 3 series of irregular blotches narrowly separated by a thin, pale line, turning to entirely dark on its posterior half; outer edge of subcaudals pale, forming a narrow line.

In life, the background coloration is as described above in preservative; the upper dorsal surface, between the dorsolateral stripes, is distinctly darker than the lateral sides; the various upper lateral and dorsolateral dark blotches are very dark grey, dark brown or blackish-brown; the dorsal stripe, rusty-brown or reddish-brown, is more visible than in preservative; the main dorsolateral blotches are bright yellowish-ochre, orange or reddish-brown; the dark ventrolateral stripe is dark brown or blackish-brown. Pale markings on the head are yellowish-ochre, greyish-yellow or reddish-brown; the elongate blotch on the temporal region, on the hind part of the head and on the neck is yellowish-ochre, reddish-ochre or reddish-brown. The background colour of the throat and venter is pale greyish-yellow, yellowish-grey or pale reddish-brown; the dark blotches forming the three parallel series of blotches or spots are in various shades of brown.

Hemipenes.—The hemipenis of this species has not been examined.

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

(1) Strongly by the difference in the number of subcaudal scales: males: 124–141 (mean = 130.0, s = 6.4); females: 113–124 (mean = 117.8, s = 4.8).

(2) Strongly by the difference in the position (counted in subcaudals) of the reduction to 6 scale rows around the tail: males: SC 14–22 (mean = 17.9, s = 2.5); females: SC 5–13 (mean = 9.6, s = 3.0).

(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: 1.2–1.8 in 8 males, 2.0– 2.4 in 5 females.

Distribution ( Fig. 12 View FIGURE 12 ).— Thailand. According to our specimens and Chan-ard et al. (2015): Chiang Mai Province. Chiang Mai; Doi Inthanon; Doi Suthep; Pa Muang (or Pamuang). Chiang Rai Province. Doi Chang (Mt. Chang), Chiang Rai District. Uthai Thani Province. Huai Kha Khaeng Wildlife Sanctuary.

Cox et al. (2012: 367) mentioned the occurrence of this species in Loei Province, North-east Thailand. According to M. J. Cox (personal communication, June 2018), this record merely results from a lapsus. There is not any record to support the occurrence of H. deschauenseei in this province.

Biology.—According to Chan-ard et al. (2015), this species inhabits semi-evergreen and mixed deciduous submontane and montane forest. It is nocturnal and terrestrial and occurs in the vicinity of forest streams. Nothing else is known of the biology of this rare species.