Trachischium guentheri Boulenger, 1890

Wang, Kai, Jiang, Ke, Jin, Jieqiong, Liu, Xu & Che, Jing, 2019, Confirmation of Trachischium guentheri (Serpentes: Colubridae) from Tibet, China, with description of Tibetan T. monticola, Zootaxa 4688 (1), pp. 101-110 : 103-104

Trachischium guentheri Boulenger, 1890

( Figs. 2–4 )

Trachischium guentheri Boulenger, 1890 , Fauna of British India, Reptilia & Batrachia, London: 285. Type locality: Sikhim [= Sikkim], India .

Specimen examined. Single adult male (KIZ 012569), collected by Kai WANG, Ke JIANG, and Junxiao YANG from Zhangmu , Nyalam County, Shigatse Prefecture, Tibet, China in June 2012 .

Description. Body elongated, SVL 341 mm, cylindrical, slender; tail short, TAL 62 mm, TAL/TOL 15.4%, relatively thick, only tapering close to most posterior end; tip of tail pointed with sharp end. Head short (HL/SVL 3.1%), ovoid, indistinguishable from neck; snout rounded, extended slightly beyond lower jaw; eye rather small, pupil rounded; head scalation complete, smooth; rostral small, slightly visible from above; nasal single, somewhat rectangular shaped, with nostril located middle anteriorly; internasals 2, narrow, wider than long, in contact with loreals; prefrontals 2, large, pentagonal, nearly as broad as long, 0.5 times as long as frontal, contacting loreals, preocular, supraoculars, and frontal; supraocular singular on each side, elongated, twice longer than wide; frontal in irregular hexagon shape, about 1.3 times longer than wide; parietals 2, large, longer than wide, about 1.5 times longer than frontal; loreal 1/1, rectangular, 2 times longer than deep, in contact with nasal, internasal, prefrontals, supralabials, and preoculars; supralabials 2-2-2, first and second in contact with nasal, second and third in contact with loreal, sixth largest; preocular 1/1, narrow, 1.5 times higher than long, in contact with prefrontal but not frontal; presubocular absent; postocular 1/1, larger than preocular, 1.5 times higher than long; temporals 1+2 on each side, anterior one larger and longer; IL 6/6, first pairs in contact with each other, first four in contact with anterior chin shields. Maxillary teeth subequal, 19 on left. Dorsal body scales smooth, iridescent; dorsal scale rows 13 throughout. Ventrals 150, not angulated; cloacal divided; subcaudals 38, paired; terminal caudal scale sharp, pointeded ( Table 1 ).

Right hemipenis reaching 7 th subcaudal in situ; retractor reaching 22 th subcaudal. When everted, left hemipenis in cylindrical shape, not deeply forked, notched slightly at tip; distinct lobes or papillae absent; distinct, small backward spines present throughout, relatively larger at base, with a single spine distinctively enlarged; sulcus simple, reaching end of notched; lips prominent ( Fig. 3 ).

Coloration in life. Overall the body surfaces of the snake are iridescent. The dorsal surfaces of head, body and tail are dark brownish grey. Five distinct, black dorsolateral lines run from the neck to the anterior one fourth of the body, which then decrease to four near midbody, and eventually reduce to two distinct black lines on the tail. Ventral surfaces of head, body, and tail are mostly uniform cream white with no pattern, except a few small grey spots on the ventral surfaces of the head and tail ( Fig. 2 ).

Coloration in preservatives. The coloration in preservative closely resembles the coloration in life, except that the dorsal surfaces of head, body, and tail become dark bluish grey ( Fig. 3 ).

Natural history. The Tibetan specimen was collected on a trail under evergreen broad-leaved forest at night, as it was crossing over the trail ( Fig. 2C ). When it was picked up, it would not bite or display threat posture, but instead tried to flee while pricking with its pointed tail. It shares the same habitat with its congener, T. tenuiceps , along with other reptiles such as Ovophis monticola , Trimeresurus tibetanus , Herpetoreas platyceps , and Japalura tricarinata . The species is known to be oviparous, producing up to four eggs; and it seems to aggregate during the breeding season and lay clutches together ( Chettri et al. 2009).

Distribution. In China, this species is only known from Zhangmu, a small town at the China-Nepal border in Nyalam County, southeastern Tibet ( Fig. 1 ). It was also reported from India, Bangladesh, Bhutan and Nepal ( Chettri et al. 2009).

Suggested Chinese Name. According to the scientific and common names (Guenther’s Worm-eating Snake), we suggest the Chinese name as “Geng Shi Ni She (ṞKaeẘ)”.

Figures

FIGURE 1. Distribution of Trachischium in the East Himalaya. Circles indicate Tibetan localities of congeners, where starts indicate the type localities. Blue: T. guentheri; and T. tenuiceps (both species share the same type locality and distribution record in Tibet, China); orange: T. monticola.

FIGURE 2. Live individuals of Trachischium tenuiceps (A), T. guentheri (B), and T. monticola (C) from Tibet, China and the microhabitats of T. tenuiceps and T. guentheri in Zhangmu, Nyalam County (D) and of T. monticola in Yarang, Medog County (E). Photos: K. Wang and K. Jiang.

FIGURE 3. Comparisons of of lateral (1), dorsal (2), and ventral (3) view of head between Trachischium guentheri KIZ 012569 (A), T. tenuiceps KIZ 011134 (B), and T. monticola KIZ 016468 (C). Photos: K. Wang and K. Jiang.

FIGURE 4. Hemipenis comparison between Trachischium guentheri (A) and T. monticola (B). Photos: K. Wang and K. Jiang.