Durand's Mountain Stream Snake

description

Description of holotype. — Body stout, cylindrical; head short (3.3 % of SVL), barely distinct from the thick neck, depressed, flat anterior to eyes, dorsally covered with large shields; snout long, 31.1 % of HL or 3.2 times longer than diameter of eye, blunt, relatively subrectangular seen from above and in profile, depressed; nostrils in dorsal position and directed forwards, crescentic and very narrow, nearly reduced to the shape of a slit, strongly oblique, piercing the middle and nearly dividing the whole of nasal; eye small, its diameter about 0.7 times of the distance between eye and lip, with a vertically elliptic pupil; tail long and tapering progressively. Measurements. — SVL: 408 mm; TaL: 130 mm; TL: 538 mm; ratio TaL / TL: 0.242; HL: 13.28 mm; SnL: 4.15 mm. Dentition. — Maxillary teeth: right maxilla with 22 small but relatively thick, curved subequal teeth, without any diastema; left maxilla with 23 teeth. Body scalation. — DSR: (21) 19 – 17 – 17 scales, relatively large, imbricate scales, smooth throughout the body; DSR 1 – 2 slightly enlarged. Dorsal scale row reductions: 6 + 7 → 6 (VEN 6) (left) 4 + 3 → 3 (VEN 15) (left) 21 ————————— 19 ————————— 17 6 + 7 → 6 (VEN 6

A new species of the genus Opisthotropis Günther, 1872 from northern Laos (Squamata: Natricidae)

diagnosis

Diagnosis. — A species of the genus Opisthotropis, characterized by a combination of the following characters: (1) 21 – 19 DSR at neck and 17 DSR at midbody, all smooth; (2) nostril narrow, long and strongly oblique, dividing the whole length of the nasal; (3) internasals triangular and strongly curved, in contact with the loreal; (4) 1 prefrontal; (5) frontal wider than long; (6) loreal large, longer than high; (7) 6 / 7 supralabials, 4 th SL entering orbit on both sides; (8) 1 preocular; (9) 1 anterior and 2 posterior temporals; (10) at least 88 subcaudals; (11) about 22 / 23 subequal maxillary teeth; (12) upper dorsal surface above the 5 th dorsal scale row uniformly dark greyish-brown with bronze tints, contrasting faintly with sides more bronze-brown, with scales broadly edged posteriorly with yellowish-ochre, this pigmentation extending downwards up to the 1 st dorsal scale row; (13) venter pinkish-ochre brown; (14) head dark greyish-brown; and (15) chin, throat and 1 st preventral largely blackish-brown with scales irregularly dotted or edged with ochre yellow. A detailed comparison with the other known species of the genus Opisthotropis, especially the 10 species that have

A new species of the genus Opisthotropis Günther, 1872 from northern Laos (Squamata: Natricidae)

distribution

Distribution (Fig. 5). Laos. Louangphabang Province. Vicinity of Muang Ngoi in Muang Ngoi District, at an elevation of 370 and 700 m a. s. l. Opisthotropis durandi is known only from the type locality and its vicinity, a hilly region located in the north of Louangphabang Province. Natural history. The general biotope of the holotype is a secondary evergreen forest growing over a steep slope at the foot of a karst formation (Fig. 6). The snake was lying under a half-immersed rock at the bottom of a small waterfall in the course of a fast-running forest stream, with an average width of one meter. This stream runs across the forest just before it enters a cultivated valley. The snake was found at 11.00 h during a period of hot, sunny weather. A few water holes of various depths, some man-made, are present along the banks of the stream. These water holes are alternately or simultaneously inhabited by fish, tadpoles, and soft water shrimps and crabs, more rarely by larva of Odonata. The paratype was staying motionless, seemingly in ambush, at the beginning of the night, in the still, shallow (at most 40 cm deep) pool at the foot of Mok Waterfall (Fig. 7). The bottom of this piece of wat

A new species of the genus Opisthotropis Günther, 1872 from northern Laos (Squamata: Natricidae)

etymology

Etymology. — This species is named in honour of Mr Frédéric Durand, president of the naturalist association “ Société d’Histoire Naturelle Alcide d’Orbigny ” (Clermont-Ferrand, France), who supported our field trips and researches of the two first authors in Laos, and thus contributed to the better understanding of the herpetology of Laos. Suggested common names. Durand’s Mountain Stream Snake (English); Opisthotropis de Durand (French).

A new species of the genus Opisthotropis Günther, 1872 from northern Laos (Squamata: Natricidae)