Opisthotropis haihaensis, Ziegler & Pham & Nguyen & Nguyen & Wang & Wang & Stuart & Le, 2019

Ziegler, Thomas, Pham, Cuong The, Nguyen, Tan Van, Nguyen, Truong Quang, Wang, Jian, Wang, Ying-Yong, Stuart, Bryan L. & Le, Minh Duc, 2019, A new species of Opisthotropis from northern Vietnam previously misidentified as the Yellow-spotted Mountain Stream Keelback O. maculosa Stuart & Chuaynkern, 2007 (Squamata: Natricidae), Zootaxa 4613 (3), pp. 579-586 : 579-586

Opisthotropis haihaensis sp. nov.

Opisthotropis maculosa Nguyen, Nguyen, Pham & Ziegler 2018: 74 .

Holotype. IEBR A.2016.34 [Field No. QN 2016.91], adult female, from the forest near Tai Chi Village , Quang Son Commune, Hai Ha District, Quang Ninh Province, 950 m asl., Vietnam [exact locality and coordinates not provided owing to threat from collection for the pet trade (below)], collected by Cuong The Pham and Tan Van Nguyen on 9 May 2016 ( Figs. 2–3 ).

Diagnosis. A species of the genus Opisthotropis characterized by having the following combination of characters: (1) internasal not in contact with loreal; (2) prefrontal not touching supraocular; (3) frontal touching preocular; (4) one preocular; (5) one postocular; (6) one anterior temporal; (7) one posterior temporal; (8) supralabials eight, fourth and fifth in contact with eye; (9) 24 maxillary teeth; (10) anterior pair of chin shields longer than posterior pair; (11) ventrals 169 (+ 2 preventrals); (12) subcaudals 79; (13) 15 dorsal scale rows at neck, at midbody and before vent; (14) body and tail scales smooth; (15) chin shields yellow with brownish black mottling; (16) body and tail dorsum dark with each a light spot per scale.

Description of the holotype. Body slender, round to oval in cross section; tail thin, pointed; head small, indistinct from neck, depressed, dorsally covered with large shields; nostrils in dorsal position and oblique, narrow, piercing the upper middle of nasal, which is divided beneath; eye small, pupil round.

Size. HL: 13.7 mm; SVL: 396 mm; TaL: 113 mm; TL: 509 mm; ratio TaL/TL: 0.22.

Dentition. Maxillary teeth: right upper maxilla with 24 subequal teeth or sockets, teeth small, curved, without diastema.

Body scalation. Dorsal scale rows 15–15–15, entirely smooth. Outer dorsal scales enlarged. All scales glossy.

169 ventrals (+ 2 preventrals); 79 subcaudals, all paired; cloacal divided.

Head scalation. Rostral heptagonal, wider than high, visible from above; nasals large, much longer than high, weakly divided below nostril by a distinct furrow; nasals surrounded by the first two supralabials, rostral, internasal, prefrontal and loreal; internasals two, strongly curved, longer than wide, in contact with rostral anteriorly, nasal, and prefrontal; prefrontal single, heptagonal, anteriorly pointed, about twice as wide as long, in contact with internasals, nasals, loreals, preoculars, and frontal; frontal pentagonal, 1.26 times wider than long, tapering posteriorly, equal to its distance from tip of snout; parietals longer than wide, in contact approximately equal to the length of frontal, 1.88 times longer than frontal; 1 / 1 supraocular, distinctly wider than high, not in contact with prefrontal; 1 / 1 loreal, pentagonal, wider than high, neither in contact with internasal nor eye, surrounded by second and third supralabials, nasal, prefrontal and preocular; 1 / 1 preocular, large, hexagonal, higher than wide, reaching frontal, in broad contact with prefrontal; subocular absent; 1 / 1 postocular, curved, higher than wide; 8 / 8 supralabials, anterior ones higher than wide, fourth and fifth entering orbit, seventh largest; 1+1 / 1+1 temporals, anterior one very long and narrow, in broad contact with SL 5–7 and parietals, posterior one more strongly developed; infralabials 8 / 8, first pair in contact behind small mental, 1–4 / 1–5 in contact with anterior chin shields, IL 5 largest, apex directed posteriorly; posterior chin shields shorter than anterior ones, separated from each other by a pair of small scales.

Coloration (in preservative). Ground colour of upper head and body surface dark brown, that of venter yellowish-beige. Dorsal scales with light blotch in the centre each. From behind the neck, the dorsal blotches become more elongated. The blotches become wider towards the body sides; they are largest at the outermost dorsal scale row, where the light blotches stretch towards the posterior scale end. Dorsal tail scales likewise with light central blotches. Dorsal head surface in part with indistinct light mottling that becomes more obvious on temporals. Anterior supralabials with light mottling, supralabials 4–7 with distinct light blotch each. Infralabials, chin shields and smaller throat scales anterior to ventrals brown with light mottling / blotches per scale. The belly with few, scattered dark flecks. Outermost edges of light ventrals brown. Ground colour of subcaudals brown with transversally enlarged light blotches at each scale end.

Coloration (in life). Eye black; scales on dorsal surface of head glossy black with scattered yellow flecking; chin shields yellow with brownish black mottling; body and tail glossy black with iridescence above, with single yellow spot on each scale, yellow spots becoming larger on sides of body; ventrals yellow with brownish black lateral margins and scattered brown flecks; subcaudals yellow with brownish black anterior and lateral margins.

Comparisons. Only six other species of Opisthotropis and the related genus Hebius have 15 midbody dorsal scale rows (see review in Ziegler et al. 2018): O. maculosa , O. jacobi Angel & Bourret , O. voquyi , O. guangxiensis Zhao, Jiang & Huang , O. kikuzatoi (Okada & Takara) , and H. annamensis Bourret (which may have 15 or 17 midbody dorsal scale rows).

Opisthotropis haihaensis sp. nov. differs from O. maculosa sensu stricto (adult male holotype from northeastern Thailand, see Stuart & Chuaynkern 2007), with which the species was confused in the previous study ( Nguyen et al. 2018), by having prefrontal not touching supraocular (versus prefrontal touching supraocular in O. maculosa ); frontal touching preocular (versus frontal not touching preocular in O. maculosa ); one postocular (versus two post- oculars in O. maculosa ); fourth and fifth supralabials in contact with eye (versus fourth supralabial in contact with eye in O. maculosa ); anterior pair of chin shields longer than posterior pair (versus vice versa in O. maculosa ); lower number of ventrals (169 + 2 preventrals versus 182 + 2 preventrals in O. maculosa ); higher number of subcaudals (79 versus 67 in O. maculosa ); and chin shields yellow with brownish black mottling (versus yellow in O. maculosa ).

Opisthotropis haihaensis sp. nov. differs from O. jacobi by having 24 maxillary teeth (versus 19–23 in O. jacobi ); smooth dorsal scales on tail, without keels (versus few faint keels usually present in O. jacobi ); body and tail dorsum dark with a light spot per scale (versus dorsum uniformly dark in O. jacobi ).

Opisthotropis haihaensis sp. nov. differs from O. voquyi by having one postocular (versus two in O. voquyi ); body and tail dorsum dark with each a light spot per scale (versus dorsal pattern dark, with dorsal scales posteriorly more or less edged with pale brown in O. voquyi ).

Opisthotropis haihaensis sp. nov. differs from O. guangxiensis by having eight supralabials (versus 9–10 in O. guangxiensis ); one postocular (versus two in O. guangxiensis ); one posterior temporal in the new species (versus two in O. guangxiensis ); 15 dorsal scale rows at neck in the new species (versus 17 in O. guangxiensis ); 79 subcaudals (versus 51–60 in O. guangxiensis ); body and tail dorsum dark with a light spot per scale (versus dorsal colour pattern dark with pale crossbars in O. guangxiensis ).

Opisthotropis haihaensis sp. nov. differs from O. kikuzatoi by having eight supralabials (versus six in O. kikuzatoi ); one preocular (versus two in O. kikuzatoi ); 169 ventrals and 79 subcaudals (versus 180–198 ventrals and 58–73 subcaudals in O. kikuzatoi ); body and tail dorsum dark with a light spot per scale (versus dorsal colour pattern dark with dorsolateral orange spots in O. kikuzatoi ).

Opisthotropis haihaensis sp. nov. differs from H. annamensis by having one preocular (versus two in H. annamensis ); 15 dorsal scale rows at neck (versus 17–19 in H. annamensis ); body scales smooth (versus keeled throughout in H. annamensis ); 79 subcaudals (versus 116–146 in H. annamensis ); body and tail dorsum dark with a light spot per scale (versus dorsum dark with orange bars and spots in H. annamensis ).

Etymology. This species is named after its type locality in Hai Ha District, Quang Ninh Province, Vietnam.

Suggested common names. Hai Ha Mountain Stream Keelback (English) and Rắn trán hải hà (Vietnamese).

Distribution. Opisthotropis haihaensis is currently known only from the type locality in Quang Ninh Province, Vietnam (see Nguyen et al., 2018).

Natural history. The adult female holotype was found at night in a small rocky stream at 2130h. The surrounding habitat was secondary evergreen forest consisting of small hardwood trees, bamboo, and shrubs (see Nguyen et al., 2018). The air temperature was 24–29 ° C and the relative humidity was 65–88%. Dissection revealed that the holotype contained three large eggs having maximum length of 16.5 mm, with folded oviducts indicating that some eggs had already been laid.

Figures

FIGURE 2. Holotype of Opisthotropis haihaensis sp. nov. (IEBR A.2016.34) in preserved state.

FIGURE 3. Head views of the holotype of Opisthotropis haihaensis sp. nov. (IEBR A.2016.34) in preserved state.