Opisthotropis cucae, David, Patrick, Pham, Cuong The, Nguyen, Truong Quang & Ziegler, Thomas, 2011

David, Patrick, Pham, Cuong The, Nguyen, Truong Quang & Ziegler, Thomas, 2011, A new species of the genus Opisthotropis Günther, 1872 (Squamata: Natricidae) from the highlands of Kon Tum Province, Vietnam, Zootaxa 2758, pp. 43-56 : 44-52

publication ID	https://doi.org/ 10.5281/zenodo.276769
DOI	https://doi.org/10.5281/zenodo.6182678
persistent identifier	https://treatment.plazi.org/id/03D487A2-FA7A-FFBF-FF29-F9B6FBA2FC55
treatment provided by	Plazi
scientific name	Opisthotropis cucae
status	sp. nov.

Treatment

Opisthotropis cucae sp. nov.

( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Holotype. IEBR A.0924, an adult female, from Chu Mom Ray National Park, Sa Thay District, Kon Tum Province (14o 26.227' N, 107o 43.268' E), 740 m asl, Vietnam, collected by Ho Thu Cuc and Pham The Cuong on 22 May 2009.

Diagnosis. A species of the genus Opisthotropis , characterized by the combination of the following characters: (1) 23 DSR at neck and 19 DSR at midbody; (2) 7 supralabials, 5th entering orbit; (3) 1 anterior and 2 posterior temporals; (4) at least 191 ventral scales; (5) about 22 subequal upper maxillary teeth; and (6) body uniform at dorsum (i.e. not banded or striped), lighter below but without any stripe making a clear separation.

A comparison with other species of the genus Opisthotropis and of morphologically similar natricine genera of Vietnam and adjacent regions is given in the Discussion. The high number of dorsal scale rows at neck and at midbody, the high number of ventral scales, and the uniform coloration of the dorsum clearly distinguish Opisthotropis cucae sp. nov. from all other species of Opisthotropis .

Description of holotype. Body stout, cylindrical; head short (3.3 % of SVL), not distinct from the thick neck, depressed, flat anterior to eyes, dorsally covered with large shields; snout long, 30.9% of HL, 5.5 times as long as diameter of eye, blunt from above and in profile, slightly depressed; nostrils in dorsal position and oblique, crescentic and very narrow, piercing the middle of divided nasal; eye small, diameter 0.5 times the distance between its inferior margin and edge of upper lip; pupil round; tail rather short and thick but incomplete in holotype. Size. – SVL: 398 mm; TaL:> 66 mm; TL:> 464 mm; HL: 13.0 mm (from tip of snout to angles of the jaws); ratio TaL/ TL:> 0.142.

Dentition. Maxillary teeth: left upper maxilla with 24 subequal teeth or tooth sockets, without any diastema.

Body scalation. DSR: 23–19–19, all smooth, rather large. Dorsal scale row reductions:

4+5 ↔ 4 (8) (left) 3+4 ↔ 3 (19) (left) 23 ————————— 21 21 ————————— 19 3+4 ↔ 3 (11) (right) 3+4 ↔ 3 (24) (right) 191 VEN (+ 3 preventrals); 44 SC (tail incomplete), all paired. Cloacal divided.

Head scalation. Rostral pentagonal, as high as wide, well visible from above; nasals large, subrectangular, much longer than high, obliquely divided just behind nostril by a distinct furrow; 2 small, narrow internasals, triangular, strongly curved, about as long as wide, in contact with rostral, nasals, loreal on right (with upper scale divided from loreal on left, obviously an abnormality), and prefrontal; a single, broad, subrectangular prefrontal, much broader than long, in contact with both preoculars, and the loreal on right or with upper scale divided from loreal on left; frontal hexagonal, 0.9 times shorter than wide, apex directed posteriorly, 1.3 times longer than prefrontal; parietals long and wide, in contact for 1.4 times length of frontal; 1 / 1 supraocular, short but wide; 1 / 1 subrectangular loreal, large and entire at right, divided into lower main scale and upper small scale on left, both broadly in contact with internasal on each side; 1 / 1 large preocular, not reaching frontal, in broad contact with prefrontal; 2 / 2 postoculars, upper largest, lower curved; 1 small subocular only on right, so that SL 5 enters orbit only at upper tip; 7 / 7 supralabials, SL 1–5 distinctly higher than long (diagnostic characters of Opisthotropis ), SL 6–7 as long as high, SL 1 slightly directed backwards, SL 1–2 contact nasal, SL 2–3 contact loreal, SL 3 strongly bent backwards in upper part, SL 4 divided on left into main scale and small scale on upper part, SL 5 entering orbit on both sides, SL 6–7 largest; 1+1+2 / 1+1+2 temporals, anterior one long and narrow, in broad contact with SL 6–7 and parietals, posterior one long but smaller, especially on left; SL 7 followed by two enlarged scales on both sides, not bordering edge of mouth; infralabials 10 / 9, first pair in contact behind small mental, IL 1–4 in contact with anterior chin shields, IL 4 largest, much elongated; posterior chin shields much shorter than anterior ones, separated from each other by 2 + 3 scales.

Coloration. In preservative, the upper body surface is uniformly dark greyish-brown, paler on the lower part of the sides due to the presence of irregular, faint streaks of pale greyish-yellow ochre in the centre of scales of 1st and 2nd DSR, more visible in the posterior part of the body; this mingling of upper and lower surface colours gives the appearance of two faint, pale irregular lines on the posterior part of the body. The tail is entirely dark greyishbrown as the body. The head is uniformly dark greyish-brown above and on its sides, slightly darker than the body. The edges between supralabials are slightly paler.

The venter is greyish-yellow ochre, finely speckled with dark greyish-brown anteriorly, becoming progressively more speckled with the same dark dots. The under surface of the tail is strongly clouded with dark greyishbrown, with some areas paler. The chin and throat are greyish-yellow ochre, with numerous scales dark greyishbrown making the middle of the throat nearly entirely dark, irregularly edged with an ill-defined paler area on each side. Infralabials and mental are dark greyish-brown with traces of paler greyish-yellow ochre.

In life, the holotype was ochre brown above and beige, speckled with dark grey below. No well defined dark lateral stripe was visible at the separation between the dorsum and the venter.

Comparison. The comparison of Opisthotropis cucae sp. nov. with other species of the genus Opisthotropis and related genera Parahelicops and Paratapinophis is based on examined specimens listed in Appendix and on the references listed in Materials and Methods.

The following species of Opisthotropis and related genera have 19 DSR at midbody: O. alcalai Brown & Leviton, 1961 , O. balteata ( Cope, 1895) , O. boonsongi ( Taylor & Elbel, 1958) , Opisthotropis cucae sp. nov., O. kuatunensis Pope, 1928 , O. typica ( Mocquard, 1890) , and Paratapinophis praemaxillaris Angel, 1929 . Opisthotropis cucae sp. nov. differs from all of them in having 23 dorsal scale rows on the neck vs. only 19 in aforementioned species. Furthermore, O. cucae sp. nov. differs from O. alcalai in having a single prefrontal (vs. 2 in O. alcalai ), 7 supralabials (vs. 12–13), and 1 preocular (vs. 2).

Opisthotropis cucae sp. nov. differs from O. balteata by its dorsal scales entirely smooth (vs. keeled posteriorly in O. balteata ), the loreal in contact with internasal (vs. not in contact), 7 supralabials (vs. 8–10), and the uniformly grey-brown dorsal pattern (vs. dark with broad, conspicuous black crossbars with pale centres).

Opisthotropis cucae sp. nov. differs from O. boonsongi by its dorsal scales entirely smooth (vs. very strongly keeled in O. boonsongi with a broad keel), the loreal in contact with internasal (vs. not in contact), a higher number of ventrals (191 vs. 136–140), 1 anterior temporal (vs. 2), and 7 supralabials (vs. 8–9).

Opisthotropis cucae sp. nov. differs from O. kuatunensis by its dorsal scales entirely smooth (vs. distinctly keeled throughout in O. kuatunensis ), the loreal in contact with internasal (vs. not in contact), 7 supralabials (vs. 13–16), 1 preocular (vs. 2), and the uniformly grey-brown dorsal pattern (vs. black lines on uniform dark background).

Opisthotropis cucae sp. nov. differs from O. typica by its dorsal scales entirely smooth (vs. weakly keeled throughout in O. typica ), the loreal in contact with internasal (vs. not in contact), a higher number of ventrals (191 vs. 160–176), 7 supralabials (vs. 11–12), 1 preocular (vs. 2), and the uniformly grey-brown dorsal pattern (vs. blackish-brown).

Lastly, Opisthotropis cucae sp. nov. differs from Paratapinophis praemaxillaris by its loreal in contact with internasal (vs. not in contact in P. praemaxillaris ), a higher number of ventrals (191 vs. 145–155), 7 supralabials (vs. 9), 1 preocular (vs. 2), and the uniformly grey-brown dorsal pattern (vs. made of narrow faint dark crossbands or large blotches).

All other species of the group of Opisthotropis have 15 or 17 DSR at midbody, i.e. O. andersonii ( Boulenger, 1888) , O. atra Günther, 1872 , O. cheni Zhao, 1999 , O. daovantieni Orlov, Darevsky & Murphy, 1998 , O. guangxiensis Zhao, Jiang & Huang, 1978 , O. jacobi Angel & Bourret, 1933 , O. kikuzatoi Okada & Takara, 1958 , O. lateralis Boulenger, 1903 , O. latouchii ( Boulenger, 1899) , O. maculosa Stuart & Chuaynkern, 2007 , O. maxwelli Boulenger, 1914 , O. rugosa (Lidth de Jeude, 1890), O. spenceri Smith, 1918 , and O. tamdaoensis Ziegler, David & Vu, 2008 . Parahelicops annamensis Bourret, 1934 also has either 15 or 17 DSR at midbody. Main additional differences between these species are detailed below and summarized in Table 1.

Opisthotropis cucae sp. nov. differs from O. andersonii by its entirely smooth dorsal scales (vs. keeled throughout in O. andersonii ), a higher number of ventrals (191 vs. 149–169), 7 supralabials (vs. 8–9), 1 preocular (vs. 1 or 2), and the uniformly grey-brown dorsal pattern (vs. uniformly dark with pale-edged scales).

Opisthotropis cucae sp. nov. differs from O. cheni by the loreal in contact with internasal (vs. not in contact), a higher number of ventrals (191 vs. 159–167), 7 supralabials (vs. 8–9), 1 preocular (vs. 2), and the uniformly greybrown dorsal pattern (vs. dark with yellow crossbars).

Opisthotropis cucae sp. nov. differs from O. guangxiensis by the loreal in contact with internasal (vs. not in contact), a higher number of ventrals (191 vs. 166–174), 7 supralabials (vs. 9), 1 preocular (vs. 2), and the uniformly grey-brown dorsal pattern (vs. dark with pale crossbars).

Opisthotropis cucae sp. nov. differs from O. jacobi by a higher number of ventrals (191 vs. 155–179) and 7 supralabials (vs. 8–9).

Opisthotropis cucae sp. nov. differs from O. kikuzatoi by its entirely smooth dorsal scales (vs. posteriorly keeled in O. kikuzatoi ), the loreal in contact with internasal (vs. not in contact), 1 anterior temporal (vs. 2), 7 supralabials (vs. 6), 1 preocular (vs. 2), and the uniformly grey-brown dorsal pattern (vs. dark with dorsolateral orange spots).

Opisthotropis cucae sp. nov. differs from O. lateralis by its dorsal scales entirely smooth (vs. keeled throughout in O. lateralis ), the loreal in contact with internasal (vs. not in contact), a higher number of ventrals (191 vs. 159–173), 7 supralabials (vs. 9–11), 1 preocular (vs. 2), and the uniformly grey-brown dorsal pattern (vs. dark with a conspicuous black lateral stripe).

Opisthotropis cucae sp. nov. differs from O. latouchii by its entirely smooth dorsal scales (vs. keeled throughout in O. latouchii ), the loreal in contact with internasal (vs. not in contact), a higher number of ventrals (191 vs. 140–168), 7 supralabials (vs. 9), 1 preocular (absent in O. latouchii ), and the uniformly grey-brown dorsal pattern (vs. dark with broad yellow and narrow black lateral stripes).

Opisthotropis cucae sp. nov. differs from O. maculosa by its loreal in contact with internasal (vs. not in contact in O. maculosa ), a higher number of ventrals (191 vs. 182), 7 supralabials (vs. 8), and especially the uniformly grey-brown dorsal pattern (vs. yellow dots on a dark background).

Opisthotropis cucae sp. nov. differs from O. maxwelli by its entirely smooth dorsal scales (vs. posteriorly keeled in O. maxwelli ), the loreal in contact with internasal (vs. not in contact), a higher number of ventrals (191 vs. 147–155), and 1 preocular (vs. 2).

Opisthotropis cucae sp. nov. differs from O. rugosa by its entirely smooth dorsal scales (vs. strongly keeled throughout in O. rugosa ), 1 prefrontal (vs. 1 or 2), a higher number of ventrals (191 vs. 170–174), and 7 supralabials (vs. 12–13).

Opisthotropis cucae sp. nov. differs from O. tamdaoensis by its entirely smooth dorsal scales (vs. posteriorly keeled in O. tamdaoensis ), the loreal in contact with internasal (vs. not in contact), a higher number of ventrals (191 vs. 171), 1 anterior temporal (vs. 2), and 7 supralabials (vs. 8–9).

Lastly, Opisthotropis cucae sp. nov. differs from Parahelicops annamensis by its entirely smooth dorsal scales (vs. keeled throughout in P. annamensis and especially strongly keeled on the posterior part of the body and the tail), 1 prefrontal (vs. often 2), a higher number of ventrals (191 vs. 163–172), 7 supralabials (vs. 8–9), 1 preocular (vs. 2), and the uniformly grey-brown dorsal pattern (vs. dark with orange bars and spots).

Morphologically, O. cucae sp. nov. is particularly similar to O. atra , O. daovantieni , and O. spenceri . The sole main difference bears on the number of dorsal scale rows at midbody, 19 rows in O. cucae sp. nov. vs. 17 rows in both other species. Opisthotropis cucae sp. nov. differs from O. atra by its dorsal scales entirely smooth (vs. strongly keeled posteriorly in O. atra ) and a higher number of ventrals (191 in the holotype vs. 170).

Opisthotropis spenceri , a species endemic to northern Thailand, differs little from O. cucae sp. nov. except for the number of dorsal scale rows at midbody (see Table 1). Its dorsal surface is more grey and darker than in O. cucae sp. nov.

Lastly, O. daovantieni (type locality: Buoenloy [now Buon Luoi], An Khe District, Gia Lai Province, Vietnam) shares most characters with O. cucae sp. nov., including the uniform dorsal pattern with the first three scale rows mingled with colour of the venter. However, O. daovantieni (holotype, male, and ZISP 26073, male) has 17–17–17 DSR vs. 23–19–19 rows in O. cucae sp. nov. (holotype, female). Given that the number of dorsal rows is conservative in the genus Opisthotropis and not sex-related, we consider this difference of taxonomic significance.

Etymology. This species is named in honour of Mrs HO Thu Cuc (Institute of Ecology and Biological Resources, Hanoi), for having collected the holotype of this new species and especially for her long lasting contribution to the better understanding of the herpetology of Vietnam.

Suggested common names. Cuc’s Mountain Snake (English) and Rắn trán cúc (Vietnamese).

Distribution. Opisthotropis cucae sp. nov. is known only from the type locality in Kon Tum Plateau, Kon Tum Province, southern Central Vietnam ( Fig. 4 View FIGURE 4 ). Kon Tum Plateau is a mountainous region on the eastern fringe of the Truong Son Range (previously known as the Annamite Range). The plateau is a part of the Central Highlands of Vietnam, straddling northern Kon Tum and southern Quang Nam provinces. Mt Ngoc Linh, the highest point of Kon Tum Plateau, reaches 2,598 m asl. ( Tordoff et al. 2000; Sterling et al. 2006).

Natural history. The holotype was found in the secondary evergreen forest at an elevation of 740 m asl. The snake was collected at night (21:30) under the water in a rocky stream ( Fig. 5 View FIGURE 5 ).