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476
Accepted by Z. Nagy: 22 Nov. 2017; published: 22 Jan. 2018
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN
1175-5334
(online edition)
Copyright © 2018 Magnolia Press
Zootaxa 4374 (4): 476
–
496
http://www.mapress.com/j/zt/
Article
https://doi.org/10.11646/zootaxa.4374.4.2
http://zoobank.org/urn:lsid:zoobank.org:pub:3B7D44F9-45E7-46BA-BE29-AA568199B205
Morphological and molecular review of Jacob’s Mountain Stream
Keelback Opisthotropis jacobi Angel & Bourret, 1933 (Squamata: Natricidae)
with description of a sibling species from northern Vietnam
THOMAS ZIEGLER
1,2,9
, PATRICK DAVID
3
, TIM N. ZIEGLER
1
, CUONG T. PHAM
4,5
,
TRUONG Q. NGUYEN
4,5
& MINH D. LE
6,7,8
1
AG Zoologischer Garten Köln, Riehler Strasse 173, D–50735 Cologne, Germany. E–mail: ziegler@koelnerzoo.de
2
Institute of Zoology, University of Cologne, Zülpicher Strasse 47b, D–50674 Cologne, Germany
3
Muséum national d’Histoire naturelle, ISyEB (Institut de Systématique, Évolution et Biodiversité). UMR 7205 (CNRS, EPHE, MNHN,
UPMC), CP 30 (Reptiles), 57, rue Cuvier, 75005 Paris, France. E–mail: pdavid95@wanadoo.fr
4
Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi,
Vietnam. E–mail: nqt2@yahoo.com, cuongiebr@gmail.com
5
Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay,
Hanoi, Vietnam
6
Faculty of Environmental Sciences, Hanoi University of Science, Vietnam National University, 334 Nguyen Trai Road, Hanoi, Viet-
nam. E-mail: le.duc.minh@hus.edu.vn
7
Central Institute for Natural Resources and Environmental Studies, Hanoi National University, 19 Le Thanh Tong, Hanoi, Vietnam
8
Department of Herpetology, American Museum of Natural History, Central Park West at 79
th
Street, New York, New York 10024
9
Corresponding author. E-mail: ziegler@koelnerzoo.de
Abstract
New morphological data including hemipenis morphology is provided for Opisthotropis jacobi, a poorly known Mountain
Stream Keelback from Vietnam and China, based on three newly collected individuals from Sa Pa (Lao Cai Province) and
Tam Dao (Vinh Phuc Province) in northern Vietnam. In addition, morphological data from Vietnam is summarized based
on the original description (Angel & Bourret 1933), on the overview book by Bourret (1936) and on a number of smaller,
little-known contributions by the latter author along with re-examination of specimens deposited in the herpetological col-
lection of the Muséum national d’Histoire naturelle, Paris. We also sequenced a fragment of the mitochondrial cytochrome
b from the newly collected specimens of the Jacob’s Mountain Stream Keelback and performed molecular analyses of new
and existing data of the genus. A recently discovered Opisthotropis population from Tay Yen Tu Nature Reserve in Bac
Giang Province, northern Vietnam, which at the first glance resembled O. jacobi morphologically, is shown to diverge
both genetically and morphologically from the existing species and is herein described as a new species. Opisthotropis
voquyi sp. nov. is characterized by the combination of the following characters: internasal not in contact with loreal; one
preocular; usually two postoculars; one anterior temporal; one posterior temporal; 7 or 8, rarely 9 supralabials; 25 maxil-
lary teeth; subcaudals 74–86; 15 dorsal scale rows at neck, at midbody and before vent; body scales smooth or only with
few faint keels; and dorsal scales being greyish, greyish-brown or brown in preservative, posteriorly more or less edged
with pale greyish-brown. Phylogenetically, the new species is supported as a sister taxon to O. jacobi, but the two taxa are
approximately 10% divergent based on cytochrome b data.
Key words: Natricidae, Opisthotropis jacobi, Opisthotropis voquyi sp. nov., morphology, phylogeny, taxonomy
Introduction
Members of the genus Opisthotropis are aquatic snakes which inhabit flowing streams of hills and mountains of
tropical and subtropical Asia. Mountain stream keelbacks are distributed across the mainland of Southeast Asia to
Sumatra (Indonesia), the Philippines and the Ryukyu Archipelago of Japan. This genus currently comprises 22
species, and is still imperfectly understood (Teynié et al. 2013, Wang et al. 2017). Up to six Opisthotropis species
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A NEW SIBL ING SPECIES OF OPISTHOTROPIS JAC OBI
have been discovered only in the past decade: O. laui Yang, Sung & Chan and O. shenzhenensis Wang, Guo, Liu,
Lyu, Wang, Luo, Sun & Zhang from China, O. maculosa from Thailand, Vietnam and China, O. durandi Teynié,
Lottier, David, Nguyen & Vogel from Laos, and O. cucae David, Pham, Nguyen & Ziegler and O. tamdaoensis
Ziegler, David & Vu from Vietnam (Stuart & Chuaynkern 2007, Ziegler et al. 2008, David et al. 2011, Teynié et al.
2013, Yang et al. 2013, Nguyen et al. in press, Wang et al. 2017). Eight species of Mountain Stream Keelbacks
have been recorded so far from Vietnam (David et al. 2011, Nguyen et al. in press), most of them are uncommon or
at least rarely collected and thus poorly known. Opisthotropis jacobi Angel & Bourret, 1933 was described more
than 80 years ago based on two individuals only from “Chapa”, nowadays known as Sa Pa, Lao Cai Province,
northern Vietnam. The species is reported from only few provinces in northern Vietnam (Nguyen et al. 2009): Lao
Cai (Sa Pa), Tuyen Quang (Sinh Long), Cao Bang (Nguyen Binh), Bac Kan (Ngan Son, Cho Don), Lang Son (Mau
Son), and Vinh Phuc (Tam Dao); recently, the species was also recorded from southern Yunnan Province in China
(Yang et al. 1980, see also Zhao & Adler 1993, Zhao 2006). The Sapa Mountain Stream Keelback, also known as
the Jacob’s Mountain Stream Keelback, is only found in streams in moderate to high mountain forests (700–1500
m) (Orlov et al. 2000, Nguyen et al. 2009). During recent field work in northern Vietnam, new records of this
poorly known species were discovered. We herein provide new morphological data including hemipenis
morphology based on three newly collected individuals from Sa Pa and Tam Dao, together with morphological data
published in the original description by Angel & Bourret (1933), in the overview book by Bourret (1936) and in a
number of smaller, little-known contributions by Bourret (1934a, 1934b, 1935a, 1935b, 1935c, 1937, 1939) and
based on re-examination of specimens deposited in the herpetological collection of the Muséum national d’Histoire
naturelle, Paris. In addition, during recent herpetological surveys, we discovered a new population of Opisthotropis
from the Tay Yen Tu Nature Reserve in Bac Giang Province, northern Vietnam, which resembled O. jacobi
morphologically. To clarify its taxonomy using an integrative approach, we sequenced a fragment of the
mitochondrial cytochrome b from the newly collected samples and analyzed all available molecular data of the
genus as well as carefully examined the morphology of available specimens. The newly discovered population
from Tay Yen Tu Nature Reserve was found to differ both morphologically and genetically from O. jacobi. We,
therefore, describe this taxon as a new species in the following.
Material and methods
Sampling. This study is based on three newly collected Opisthotropis jacobi from Sa Pa, Lao Cai Province (IEBR
2910, coll. S. Ryabov et al. in 2006) and from Tam Dao National Park, Vinh Phuc Province (ZFMK 100818 [Field
No. TD 2014.7], collected by Cuong The Pham et al. on 1st June 2014; IEBR 4329 [Field No. VP 2014.2],
collected by Cuong The Pham on 31 May 2014 and seven newly collected Opisthotropis from Tay Yen Tu Nature
Reserve, Bac Giang Province (collected by Cuong The Pham et al. in June 2013, May 2014, and May 2015). Tissue
samples were preserved separately in 95% ethanol and voucher specimens were euthanized in a closed vessel with
a piece of cotton wool containing ethyl acetate (Simmons 2002), fixed in 85% ethanol and subsequently stored in
70% ethanol. Individuals were subsequently deposited in the following zoological collections: IEBR - Institute of
Ecology and Biological Resources, Vietnamese Academy of Science and Technology, Hanoi, Vietnam; VNMN -
Vietnam National Museum of Nature, Hanoi, Vietnam; ZFMK - Zoologisches Forschungsmuseum Alexander
Koenig, Bonn, Germany. In addition, specimens of O. jacobi from the MNHN - Muséum national d’Histoire
naturelle, Paris, France, were also included in this study.
Morphological examination. Identification of sex was performed by dissection (inspection of gonads and
inspection of presence of hemipenes). Measurements were taken after preservation with a measuring tape. The
number of ventral scales was counted according to Dowling (1951). The numbers of dorsal scale rows are given at
one head length behind head, at midbody, and at one head length before vent, respectively. Maxillary teeth were
counted by dissecting the right maxilla for teeth / sockets, except where otherwise stated. Scalation and maxillary
teeth number were studied by using a binocular dissecting microscope. We herein use the term precloacal instead of
anal. Bilateral values were given as left / right.
Abbreviations of morphological characters used in the text are as follows:—Measures and ratios: SVL: snout-
vent length.—TaL: tail length.—TL: total length (SVL + TaL).—TaL/TL: ratio tail length/total length.—Meristic
characters: ATem: anterior temporal scales (in contact with postocular scale / scales).—BodySc: body scales.—
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InN/Lor: Internasal and loreal in contact.—DSR: dorsal scale rows.—IL: infralabial scales.—Lor: loreal scales.—
PreOc: preocular scales.—PreVen: preventral scales.—PostOc: postocular scales.—PTem: posterior temporal
scales (in contact with anterior temporal scale / scales).—SL: supralabial scales.—SL/orbit: supralabial scale /
scales touching the orbit.—Subc: subcaudal scales (without tail tip).—SubOc: subocular scales.—TailSc: tail
scales.– Ven: ventral scales.
Molecular analyses. The mitochondrial cytochrome b gene was employed in this study, because it has been
successfully used in previous molecular analyses of Natricidae (e.g., Guo et al. 2012, Wang et al. 2017). We
included seven new sequences of samples collected from Tay Yen Tu Nature Reserve, Bac Giang Province, and
from Tam Dao, Vinh Phuc Province. Other sequences of related species were obtained directly from authors of
Wang et al. (2017) and Ziegler et al. (2017), or GenBank. Three species, Sinonatrix aequifasciata (Barbour), S.
annularis (Hallowell), and S. percarinata (Boulenger) were used as outgroups (see Guo et al. 2012).
We used the protocols of Le et al. (2006) for DNA extraction, amplification, and sequencing. A fragment of the
mitochondrial cytochrome b was amplified using the primer pair L14910/H16064 (Burbrink et al. 2000). After
sequences were aligned by Clustal X v2 (Thompson et al. 1997), data were analyzed using maximum parsimony
(MP) and combined (single model of molecular evolution) maximum likelihood (ML) as implemented in
PAUP*4.0b10 (Swofford 2001) and Bayesian combined partitioned analysis (BA) as implemented in MrBayes
v3.2 (Ronquist et al. 2012). Settings for MP, combined ML, and Bayesian analyses followed Le et al. (2006),
except that the number of generations in the Bayesian analysis was increased to 1×10
7
. For MP analysis, heuristic
analysis was conducted with 100 random taxon addition replicates using tree-bisection and reconnection (TBR)
branch swapping algorithm, with no upper limit set for the maximum number of trees saved. Bootstrap support was
calculated using 1000 pseudo-replicates and 100 random taxon addition replicates. All characters were equally
weighted and unordered. The optimal model for nucleotide evolution was set to TrN+I+G for combined ML and
Bayesian analyses as selected by ModelTest v3.7 (Posada & Crandall 1998). The cutoff point for the burn-in
function was set to 10 in the Bayesian analysis, as –lnL scores reached stationarity after 10,000 generations in both
runs. Nodal support was evaluated using Bootstrap replication (BP) as estimated in PAUP and posterior probability
(PP) in MrBayes v3.2. BP ≥ 70% and PP ≥ 95% are regarded as strong support for a clade. Uncorrected pairwise
divergences (p-distance) were calculated in PAUP*4.0b10.
Results
The newly collected snakes are thought to be closely related to known Opisthotropis because they possess the
following morphological characters (e.g., David et al. 2011, Teynié et al. 2013): head depressed, indistinct from
neck; body rather stout; eye moderate or small, with a rounded or vertically elliptical pupil; nostril in the nasal,
placed in dorsal position on the snout, directed upwards and outwards; prefrontal very broad, usually single,
forming a long suture with the frontal; scales smooth or keeled, without apical pits, usually in 15 to 19 dorsal rows
at midbody; precloacal scale divided; subcaudals paired; and upper maxillary teeth 20–40, small, subequal.
The three newly collected Opisthotropis from Sa Pa and Tam Dao (Figs. 1–3) matched the original description
of O. jacobi by Angel & Bourret (1933) except that the tail dorsum may bear few faint keels. We also found a
mismatch regarding the maxillary teeth count, which was given as 20 for O. jacobi in the original description (Angel
& Bourret 1933) and as 29 in the overview work by Bourret (1936). In combination with the maxillary teeth counts
taken in this study for O. jacobi (19–23, see Table 1), this points to a transcription error in Bourret (1936), in which
29 was given instead the value 20 from the original description. While applying the identification key provided in
David et al. (2011) it became obvious that the condition of the internasal being in contact with the loreal as given on
their page 52 does not apply for O. jacobi; this mistake was later corrected in Teynié et al. (2013).
In Table 1 we have summarized morphological data of the newly recorded O. jacobi from Sa Pa and Tam Dao
together with O. jacobi deposited in the Muséum national d’Histoire naturelle, Paris, which were re-examined by
us. In Table 2 we have summarized available data on the morphology of Vietnamese O. jacobi from the literature;
some of these individuals might be identical with specimens deposited in the Muséum national d’Histoire naturelle,
Paris (see Table 1).
In the male individuals IEBR 2910 and ZFMK 100818, the hemipenes were everted: in IEBR 2910 only in
part, in ZFMK 100818 the left hemipenis was nearly fully everted, ending in two short, inwards curved lobes (Fig.
1D). The sulcus spermaticus is undivided, stretching to the slightly smaller lobe only. Hemipenes covered with
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small spines, curved backwards. Only the terminal area of the hemipenes between the lobes without spines. Upper
truncus of hemipenes with ring of enlarged spines. Largest spines stretching from next to the sulcus spermaticus to
hemipenis sides, with the lowermost one being the most distinct. Proximal truncus of hemipenes with tiny spines.
The newly collected Opisthotropis jacobi were found at 19:00–22:00 h along small rocky streams. The snakes
were found on rocks close to the water (Fig. 4). The surrounding habitat was secondary evergreen forest of big,
medium, and small hardwoods. The air temperature was 19.5–25.1
o
C and the relative humidity was 75–90%.
FIGURE 1. Head portraits of the new collection of Opisthotrophis jacobi from A, B) Tam Dao and C, D) Sa Pa: A) ZFMK
100818, B) IEBR 4329, C) IEBR 2910, and everted hemipenes D) of IEBR 2910. Photos: T. Ziegler.
FIGURE 2. Drawing of the head of Opisthotrophis jacobi (ZFMK 100818) from Tam Dao, Vinh Phuc Province. Drawing: T.
Ziegler.
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FIGURE 3. The new collection of Opisthotrophis jacobi in A) dorsal and B) ventral view. From left to right: IEBR 4329,
ZFMK 100818 from Tam Dao, Vinh Phuc Province, and IEBR 2910 from Sa Pa, Lao Cai Province. Photos: T. Ziegler.
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A NEW SIBL ING SPECIES OF OPISTHOTROPIS JAC OBI
FIGURE 4. Habitat of Opisthotrophis jacobi in Tam Dao, Vinh Phuc Province. Photo: C. T. Pham.
Specimens of Opisthotrophis which were superficially similar to O. jacobi and which were collected at the Tay
Yen Tu Nature Reserve in Bac Giang Province proved to be genetically distinct. In the molecular analyses, the final
matrix consisted of 1,100 aligned characters, of which 420 were parsimony informative. The alignment did not
contain gaps. The MP analysis recovered a single most parsimonious tree with 1,405 steps (CI = 0.47; RI = 0.73).
In the ML analysis, the score of the single best tree found was 7,383.68 after 10016 arrangements were tried. Most
ingroup nodes received strong statistical support from all analyses. Topology of the phylogeny is almost identical
to those presented in Wang et al. (2017) and Ziegler et al. (2017). Opisthotropis jacobi was supported as a sister
taxon of the population from Tay Yen Tu Nature Reserve with high statistical values from all analyses (Fig. 5).
Genetically, the two forms were approximately 10% divergent from each other based on the cytochrome b
fragment. Subsequent morphological comparisons also revealed distinct differences in scalation and dentition
between previously known Opisthotropis jacobi and the population from Tay Yen Tu. Thus, the latter
Opisthotrophis population is described as a new species in the following:
Opisthotropis voquyi sp. nov.
Holotype. IEBR 4326 [Field No. TYT.2013.4], an adult male, from Tay Yen Tu Nature Reserve, Bac Giang
Province, 437 m asl., Vietnam, collected by Cuong The Pham et al. on 14 June 2013 (Figs. 6–8).
Paratypes. VNMN 06315 [Field No. TYT 2013.1], male, collected by Cuong The Pham et al. in June 2013;
VNMN 06316 [Field No. BG 2015.13], female, collected by Cuong The Pham et al. on 17 May 2015; IEBR 4327
[Field No. BG 2015.33], female, collected by Cuong The Pham et al. on 22 May 2015; IEBR 4328 [Field No. BG
2015.34], female, collected by Cuong The Pham et al. on 22 May 2015; ZFMK 100819 [Field No. BG 2015.35],
female, collected by Cuong The Pham et al. on 22 May 2015; ZFMK 100820 [Field No. TYT 2014.11], female,
collected by Hang An Thi in May 2014, all paratypes same locality data as the holotype (Figs. 8–10).
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TABLE 1. Sex, morphometry and scalation of examined representatives of Opisthotropis jacobi from Vietnam; values given in brackets indicate infrequent condition. * counted on left side (because
right side was broken); ** counted on right side: *** counted without dissection
MNHN
1938.0126
MNHN
1938.0127
IEBR
2910
ZFMK
100818
Range
(males)
MNHN
1933.0010
MNHN
1935.0083
MNHN
1938.0457
IEBR
4329
Range
(females)
Range
(total)
Sex male male male male female female female female
TL 437 549 423 442 max. 549 480 431 – 519 max.
519
max. 549
SVL 325 405 320 325 max. 405 383 347 269 410 max.
410
max. 410
TaL 112 144 103 117 max. 144 97 84 – 109 max.
109
max. 144
TaL/TL 0.256 0.262 0.243 0.265 0.243–0.265 0.202 0.195 – 0.210 0.195–0.210 0.195–0.265
Teeth max – – 19* 23** 19–23 – – – 21*** 21 19–23
SL 7/7 7/7 7/7 8/8 7(8) 7/7 7/7 7/7 8/7 7(8) 7(8)
SL/orbit 4–5/4–5 4–5/4–5 4–5/4–5 5/4–5 4–5(5) 4–5/4–5 4–5/5 4–5/4–5 4–5/4–5 4–5(5) 4–5(5)
IL 7/7 8/8 7/7 9/9 7(8,9) 8/8 7/9 8/8 9/8 8(7,9) 7–8(9)
PreOc 1/1 1/1 1/1 1/1 1 1/1 1/1 1/1 1/1 1 1
PostOc 1/1 1/1 1/1 1/1 1 1/1 1/1 1/1 1/1 1 1
Lor 1/1 1/1 1/1 1/1 1 1/1 1/1 1/1 1/1 1 1
InN/Lor no no no no no no no no no no no
Atem 1/1 1/1 1/1 1/1 1 1/1 1/1 1/1 1/1 1 1
PTem 2/2 1/1 1/1 1/1 1(2) 1/1 1/1 1/1 1/1 1 1(2)
DSR 15–15–15 15–15–15 15–15–15 15–15–15 15–15–15 15–15–15 15–15–15 15–15–15 15–15–15 15–15–15 15–15–15
PreVen 1 0 1 2 1–2 1 1 1 1 1 1–2
Ven 174 174 173 182 173–182 176 176 168 174 168–176 168–182
Prec divided divided divided divided divided divided divided divided divided divided divided
Subc 78 77 77 92 77–92 67 66 – 70 67–70 67–92
BodySc smooth smooth smooth smooth smooth smooth smooth smooth smooth smooth smooth
TailSc few faint
keels
distinct keels few very
faint keels
few faint
keels
usually few
faint keels
few faint
keels
few faint
keels
few faint
keels
few faint
keels
few faint
keels
usually few
faint keels
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TABLE 2a. Sex, morphometry and scalation of Opisthotropis jacobi from Vietnam after Angel & Bourret (1933) and Bourret (1934a,
1934b, 1935a, 1935b, 1935c, 1936); * = most probably transcription error from value 20 given in Angel & Bourret (1933)
TABLE 2b. Sex, morphometry and scalation of Opisthotropis jacobi from Vietnam after Bourret (1937, 1939); * = on one side only;
** = divided on one side
Angel & Bourret
(1933)Sa Pa
syntype
Angel & Bourret
(1933)Sa Pa
syntype
M.259 Chapa
Bourret (1934a)
A.57 Tamdao?
(1934b)
M.518 Chapa
Bourret (1935a)
X.953 Chapa
Bourret (1935a)
X.954 Chapa
Bourret (1935a)
M.451 Tam Dao
Bourret (1935b)
X.794 Tam Dao
Bourret (1935b)
M.498 NganSon
Bourret (1935c)
Bourret (1936)
Sex male female
TL 475 481 544 304 646 577 432 479 349 538 Max. 538
SVL 380 370 402 235 520 455 350 362 260 400
TaL 95 111 142 69 126 122 82 117 89 138
TaL/TL 0.20 0.25 0.26 0.23 0.19 0.21 0.19 0.24 0.26 0.26 0.19-0.26
Teeth max 20 29*
SL 8 9/8 9 8/7 (7)8-9
SL/orbit 4-5 5-6/4-5 5-6 4-5/4 4-5
IL 8 8
PreOc 1 1
PostOc 1 1
Lor 1 1
Atem 1/1 1/1
PTem 1/1 1/1
DSR 1515 151515 15-15-15
Ven 177 179 174 176 178 178 172 170 172 159 159-179
Prec divided divided
Subc 69 79 79 82 71 69 69 83 79 90 69-90
BodySc smooth smooth smooth
X.1461
Chapa
Bourret (1937)
X.1462
Chapa
Bourret (1937)
X.1529
Chapa
Bourret (1937)
X.1530
Chapa
Bourret (1937)
M.564
Ngan-Son
Bourret (1937)
X.1762
Chapa
Bourret (1939)
M.620
Ngan Son
Bourret (1941)
Sex female female female
TL 407 475 537 502 184 503 434
SVL 306 380 390 381 132 380 320
TaL 101 95 147 121 52 123 114
TaL/TL 0.25 0.20 0.27 0.24 0.28 0.24 0.26
Teeth max
SL 6*
...Continued on next page
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Diagnosis. A species of the genus Opisthotropis, characterized by a combination of the following characters:
(1) internasal not in contact with loreal; (2) one preocular; (3) usually two postoculars; (4) one anterior temporal;
(5) one posterior temporal; (6) 7 or 8, rarely 9 supralabials; (7) 25 maxillary teeth; (8) subcaudals 74–86; (9) 15
dorsal scale rows at neck, at midbody and before vent; (10) body scales smooth or only with few faint keels; (11)
dorsal scales being grey, greyish-brown or brown in preservative, posteriorly more or less edged with pale greyish-
brown.
Description of holotype. Body stout, oval in cross section; head short, slightly broader than neck, depressed,
dorsally covered with large shields; nostrils in dorsal position and oblique, narrow, piercing the middle of nasal,
which is divided beneath; eye small, pupil round.
Size. SVL: 337 mm; TaL: 106 mm; TL: 443 mm; ratio TaL/TL: 0.239.
Dentition. Maxillary teeth: right upper maxilla with 25 subequal teeth or sockets, without diastema.
Body scalation. Dorsal scale rows 15–15–15, smooth, with few faint keels.
181 ventrals (+ 1 preventral); 85 subcaudals, all paired; precloacal divided.
Head scalation. Rostral heptagonal, wider than high, readily visible from above; nasals large, much longer
than high, divided below nostril by a distinct furrow; internasals two, strongly curved, longer than wide, in contact
with rostral, nasals, and prefrontal; prefrontal single, anteriorly pointed, much broader than long, in contact with
internasals, nasals, loreals, preoculars, and frontal; frontal pentagonal, slightly wider than long, apex directed
posteriorly, 1.3 times longer than prefrontal; parietals longer than wide, in contact approximately the length of
frontal; 1 / 1 supraocular, distinctly wider than high; 1 / 1 loreal, pentagonal, slightly wider than high, not in contact
with internasal; 1 / 1 preocular, large, hexagonal, distinctly higher than wide, reaching frontal, in broad contact with
prefrontal; 2 / 2 postoculars, upper largest, curved, higher than wide, lower distinctly wider than high; 8 / 7
supralabials, anterior ones distinctly higher than long, fourth entering orbit (the fourth supralabial on the right side
fused with the subsequent supralabial), SL 7 / 6 largest; 1+1 / 1+1 temporals, anterior one very long and narrow, in
broad contact with SL 6–7 / 5–6 and parietals, posterior one more strongly developed; infralabials 9 / 9, first pair in
contact behind small mental, IL 1–4 in contact with anterior chin shields, IL 5 largest, apex directed posteriorly;
posterior chin shields about the same length than anterior ones, separated from each other by 2 + 4 scales.
TABLE 2b. (Continued)
X.1461
Chapa
Bourret (1937)
X.1462
Chapa
Bourret (1937)
X.1529
Chapa
Bourret (1937)
X.1530
Chapa
Bourret (1937)
M.564
Ngan-Son
Bourret (1937)
X.1762
Chapa
Bourret (1939)
M.620
Ngan Son
Bourret (1941)
SL/orbit 3-4*
IL
PreOc
PostOc 1**
Lor
Atem
PTem
DSR
Ven 181 177 175 179 164 179 156
Prec
Subc 79 65 81 79 90 76 85
BodySc
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FIGURE 5. Phylogram based on the Bayesian analysis. Number above and below branches are MP/ML bootstrap values and
Bayesian posterior probabilities (>50%) for major clades, respectively. Asterisk represents 100% value.
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TABLE 3. Sex, morphometry and scalation of the type series of Opisthotropis voquyi sp. nov.; values given in brackets indicate infrequent condition. * fourth supralabial fused with subsequent
supralabial; ** on right side fused with supraocular; *** fourth supralabial fused with subsequent supralabial and next supralabial only half separated; **** on left side fifth and subsequent
supralabial scale fused; ***** on left side lower postocular equals subocular; ****** postmental separated from first supralabial
IEBR 4326
holotype
VNMN 06315 Range
(males)
VNMN 06316 IEBR 4327
IEBR 4328
ZFMK 100819 ZFMK 100820 Range
(females)
Range
(total)
Sex male male female female female female female
TL 443 409 max. 453 517 561 410 409 532 max. 561 max. 561
SVL 337 303 max. 337 404 433 322 320 413 max. 433 max. 433
TaL 106 106 max. 106 113 128 88 89 119 max. 128 max. 128
TaL/TL 0.239 0.259 0.239-0.259 0.219 0.228 0.215 0.218 0.224 0.215-0.228 0.215-0.259
Teeth max 25 - 25 25 25 - - 25 25 25
SL 8/7 7/7 7(8) 8/8 8/8 8/7 7/7**** 8/9 8(7,9) 8(7,9)
SL/orbit 4/4* 4-5/4 4(4-5) 4-5/4-5 4-5/4-5 4-5/4*** 4/4**** 4-5/5-6 4-5(4,5-6) 4-5(4,5-6)
IL 9/9 8/8 8-9 9/9 8/9 9/9 9/8 9/9****** 9(8) 9(8)
PreOc 1/1 1/1 1 1/1 1/1** 1/1 1/1 1/1 1 1
PostOc 2/2 2/2 2 2/1 2/2 2/2 2/2***** 2/2 2(1) 2(1)
Lor 1/1 1/1 1 1/1 1/1 1/1 1/1 1/1 1 1
InN/Lor No no No no no No No no no no
Atem 1/1 1/1 1 1/1 1/1 1/1 1/1 1/1 1 1
PTem 1/1 1/1 1 1/1 1/1 1/1 1/1 1/1 1 1
DSR 15-15-15 15-15-15 15-15-15 15-15-15 15-15-15 15-15-15 15-15-15 15-15-15 15-15-15 15-15-15
PreVen 1 2 1-2 1 1 1 2 2 1-2 1-2
Ven 181 182 181-182 165 169 169 169 167 165-169 165-182
Prec divided divided divided divided divided divided divided divided divided divided
Subc 85 86 85-86 79 81 77 74 75 74-81 74-86
BodySc few faint keels smooth smooth or with
few faint keels
smooth smooth smooth smooth few faint keels smooth (few
faint keels)
smooth (few
faint keels)
TailSc few faint keels few faint keels few faint keels smooth smooth smooth smooth few faint keels smooth (few
faint keels)
smooth (few
faint keels)
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FIGURE 6. Holotype (IEBR 4326) of Opisthotropis voquyi sp. nov. in preserved state. Photos: T. Ziegler.
Hemipenes. Only the left hemipenis fully everted, ending in two short, inwards curved lobes (Fig. 7). Sulcus
spermaticus undivided, extending only to the slightly smaller lobe. Hemipenes covered with small spines, curved
backwards. Only the terminal area of the hemipenes between the lobes without spines. Upper truncus of hemipenes
with ring of enlarged spines. Largest spines extending from sulcus spermaticus to hemipenis sides, with the
lowermost one being the most distinct. Lower truncus of hemipenes covered with tiny spines.
Coloration (in preservative). Upper head and body surface brown, the venter yellowish-beige. Dorsal scales
posteriorly more or less edged with pale brown. Dorsal head surface paler around nostrils and in the middle of
parietals. Infralabials same colour as dorsal scales, adjoining scales becoming gradually paler towards mental
groove. Outermost edges of ventrals and subcaudals the same colour as dorsal scales. Subcaudals speckled with
small dark spots, becoming more numerous towards the tail tip.
Variation of paratypes. An overview of the meristic and scalation data of the type series of Opisthotropis
voqyui sp. nov. is given in Table 3. The dorsal ground coloration varies between greyish, greyish brown, and
brown. Concerning a potential sexual dimorphism, males seem to be brown, females grey or greyish brown.
Females also seem to grow larger. The dorsal tail scales in the males had few faint keels, which was only the case
for one female; the remaining four females had smooth dorsal tail scales. The paratype series generally accorded
well with the holotype description. Of the type series six individuals had two postoculars, only one individual had 2
postoculars on the left side and one postocular on the right side.
Comparisons. The comparison of Opisthotropis voquyi sp. nov. with other species of the genus Opisthotropis
and the genera Parahelicops and Paratapinophis was based on the following references: Stuart & Chuaynkern
(2007), David et al. (2011), Teynié et al. (2013), Nguyen et al. (in press), and Wang et al. (2017).
There are only few species of Opisthotropis and other genera with 15 midbody dorsal scale rows (see Table 4).
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FIGURE 7. Everted hemipenes of the holotype (IEBR 4326) of Opisthotropis voquyi sp. nov.: A) Sulcal view, and B) asulcal
view of the fully everted left hemipenis. Photos: T. Ziegler.
TABLE 4. Midbody dorsal scale rows in Opisthotropis, Paratapinophis praemaxillaris and Parahelicops annamensis
(after Stuart & Chuaynkern 2007, David et al. 2011, Teynié et al. 2013, Wang et al. 2017 and Nguyen et al. in press).
15 15 or 17 17 19 23
Opisthotropis alcalai Brown & Leviton, 1961 x
O. andersonii (Boulenger, 1888) x
O. atra Günther, 1872 x
O. balteata (Cope, 1895) x
O. cheni Zhao, 1999 x
O. cucae David, Pham, Nguyen & Ziegler, 2011 x
O. daovantieni Orlov, Darevsky & Murphy, 1998 x
O. durandi Teynié, Lottier, David, Nguyen & Vogel, 2013 x
O. guangxiensis Zhao, Jiang & Huang, 1978 x
O. jacobi Angel & Bourret, 1933 x
O. kikuzatoi Okada & Takara, 1958 x
O. kuatunensis Pope, 1928 x
O. lateralis Boulenger, 1903 x
O. latouchii (Boulenger, 1899) x
O. laui Yang, Sung & Chan, 2013 x
...Continued on next page
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Main additional differences between Opisthotropis voquyi sp. nov. and Parahelicops annamensis are: one
preocular in the new species versus two in P. annamensis; internasal not in contact with loreal in the new species
versus in contact in P. annamensis; body scales smooth or only with few faint keels in the new species versus
keeled throughout in P. annamensis and especially strongly keeled on the posterior part of the body and the base of
the tail; body dorsum grey to greyish-brown or brown, with dorsals posteriorly more or less edged with pale
greyish-brown in the new species versus dorsum with orange bars and spots in P. annamensis.
FIGURE 8. Drawings showing the head scalation of the male holotype A) IEBR 4326 of Opisthotropis voquyi sp. nov. and of
the female paratype B) IEBR 4327 (note that pre- and supraocular are fused). Drawings: T. Ziegler.
TABLE 4. (Continued)
15 15 or 17 17 19 23
O. maculosa Stuart & Chuaynkern, 2007 x
O. maxwelli Boulenger, 1914 x
O. rugosa (Lidth de Jeude, 1890) x
O. shenzhenensis Wang, Guo, Liu, Lyu, Wang, Luo, Sun & Zhang, 2017 x
O. spenceri Smith, 1918 x
O. tamdaoensis Ziegler, David & Vu, 2008 x
O. typica (Mocquard, 1890) x
Parahelicops annamensis Bourret, 1934 x
Paratapinophis praemaxillaris Angel, 1929 x
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FIGURE 9. Female paratype (IEBR 4327) of Opisthotropis voquyi sp. nov. in preserved state. Photos: T. Ziegler.
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FIGURE 10. Preserved paratype series of Opisthotropis voquyi sp. nov. (except for desiccated specimen VNMN 06315) in A)
dorsal and B) ventral views. Photos: T. Ziegler.
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Opisthotropis voquyi sp. nov. differs from O. guangxiensis by 7–9 versus 9–10 supralabials, one posterior
temporal (versus two), 74–86 versus 51–58 subcaudals, dorsal scales arranged in 15–15–15 versus 17–15–15 rows,
and a greyish to greyish–brown or brown dorsum, dorsal scales posteriorly more or less edged with pale greyish-
brown in the new species versus dark body with pale crossbars in O. guangxiensis.
Opisthotropis voquyi sp. nov. differs from O. kikuzatoi by 7–9 supralabials (versus 6), one preocular (versus
two), one anterior temporal (versus two), and the greyish to greyish-brown or brown dorsal pattern, with the dorsals
posteriorly being more or less edged with pale greyish-brown in the new species (versus dark dorsum with
dorsolateral orange spots).
Opisthotropis voquyi sp. nov. differs from O. maculosa by a grey to greyish-brown or brown dorsum, with
dorsals being posteriorly more or less edged with pale greyish-brown in the new species versus with yellow dots on
a dark background in O. maculosa.
FIGURE 11. Map of Vietnam showing the localities where the new series of Opisthotrophis jacobi was collected 1) Tam Dao,
Vinh Phuc Province, 2) Sa Pa, Lao Cai Province, and 3) Tay Yen Tu Nature Reserve, Bac Giang Province, the type locality of
Opisthotropis voquyi sp. nov.
In external morphological characters, O. voquyi sp. nov. is particularly similar to O. jacobi, from which it
differs in usually having two postoculars versus only one in O. jacobi, in the number of maxillary teeth: 25 in the
new species versus 19–23 in O. jacobi, and in the dorsal scales being grey to greyish–brown or brown versus
blackish–brown in O. jacobi.
Etymology. The specific epithet is a noun in the genitive case. This species is named in honour of Professor
Doctor Vo Quy of Vietnam National University, Hanoi, who passed away on 10 January 2017, and who played a
pioneering role in nature conservation in Vietnam. He inspired later generations of conservation biologists,
including authors of this study.
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FIGURE 12. A) Macro- and B) micro-habitat of Opisthotrophis voquyi sp. nov. in Tay Yen Tu Nature Reserve, Bac Giang
Province. Photos: C. T. Pham.
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Suggested common names. Vo Quy’s Mountain Stream Keelback (English) and Rắn trán võ quý
(Vietnamese).
Distribution. Opisthotropis voquyi is currently known only from the type locality in Bac Giang Province (Fig.
11).
Natural history. Specimens were found at night between 19:30 and 23:00 h in and around small rocky
streams, where the snakes were observed in the water or on the rocks close to the water. The surrounding habitat
was secondary evergreen forest of medium and small hardwoods mixed with bamboo, shrubs, and vines (Fig. 12).
The air temperature was 29.2–36.5
o
C and the relative humidity was 55–73%. Other species co-occurring with
Opisthotropis voquyi include Cyclophiops multicinctus, Opisthotropis lateralis, Sinonatrix percarinata, Gekko
palmatus, Sphenomorphus cryptotis, and Shinisaurus crocodilurus vietnamensis.
Discussion
Opisthotrophis voquyi is similar to O. jacobi in morphology. This is also reflected by identical hemipenis
morphology, which we illustrate in this study for the first time. However, we found significant differences in
scalation, dentition, and nucleotide sequence variation, which strongly support recognition of the new species.
There is 10% genetic distance between Opisthotrophis voquyi and its sister taxon O. jacobi. Between O. lateralis
and the recently described O. tamdaoensis, there are distinct morphological differences and a genetic divergence of
6 % in the same gene fragment (Ziegler et al. 2017). This is a further example demonstrating that Tam Dao massif,
where O. jacobi is found, shows clear separation in herpetofauna from the Tay Yen Tu Mountain range, where O.
voquyi occurs. The aforementioned O. tamdaoensis is endemic to Tam Dao while O. lateralis is restricted to Tay
Yen Tu (Ziegler et al. 2017). Among amphibians, Odorrana nasica can be found only in Tam Dao whereas the
sister species O. yentuensis is endemic to Tay Yen Tu (e.g., Tran et al. 2008, Nguyen et al. 2009, Hecht et al. 2013).
It is still unclear which geological or paleo-climate factors resulted in the evolutionary separation between the two
isolated mountain ranges; however, it appears the fauna in the two ranges share a common history.
Acknowledgements
We are grateful to the directorates of the Forest Protection Departments of Bac Giang and Vinh Phuc Provinces for
supporting our field work and issuing relevant permits. We thank E. Sterling (New York) and K. Koy (Berkeley)
for providing the map. Thanks to D.A. Kizirian (New York) for his helpful comments improving the manuscript.
Ying-Yong Wang and Zuyao Liu, State Key Laboratory of Biocontrol, the Museum of Biology, School of Life
Sciences, Sun Yat-sen University, Guangzhou, China, kindly provided original data from their latest Opisthotropis
publication. We thank A. Rauhaus (Cologne Zoo) for kindly arranging the plates and H.T. Ngo (Hanoi University
of Science) for laboratory assistance. For the fruitful cooperation within joint biodiversity research and
conservation projects we cordially thank S.V. Nguyen (IEBR, Hanoi), T. Pagel and C. Landsberg (Cologne Zoo).
Field surveys in Tay Yen Tu Nature Reserve were partially funded by the Cologne Zoo (Germany).
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