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A new species of Lycodon Boie, 1826 (Serpentes, Colubridae) from northern Vietnam
expand article infoHelen Y. Janssen§, Cuong T. Pham|, Hanh Thi Ngo, Minh Duc Le#¤, Truong Q. Nguyen«|, Thomas Ziegler§
‡ AG Zoologischer Garten Köln, Cologne, Germany
§ University of Cologne, Cologne, Germany
| Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, Hanoi, Vietnam
¶ Hanoi University of Science, Hanoi, Vietnam
# Hanoi National University, Hanoi, Vietnam
¤ American Museum of Natural History, New York, United States of America
« Graduate University of Science and Technology, Hanoi, Vietnam
Open Access

Abstract

A new species of the genus Lycodon is described from Cao Bang Province, Vietnam, based on three individuals with distinct differences in morphology and molecular data. The new species is differentiated from its congeners by a combination of the following characters: dorsal scales in 17-17-15 rows, smooth throughout; supralabials usually eight (rarely nine); infralabials ten; one elongated loreal on each side, in contact with the eye; precloacal plate single; ventral scales 212–218 (plus one or two preventral scales); subcaudals 90 or 91; maxillary teeth 13 or 14; dorsal surface of body with 28 or 29 light body bands; dorsal surface of tail with 13 cream bands, forming a distinct blotch in the vertebral region. Based on phylogenetic analyses of mitochondrial cytochrome b sequence data, the new species is recovered as the sister species to a clade containing L. multizonatus and L. liuchengchaoi with strong support from the Bayesian analysis. The new species is at least 7.5% divergent from other species within this clade in uncorrected pairwise distance calculated using a fragment of more than 1000 bp of the mitochondrial cytochrome b. This discovery increases the number of Lycodon species known from Vietnam to 16.

Keywords

Cao Bang Province, Lycodon pictus sp. nov., morphology, phylogeny, taxonomy

Introduction

The genus Lycodon Boie, 1827 is one of the most diverse genera of colubrid snakes, with 61 currently recognised species (Uetz et al. 2019, Luu et al. 2019). Recent phylogenetic studies showed that the genera Dinodon, Dryocalamus and Lepturophis nested within Lycodon and suggested to place them into the genus Lycodon sensu lato (Guo et al. 2013; Siler et al. 2013; Figueroa et al. 2016). The members of this genus have a broad distribution from eastern Iran to southern China and Japan, southward to the Philippines as well as the Indo-Australian Archipelago (Lanza 1999; Siler et al. 2013; Neang et al. 2014). Six species of Lycodon have been described in the last five years, namely L. zoosvictoriae Neang, Hartmann, Hun, Souter & Furey, 2014 from Cambodia; L. cavernicolus Grismer, Quah, Anuar, Muin, Wood & Nor, 2014 from Malaysia; L. sidiki Wostl, Hamidy, Kurniawan & Smith, 2017 from Indonesia; L. banksi Luu, Bonkowski, Nguyen, Le, Calame & Ziegler, 2018 from Laos, L. namdongensis Luu, Ziegler, Ha, Le & Hoang, 2019 from Vietnam and L. gibsonae Vogel & David, 2019 from Thailand. From Vietnam, fifteen species of Lycodon have been reported to date, comprising L. capucinus (Boie, 1827), L. cardamomensis (Daltry & Wüster, 2002), L. davisonii (Blanford, 1878), L. fasciatus (Anderson, 1879), L. flavozonatus (Pope, 1928), L. futsingensis (Pope, 1928), L. laoensis Günther, 1864, L. meridionalis (Bourret, 1935), L. namdongensis Luu, Ziegler, Ha, Le & Hoang. 2019, L. paucifasciatus Rendahl in Smith, 1943, L. rosozonatus (Hu & Zhao, 1972), L. rufozonatus Cantor, 1842, L. ruhstrati abditus Vogel, David, Pauwels, Sumontha, Norval, Hendrix, Vu & Ziegler, 2009, L. septentrionalis (Günther, 1875), and L. subcinctus Boie, 1827 (Uetz et al. 2019, Luu et al. 2019).

Our recent field surveys in the Ha Lang and Trung Khanh districts, Cao Bang Province, northern Vietnam, revealed a snake population that was referable to the genus Lycodon based on the following characters: nostril enlarged; robustly arched upper maxillary bone with an inward curve in the anterior part; anterior and posterior maxillary teeth interrupted by a diastema; dorsal scales smooth or weakly keeled, in 17 rows anteriorly and at midbody, and posteriorly 15 rows (Lanza 1999; Grismer et al. 2014). However, the series of three individuals from Cao Bang were morphologically distinct from other named species. These morphological results were further corroborated by the analysis of a fragment of the mitochondrial cytochrome b gene, and so herein we describe the population from Cao Bang Province, northern Vietnam, as a new Lycodon species.

Materials and methods

Sampling

The field surveys were led by TQN in October 2011 and from April to May 2012. The collected specimens were euthanised with ethyl-acetate, fixed in approximately 85% ethanol for 10 hours, and subsequently transferred to 70% ethanol for permanent storage. Liver tissue samples were preserved separately in 95% ethanol. The specimens were deposited in the collections of the Institute of Ecology and Biological Resources (IEBR), Hanoi, Vietnam and of the Zoologisches Forschungsmuseum Alexander Koenig (ZFMK), Bonn, Germany.

Morphological analysis

Identification of sex was performed by dissection (inspection of gonads and presence of hemipenes). Maxillary teeth were counted by dissecting the right maxilla for teeth / sockets. Scalation and maxillary teeth number were examined with a binocular dissecting microscope. Measurements were taken following Ziegler et al. (2018) with a measuring tape to the nearest 1 mm.

Abbreviations of morphological characters are as follows:

SVL Snout-vent length (from tip of snout to vent);

TaL tail length;

TaL / TL ratio of tail length / total length;

TL total length;

DSR dorsal scale rows number at one head length posterior to the head – number of dorsal scale rows at midbody – number of dorsal scale rows at one head length anterior to the vent;

SL supralabials (counted on upper lips);

SL / orbit number of supralabials entering orbit;

IL infralabials (counted on lower lips);

Lor loreals;

Lor / eye loreal scale touching the eye (yes or no);

PreOc preoculars;

PostOc postoculars;

Atem number of anterior temporals;

PTem number of posterior temporals;

BodySc scalation of the body (keeled or smooth);

PreVen number of preventral scales;

Ven number of ventral scales;

SubC number of subcaudal scales;

Prec precloacal (or cloacal) plate (single or divided);

Teeth max number of maxillary teeth / alveoli.

Scale counts were taken following Vogel et al. (2009). Ventral scales (Ven) were counted according to Dowling (1951). Bilateral scale counts were given as left / right.

Comparisons were mainly based on the data provided by Boulenger (1893), Pope (1928), Smith (1943), Leviton (1965), Ota and Ross (1994), Manthey and Grossmann (1997), Lanza (1999), Vogel et al. (2009), Vogel and David (2010) and Neang et al. (2014), with additional references provided in the comparisons and legends of the tables. Additionally, studied specimens are listed in the Appendix 1.

Molecular data and phylogenetic analyses

Representative taxa of the genus Lycodon were included in the study. Sequences of the species were downloaded from GenBank. Two samples of the population from Cao Bang Province (ZFMK 93746, ZFMK 93747) were incorporated in the analysis. Boiga cynodon (Boie 1827) and Dipsadoboa flavida broadleyi (Broadley & Stevens, 1971) were used as outgroups based on Figueroa et al. (2016).

DNA was extracted using DNeasy Blood and Tissue kit (Qiagen, Germany) following the manufacturer’s instructions. A fragment of the mitochondrial cytochrome b gene was amplified using the primer pair L14910 (5’–GACCTGTGATMTGAAAACCAYCGTTGT-3’) and H16064 (5’– CTTTGGTTTACAAGAACAATGCTTTA-3’; Burbrink et al. 2000). Extracted DNA was amplified using HotStarTaq Mastermix (Qiagen, Germany) with 21 µl volume consisting of 10 µl of Mastermix, 5 µl of water, 2 µl of each primer at 10 pmol/ml and 2 µl of DNA. PCR conditions were 95 °C for 15 minutes to activate the Taq, with 40 cycles of 95 °C for 30 s, 45 °C for 45 s, 72 °C for 60 s, and a final extension at 72 °C for six minutes. The mitochondrial cytochrome b gene was utilised in this study because it has been widely used in previous molecular analyses of Lycodon (e.g., Guo et al. 2013, Siler et al. 2013), and has been shown to be informative in revealing new species of Lycodon (e.g., Grismer et al. 2014, Luu et al. 2018, 2019).

PCR products were visualised using gel electrophoresis through a 2% low melting-point agarose gel stained with ethidium bromide. Successful amplifications were purified to eliminate PCR components using GeneJETTM PCR Purification kit (ThermoFisher Scientific, Lithuania). Purified PCR products were sent to FirstBase (Malaysia) for sequencing.

The obtained sequences were aligned in ClustalX 1.8.3 (Thompson et al. 1997) using the default settings. Data were analysed using maximum parsimony (MP) as implemented in PAUP*4.0b10 (Swofford 2001) and Bayesian inference (BI) as implemented in MrBayes v3.2 (Ronquist et al. 2012). Settings for these analyses followed Le et al. (2006), except that the number of generations in the Bayesian analysis was increased to 1×107. For the maximum likelihood (ML) analysis, we used IQ-TREE v.1.6.7.1 (Nguyen et al. 2015) with a single model and 10,000 ultrafast bootstrap replications. For ML and BI, the optimal model for nucleotide evolution was set to TrN+I+G by Modeltest v3.7 (Posada and Crandall 1998). For BI, the analysis was conducted with a random starting tree and run for 107 generations. Four Markov chains, one cold and three heated (utilising default heating values), were sampled every 1000 generations. Log-likelihood scores of sample points were plotted against generation time to detect stationarity of the Markov chains. The burn-in value was set to 26 in the BI analysis, as -lnL scores reached stationarity after 26,000 generations in both runs. Two independent analyses were run simultaneously. Nodal support was evaluated using Bootstrap replication (BP) as estimated in PAUP*4.0b10 and IQ-TREE v1.6.7.1 and posterior probability (PP) in MrBayes v3.2. BP ≥ 70 and PP ≥ 95% are regarded as strong support for a clade. Uncorrected pairwise distances (p) were calculated in PAUP*4.0b10.

Results

Molecular data and phylogenetic analyses

The final matrix consisted of 1011 bp aligned characters and the alignment contained no gaps. In total, 404 characters were found to be parsimony informative. MP analysis resulted in five most parsimonious trees having 1662 steps (CI = 0.41, RI = 0.72). Our tree topologies are very similar to those recovered by Guo et al. (2015) and Luu et al. (2018). The new species was recovered to be the sister species to a clade containing L. multizonatus + L. liuchengchaoi, with strong support in BI (PP = 96), but weak support in MP and ML (BPMP = 56, BPML = 69) (Fig. 1). The new species has an uncorrected p-distance of at least 7.5% and 8.1% from Lycodon liuchengchaoi Zhang, Jang, Vogel & Rao, 2011 and L. multizonatus Zhao & Jiang, 1981, respectively.

Figure 1. 

Bayesian cladogram based on the partial mitochondrial cytochrome b gene of snakes belonging to the genus Lycodon. Numbers above and below branches are bootstrap values of MP/ML analyses (≥ 50%) and Bayesian posterior probabilities (BC), respectively.

Lycodon pictus sp. nov.

Figs 2, 3, 4, 5, 6

Holotype

IEBR 4166 (field number CB 2012.97), adult male, collected on 18 April 2012 by TQN et al. (altitude 701 m a.s.l.), Trung Khanh District, Cao Bang Province.

Paratypes

ZFMK 93747, juvenile, collected on 15 October 2011 by TQN et al. (altitude 588 m a.s.l.), Ha Lang District, Cao Bang Province; ZFMK 93746, adult female, collected on 10 April 2012 by TQN et al., Ha Lang District, Cao Bang Province.

Diagnosis

Lycodon pictus sp. nov. can be differentiated from its congeners by the following morphological characters: dorsal scales in 17–17–15 rows, all smooth; supralabials usually eight (rarely nine); infralabials ten; one elongated loreal on each side, in contact with the eye; precloacal plate single; ventral scales 212–218 (plus one or two preventral scales); subcaudals 90 or 91; a total length of 597+ mm in males and 543 mm in females; tail / total length ratio 0.211–0.215; maxillary teeth 13 or 14; dorsal surface of body with 28 or 29 light body bands; dorsal surface of tail with 13 cream bands forming a distinct blotch in the vertebral region; ventral surface of body and tail mostly cream with the dark body bands in part extending towards the venter, sometimes forming complete dark bands around the body.

Figure 2. 

Holotype of Lycodon pictus sp. nov. (IEBR 4166) in life. Photograph T. Lehmann.

Figure 3. 

Head views of Lycodon pictus sp. nov. (IEBR 4166) in preservative (scale bar refers to head in dorsal view). Photographs T. Ziegler (upper), C.T. Pham (lower).

Description of the holotype

Head elongate, moderately distinct from the neck, rather flattened, longer than wide, narrow anteriorly; nostril lateral, located in the middle of the nasal; eye large, pupils vertically elliptic; rostral triangular, much broader than high, hardly visible from above; nasal divided into two scales by a vertical ridge along posterior edge of nostril; two internasals, anteriorly rounded, slightly wider than high, bordered by two large, pentagonal prefrontals posteriorly; frontal single, enlarged, pentagonal to hexagonal, narrowed posteriorly; parietals longer than wide, in contact with each other medially, with upper anterior and posterior temporals, paraparietal laterally and four nuchal scales posteriorly; paraparietals elongated, anterior part widened; loreal 1/1, elongate, not entering orbit; supralabials 8/8, first and second in contact with nasal, third to fifth entering orbit, sixth largest; infralabials 10/10, first pair in broad contact with each other, first to fifth in contact with anterior pair of chin shields; anterior and posterior pairs of chin shields elongate, of the same size and shape, second pair not meeting in midline; preocular 1/1; postoculars 2/2, lowermost smaller, bordering anterior temporals; anterior temporals 2/2, posterior temporals 3/3, upper ones thinner than lower ones. Left maxilla arched, with an angular apex, distinctly bent inwards anteriorly. A total of 13 maxillary teeth or teeth alveola, with the following formula: five small anterior teeth, with the last two ones being somewhat enlarged + two strongly enlarged teeth, thick, and not much curved + a wide gap, somewhat wider than the length of the largest teeth + four small teeth + a small gap + two enlarged posterior teeth.

Body elongate, SVL 488 mm; TaL > 109 mm (tail tip lost); preventral 1, ventrals 212, from behind neck region distinctly notched laterally; subcaudals > 54 (tail tip lost), paired; precloacal plate single; DSR 17-17-15, all smooth; the vertebral scales not enlarged; DSR reduction from 17 to 15 at the position of ventral 150.

Coloration in preservative

Head, neck, and dorsal surface of body brownish black; light body bands beginning after 1.5 times the head length behind the head, in total 29 transverse light bands on body and at least nine light bands on tail; the first four body bands yellowish cream, and distinctly widened towards the venter, increased in size posteriorly; a dark mottling in the vertebrate region more prominent posteriorly; the subsequent light body bands with two distinct indentations on each side, fused in the middle in the last third of the body. In dorsal view the light bands forming a distinct blotch in the vertebral region, with a dark centre and a lighter frame; laterally, the middle part of the light bands forming blotches, but wider and with an extended dark centre, fused laterally in the last third part of the body; the lower and widest part of the light body bands with a dark small blotch in the centre in the anterior part of body; the light bands on the tail with a blotch like pattern in the vertebral region, but less pronounced than that on body, and one light blotch at the lateral side of tail, widened towards the venter, with a dark centre; ventral surface of head and neck yellowish cream, belly cream and greyish cream in the last third part of body and on lower tail surface; the dark dorsal bands (28 on body and at least nine on tail) in part extending towards the venter (most prominent in the anterior five dark body bands), not forming complete dark bands around the body, but complete on the tail; lateral side of the head dark above and light below, with the lighter pattern beginning in the supralabial region; tip of lower jaw and infralabial region in part greyish; dorsal surface of the head and upper head sides a bit paler than the remaining head dorsum.

Figure 4. 

Female paratype of Lycodon pictus sp. nov. (ZFMK 93746) in life. Photographs T.Q. Nguyen.

Hemipenis

Hemipenes elongated, not fully everted, not turgid. Truncus without spines. Spine ornamentation starting at truncus region with somewhat enlarged, medium sized spines. Apex with microspines. Sulcus stretches in the middle to apex. Apex not fully everted, ending somewhat widened with an oblique opening, with microspines inside, pointing to the not fully everted condition of the outer genital organ.

Variations

In the juvenile ZFMK 93747, the number of supralabials on the left side is nine, with fourth to sixth entering the orbit. The loreal does not touch the eye on the right side. The lower anterior temporal scale is not touching the postocular scale on the left side. In general, the coloration is more intense in the juvenile. The creamy pattern on the posterior third of the body sides is connected by a horizontal cream-colored stripe. It has a yellowish cream band on the head that reaches from SL 5 behind the jaws and distinctly lightens the posterior half of the head but does not touch the frontal. In the juvenile, the banded pattern is more simple, consisting of dark bands which narrow towards the venter and light bands which widen towards the venter and bear a dark pattern and a more or less distinct dark blotch at the lower side (see Fig. 5).

In the female ZFMK 93746, the lower anterior temporal scale is not touching the postocular scale on the right side. For measurements and scalation data of the examined specimens see Table 1.

Figure 5. 

Juvenile paratype of Lycodon pictus sp. nov. (ZFMK 93747) in preservative (upper, dorsal view; lower, ventral view). Photographs T. Ziegler.

Sex, measurements (in mm), scalation data, and coloration pattern of Lycodon pictus sp. nov. For abbreviations see Materials and methods. Key: asterisk (*) lower Atem not touching PostOc; plus sign (+) tail tip lost.

Holotype IEBR 4166 Paratype ZFMK 93746 Paratype ZFMK 93747
Sex male female juvenile
TL 597 543 237
SVL 488 426 187
TaL 109+ 117 50
TaL/TL 0.215 0.211
Teeth max 13 13 14
SL 8/8 8/8 9/8
SL/orbit 3–5 3–5 4–6/3–5
IL 10/10 10/10 10/10
PreOc 1/1 1/1 1/1
PostOc 2/2 2/2 2/2
Lor 1/1 1/1 1/1
Atem 2/2 2*/2 2/2*
PTem 3/3 3/3 3/3
DSR 17-17-15 17-17-15 17-17-15
PreVen 1 2 1
Ven 212 216 218
Prec single single single
Subc 54+ 91 90
BodySc smooth smooth smooth
Dark bands on body 28 29 28
Light bands on body 29 29 28
Dark bands on tail 9 13 13
Light bands on tail 9+ 13 13

Dentition

Female ZFMK 93746 and juvenile ZFMK 93747: Left maxilla arched, with an angular apex, distinctly bent inwards anteriorly. A total of 13 (in female) or 14 (in juvenile) maxillary teeth or teeth alveola, with the following formula: five small anterior teeth, with the last two ones being somewhat enlarged + two strongly enlarged teeth, thick, and not much curved + a wide gap, somewhat wider than the length of the largest teeth + four small teeth + a small gap + two enlarged posterior teeth in the female and three posterior teeth in the juvenile, with the anterior two ones enlarged.

Comparisons

In our phylogenetic analysis, Lycodon pictus sp. nov. is most closely related to L. liuchengchaoi and L. multizonatus. From L. liuchengchaoi, the new species differs in terms of body scalation (all smooth in the new species vs. feebly keeled in several median rows in L. liuchengchaoi), head scalation (ten infralabials vs. 7–9) and dentition (13 or 14 maxillary teeth vs. 8 or 9). In addition, the new species differs from the latter in having 28 or 29 cream body bands (vs. 40 yellow rings on the body in L. liuchengchaoi) (Zhang et al. 2015).

The new species differs from L. multizonatus by having more maxillary teeth (13 or 14 vs. 10 or 11 in L. multizonatus), more infralabials (10 vs. 8) and a single precloacal plate (vs. divided). In addition, the new species differs from the latter in terms of body scalation (minimum 212 ventrals and minimum 90 subcaudals vs. 190–195 ventrals and 68–75 subcaudals in L. multizonatus). Furthermore, L. pictus sp. nov. has fewer light body bands (28 or 29 vs. 55–73 in L. multizonatus) (Lei et al. 2014).

From its Vietnamese congeners, the new species can be differentiated as follows: Lycodon pictus sp. nov. differs from L. capucinus in having a single precloacal plate (vs. divided), a loreal touching the eye (vs. not in contact with the eye), in having more ventrals (minimum 212 vs. 182–211) and more subcaudals (90 or 91 vs. 59–74), and in terms of dorsal pattern (banded vs. reticulated) (Luu et al. 2019).

Lycodon pictus sp. nov. differs from L. cardamomensis in terms of dorsal scalation (17-17-15 smooth DSR vs. 19-17-15 weakly keeled DSR), in having a loreal in contact with the eye (vs. separated) and in having 28 or 29 light body bands (vs. 12-14 pinkish orange body bands) (Daltry and Wüster 2002, Do et al. 2017).

Lycodon pictus sp. nov. differs from L. davisonii in having 17 midbody dorsal scale rows (vs. 13 midbody dorsal scale rows), fewer ventral scales (maximum 218 vs. 235–265), more infralabials (10 vs. 8) and the absence of preocular (vs. present). In addition, the new species differs from the latter in having a different dorsal pattern (28 or 29 cream bands on body vs. 36 white rings on the body) (Blanford 1878, Boulenger 1893).

Lycodon pictus sp. nov. differs from L. fasciatus in having smooth dorsal scales (vs. keeled) and more maxillary teeth (13 or 14 vs. 11). Additionally, the colour pattern of Lycodon pictus sp. nov. differs in being dark brownish black with light body bands turning into a marbling posteriorly, whereas L. fasciatus is black or purplish black above with yellowish cross-bars of irregular outline and has a dark median stippling (Pope 1928, Smith 1943). Werner (1922) described Dinodon yunnanensis from Yunnan Fu, now Kunming, Yunnan Province, southwestern China. This species was synonymized with Lycodon fasciatus by Pope (1935: 188), but according to Vogel and David (2010), this taxon might be a distinct species (see also Vogel and David 2019). Lycodon pictus sp. nov. differs from Dinodon yunnanensis Werner, 1922 in having more ventrals (minimum 212 vs. 193), more subcaudals (90 or 91 vs. 66), more infralabials (10 vs. 9) and more light body bands (28 or 29 vs. 23) (Werner 1922, Vogel and David 2010, Vogel and David 2019).

Lycodon pictus sp. nov. differs from L. flavozonatus in terms of dorsal scalation (smooth vs. keeled), in having more subcaudals (90 or 91 vs. 80–88), the loreal in contact with the eye in Lycodon pictus sp. nov. (vs. separated in L. flavozonatus) and in coloration pattern (brownish black with 28 or 29 cream body bands and 9–13 light bands on the tail vs. black with 68 yellow body bands and 21 on the tail) (Pope 1928, Vogt in Pope 1928).

Lycodon pictus sp. nov. differs from L. futsingensis in having more ventrals (minimum 212 vs. 193–208) and more subcaudals (minimum 90 vs. 72–87). Additionally, the loreal does not enter the orbit in L. futsingensis, whereas it enters the orbit in Lycodon pictus sp. nov. (Vogel et al. 2009).

Lycodon pictus sp. nov. differs from L. laoensis in having a single precloacal plate (vs. divided), more ventral scales (minimum 212 vs. 163–192), more subcaudal scales (minimum 90 vs. 60–76), an elongated loreal scale in contact with the orbit (vs. separated) and cream body bands (vs. yellow) (Grismer et al. 2014, Neang et al. 2014).

Lycodon pictus sp. nov. differs from L. meridionalis in having smooth dorsals (vs. feebly keeled in 10–12 median rows), a lower ventral scale count (maximum 218 vs. 227–240) and fewer subcaudals (maximum 91 vs. 96–106). In addition, the new species differs in having cream body bands (vs. yellow thin crossbars) (Gawor et al. 2016 and examined ZFMK specimens, see Appendix 1).

Lycodon pictus sp. nov. differs from L. namdongensis in having more subcaudals (90 or 91 vs. 85) and the loreal in contact with the eye (vs. separated from the eye in L. namdongensis). The new species also differs in coloration pattern (brownish black with 28 or 29 light bands on the body vs. grey with 23 cream cross rings on the body in L. namdongensis), and in having irregular bands turning into a marbling posteriorly (vs. clearly demarcated cross bands on the body) (Luu et al. 2019).

Lycodon pictus sp. nov. differs from L. paucifasciatus in terms of dorsal scalation (17-17-15 smooth DSR vs. 19-(19-17)-15 DSR, the upper one or two plus vertebral row distinctly keeled) and fewer ventral scales (maximum 218 vs. 219–222). In addition, the new species has a loreal entering the eye (vs. separated) and 28 or 29 light body bands (vs. 14–25 beige or dirty cream body bands) (Vogel et al. 2009).

Lycodon pictus sp. nov. differs from L. rosozonatus in having 17-17-15 smooth DSR (vs. 19-19- 15(17) keeled DSR), fewer ventral scales (maximum 218 vs. 221–234) and a loreal in contact with the eye (vs. separated). In addition, the new species has cream body bands (vs. pinkish red) (Hu et al. 1975, Neang et al. 2014).

Lycodon pictus sp. nov. differs from L. rufozonatus in having a loreal in contact with the eye (vs. separated), smooth dorsal scales (vs. feebly keeled in the posterior body part), and in coloration pattern (28 or 29 cream body bands vs. 44–52 light red body bands) (Zhao 2006, Luu et al 2018).

Lycodon pictus sp. nov. differs from L. ruhstrati abditus in having smooth dorsals (vs. 7–8 dorsal scale (including vertebral) rows keeled), an elongated loreal in contact with the eye (vs. separated), and in having irregular bands turning into a marbling posteriorly (vs. clearly demarcated cross bands on the body) (Vogel et al. 2009).

Lycodon pictus sp. nov. differs from L. septentrionalis by its smooth dorsal scales (vs. 7–9 median rows feebly keeled), 10 infralabials (vs. 7 or 8), and the loreal entering the orbit (vs. separated in L. septentrionalis). In addition, the new species differs in having cream irregular bands on a brown body (vs. white narrow bands on a black body forming complete annuli) (Günther 1875, Boulenger 1893, Neang et al. 2014).

Lycodon pictus sp. nov. differs from L. subcinctus in having 10 infralabials (vs. 8 or 9), one preocular (vs. preocular absent), smooth dorsal scales (vs. feebly keeled) and 28 or 29 cream bands on the body and 9–13 on the tail (vs. 9–15 bands on the body and none on the tail) (Boulenger 1893, Neang et al. 2014).

Lycodon pictus sp. nov. differs from L. ophiophagus, a species from southern Thailand but with similar scalation, in having a loreal entering the eye (vs. separated) and in dorsal colour pattern (28 or 29 light bands on a brown body vs. 20 or 21 white bands on a dark body) as well as and in having irregular bands turning into a marbling posteriorly (vs. clearly demarcated cross bands on the body) (Vogel et al 2009).

For additional measurements, dentition, and scalation data see Tables 28.

Figure 6. 

Dorsal head and neck pattern of the juvenile paratype of Lycodon pictus sp. nov. (ZFMK 93747) in preservative. Photograph T. Ziegler.

Distribution

Lycodon pictus sp. nov. is currently known only from Ha Lang and Trung Khanh districts, Cao Bang Province, northern Vietnam (Fig. 7).

Etymology

The name of the species pictus means painted or decorated in Latin and refers to its unique dorsal colour pattern.

Natural history

Lycodon pictus sp. nov. seems to be closely associated with karst environment. Specimens were found at night between 19:00 and 23:00, on forest paths or on the ground near cave entrances. The surrounding habitat was secondary karst forest, consisting of medium and small hardwood trees mixed with shrubs and vines. Air temperature was 23.4–29.6°C and humidity was 66–79%. Other reptiles were also found at the site, including Acanthosaura lepidogaster (Cuvier, 1829), Gekko adleri Nguyen, Wang, Yang, Lehmann, Le, Ziegler & Bonkowski, 2013, Goniurosaurus luii Grismer, Viets & Boyle, 1999, Lycodon futsingensis (Pope, 1928), and Protobothrops trungkhanhensis Orlov, Ryabov & Nguyen, 2009 (Fig. 8).

Figure 7. 

Map showing the type locality of Lycodon pictus sp. nov. in Cao Bang Province.

Figure 8. 

Habitat of Lycodon pictus sp. nov.: the female paratype (ZFMK 93746) was found in Ha Lang District, Cao Bang Province.

Measurements (in mm), dentition, and scalation data of Lycodon species from Vietnam. Data taken from Blanford (1878), Pope (1928), Smith (1943), Boulenger (1893), Daltry and Wüster (2002), Jackson and Fritts (2004), Vogel et al. (2009), Neang et al. (2014), Do et al. (2017), and Luu et al. (2019); distinguishing characters are marked in bold. For abbreviations see Materials and methods.

Lycodon pictus sp. nov. L. capucinus L. cardamomensis L. davisonii L. fasciatus L. flavozonatus L. futsingensis L. laoensis
TL 597 816 896 920 ♂ 894 1440 ♂,1210 ♀ 850 ♂ 773 ♀ 470
Teeth max 13 or 14 15 10–12 11 13 12–15
SL 8 9 or 10 8 7 8 8 8 (7) 9 or 10
SL/orbit 3–5 3–5 3–5 3–4 3–5 3–5 3–5 (4–5; 2–4;4–6) 3–5
IL 10 9 or 10 10 8 9 (8, 10) 10 10 (9, 11) 10
PreOc 1 1 1 0 1 1 1 1
PostOc 2 2 2 or 3 1 or 2 2 2 2 (3) 2 (3)
Lor 1 1 1 1 1 1 1 1
Lor/eye yes no no yes yes no no no
Atem 2 2 2 1 or 2 2 2 2 (1) 2
PTem 3 3 2 or 3 2 2 2 or 3 3 (2) 3
DSR 17-17-15 17-17-15 19-17-15 13 17-17-15 17-17-15 17-17 (16)- 15 17-17-15
Ven 212-218 182-211 215-228 233-265 182-225 211-221 ♂ 212-218 ♀ 193-204 ♂, 198-208 163-192
Prec single divided single single single divided/ single single divided
Subc 90 or 91 59-74 87-93 90-108 65-94 81-88 ♂, 80-84 72-87 ♂, 78-85 60-76
BodySc smooth weakly keeled weakly keeled smooth keeled 7 rows feebly keeled at midbody smooth smooth

Measurements (in mm), dentition, and scalation data of Lycodon species from Vietnam (continuation of Table 2). Data from Günther (1875), Boulenger (1893), Hu et al. (1975), Zhao (2006), Vogel et al. (2009), Guo et al. (2013), Neang et al. (2014), Gawor et al. (2016), Luu et al. (2018), Luu et al. (2019), and based on examined specimens from ZFMK (see Appendix 1). Key: distinguishing characters are marked in bold; * Luu et al. (2019) mention 240 ventrals as maximum for L. rufozonatus; however, that is a transcription error from Bourret (1935) who gave 204 as the maximum number of ventrals. For abbreviations see Materials and methods.

L. meridionalis L. namdongensis L. paucifasciatus L. rosozonatus L. rufozonatus L. ruhstrati abditus L. septentrionalis L. subcinctus
TL 1139 723 763 1060 1234 964 1163 1000
Teeth max 11 12 11 or 12 12 or 13 11–13 11–13 7 8–14
SL 8 8 8 8 8 8 8 8
SL/orbit 3–5 3–5 3–5 3–5 3–5 3–5 3–5 (3–6)
IL 10 10 10 10 (9) 10 (9,11) 7 or 8 8 or 9
PreOc 1 2/1 1 1 1 1 1 0
PostOc 2 3 2 2 2 2 2 2 or 3
Lor 1 1 1 1 1 1 1 1
Lor/eye no no no no no no no yes
Atem 2 2 2 2 2 2 (1) 2 1
PTem 3 2 3 3 3 3 (2) 3 2
DSR 17-17-15 17-17-15 19- (19-17)- 15 19-19- 15(17) (19-17)-17-15 17-17-15 17-17-15 17-17-15
Ven 227-240 218 219-222 221-234 184-225* 197-229 202-224 192-230
Prec divided single single single single single divided (rarely single)
Subc 96-106 85 90-92 53-98 90-103 83-104 60-91
BodySc dorsals feebly keeled in 10-12 median rows, smooth in outer rows smooth upper 1 or 2 dorsal scale row(s) plus vertebral row distinctly keeled weakly keeled feebly keeled in the posterior body part smooth (DSR 1-6), distinctly keeled (DSR 7-8 and vertebral row) 7 or 9 median rows feebly keeled feebly keeled

Measurements (in mm), dentition and scalation data of Lycodon species from China, Laos and Cambodia. Data taken from Zhao and Jiang (1981), Boulenger (1893), Vogel and David (2010) Vogel and Luo (2011), Zhang et al. (2011), Vogel et al. (2012), Lei et al. (2014), Neang et al. (2014), Zhang et al. (2015), Ganesh and Vogel (2018), and Luu et al. (2018). Key: plus sign (+) tail incomplete; distinguishing characters are marked in bold. For abbreviations see Materials and methods.

L. aulicus L. banksi L. davidi L. gongshan L. liuchengchaoi L. multizonatus L. synaptor L. zoosvictoriae
TL 719 465 + 389.5 963 ♂ 676 505 487 520.7
Teeth max 11 8 or 9 10 or 11 10 9
SL 9 (8 or 10) 8 8 8 7 or 8 8 (rarely 7) 8 8
SL/orbit 3–5 3–5 3–5 3–5 3–5 3–5 3–5 3–5/4–5
IL 10 or 11 10 10 8 8 (7,9) 8 (7) 8 10
PreOc 1 1 1 1 1 0 or 1 1 1 or 2
PostOc 2 2 2 2 2 2 2 2
Lor 1 1 1 1 1 1 1 1
Lor/eye no yes no yes yes yes no no
Atem 2 2 2 2 1-3 2 (1) 2 2
PTem 3 3 2 or 3 2 or 3 1-3 3 (2) 2 2
DSR 17-17-15 17-17-15 17-17-15 17-17-15 17-17-15 17-17-15 15 or 17-17-15 17-17-15
Ven 180-215 241 224 210–216 ♂, 215 ♀ 190-228 190-195 201-203 213 ♀
Prec divided single single single divided divided single single
Subc 57-78 26 + 99 95 or 96 ♂, 92 68-77 68-75 68 or 69 85
BodySc smooth and glossy smooth (six central DSR of posterior 1/3 feebly keeled) middorsal scale rows slightly keeled, outermost rows entirely smooth upper dorsal rows 6–12 and vertebral row keeled feebly keeled in median rows smooth 6-7 upper rows and vertebral row feebly keeled weakly keeled

Measurements (in mm), dentition, and scalation data of Lycodon species from Thailand and Myanmar. Data taken from Günther (1864), Boulenger (1893), Boulenger (1900), Smith (1943), Lanza (1999), Slowinski et al. (2001), Daltry and Wüster (2002), Vogel et al. (2009), Bahuguna and Bhuta (2010), Grismer et al. (2014), Luu et al. (2018), and Vogel and David (2019); distinguishing characters are marked in bold. For abbreviations see Materials and methods.

L. albofuscus L. butleri L. effraenis L. gibsonae L. gracilis L. jara L. kundui L. ophiophagus L. subannulatus L. zawi
TL 1480 876 700 906 533 535 ♂, 550 ♀ 909 684 480
Teeth max 12 13 9 11-13 8 or 10 12
SL 8 8 or 9 9 8 8 8 or 9 7 8 7 8 or 9
SL/orbit 3–5 3–5 3–5 3–4 and 3–5 3–4 3–5 3–4 3–5 3–4 3–5
IL 9 or 10 10 or 11 10 10 8 9 or 10
PreOc 1 1 1 1 2 1 1 1 1
PostOc 2 2 2-3 2 2 2 2 2 2 2 (1)
Lor 1 1 0 1 1 (united with lower PreOc) 1 1 1 1 1
Lor/eye no yes no Lor yes yes no no no yes no
Atem 2 2 2 2 2 1 or 2 1 2 2 2 (3)
PTem 2 2 2 or 3 3 3 2 or 3 2 3 2 3 (4)
DSR 17 19 (17 in Boulenger 1900) 17 17-17-15 15 17-17-15 15-15-15 17-17-15 15-15-15 17-17-15
Ven 241 220-227 215-228 223-226 234 167-188 186 211-212 225-244 179-194 ♂, 207
Prec divided single single single single divided divided (entire in Lanza 1999) single single divided
Subc 155-208 81-96 72-99 91-92 ♂ 81-83 52-74 70 87-90 93-111 45-75
BodySc keeled keeled smooth upper 3 or 4 rows keeled keeled smooth smooth smooth keeled smooth

Measurements (in mm), dentition and scalation data of Lycodon species from India. Data taken from Boulenger (1893), Wall (1906), Smith (1943), Taylor (1950), Captain (1999), Vijayakumar and David (2005), Mukherjee and Bhupathy (2007), Mistry et al. (2007), Vogel and Luo (2011), Vogel and Harikrishnan (2013), Ganesh and Vogel (2018), and Melvinselvan et al. (2018); distinguishing characters are marked in bold. For abbreviations see Materials and methods.

L. anamallensis L. flavicollis L. flavomaculatus L. gammiei L. hypsirhinoides L. mackinnoni L. nympha L. striatus L. tiwarii L. travancoricus
TL 522 543 520 1150 717 ♂, 563 ♀ 365 574 432 790 600 ♂, 625 ♀
Teeth max 8–10
SL 9 9 9 8 (7,9) 9 8 (7) 7 (8 or 6) 9 9
SL/orbit 3–5 3–5 3–5 3–5 (3–4) 3–5 3–5 3–4 3–5 3–5
IL 10 or 11 11 10 10 8 11
PreOc 1 1 1 1 1 1 1 or 2 1 1
PostOc 2 or 3 2 2 2 (1) 2 2 2 2 2
Lor 1/1 (except Holotype 2/2) 1 1 1 1 1 (0 in Wall 1906) 1 1 1
Lor/eye no no no no no yes no no
Atem 2 2 (3) 2 (1) 2 or irregular 2 1 or 2 2 2 rarely 1 2 or 3
PTem 3+4 3 (rarely 2) 3 (rarely 2) 2 or irregular 3 2 or 3 2 or 3 3 rarely 2 3
DSR 17-17-15 17-17-15 17-17-15 17-17 (19)-15 17-17-15 17-17-15 13-13-13 17-17-15 ?-17-15 17-17-15
Ven 174–186 ♂, 186–204 210-224 165-183 205-220 188–202 ♂, 199–210 163- 187 200-243 153-178 218-237 176-206
Prec divided (except holotype) divided divided single divided divided divided divided divided single
Subc 63–73 ♂, 60–74 65-72 53-63 98-111 68–75 ♂, 61–68 48-56 65-88 42-66 61-102 64-76
BodySc smooth smooth with single apical pit smooth 9 dorsal rows keeled, 5 rows at each side smoot smooth smooth keeled smooth smooth

Measurements (in mm), dentition and scalation data of Lycodon species from the Philippines. Data taken from Griffin (1909), Taylor (1922), Leviton (1965), Ota and Ross (1994), Lanza (1999), Gaulke (2002), and Gaulke et al (2003); distinguishing characters are marked in bold. For abbreviations see Materials and methods.

L. alcalai L. bibonius L. chrysoprateros L. dumerilii L. fausti L. ferroni L. muelleri L. philipinus L. solivagus L. tessellatus
TL 787 ♂ 511 727 547 ♂, 521 ♀ 337 382 302 ♂, 204 ♀ 486 946 900
Teeth max 11–13 11–14 11–13 13–15 13 12 14–15 8 11–13
SL 9 7–9 9 11–13 9 10 9 7 9 8 or 9
SL/orbit 4–5 3–5 (4–5) 3–5 4–5 4–5 4–6 4–5 3–4 4–5 4–5
IL 10 9 or 10 10 9 or 10 9 or 10 10 10 7 10
PreOc 2 2 2 1 or 2 2 2 1 or 2 0 or 1 2 1
PostOc 3 2 or 3 2 or 3 2 3 2 2 or 3 2 or 3 2 or 3 2
Lor 1 1 1 1 1 1 1 1 1 1
Lor/eye no no no no (only when fused with PreOc) no no yes no no
Atem 2 2+3 2+3+4 2 2 2 2 2 2 2
PTem 3 2+3+3 2+3+3 3 3 or 2 3+4 3+4 3 3 2 or 3
DSR 19-17-15 19-17-15 19-17-15 19-17-15 19- 17- 15 19-17-15 19-17-15 15 19-17-15 17 or 21
Ven 203-207 204-212 186-194 195-221 207 or 215 203 205-213 216-225 198-203 222-232
Prec single single single single single single single single single divided
Subc 108-126 110-120 111-117 111-120 135-148 109 112-117 87-99 112-115 56
BodySc smooth smooth smooth smooth smooth smooth smooth smooth

Measurements (in mm), dentition and scalation data of Lycodon species from Sri Lanka, Malaysia, Japan and Indonesia. Data taken from Boulenger (1893), Stejneger (1907), Smith (1943), Vogel et al. (2009), Grismer et al. (2014), and Wostl et al. (2017); distinguishing characters are marked in bold. For abbreviations see Materials and methods.

L. carinatus L. cavernicolus L. multifasciatus L. orientalis L. semicarinatus L. sidiki L. stormi L. tristrigatus
TL 730 508.2 700 660 1100 715 597 360
Teeth max 10 or 11 7 8 or 10
SL 8 or 9 9 or 10 8 8 8 8 7
SL/orbit 3-5 4-6 3-5 3-5 3-5 3-4 3-4
IL 10 or 11 10/9
PreOc 1 1 0 1 0 1 0
PostOc 2 2 2 2 2 2 2
Lor 1 1 1 1 1 1 1
Lor/eye no yes no yes no yes no yes
Atem 2 3 (2) 2 2 2 1 2
PTem 2 or 3 3 or 4 3 3 2 3 2 or 3
DSR 17 or 19-19-17 17-17-15 17-17-? 17 17 17-17-15 19 15
Ven 185-202 245 ♂, 232 232-237 ♂ 229-235 200-208 211-234 195 217 224
Prec single single divided single divided single single
Subc 51-64 113 ♂, 92 115-119 ♂ 106- 117 68-74 65-105 85 75 86
BodySc strongly keeled the 8 medial rows weakly keeled keeled scales with a very faint keel along their anterior half scales keeled along anterior half (4 outer rows smooth, other with a feeble though distinct keel on the basal half of each scale) keeled smooth keeled

Discussion

Our phylogenetic analyses reveal Lycodon pictus sp. nov. to be the sister taxon to a clade containing L. multizonatus and L. liuchengchaoi from China, but only with strong statistical support in the BI. The new species differed from the latter by at least 7.5% in uncorrected pairwise sequence distance. There has been some taxonomic confusion in the genus Lycodon. Two of the L. liuchengchaoi sequences (KC733201, KC733202) in the phylogenetic tree had previously been identified as L. fasciatus, but the phylogenetic analysis by Guo et al. (2015) correctly assigned them to L. liuchengchaoi. Lycodonflavozonatus”, on the other hand, appears to be paraphyletic with Lycodonmeridionalis” (MH669271, MH669268). Moreover, the Lycodon subcinctus species group is likely to contain cryptic diversity. In terms of uncorrected pairwise genetic distance of populations within this species group, two samples (GenBank numbers KX822581 and KX822582) are approximately 9.1–9.2% divergent from KC733203 and 6.3–6.5% from KC010384 and KC010385. The latter two clades differ by approximately 8.0% from each other. These issues need to be further investigated in future studies.

This new discovery increases the number of Lycodon known from Vietnam to 16, of which nine are confined to karst formations, underlining the importance of this habitat in promoting reptile speciation (Luu et al. 2018). Although Vietnam is located in the region with one of the most extensive limestone outcrops in the world (Day and Urich 2000) many of the areas are still poorly surveyed, and likely contain a high level of cryptic diversity. Recent studies show that this habitat harbours a significant portion of endemic diversity in the region and should be protected from anthropogenic threats (Clement et al. 2006, Nguyen et al. 2015, Luu et al. 2016).

Acknowledgements

We are grateful to the directorates of the Forest Protection Department of Cao Bang Province, Forest Protection Units of Ha Lang and Trung Khanh districts for support of our field work and issuing relevant permits. Thanks to D.T. Le, H.T. An (Hanoi), S. Herbst, T. Lehmann, and M. Bonkowski (Cologne) for their assistance, E. Sterling (New York) and K. Koy (Berkeley) for providing the map. We thank J. Wang from the State Key Laboratory of Biocontrol / The Museum of Biology, School of Life Sciences, Sun Yat-sen University, Guangzhou for kindly providing the translation of the original description of Lycodon multizonatus. Many thanks also to B.L. Stuart (Raleigh) and T.T. Nguyen (Hanoi) for helping to improve a previous version of the manuscript. For the fruitful cooperation within joint research projects we cordially thank S.V. Nguyen (IEBR, Hanoi), as well as T. Pagel and C. Landsberg (Cologne Zoo). Cologne Zoo is partner of the World Association of Zoos and Aquariums (WAZA): Conservation Project 07011 (Herpetodiversity Research). This research is supported by the National Foundation for Science and Technology Development (NAFOSTED, Grant No. 106.05-2017.329). Field work in Cao Bang was partially supported by the Nagao Natural Environment Foundation (Japan).

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Appendix 1

Comparative specimens examined

Lycodon fasciatus. Vietnam: Quang Binh Province (ZFMK 86448)

Lycodon fasciatus. Vietnam: Quang Binh Province (ZFMK 86449)

Lycodon fasciatus. Vietnam: Quang Binh Province (ZFMK 86450)

Lycodon futsingensis. Vietnam: Cao Bang (IEBR 4165)

Lycodon futsingensis. Vietnam: Cao Bang (IEBR 4170)

Lycodon futsingensis. Vietnam: Vinh Phuc (ZFMK 89385)

Lycodon laoensis. Cambodia: Phnom Penh (ZFMK 54886)

Lycodon laoensis. Vietnam: Dong Nai (ZFMK 88928)

Lycodon meridionalis. Vietnam: Quang Ninh (ZFMK 95193)

Lycodon meridionalis. Vietnam: Hai Phong (ZFMK 94906)

Lycodon meridionalis. Vietnam: Bac Giang (ZFMK 89389)

Lycodon meridionalis. Vietnam: Vinh Phuc (ZFMK 89225)

Lycodon paucifasciatus. Vietnam: Quang Binh (ZFMK 86452)

Lycodon paucifasciatus. Vietnam: Quang Binh (ZFMK 80661)

Lycodon paucifasciatus. Vietnam: Quang Binh (ZFMK 80662)

Lycodon subcinctus. Indonesia: Bali (ZFMK 95499)

Lycodon subcinctus. Vietnam: Dong Nai (ZFMK 91899)