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A new species of Pareas (Squamata, Pareidae) from southern Vietnam
expand article infoDuong T. T. Le§, Thinh G. Tran, Huy D. Hoang§, Bryan L. Stuart|
‡ University of Science, Ho Chi Minh, Vietnam
§ Vietnam National University, Ho Chi Minh, Vietnam
| North Carolina Museum of Natural Sciences, Raleigh, United States of America
Open Access

Abstract

We describe a new species of pareid snake from the Di Linh Plateau in Lam Dong Province of southern Vietnam based on morphological and molecular evidence. Pareas temporalis sp. nov. is distinguished from its congeners by having the combination of yellow-brown body colouration; hexagonal-shaped frontal, with lateral sides parallel to the body axis; 16–17 temporals, with 4–5 anterior temporals; loreal and prefrontal not contacting eye; 2–3 preoculars; two suboculars; 2–3 postoculars; 8–9 supralabials; 8–9 infralabials; 15–15–15 dorsal scale rows, all keeled, three vertebral scale rows enlarged; 191 (+1 preventral) ventrals, smooth; 92 subcaudals, all divided; undivided anal scale; two postocular stripes; and a solid dark brown vertebral stripe extending from rear of nuchal collar along the entire length of body and tail. Phylogenetic analyses of mitochondrial DNA data recovered the new species to be nested within the P. carinatus complex and to be the sister taxon to P. nuchalis from Borneo.

Keywords

Di Linh Plateau, integrative taxonomy, Pareatinae, Pareas menglaensis, Southeast Asia

Introduction

The genus Pareas is the most species-diverse genus in the subfamily Pareatinae and is distributed throughout tropical and subtropical parts of Asia (Rao and Yang 1992). It differs from other pareid genera by having 15 rows of dorsal scales at midbody, divided subcaudals, suboculars, supralabials not touching the eye, no anterior single inframaxillary, and three pairs of inframaxillaries (Grossmann and Tillack 2003). The monophyly of Pareas with respect to other pareid genera has been recovered with statistical support in some studies (e.g., Ding et al. 2020; Vogel et al. 2020), but not in others (e.g., Guo et al. 2011; Pyron et al. 2013; You et al. 2015; Figueroa et al. 2016; Liu and Rao 2021).

After 77 years without any descriptions of new species in the genus (from 1937 to 2014), seven new species have been described since 2015, mostly based on integrative taxonomic approaches incorporating molecular analyses and morphological comparisons (Liu and Rao 2021; Uetz et al. 2021; Vogel et al. 2021). These integrative taxonomic approaches have also clarified some taxonomic uncertainties in previously described species. For example, recent studies have shown P. macularius Theobald, 1868 to be a species distinct from P. margaritophorus (Jan, 1866) (e.g., Hauser 2017; Suntrarachun et al. 2020; Vogel et al. 2020) following their synonymy by Huang (2004). To the contrary, Liu and Rao (2021) considered P. mengziensis, a new species very recently described by Wang et al. (2020), to be conspecific with P. niger Pope, 1928 based on molecular and morphological data.

During field work in the Di Linh Plateau at the southernmost tip of the Truong Son mountain range in Vietnam, we discovered a single specimen of Pareas that differed in morphological and molecular data from all members of the genus. Based on these corroborated lines of evidence, we describe this species as new.

Methods

Fieldwork was carried out by DTTL and TGT in Doan Ket Commune, Da Huoai District, Lam Dong Province, Vietnam, in July 2020. The specimen was stored in 75% ethanol after preserving liver in 99% ethanol. Specimens and tissue samples were deposited at the Lab of Zoology, University of Science, Ho Chi Minh City (UNS).

Morphometrics

Measurements of the single Di Linh specimen were taken to the nearest 0.1 mm with dial calipers. Paired meristic characters are given as left/right. Measurements and meristic counts were taken following Wang et al. (2020). Morphological measurements (all in mm) and scale counts included snout-vent length (SVL); tail length (TaL); total length (TL); relative tail length (TaL/TL); number of dorsal scales counted at approximately one head length behind the head, midbody, and one head length before vent; ventral scales; subcaudal scales; supralabials; infralabials; number of keeled dorsal scale rows at midbody; anterior temporals; posterior temporals; preoculars; and postoculars.

Comparative data for other species were taken from relevant publications (Boulenger 1900; Boulenger 1914; Malkmus et al. 2002; Guo and Deng 2009; Stuebing et al. 2014; Vogel 2015; You et al. 2015; Bhosale et al. 2020; Ding et al. 2020; Suntrarachun et al. 2020; Vogel et al. 2020; Wang et al. 2020; Liu and Rao 2021; Vogel et al. 2021).

Molecular sequencing

Total DNA was extracted from liver preserved in 99% ethanol using aTopPURE genomic DNA extraction kit (ABT Biological solutions company limited, Vietnam). Two mitochondrial gene fragments, cytochrome b (cytb) and NADH dehydrogenase subunit 4 and its flanking tRNAs (ND4), were amplified by the polymerase chain reaction (PCR) using the primers L14910/H16064 (Burbrink et al. 2000) and ND4/Leu (Arèvalo et al. 1994). PCR conditions for cytb were denaturation at 94°C for seven minutes, followed by 40 cycles at 94°C for 40 seconds, 46°C for 30 seconds and 72°C for one minute, with a final extension step at 72°C for seven minutes. PCR conditions for ND4 were denaturation at 92°C for three minutes, followed by 35 cycles at 92°C for 45 seconds, 40°C for two minutes and 70°C for 1.5 minutes, with a final extension step at 70°C for five minutes. Sequences were edited using Chromas 2.6.6 (Technelysium Pty. Ltd.) and Geneious Prime 2021.1 (Biomatters Ltd.).

In addition, a 1,071 bp fragment of cytb of P. nuchalis (FK 2626; Table 1) was provided to the authors after being obtained as bycatch during a phylogenomic analysis by D. L. Rabosky et al. (in prep.). Newly generated sequences were deposited in GenBank under accession numbers MZ603792MZ603794 (Table 1).

Table 1.

Samples used in the molecular phylogenetic analyses. Institutional and collector abbreviations of vouchers are defined in the source publications.

Taxon Voucher Locality cytb ND4 Sources
Achalinus rufescens HS 14023 China, Anhui, Qimen KT897595 KT897595 Zhang et al. (2017)
Aplopeltura boa KIZ 011963 Malaysia JF827673 JF827650 Guo et al. (2011)
Ap. boa LSUHC 7248 Malaysia, Sabah, Sepilok KC916746 Loredo et al. (2013)
Ap. boa UMMZ 201905 Brunei, Belait ABU49312 Kraus and Brown (1998)
Asthenodipsas laevis FMNH 241296 Malaysia, Sabah, Lahad Datu KX660468 KX660596 Figueroa et al. (2016)
As. laevis FMNH 273617 Malaysia, Sarawak, Bintulu KX660469 KX660597 Figueroa et al. (2016), Quah et al. (2019)
Pareas andersonii CAS 235359 Myanmar, Chin, Mt. Natmataung MT968772 MW287040 Ding et al. (2020), Vogel et al. (2020)
P. atayal NMNS 05594 China, Taiwan, Yilan, Beiheng KJ642124 MW287041 You et al. (2015), Ding et al. (2020)
P. atayal HC 000618 China, Taiwan, Yilan JF827685 JF827662 Guo et al. (2011)
P. atayal HC 000628 China, Taiwan, Taoyuan JF827686 JF827663 Guo et al. (2011)
P. boulengeri None China, Anhui, Qimen, Huangjialing MN866896 MN866896 Huang et al. (2020)
P. boulengeri KIZ 09965 China, Hubei, Enshi JF827678 JF827655 Guo et al. (2011)
P. boulengeri GP 2923 China, Guizhou, Jiangkou MK135090 MK805355 Wang et al. (2020)
P. boulengeri GP 207 China, Sichuan, Anxian MK135091 MK805356 Wang et al. (2020)
P. boulengeri GP 3095 = YBU 13323A China, Hubei, Wufeng MK135092 MK805357 Wang et al. (2020)
P. boulengeri GP 4716 Yidu, Hubei, China MK135093 MK805358 Wang et al. (2020)
P. boulengeri GP 3428 China, Anhui, Yixian MK135094 MK805359 Wang et al. (2020)
P. boulengeri GP 4827 = YBU 17155 China, Zhejiang, Chunan MK135095 MK805360 Wang et al. (2020)
P. boulengeri GP 4886 = YBU 17245 China, Zhejiang, Chunan MK135096 MK805361 Wang et al. (2020)
P. carinatus DL 2008-S039 Malaysia JF827677 JF827653 Guo et al. (2011)
P. carinatus GP 1079 Malaysia, Kuala Lumpur MK135110 MK805375 Wang et al. (2020)
P. carinatus GP 5131 = KIZ 011972 Malaysia, Kuala Lumpur MK135111 MK805376 Wang et al. (2020)
P. carinatus GP 5129 = KIZ 011970 Malaysia, Kuala Lumpur MK135112 MK805377 Wang et al. (2020)
P. carinatus CAS 247982 Myanmar, Tanintharyi, Yaephyu MT968778 Vogel et al. (2020)
P. carinatus LSUHC 10604 Malaysia, Kedah, Sungai Sedim KC916748 Loredo et al. (2013)
P. chinensis CIB 098269 China, Sichuan, Tianquan JF827691 JF827668 Guo et al. (2011)
P. chinensis GP 2196 China, Sichuan, Junlian MK135088 MK805353 Wang et al. (2020)
P. chinensis GP 2383 China, Sichuan, Hongya MK135089 MK805354 Wang et al. (2020)
P. formosensis GP 2146 = YBU 12015 China, Hainan MK135068 MK805333 Wang et al. (2020)
P. formosensis GP 2164 China, Hainan MK135069 MK805334 Wang et al. (2020)
P. formosensis GP 2165 China, Hainan MK135070 MK805335 Wang et al. (2020)
P. formosensis GP 2170 = YBU 12032 China, Hainan MK135071 MK805336 Wang et al. (2020)
P. formosensis GP 4581 China, Zhejiang, Jingning MK135072 MK805337 Wang et al. (2020)
P. formosensis GP 4659 = YBU 17029 China, Hainan MK135073 MK805338 Wang et al. (2020)
P. formosensis GP 2332 = YBU 12090 China, Guizhou, Leishan MK135074 MK805339 Wang et al. (2020)
P. formosensis GP 2384 = YBU 12115 China, Guizhou, Rongjiang MK135075 MK805340 Wang et al. (2020)
P. formosensis GP 3911 = YBU 14508 China, Guangxi MK135076 MK805341 Wang et al. (2020)
P. formosensis GP 3696 China, Jiangxi, Yanshan MH046857 MK805382 Wang et al. (2020)
P. formosensis GP 3808 China, Jiangxi, Yanshan MH046858 MK805383 Wang et al. (2020)
P. formosensis GP 3859 = YBU 14573 China, Jiangxi, Yanshan MH046859 MK805384 Wang et al. (2020)
P. formosensis NMNH 05637 China, Taiwan, Nantou, Xitou MW287060 MW287042 Ding et al. (2020)
P. formosensis H26-HAM01 China, Guangdong MW287061 MW287043 Ding et al. (2020)
P. formosensis ZMMU R-16684 Vietnam, Cao Bang, Phia Bac MW287062 MW287044 Ding et al. (2020)
P. formosensis ZMMU NAP-08868 Vietnam, Quang Nam, Song Thanh MW287063 MW287045 Ding et al. (2020)
P. formosensis ZMMU R-13709 Vietnam, Lam Dong, Bidoup - Nui Ba MW287064 MW287046 Ding et al. (2020)
P. formosensis ZMMU R-14072 Vietnam, Dak Lak, Chu Yang Sin MW287065 MW287047 Ding et al. (2020)
P. formosensis ZMMU R-16333 Vietnam, Gia Lai, Kon Chu Rang MW287066 MW287048 Ding et al. (2020)
P. geminatus ZMMU NAP-09280 = R-16695 Laos, Xaisomboun, Long Tien MW287073 MW287049 Ding et al. (2020)
P. geminatus ZMMU R-16478 Thailand, Chiang Mai, Doi Inthanon MW287074 MW287050 Ding et al. (2020)
P. geminatus ZMMU R-16477 Thailand, Chiang Mai, Mae Kampong MW287075 MW287051 Ding et al. (2020)
P. geminatus AUP-00176 Thailand, Chiang Mai, Doi Inthanon MW287076 MW287052 Ding et al. (2020)
P. hamptoni GP 5127 = YPX 18219 Myanmar, Kachin MK135077 MK805342 Wang et al. (2020)
P. hamptoni GP 5128 = YPX 18604 Myanmar, Kachin MK135078 MK805343 Wang et al. (2020)
P. hamptoni ZMMU NAP-09087 Vietnam, Lao Cai, Bat Xat MW287078 MW287054 Ding et al. (2020)
P. hamptoni ZMMU NAP-09088 Vietnam, Lao Cai, Bat Xat MW287079 MW287053 Ding et al. (2020)
P. iwasakii I03-ISG1 Japan, S. Ryukyu, Ishigaki KJ642158 You et al. (2015)
P. kaduri BNHS 3574 India, Arunachal Pradesh, Lohit MT188734 Bhosale et al. (2021)
P. komaii HC 000669 China, Taiwan, Taitung, Lijia JF827687 JF827664 Guo et al. (2011)
P. komaii NMNS 05625 China, Taiwan, Hualien KJ642189 MW287055 You et al. (2015), Ding et al. (2020)
P. komaii NMNS 05618 China, Taiwan, Taitung, Lijia KJ642185 MW287056 You et al. (2015), Ding et al. (2020)
P. macularius GP 815 China, Hainan MK135101 MK805366 Wang et al. (2020)
P. macularius GP 2110 China, Hainan MK135102 MK805367 Wang et al. (2020)
P. macularius GP 2147 = YBU 12016 China, Hainan MK135103 MK805368 Wang et al. (2020)
P. macularius GP 4660 = YBU 17030 China, Hainan MK135104 MK805369 Wang et al. (2020)
P. macularius GP 4715 = YBU 17078 China, Yunnan, Jingdong MK135105 MK805370 Wang et al. (2020)
P. macularius GP 4699 = YBU 17062 China, Yunnan, Jingdong MK135106 MK805371 Wang et al. (2020)
P. macularius ZMMU R-16629 Myanmar, Sagaing, Ban Mauk MT968771 MW287057 Ding et al. (2020), Vogel et al. (2020)
P. margaritophorus GP 4410 = YBU 16061 China, Guangxi, Cangwu MK135097 MK805362 Wang et al. (2020)
P. margaritophorus GP 4837 = YBU 17164 China, Guangxi, Cangwu MK135098 MK805363 Wang et al. (2020)
P. margaritophorus GP 4437 China, Guangxi, Cangwu MK135099 MK805364 Wang et al. (2020)
P. margaritophorus GP 4465 = YBU 16095 China, Guangxi, Cangwu MK135100 MK805365 Wang et al. (2020)
P. margaritophorus M01 Vietnam, Binh Phuoc, Bu Gia Map KJ642195 MW287058 You et al. (2015), Ding et al. (2020)
P. menglaensis GP 1292 China, Yunnan, Mengla MK135113 MK805378 Wang et al. (2020)
P. menglaensis GP 3356 = YBU 14124 China, Yunnan, Mengla MK135114 MK805379 Wang et al. (2020)
P. menglaensis GP 3376 = YBU 14141 China, Yunnan, Mengla MK135115 MK805380 Wang et al. (2020)
P. menglaensis GP 3377 = YBU 14142 China, Yunnan, Mengla MK135116 MK805381 Wang et al. (2020)
P. modestus MZMU 1293 India, Mizoram, Aizawl, Tanhril MT968773 Vogel et al. (2020)
P. monticola ZMMU R-16631 Myanmar, Sagaing, Ban Mauk MW438296 MW438301 Vogel et al. (2021)
P. monticola ADR 507 India, Assam, Orang MN970038 MN970043 Deepak et al. (2020)
P. monticola GP 2027 China, Xizang, Motuo MK135107 MK805372 Wang et al. (2020)
P. monticola GP 5132 = KIZ 047036 China, Yunnan, Pingbian MK135108 MK805373 Wang et al. (2020)
P. monticola GP 5133 = KIZ 014167 China, Xizang, Motuo MK135109 MK805374 Wang et al. (2020)
P. niger GP 1294 China, Yunnan, Mengzi MK135079 MK805344 Wang et al. (2020)
P. niger GP 3551 = YBU 14251 China, Yunnan, Mengzi MK135080 MK805345 Wang et al. (2020)
P. niger GP 3552 = YBU 14252 China, Yunnan, Mengzi MK135081 MK805346 Wang et al. (2020)
P. niger GP 3553 = YBU 14253 China, Yunnan, Mengzi MK135082 MK805347 Wang et al. (2020)
P. niger GP 3588 = YBU 14288 China, Yunnan, Mengzi MK135083 MK805348 Wang et al. (2020)
P. niger GP 4122 = YBU 15100 China, Yunnan, Kaiyuan MK135084 MK805349 Wang et al. (2020)
P. niger GP 4123 = YBU 15114 China, Yunnan, Kaiyuan MK135085 MK805350 Wang et al. (2020)
P. nigriceps CHS 656 = SYSr001222 China, Yunnan, Gaoligongshan MK201455 Li et al. (2020)
P. nuchalis FK 2626 Brunei, Belait MZ603794 U49311 This study, Kraus and Brown (1998)
P. stanleyi GP 229 China, Guangxi MK135086 MK805351 Wang et al. (2020)
P. stanleyi GP 2343 = YBU 12094 China, Guizhou, Leishan MK135087 MK805352 Wang et al. (2020)
P. stanleyi HM 2007-S001 China, Guangxi, Guilin JN230704 JN230705 Guo et al. (2011)
P. temporalis sp. nov. UNS 09992 Vietnam, Lam Dong, Da Huoai MZ603793 MZ603792 This study
P. victorianus CAS 235254 Myanmar, Chin, Mt. Natmataung MW438300 MW438302 Vogel et al. (2021)
P. vindumi CAS 248147 Myanmar, Kachin, Chipwi, Lukpwi MW287080 MW287059 Ding et al. (2020)
P. xuelinensis KIZ XL 1 China, Yunnan, Lancang MW436709 Liu and Rao (2021)
Xylophis captaini BNHS 3376 India, Kerala, Kottayam, Kannam MK340914 MK340912 Deepak et al. (2018)
X. perroteti BNHS 3582 India, Tamil Nadu, Nilgiri, Sholur MN970042 MN970046 Deepak et al. (2020)

Phylogenetic analysis

Homologous sequences of all currently recognized species of Pareas, two representatives of each of the pareid genera Aplopeltura, Asthenodipsas, and Xylophis, and the xenodermatid outgroup Achalinus rufescens (following Figueroa et al. 2016, Deepak et al. 2018, Li et al. 2020) were downloaded from GenBank (Table 1). Newly generated and downloaded sequences were aligned using the default parameters in the MAFFT 7.45 alignment algorithm (Katoh and Standley 2013) implemented in Geneious Prime 2021.1.1 (Biomatters Ltd.). Alignments were visually checked to ensure that insertion-deletions did not disrupt translation of coding regions. The dataset was partitioned by tRNA and codon positions of cytb and ND4 for a total of seven partitions. The best-fit partitioning scheme and models of sequence evolution were selected using the Akaike Information Criterion (AICc) in Partition Finder 2 (Lanfear et al. 2017). Four partitions were selected with the models TVM+I+G for tRNA, and cytb and ND4 first codon positions; TVM+I+G for cytb and ND4 second codon positions; TRN+I+G for cytb third codon position; and TIM+I+G for ND4 third codon position.

Bayesian inference (BI) was performed on the partitioned dataset using MrBayes 3.2.7a (Ronquist et al. 2012) on the Cyber infrastructure for Phylogenetic Research (CIPRES) Science Gateway version 3.3 (Miller et al. 2010). In each of four independent analyses, four chains were run for 20 million generations using the default priors, trees were sampled every 4,000 generations, and the first 25% of trees were discarded as ‘burn-in’. The resulting trace plots were viewed using Tracer v.1.7 (Rambaut et al. 2018). A 50% majority-rule consensus of the post burn-in trees was constructed to calculate the posterior probabilities of nodes. Maximum likelihood (ML) analysis was performed on the partitioned dataset using raxml GUI 2.0 (Edler et al. 2021). The GTR+I+G model was applied to the four partitions selected by PartitionFinder 2 (Lanfear et al. 2017) in a single analysis. Nodal support values were estimated by the thorough bootstrap with 1,000 pseudoreplicates. Nodes with posterior probabilities ≥ 0.95 and bootstrap values ≥ 70 were considered to be supported. Uncorrected pairwise (p) distances were calculated using PAUP* version 4.0a165 (Swofford 2003).

Results

Phylogenetic analysis

The dataset contained 1,971 aligned characters and 100 taxa. In the BI analysis, the standard deviation of split frequencies was 0.003490 among the four runs, and the Estimated Sample Sizes (ESS) of parameters were ≥ 2,248. The Di Linh Plateau taxon was deeply nested within the P. carinatus complex (sensu Ding et al. 2020; Vogel et al. 2021) and recovered with strong support in both the BI and ML analyses to be the sister taxon of P. nuchalis, with a Bayesian posterior probability (PP) of 0.99 (Fig. 1) and a ML bootstrap (BS) value of 74 (Fig. 2). In turn, these two species were sister to a clade containing P. carinatus and P. menglaensis, with a Bayesian PP of 1.00 (Fig. 1) and a ML BS value of 100 (Fig. 2).

Figure 1. 

Fifty percent majority-rule consensus phylogram resulting from partitioned Bayesian analysis of 1,971 aligned characters of the mitochondrial cytochrome b (cytb), NADH dehydrogenase subunit 4 (ND4), and flanking tRNA genes of pareid snakes. Trees were rooted with Achalinus rufescens (not shown). Numbers at nodes are Bayesian posterior probabilities. Sample information is provided in Table 1.

Figure 2. 

Maximum likelihood phylogeny based on a partitioned dataset containing 1,971 aligned characters of the mitochondrial cytochrome b (cytb), NADH dehydrogenase subunit 4 (ND4), and flanking tRNA genes of pareid snakes. Trees were rooted with Achalinus rufescens (not shown). Numbers at nodes are bootstrap values based on 1,000 pseudoreplicates. Sample information is provided in Table 1.

The Di Linh specimen had an uncorrected pairwise divergence in the coding region of cytb of 19.8% from P. nuchalis (n = 1), 19.8–20.2% from P. carinatus (n = 6), and 20.5–21.0% from P. menglaensis (n = 4). The Di Linh specimen had an uncorrected pairwise divergence in the coding region of ND4 of 17.9% from P. nuchalis (n = 1), 19.7–19.8% from P. carinatus (n = 4), and 19.6–19.8% from P. menglaensis (n = 4).

Taxonomy

Pareas temporalis sp. nov.

Figures 3, 4, 5

Suggested Common Names

Di Linh Snail-eating Snake (English), Rắn hổ mây Di Linh (Vietnamese).

Holotype

UNS 09992 (field number LD25711), adult female, Vietnam, Lam Dong Province, Da Huoai District, Doan Ket Commune, 11.340370°N, 107.620561°E, 496 m a.s.l., coll. 25 July 2020 by Duong T.T. Le and Thinh G. Tran.

Diagnosis

Pareas temporalis sp. nov. is distinguished from all other Pareas by having the combination of yellow-brown body colouration; hexagonal-shaped frontal, with lateral sides parallel to the body axis; 16–17 temporals, with 4–5 anterior temporals; loreal and prefrontal not contacting eye; 2–3 preoculars; two suboculars; 2–3 postoculars; 8–9 supralabials; 8–9 infralabials (Fig. 4); 15–15–15 dorsal scale rows, all keeled (Fig. 3b), three vertebral scale rows enlarged; 191 (+1 preventral) ventrals, smooth; 92 subcaudals, all divided; undivided anal scale; two postocular stripes; and a solid dark brown vertebral stripe extending from rear of nuchal collar along the entire length of body and tail.

Figure 3. 

Holotype female (UNS 09992) of Pareas temporalis sp. nov. in preservative. a: whole body in lateral view; b: keeled dorsal scales at midbody; c: ventral view of head; d: dorsal view of head; e and f: lateral views of head. Scale bars: 5 mm.

Figure 4. 

Head scalation of holotype female (UNS 09992) of Pareas temporalis sp. nov. in ventral, dorsal and lateral views. Illustration by Vo Ngoc Thinh.

Description of the holotype

Adult female (Figs 3a, 5), SVL 426 mm; TaL 152 mm; TL 578 mm; TaL/TL 0.263. Body slender, compressed; head elongate, clearly distinct from neck; snout round in dorsal view; eye slightly enlarged, pupil vertical and slightly elliptical; rostral slightly visible in dorsal view; nasal scale single; two internasals, wider than long, contacting rostral, loreal, nasals, prefrontals; two prefrontals, large, not contacting eye; frontal hexagonal-shaped with lateral sides parallel to the body axis, frontal smaller than parietals; single loreal contacting nasal, internasal, prefrontal, preocular, 2nd and 3rd supralabial (left) or 2nd supralabial (right), but not contacting eye; 1/1 supraocular; 2/2 suboculars; 2/3 preoculars; 2/3 postoculars; 9/8 supralabial scales, 5th, 6th, 7th/4th, 5th, 6th below (not touching) eye, 9th/8th longest;16–17 temporals (4+3+4+6/5+3+4+4); 8/9 infralabials, without mental groove; three pairs of chin shields, not equal in size, anterior pair of chin shields longer than broad, slightly longer than two posterior pairs; dorsal scales in 15–15–15 rows, all keeled without apical pits; three enlarged vertebral scale rows; 191 ventrals (+1 preventral), all smooth; 92 subcaudals, all divided; undivided anal scale.

Figure 5. 

Holotype female (UNS 09992) of Pareas temporalis sp. nov. in life (above) and view of habitat at its type locality (below).

Colouration

In life, top of head light brown with dark brown spots. Sides of head with two postocular stripes: lower stripe extends from the postorbital to the 9th/ 8th supralabial; upper stripe extends from the upper corner of the eye to the temporal area, then divides into two long stripes, with the upper arms meeting at the nape, while the lower arm extends to the corner of the jaw and sides of the neck before converging to form a black nuchal collar (collar six scales long at mid-dorsals). Ground colour of dorsum brown with dark-brown speckling and numerous irregular black cross-bands on lateral sides of body from neck to vent (64 bands on left and 62 bands on right), and a solid dark-brown vertebral stripe extending from the posterior end of the black nuchal collar along entire length of body and tail. Ventrals light brown with dark brown spots on lateral edges and middle of each scale, spotting weaker on chin shields. Ventral surface of tail dark brown. Colouration in preservative as in life, but with dorsum faded to yellowish brown.

Distribution and natural history

Pareas temporalis sp. nov. is currently only known by the holotype specimen from Da Huoai District, Lam Dong Province, southern Vietnam (Fig. 6). The sampling site is located near to the boundary of BinhThuan Province, and so it is likely that the new species is also found in forested areas of that province. The holotype was found at night (2100 hours) on a tree branch 1.5 m above the ground in disturbed mixed broadleaf and bamboo forest, where it occurred in sympatry with P. margaritophorus (e.g., UNS 09993). No further information is currently known on the biology of the new species.

Figure 6. 

Holotype locality of Pareas temporalis sp. nov. (black star) in Lam Dong Province, Vietnam.

Etymology

The specific epithet temporalis L. refers to the high number of temporal scales in the new species.

Comparisons

Pareas temporalis sp. nov. differs from P. margaritophorus, P. macularius, P. modestus Theobald, 1868 and P. andersonii (Boulenger, 1888) by having a light brown dorsum with irregular dark bands (vs. uniform grey to black to dark colouration, and with bicolored spots in P. margaritophorus, P. macularius and P. andersonii); prefrontal not contacting the eye (vs. contacting); fully keeled dorsal scale rows at midbody (vs. not fully keeled); three enlarged vertebral scales (vs. not enlarged); and frontal hexagonal with lateral sides parallel to body axis (vs. frontal subhexagonal with lateral sides converging posteriorly) (Ding et al. 2020; Suntrarachun et al. 2020; Vogel et al. 2020; Wang et al. 2020; Vogel et al. 2021).

Pareas temporalis sp. nov. differs from P. boulengeri (Angel, 1920), P. monticola (Cantor, 1839), P. stanleyi (Boulenger, 1914), P. vindumi (Vogel, 2015), P. victorianus (Vogel, Nguyen, Zaw & Poyarkov, 2021) and P. yunnanensis Vogt, 1922 by having the prefrontal not contacting the eye (vs. contacting); loreal not contacting the eye (vs. contacting); two suboculars (vs. 0–1 or suboculars fused with postoculars); 2–3 postoculars (vs 1–2 or postoculars fused with suboculars); fully keeled dorsal scale rows at midbody (vs. not fully keeled); 4–5 anterior temporals (vs. 1–2); and frontal hexagonal with lateral sides parallel to body axis (vs. frontal subhexagonal with lateral sides converging posteriorly) (Boulenger 1914; Guo and Deng 2009; Vogel 2015; Wang et al. 2020; Liu and Rao 2021; Vogel et al. 2021).

Pareas temporalis sp. nov. differs from P. geminatus Ding, Cheng, Suwannapoom, Nguyen, Poyarkov & Vogel, 2020, P. atayal You, Poyarkov & Lin, 2015, P. chinensis (Barbour, 1912), P. formosensis (Van Denburgh, 1909), P. hamptoni (Boulenger, 1905), P. iwasakii (Maki, 1937), P. komaii (Maki, 1931), P. niger Pope, 1928, P. xuelinensis Liu & Rao, 2021, P. nigriceps Guo & Deng, 2009 and P. kaduri Bhosale, Phansalkar, Sawant, Gowande, Patel & Mirza, 2020 by having the prefrontal not contacting eye (vs. contacting, except in P. nigriceps); two suboculars (vs. one or suboculars fused with postoculars); 2–3 preoculars (vs. one); fully keeled dorsal scale rows at midbody (vs. not fully keeled); 4–5 anterior temporals (vs. 1–3); and frontal hexagonal with lateral sides parallel to body axis (vs. frontal subhexagonal with lateral sides converging posteriorly) (Guo and Deng 2009; You et al. 2015; Bhosale et al. 2020; Ding et al. 2020; Wang et al. 2020; Liu and Rao 2021; Vogel et al. 2021).

Pareas temporalis sp. nov. is most closely related (Figs 12) and morphologically similar to other members of the P. carinatus complex, consisting of P. carinatus (Wagler, 1830), P. nuchalis (Boulenger, 1900), and P. menglaensis Wang, Che, Liu, Li, Jin, Jiang, Shi & Guo, 2020. Pareas temporalis sp. nov. differs from all three species by having 4–5 anterior temporals (vs. three); and a dark brown vertebral stripe on body and tail (vs. absent). Pareas temporalis sp. nov. further differs from P. carinatus by having 2–3 preoculars (vs. one); and all 15 dorsal scale rows keeled at midbody (vs. 0–11). Pareas temporalis sp. nov. further differs from P. nuchalis by having prefrontal not contacting eye (vs. contacting); 191 ventrals (vs. 195–220); and 92 subcaudals (vs. 102–120). Pareas temporalis sp. nov. further differs from P. menglaensis by having 191 ventrals (vs. 176–177); 92 subcaudals (vs. 65–79); 2–3 postoculars (vs. one); 15 dorsal scale rows keeled at midbody (vs. 11); and two black postorbital stripes on lateral side of head (vs. one thin postorbital stripe extending from postocular to neck on lateral side of head) (Boulenger 1900; Malkmus et al. 2002; Guo and Deng 2009; Stuebing et al. 2014; Ding et al. 2020; Wang et al. 2020; Vogel et al. 2021).

Discussion

Recent phylogenetic analyses of Pareas have revealed that the genus contains two major clades, the P. carinatus complex/group (Ding et al. 2020; Vogel et al. 2021; referred to “Pareas I” by Guo et al. 2011) consisting of P. carinatus, P. nuchalis, and P. menglaensis, and a second clade consisting of all other congeners (Guo et al. 2011; Ding et al. 2020; Vogel et al. 2020; Wang et al. 2020; Vogel et al. 2021). Guo et al. (2011) suggested that the P. carinatus complex (as “Pareas I”) may represent a distinct genus from other “Pareas” on the basis of large p-distances, their lack of statistical support for the monophyly of Pareas with respect to Aplopeltura and Asthenodipsas, and morphological diagnosability in having at least three anterior temporals, the frontal scale hexagonal with the lateral sides parallel to the body axis, and the anterior pair of chin shields broader than long. Our molecular phylogenetic analyses found P. temporalis sp. nov. to be a fourth member of the P. carinatus complex, and consistent with Guo et al.’s (2011) morphological diagnosis of the clade.

The description of Pareas temporalis sp. nov. from southern Vietnam brings the total number of recognized Pareas species to 25, of which seven occur in Vietnam (P. carinatus, P. formosensis, P. hamptoni, P. macularius, P. margaritophorus, P. monticola, and P. temporalis sp. nov.) (Nguyen et al. 2009; Ding et al. 2020). However, with only one specimen collected, information on the precise distribution, natural history, ecology, population status and conservation of the new species is unknown, as with many other Pareas species (see IUCN 2021; Uetz et al. 2021). We suggest that the new species be considered Data Deficient (DD) following IUCN’s Red List categories (IUCN 2021). However, it should be noted that the type locality of P. temporalis sp. nov. consists of disturbed forest on the Di Linh Plateau where no protected areas have been established. Remaining natural forests in the area are under high degree of threat from conversion to agricultural lands and commercial crops. Further surveys for P. temporalis sp. nov., and the possible existence of other endemic lineages on the Di Linh Plateau, are warranted.

An updated key to the P. carinatus complex is provided below

1 Prefrontal in contact with eye, ≥ 102 subcaudals (Borneo) P. nuchalis
Prefrontal not in contact with eye, < 102 subcaudals 2
2 All dorsal scale rows keeled at midbody, 4–5 anterior temporals, anterior pair of chin shields longer than broad P. temporalis sp. nov.
Some dorsal scale rows keeled at midbody, three anterior temporals, anterior pair of chin shields broader than long 3
3 One preocular, a black line from eye to nape, and another from behind eye to angle of mouth P. carinatus
Two preoculars, a thin postorbital stripe extending from postocular to neck P. menglaensis

Funding

This research was supported by funding from The Nagao Natural Environment Foundation (NEF).

Competing interests

The authors have declared that no competing interests exist.

Acknowledgements

The People’s Committee of Doan Ket Commune, Da Huoai District, Lam Dong Province, Vietnam, kindly facilitated surveys and issued a specimen collection permit (permit number 0025/GGT-KHTN). Ka Giang assisted with fieldwork. Pham Manh Hung assisted with DNA sequencing. Vo Ngoc Thinh illustrated Figure 4. Fred Kraus, Greg Schneider, and Ulmar Grafe helped to determine the disposition of the P. nuchalis specimen bearing field number FK 2626, and Dan Rabosky and Sonal Singhal generously donated the cytb sequence from that sample that they obtained as bycatch in a phylogenomic analysis that is underway. Ke Jiang provided additional locality data for the P. carinatus samples used in Wang et al. (2020). For all this assistance we are most grateful.

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