A New Species of Herpetoreas Günther, 1860 (Serpentes: Natricidae) from Yunnan, China

Abstract

A new species of the genus Herpetoreas is described from Yunnan Tongbiguan Provincial Nature Reserve, Yingjiang County, Dehong Prefecture, Yunnan Province, China. The new species can be separated from its congeners by a combination of the following characteristics: tail length to total length being 0.29, dorsal scales being all strongly keeled, 165 ventrals, divided cloacal plate, 89 pairs of subcaudals, 24 maxillary teeth, last two maxillary teeth being distinctly enlarged, approximately 13 white speckles presenting on anterior lateral surface of body, pale pink anterior venter, pink posterior venter, and rose red ventral tail. The genetic divergence between the new species and other species of this genus ranged from 6.7% to 13.0% in the mitochondrial cytochrome b gene. The new taxon represents the fifth species of the genus Herpetoreas in China and the first species of this genus in Yunnan Province.

1. Introduction

Herpetoreas Günther, 1860 is a genus that was separated from the Amphiesma Duméril, Bibron and Duméril, 1854 sensu lato [1], it is characterized by: body cylindrical, maximum total length of 943 mm; head moderately distinct from neck; nostrils and eye directed laterally; supralabials 8–9, usually third to fifth or fourth and fifth bordering orbit; dorsal scales in 19–19–17 rows, weakly to distinctly keeled, notched at apical apex; ventrals 136–234; tail length/total length 0.227–0.317; maxillary teeth 13–23, slightly increasing in size, last two or three distinctly enlarged, separated from anterior ones by a small diastema [2]. Currently, this genus comprises eight species, namely: H. burbrinki Guo, Zhu, Liu, Zhang, Li, Huang and Pyron, 2014, H. davidi Nguyen, Lalremsanga, Biakzuala and Vogel, 2024, H. murlen Lalremsanga, Bal, Vogel and Biakzuala, 2022, H. pealii (Sclater, 1891), H. platyceps (Blyth, 1854), H. sieboldii Günther, 1860, H. tpser Ren, Jiang, Huang, David and Li, 2022, and H. xenura (Wall, 1907) [3,4]. However, the diversity of this genus is still underestimated [1,2,3,5,6,7].

Most species of the genus Herpetoreas are distributed in or near the southern foothills of the Himalayas, with the exception of H. davidi, which is found on the west coast of Myanmar far from the foothills of the Himalayas. Four species of this genus have been reported from China, and all are distributed in Xizang Autonomous Region [8].

During our recent field works in western Yunnan Province, China, a snake specimen that can be assigned to the genus Herpetoreas was collected from Yunnan Tongbiguan Provincial Nature Reserve in Yingjiang County, Dehong Prefecture. Detailed morphological comparison and molecular data analysis showed that this specimen is a new species of Herpetoreas. We name and describe it herein.

2. Materials and Methods

The field survey in Yunnan Tongbiguan Provincial Nature Reserve was conducted under the permit from Yunnan Tongbiguan Provincial Nature Reserve Management and Protection Bureau. A specimen was collected by hand and stored in 75% ethanol after being photographed, and then deposited at Kunming Natural History Museum of Zoology, Kunming Institute of Zoology, Chinese Academy of Sciences (KIZ).

The following measurements and scale counts were noted: total length, snout–vent length, tail length, head length (from the tip of the snout to the posterior margins of the parietals), head width, internasals, prefrontals, frontals, parietals, loreals, preoculars, postoculars, supraoculars, suboculars, supralabials, infralabials, anterior temporals, posterior temporals, chin shields, dorsal scale rows (at one head length behind head-at midbody-at one head length before vent), ventrals (excluding preventrals, determination of first ventral according to Dowling [9]), cloacal plate, subcaudals (excluding terminal scute), and maxillary teeth. For comparison with other taxa, we relied on original and supplementary species descriptions [1,2,3,5,7,8,10,11,12,13,14,15,16,17,18,19,20,21,22,23].

Micro-CT scanning was performed using an in vivo and in vitro integrated commercial micro-CT device NEMO^® NMC-200 (PINGSENG Healthcare Inc., Kunshan, China). The skull images were exported from the virtual 3D model which was reconstructed by the software Avatar 2.0.12.9 (PINGSENG Healthcare Inc., Kunshan, China).

Total Genomic DNA was extracted from the liver tissue. A fragment of the mitochondrial cytochrome b gene (Cyt b) was amplified using the forward (L14910: 5′-GACCTGTGATMTGAAAAACCAYCGTTGT-3′) and reverse (H16064: 5′-CTTTGGTTTACAAGAACAATGCTTTA-3′) primers [24]. The amplification products were purified and sequenced by Sangon Biotech (Shanghai, China) Co., Ltd. The sequence was edited and managed using SeqMan in Lasergene 7.1 [25] and MEGA 11 [26]. The newly generated sequence is 1090 bp in length and has been deposited in GenBank. All GenBank accession numbers of the taxa used in this study are listed in

Table 1. Sequences (Cyt b) used in this study.

Species	Voucher	Locality	Accession
Herpetoreas abros sp. nov.	KIZ 2024150	Yingjiang, Yunnan, China	PQ670138
Herpetoreas burbrinki	YBU 071128	Chayu, Xizang, China	GQ281781
Herpetoreas burbrinki	HSR 19252	Chayu, Xizang, China	MZ358098
Herpetoreas davidi	CAS 220256	Gwa, Rakhine, Myanmar	OK315830
Herpetoreas murlen	MZMU 2473	Mizoram, India	ON204025
Herpetoreas pealii	WII ADR547	Arunachal Pradesh, India	MT571586
Herpetoreas platyceps	KIZ YPX26317	Jilong, Xizang, China	MW111464
Herpetoreas platyceps	GP2096	Xizang, China	KJ685690
Herpetoreas cf. sieboldii	WII ADR183	Chamoli, Uttarakhand, India	MT571587
Herpetoreas tpser	CIB 107855	Motuo, Xizang, China	OM313292
Herpetoreas tpser	CIB 118524	Motuo, Xizang, China	OM313293
Herpetoreas tpser	KIZ 06681	Motuo, Xizang, China	MW111476
Herpetoreas tpser	CHS 849	Motuo, Xizang, China	MK201567
Herpetoreas xenura	PUCZM X SL1	Mizoram, India	MN993850
Herpetoreas xenura	PUCZM X SL17	Mizoram, India	MN993852
Herpetoreas xenura	PUCZM X SL16	Mizoram, India	MN993851
Herpetoreas xenura	AD 633	Assam, India	MN993891
Hebius khasiensis	CAS 221504	Putao, Kachin, Myanmar	KJ685668
Hebius venningi	MZMU 1313	Mizoram, India	OR389975

.

Sequences were aligned using ClustalW [27] with default parameters. The best-fit substitution models for MrBayes and IQ-TREE, respectively, were chosen using the Akaike information criterion in ModelFinder [28]. Bayesian inference was performed in MrBayes 3.2.6 [29] using the suggested model GTR+F+I, and the Markov chains were run for 5,000,000 generations and sampled every 100 generations. Maximum likelihood analysis was performed in IQ-TREE 1.6.12 [30] using the suggested model TVM+F+I+G4, and nodal support was estimated by 1000 ultrafast bootstrap replicates. The genetic divergence (uncorrected p-distance) between species was calculated in MEGA 11.

The electronic edition of this article conforms to the requirements of the amended International Code of Zoological Nomenclature. The new name is available under the code in the electronic edition of this article. This publication and new name have been registered in ZooBank, the online registration system for the ICZN [31].

3. Results

3.1. Molecular Phylogeny

The phylogenetic trees resulted in essentially identical topologies by Bayesian inference and Maximum likelihood analysis (Figure 1). The sequence of the newly collected specimen from Yunnan was nested within the genus Herpetoreas and formed a clade sister to H. burbrinki but with no support. The genetic divergence (uncorrected p-distance) between the sequence of the newly collected specimen and the sequences of H. burbrinki was 6.7% and the genetic divergence (uncorrected p-distance) between the sequence of the newly collected specimen and the sequences of other species of this genus ranged from 8.1% to 13.0% (

Table 2. Uncorrected p-distances (%) between species of the genus Herpetoreas estimated from Cyt b gene sequences.

	1	2	3	4	5	6	7	8
1 Herpetoreas abros sp. nov.
2 Herpetoreas burbrinki	6.7
3 Herpetoreas davidi	11.3	11.3
4 Herpetoreas murlen	8.1	8.4	11.5
5 Herpetoreas pealii	12.7	11.3	10.8	13.7
6 Herpetoreas platyceps	13.0	13.6	12.5	13.3	14.2
7 Herpetoreas cf. sieboldii	11.8	12.8	12.0	12.4	13.0	4.5
8 Herpetoreas tpser	8.5	9.8	11.8	10.2	13.2	12.3	11.0
9 Herpetoreas xenura	12.7	12.8	10.8	13.4	11.8	13.5	12.3	13.4

).

3.2. Systematics

Herpetoreas abros sp. nov.

urn:lsid:zoobank.org:act:C7F293A2-DB3A-49DB-9F89-C77A7DD6D0BE

Figure 2, Figure 3, Figure 4 and Figure 5,

Table 3. Morphological characters of the holotype of Herpetoreas abros sp. nov. Measurements are in mm, symmetrical head characters were given as left/right.

	KIZ 2024150		KIZ 2024150
total length	775	postoculars	3/3
snout–vent length	554	supraoculars	1/1
tail length	221	suboculars	0/0
tail length/total length	0.29	supralabials	2-3-3/2-3-3
head length	15.7	infralabials	10/9
head width	11.5	anterior temporals	1/2
head length/head width	1.37	posterior temporals	1/1
internasals	2	chin shields	2/2
prefrontals	2	dorsal scale rows	19–19–17
frontals	1	ventrals	165
parietals	2	cloacal plate	divided
loreals	1/1	subcaudals	89
preoculars	1/1	maxillary teeth	22+2/22+2

.

Holotype: KIZ 2024150, adult female, collected from Xima Town, Yingjiang County, Dehong Prefecture, Yunnan Province, China (24°47′17″ N, 97°40′30″ E, 1550 m), on 16 October 2024 by local forest rangers.

Diagnosis: Body cylindrical, snout–vent length 554 mm, total length 775 mm; tail relatively long, tail length/total length 0.29; dorsal scales in 19–19–17 rows, all strongly keeled; ventrals 165; cloacal plate divided; subcaudals 89, paired; preocular one, postoculars three; supralabials eight, third–fifth entering orbit; maxillary teeth 24, last two distinctly enlarged, separated from anterior teeth by a small diastema; upper lips white, three black vertical stripes on anterior upper lip on each side; approximately 13 white speckles on anterior lateral surface of body; anterior venter pale pink and posterior venter pink; ventral tail rose red.

Description of the holotype: Body cylindrical, slender (total length 775 mm), tail relatively long (tail length/total length 0.29); head slender (head length/head width 1.37), distinct from neck; snout narrow, tip obtuse; eyes large, pupils round; nostrils oriented laterally.

Rostral wider than higher, approximately 1.6 times as wide as high, slightly visible from above; nasals crescentic, completely divided; internasals two, not in contact with loreal; prefrontals two, in contact with loreal, prefrontal suture slightly longer than internasal suture; frontal shield shaped, elongate, approximately 1.5 times longer than wider, more than twice longer than prefrontal; supraocular one on each side, large; parietals two, large, approximately 1.7 times longer than wider, 1.3 times length of frontal, parietal suture nearly equal to length of frontal; loreal one on each side, in contact with second–third supralabials, not entering orbit; preoculars one on each side, vertically elongate, in contact with third supralabial; postoculars three on each side, size decreasing from top to bottom; supralabials eight on each side, first–second in contact with nasals, third–fifth entering orbit, penultimate one largest; anterior temporals one on left side and two on right side, posterior temporal one on each side; mental triangular, small; infralabials ten on left side and nine on right side, first pair in contact with each other after mental, first–fifth in contact with anterior chin shield; chin shield two pairs; posterior chin shields much longer than anterior ones; mental groove apparent.

Dorsal scale rows 19–19–17, all strongly keeled, slightly notched at apex; two preventrals, ventrals 165; subcaudals 89, all paired, with single terminal scute; cloacal plate divided. Position of reduction to six dorsal tail scale rows at 14th subcaudal; portion with six dorsal tail scale rows spanned from 15th subcaudal to 59th subcaudal, 45 subcaudals in total; portion with four dorsal tail scale rows spanned from 60th subcaudal to 89th subcaudal, 30 subcaudals in total; ratio of subcaudal scale number for portion with four dorsal tail scale rows to subcaudal scale number for portion with six dorsal tail scale rows 0.67.

Maxillary teeth 24 with last two distinctly enlarged on each side, 18 present teeth with six empty sockets on left side, and 16 present teeth with eight empty sockets on right side, enlarged ones ungrooved, separate from anterior ones by a small diastema.

Coloration in life: Head dorsum brown; a small round yellowish-brown spot on anteriormost parietal suture just posterior to frontal, followed by a pair of small oval yellowish white spots symmetrically on inner sides of parietals just separated by parietal suture; a narrow brownish white stripe on middle line of occiput region just posterior to parietal suture. Upper lateral surface of head blacking brown, a short white slightly tilted horizontal stripe on posterior temporal region on each side; lower lateral surface of head grayish white; three black vertical stripes on anterior upper lip on each side; a short black strip on lower posterior eye, followed by a brown blotch on each side. Iris dark yellowish brown. Ventral surface of head whitish.

Body dorsum grayish brown; two yellow-white stripes on dorsal surface of neck, gradually approaching each other posteriorly from regions of jaw corners, then forming two parallel longitudinal strips when nearly approaching each other; many yellowish white and black speckles on dorsum, speckles roughly arranged in longitudinal rows. Approximately 13 white speckles gradually decrease in size posteriorly on anterior lateral surface of body. Anterior ventral surface of body pale pink, posterior ventral surface of body pink. Ventro-lateral blotch absent.

Dorsal surface of tail brownish gray with many grayish-black speckles. Ventral surface of tail rose red.

Comparisons: The main distinguishing characters between Herpetoreas abros sp. nov. and other species of the genus Herpetoreas are summarized in

Table 4. Morphological comparison of Herpetoreas abros sp. nov. with congeners of the genus Herpetoreas. Data for species except Herpetoreas abros sp. nov. were obtained from original descriptions of each species and Ren et al. [2], Nguyen et al. [3], and Peng et al. [5].

	Tail length/Total Length	Ventrals	Cloacal Plate	Subcaudals	Subcaudals Condition	Maxillary Teeth	Venter Color	Ventrolateral Blotch
Herpetoreas abros sp. nov.	0.29	165	divided	89	paired	24	pale pink to pink	absent
Herpetoreas burbrinki	0.285–0.304	169–172	divided	94–96	paired	21	tangerine to red	present
Herpetoreas davidi	0.207–0.310	151–155	undivided	97–100	single	N/a	whitish or yellowish	barely present
Herpetoreasmurlen	0.23	179	divided	78	paired	13	light sand-brown	present
Herpetoreas pealii	0.227–0.259	136–142	undivided	69–77	paired	13–21	pale with brown patches	present
Herpetoreas platyceps	0.232–0.286	180–234	divided	78–99	paired	18–22	usually immaculate	present or absent
Herpetoreas sieboldii	0.242–0.300	168–216	divided	81–111	paired	19–23	darkened posteriorly	usually absent
Herpetoreas tpser	0.262–0.317	153–167	divided	79–97	paired	20–21	jacinth to scarlet	present
Herpetoreas xenura	0.220–0.302	155–165	undivided	82–110	single	22–23	whitish or yellowish	present

.

Herpetoreas abros sp. nov. differs from H. davidi and H. xenura by having paired subcaudals (vs. subcaudals being single). Herpetoreas abros sp. nov. differs from H. pealii by having a divided cloacal plate (vs. cloacal plate being undivided).

Herpetoreas abros sp. nov. differs from H. burbrinki by having fewer ventrals (165 vs. 169–172), fewer subcaudals (89 vs. 94–96), more maxillary teeth (24 vs. 21), different venter colors (anterior part being pale pink and posterior part being pink vs. anterior part being tangerine and posterior part being red), and the absence of ventrolateral blotch (vs. ventrolateral blotch being present).

Herpetoreas abros sp. nov. differs from H. murlen by having a relatively longer tail (tail length/total length 0.29 vs. 0.23), fewer ventrals (165 vs. 179), more subcaudals (89 vs. 78), more maxillary teeth (24 vs. 13), different venter colors (anterior part being pale pink and posterior part being pink vs. venter being uniformly light sand-brown), and the absence of ventrolateral blotch (vs. ventrolateral blotch being present).

Herpetoreas abros sp. nov. differs from H. platyceps by having fewer ventrals (165 vs. 180–234), more maxillary teeth (24 vs. 18–22), and different venter colors (anterior part being pale pink and posterior part being pink vs. venter being usually immaculate).

Herpetoreas abros sp. nov. differs from H. tpser by having more maxillary teeth (24 vs. 20–21), different venter colors (anterior part being pale pink and posterior part being pink vs. venter being glossy bright jacinth, reddish-orange, or scarlet), and the absence of ventrolateral blotch (vs. ventrolateral blotch being present).

For the species without available molecular data, Herpetoreas abros sp. nov. differs from H. sieboldii by having fewer ventrals (165 vs. 168–216), more maxillary teeth (24 vs. 19–23), different subcaudal scale positions of the reduction in dorsal tail scales from eight to six rows (14th vs. 25th–28th), more subcaudal scales the portion of dorsal tail scales in six rows spanned (45 vs. 27–38), more subcaudal scales the portion of dorsal tail scales in four rows spanned (30 vs. 20), and different ratios of the subcaudal scale numbers that the portion of dorsal tail scales in four rows spanned to the portion of dorsal tail scales in six rows spanned (0.67 vs. 0.53).

Distribution: The new species is currently known only from its type locality in Xima Town, Yingjiang County, Dehong Prefecture, Yunnan Province, China (Figure 6). It probably also occurs in northern Myanmar.

Ecology notes: The specimen of the new species was discovered on the ground during the day, not far from a river and a hydroelectric power station. More ecological information about this species is unknown. Sympatric amphibians and reptiles include Calotes yunnanensis Annandale, 1905, Diploderma yunnanense (Anderson, 1878), Odorrana yunnanensis (Anderson, 1879), Oligodon hamptoni Boulenger, 1918, Pseudocalotes kakhienensis (Anderson, 1879), Theloderma moloch (Annandale, 1912), and Amolops viridimaculatus (Jiang, 1983).

Etymology: The specific epithet “abros” is a Latinized adjective in a nominative singular derived from the classical Greek word “abros” (aβρός), meaning “cute”, “handsome”, and “delicate”. The name is given in reference to the cute appearance of this species. We suggest “Cute Himalayas Keelback” as its English common name and “铜壁关腹链蛇 (Pinyin: tóng bì guān fù liàn shé)” as its Chinese common name according to its type locality.

4. Discussion

Previously, four species of Herpetoreas were recorded from China, all of which are from Xizang Autonomous Region [2,4,8]. Herpetoreas abros sp. nov. is the first species of the genus Herpetoreas in Yunnan Province. Previously, there were 50 genera of snakes recorded in Yunnan Province [32]; this study increased the number of snake genera in Yunnan Province to 51.

Ren et al. [2] speculated that Hebius lacrima Purkayastha and David, 2019 and Heb. parallelus (Boulenger, 1890) belong to Herpetoreas based on morphological data, but they did not change their generic assignments due to the lack of available molecular data for these two species. We agree with Ren et al. [2] that these two species will likely be transferred to the genus Herpetoreas in future studies. However, Herpetoreas abros sp. nov. can be easily distinguished from these two species by having different dorsal, and ventral coloration, and the absence of ventrolateral blotch. Therefore, even if these two species do belong to Herpetoreas, they do not affect the validity of the new species.

The specimen of the new species was found on land, but not far from a river. In addition, the dorsal scales of this species are distinctly keeled. We speculate that this species is a semi-aquatic snake. The discovery site of the new species is located in Yunnan Tongbiguan Provincial Nature Reserve. There are large areas of virgin forest in the nature reserve and are legally protected. Therefore, we consider that this species is currently not threatened by humans.