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. 2023 Sep 28;1181:9–27. doi: 10.3897/zookeys.1181.109462

Discovery of a new cryptic Achalinus Peters, 1869 (Serpentes, Xenodermidae) species from Hunan Province, China

Shun Ma 1,2, Yu-Hao Xu 3,4, Shuo Qi 5, Ying-Yong Wang 5, Shan-Shan Tang 6, Song Huang 4,✉, Jian-Ping Jiang 1,2,✉
PMCID: PMC10556878  PMID: 37810461

Abstract

A new species, Achalinusshenisp. nov., from central Hunan Province is described, based on the results of molecular systematics and morphological characters according to five specimens. Our molecular phylogeny inferred from the mitochondrial CO1 gene fragment revealed that this new species is most closely related to A.yunkaiensis, but a considerable amount of genetic divergence exists between them (p-distance ranging from 5.8% to 6.4%) and much distinct genetic divergence exists compared with other known Achalinus species (p-distance ranging from 10.4% to 15.8%), supporting its validity. Morphologically, it can be distinguished from its congeners by: (1) dorsal scales strongly keeled, 23 rows throughout the body, the outmost row smooth and significantly enlarged; (2) tail relatively short, TaL/TL 0.183 ~ 0.224; (3) the suture between internasals subequal to the suture between prefrontals; (4) loreal one, subrectangular, LorH/LorL 0.53 ~ 0.57; (5) ventrals 161–170, anal entire, subcaudals 55–61, not paired; (6) the length of supraocular equal to or longer than the length of upper anterior temporal; and (7) vertebral line inconspicuous and subcaudal streak absent. Currently, 27 species of Achalinus are known in the world, amongst which 20 species are distributed in China. Moreover, a key to species of the genus Achalinus is provided in this study.

Key words: Identification key, molecular systematics, morphological characters, snake, taxonomy

Introduction

The odd-scaled snakes (burrowing snakes), genus Achalinus Peters, 1869, are a group of small to medium-sized, nocturnal, fossorial, low-aggressive and non-venomous snakes, widely distributed in Vietnam, China and Japan (Zhao et al. 1998; Zhao 2006). Currently, 26 species of this genus have been documented and more than half of them (17 species) were described in the past five years (Wang et al. 2019; Ziegler et al. 2019; Li et al. 2020; Luu et al. 2020; Miller et al. 2020; Hou et al. 2021; Huang et al. 2021; Li et al. 2021; Ha et al. 2022; Yang et al. 2022; Ma et al. 2023b; Pham et al. 2023; Yang et al. 2023). Although a great deal of taxonomic studies have been conducted recently, the interspecific and intraspecific relationships of A.ater Bourret, 1937, A.formosanus Boulenger, 1908, A.huangjietangi Huang, Peng & Huang, 2021, A.niger Maki, 1931, A.rufescens Boulenger, 1888 and A.spinalis Peters, 1869 remain unresolved (Zhao et al. 1998; Miller et al. 2020; Huang et al. 2021; Ma et al. 2023a, 2023b; Zhang et al. 2023). Additionally, there is also a lack of molecular information for A.hainanus Huang, 1975 and A.werneri Van Denburgh, 1912, indicating that the phylogenetic positions of these species are unknown. Therefore, it is important to continue conducting relevant research of this diversity-underestimated and poorly-known genus.

During our recent herpetological field survey in Hunan Province, China, five snakes were collected (Fig. 1). These specimens were assigned to Achalinus by their small, slender and cylindrical body shapes; lanceolate-shaped, metallic lustre and strongly-keeled dorsal scales; and absence of the preocular and postocular. However, they could not be identified as any particular Achalinus species morphologically. Furthermore, preliminary molecular analyses supported that these specimens comprise a separate evolutionary lineage; thus, we described them as a new species through further data analysis and investigation herein. Moreover, a key to species of the genus Achalinus is provided in this study.

Figure 1.

Figure 1.

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Distribution of Achalinussheni sp. nov. and A.yunkaiensis. A.sheni sp. nov.: the type locality (red star) and another site (red dot). A.yunkaiensis: the type locality (black star) and other three sites (black dots).

Materials and methods

Molecular phylogenetic analyses

Five specimens were collected in the Hunan Province of China: four specimens (ANU20230012–ANU20230015) were collected in Lianyuan City and one specimen (CIB 119043) was collected in the Nanyue District (Fig. 1). Snakes were humanely euthanised with an injection of 0.7% tricaine methanesulphonate (MS222) solution and fresh liver tissue was extracted and immediately preserved in 95% ethanol. The specimens were fixed in 10% formalin for one day, subsequently preserved in 75% ethanol and deposited in the Anhui Normal University Museum (ANU) and Chengdu Institute of Biology (CIB) of Chinese Academy of Sciences (CAS), respectively. Sampling procedures involving live snakes were in accordance with the Wild Animals Protection Law of China.

Genomic DNA was extracted from the preserved liver tissues using QIAamp DNA Mini Kit (QIAGEN, Changsheng Biotechnology Co. Ltd.). A fragment of the mitochondrial cytochrome c oxidase subunit 1 (CO1) gene was amplified using the primer pairs: dglco and dghco (Meyer et al. 2005). The polymerase chain reaction (PCR) was performed in 25 μl reactant with the following cycling conditions: 95 °C for 4 min; 35 cycles of denaturing at 95 °C for 30 s, annealing at 48 °C for 30 s and extending at 72 °C for 60 s; and a final extending step of 72 °C for 10 min (Wang et al. 2019). PCR products were sequenced by Beijing Qingke New Industry Biotechnology Co., Ltd.

For our phylogenetic analysis, 38 sequences were used (Table 1), amongst which 33 (No. 6–38) were obtained from GenBank including 30 sequences of 23 Achalinus species and three sequences of Fimbriosklossi Smith, 1921, Parafimbrioslao Teynié, David, Lottier, Le, Vidal & Nguyen, 2015 and Xenodermusjavanicus Reinhardt, 1836, which were used as outgroups (Ma et al. 2023b).

Table 1.

Localities, voucher information, GenBank numbers and references for all samples used in this study.

NO. Species name Locality Voucher NO. GenBank No. References
1 A.sheni sp. nov. Lianyuan, Hunan, China ANU20230012 OR178145 This study
2 A.sheni sp. nov. Lianyuan, Hunan, China ANU20230013 OR178146 This study
3 A.sheni sp. nov. Lianyuan, Hunan, China ANU20230014 OR178147 This study
4 A.sheni sp. nov. Lianyuan, Hunan, China ANU20230015 OR178148 This study
5 A.sheni sp. nov. Nanyue, Hunan, China CIB 119043 OR189183 This study
6 A.yunkaiensis Dawuling Forestry Station, Guangdong, China SYS r001443 MN380329 Wang et al. (2019)
7 A.yunkaiensis Dawuling Forestry Station, Guangdong, China SYS r001502 MN380330 Wang et al. (2019)
8 A.yunkaiensis Dawuling Forestry Station, Guangdong, China SYS r001503 MN380331 Wang et al. (2019)
9 A.yunkaiensis Dawuling Forestry Station, Guangdong, China SYS r001902 MN380332 Wang et al. (2019)
10 A.yunkaiensis Dawuling Forestry Station, Guangdong, China SYS r001903 MN380333 Wang et al. (2019)
11 A.yunkaiensis Maoershan Nature Reserve, Guangxi, China YBU 14612 MT365525 Yu et al. (2020)
12 A.yunkaiensis Xinning, Hunan, China CIB 119041 OQ978852 Ma et al. (2023a) (in press)
13 A.ater Huaping Nature Reserve, Guangxi, China SYS r00852 MN380334 Wang et al. (2019)
14 A.dabieshanensis Yaoluoping Nature Reserve, Anhui, China AHU2018EE0710 MW316598 Zhang et al. (2023)
15 A.damingensis Nanning, Guangxi, China ANU20220009 OP644487 Yang et al. (2023)
16 A.dehuaensis Dehua, Fujian, China YBU 13013 MZ442642 Li et al. (2021)
17 A.emilyae Dong Son-Ky Thuong Nature Reserve, Hoanh Bo, Vietnam IEBR 4465 MK330857 Ziegler et al. (2019)
18 A.formosanus Taiwan, China RN2002 KU529452 Unpublished
19 A.hunanensis Huaihua, Hunan, China CIB 119039 OQ848425 Ma et al. (2023b)
20 A.hunanensis Ningxiang, Hunan, China CIB 119040 OQ848426 Ma et al. (2023b)
21 A.huangjietangi Huangshan, Anhui, China HSR18030 MT380191 Huang et al. (2021)
22 A.juliani Ha Lang, Cao Bang, Vietnam IEBR A.2018.8 MK330854 Ziegler et al. (2019)
23 A.meiguensis Mianyang, Sichuan, China GP835 MZ442641 Li et al. (2021)
24 A.niger Taiwan, China RN0667 KU529433 Unpublished
25 A.ningshanensis Ningshan, Shaanxi, China ANU 20220006 ON548422 Yang et al. (2022)
26 A.panzhihuaensis Yanbian, Sichuan, China KIZ 040189 MW664862 Hou et al. (2021)
27 A.pingbianensis Honghe, Yunnan, China YBU 18273 MT365521 Li et al. (2021)
28 A.quangi Phu Yen, Son La, Vietnam ZVNU.2022.08 OQ197471 Pham et al. (2023)
29 A.rufescens Hongkong, China SYS r001866 MN380339 Wang et al. (2019)
30 A.spinalis Badagong Mountains, Hunan, China SYS r001327 MN380340 Wang et al. (2019)
31 A.timi Thuan Chau, Son La, Vietnam IEBR A.2018.10 MK330856 Ziegler et al. (2019)
32 A.tranganensis Ninh Binh, Vietnam VNUF R.2018.21 MW023086 Luu et al. (2020)
33 A.vanhoensis Van Ho, Son La, Vietnam VNUF R.2019.13 ON677935 Ha et al. (2022)
34 A.yangdatongi Wenshan Nature Reserve, Yunnan, China KIZ 034327 MW664865 Hou et al. (2021)
35 A.zugorum Bac Me, Ha Giang, Vietnam IEBR 4698 MT502775 Miller et al. (2020)
36 Fimbriosklossi Quang Ngai, Vietnam IEBR 3275 KP410744 Teynié et al. (2015)
37 Parafimbrioslao Louangphabang, Laos MNHN 2013.1002 KP410746 Teynié et al. (2015)
38 Xenodermusjavanicus Sumatera Barat, Sumatra, Indonesia – KP410747 Teynié et al. (2015)
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CO1 sequences (618 bp) were input in MEGA11 (Tamura et al. 2021) and aligned by MUSCLE (Edgar 2004). Then we calculated the uncorrected pairwise distances (p-distance) in MEGA11. IQ-TREE 1.6.12 was performed to conduct the Maximum Likelihood (ML) analysis (Nguyen et al. 2015) under the best-fit model TN+F+I+G4 computed by ModelFinder according to Bayesian Information Criterion (BIC) (Kalyaanamoorthy et al. 2017). Ultrafast Bootstrap Approximation (UFB) node support was assessed by using 5000 ultrafast bootstrap replicates and the UFB (%) ≥ 95 was considered significantly supported (Hoang et al. 2018). The single branch tests were conducted by SH-like approximate likelihood ratio test (SH-aLRT) by 1000 replicates and the nodal support (SH, %) ≥ 80 was also considered supported well (Stephane et al. 2010). The Bayesian Inference (BI) analysis was conducted via MrBayes (Ronquist et al. 2012) in PhyloSuite 1.2.3 (Zhang et al. 2020) by using a four chains run calculated for 10 million generations under the best model TN+F+I+G4, sampling every 1000 with the first 25% of samples discarded as burn-in and the nodal support Bayesian posterior probabilities (BI, %) ≥ 95 were considered significantly supported.

Morphological characters

Morphological data were obtained from the five newly-collected specimens, examination of museum specimens (Appendix 1) and many key references (Boulenger 1888, 1893, 1896; Denburgh 1912; Bourret 1935, 1937; Hu and Zhao 1966; Hu et al. 1973; Koshikawa 1982; Zong and Ma 1983; Ota and Toyama 1989; Zhao et al. 1998; Zhao 2006; Wang et al. 2019; Ziegler et al. 2019; Li et al. 2020; Luu et al. 2020; Miller et al. 2020; Yu et al. 2020; Hou et al. 2021; Huang et al. 2021; Li et al. 2021; Chen et al. 2022; Ha et al. 2022; Yang et al. 2022; Li et al. 2023; Ma et al. 2023a, b; Pham et al. 2023; Xu et al. 2023; Yang et al. 2023; Zhang et al. 2023).

Morphological descriptions followed Zhao (2006) and Ma et al. (2023b): three measurement characters were measured to the nearest 0.1 mm using a Deli Stainless Ruler (No. 8460): snout-vent length (SVL), tail length (TaL) and total length (TL); other measurement characters were measured to the nearest 0.01 mm using a Deli Digital Vernier Caliper (DL91150): head length (HL), head width (HW), eye horizontal diameter (ED), loreal height (LorH), loreal length (LorL), length of the suture between internasals (LSBI), length of the suture between prefrontals (LSBP), length of supraocular (SPOL: horizontal distance between anterior and posterior tip of supraocular) and length of upper anterior temporal (ATUL: horizontal distance between anterior and posterior tip of upper anterior temporal). We also directly compared the length of the sutures between internasals and prefrontals (LSBI vs. LSBP). Scalation features and their abbreviations are as follows: loreals (Loreal), supralabials (SPL), infralabials (IFL), the number of infralabials touching the first pair of chin shields (IFL-1st Chin), supraoculars (SPO), temporals (TEM), the number of anterior temporals touching the eye (aTEM-Eye), ventral scales (VEN), subcaudal (SC), entire or divided of the cloacal plate (Anal), dorsal scale rows (DSR) (counted at one-head-length behind the head, at midbody, at one-head-length before the cloacal plate). We also counted the number of maxillary teeth (MT) under the microscope. Bilateral scale counts were given as left/right.

Results

Molecular systematics

The unnamed Achalinus specimens form a sister lineage (SH 99/UFB 100/BI 100) to the species A.yunkaiensis Wang, Li & Wang, 2019 (SH 96/UFB 95/BI 100) with a significantly high nodal support (SH 97/ UFB 100/BI 99) (Fig. 2).

Figure 2.

Figure 2.

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Phylogenetic tree of the genus Achalinus inferred from the CO1 gene fragment (618 bp) using Maximum Likelihood. The support values of each node present on the tree: SH / UFB / BI (the ones lower than 50 are displayed as “-”). A.yunkaiensis is noted in blue and A.sheni sp. nov. is noted in red.

Amongst the Achalinus species studied in this work, the genetic distances inferred from the mitochondrial CO1 gene fragment range from 3.2% (A.hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023 vs. A.ningshanensis Yang, Huang, Jiang, Burbrink, Gong, Yu, Zhang, Huang & Huang, 2022) to 18.1% (A.meiguensis Hu & Zhao, 1966 and A.dehuaensis Li, Wu, Xu, Zhu, Ren, Guo & Dong, 2021), while the genetic distances between the lineage formed by the newly-collected Achalinus specimens and its congeners range from 5.8% (vs. A.yunkaiensis) to 15.8% (vs. A.dabieshanensis Zhang, Liu, Huang & Zhang, 2023), indicating that these newly-collected specimens have distinct genetic differentiation from the other Achalinus species (Table 2).

Table 2.

Uncorrected p-distances (%) amongst Achalinus species, based on the mitochondrial CO1 gene.

1–5 6–12 13 14 15 16 17 18 19–20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
1–5 A.sheni sp. nov. 0–0.2
6–12 A.yunkaiensis 5.8–6.4 0–2.8
13 A.ater 12.8–12.9 11.5–12.9
14 A.dabieshanensis 15.6–15.8 14.9–15.8 14.7
15 A.damingensis 13.6–13.8 12.3–12.6 7.9 15.8
16 A.dehuaensis 13.4–13.6 13.9–14.7 16.3 18.4 16.0
17 A.emilyae 13.1 12.4–13.3 11.5 17.7 12.8 15.2
18 A.formosanus 12.8–12.9 12.2–12.6 13.9 19.0 14.9 15.7 13.8
19–20 A.hunanensis 12.0–12.5 12.5–13.1 7.1–7.3 16.9–17.1 6.1–6.3 15.1–15.3 13.0–13.3 13.8–14.0 0.5
21 A.huangjietangi 13.3–13.5 12.1–12.5 15.0 8.9 16.2 16.4 14.1 15.3 16.8–16.9
22 A.juliani 13.6–13.8 11.4–12.3 7.0 15.8 8.4 14.7 12.3 12.5 8.7–8.8 14.4
23 A.meiguensis 13.9–14.1 12.2–13.1 15.4 17.7 16.8 18.1 15.4 15.6 16.4 15.2 16.8
24 A.niger 12.3–12.5 12.2–12.6 13.6 15.8 14.1 15.7 12.0 8.9 13.3 13.9 12.3 13.9
25 A.ningshanensis 14.1–14.2 15.2–16.0 7.5 17.2 7.7 16.2 14.1 14.8 3.2–3.3 17.0 9.7 17.0 14.6
26 A.panzhihuaensis 14.6 10.5–12.3 16.2 16.6 15.5 15.3 16.6 16.0 16.2 15.2 15.5 11.6 14.4 17.4
27 A.pingbianensis 11.5–11.6 12.8–13.9 11.8 15.3 11.3 14.9 13.0 14.6 11.2 13.0 12.1 16.8 11.8 11.7 14.9
28 A.quangi 13.9 15.5–15.8 11.5 18.1 12.9 15.0 3.6 13.8 13.1–13.2 14.6 12.6 15.2 11.7 13.3 16.9 13.9
29 A.rufescens 12.9 11.6–12.1 12.5 16.9 13.6 13.9 8.1 13.9 12.1–12.2 13.9 12.3 17.3 12.5 12.2 16.0 13.0 7.9
30 A.spinalis 11.2–11.3 12.2–13.6 15.2 16.6 15.0 14.1 13.9 13.9 14.0–14.3 13.1 14.1 16.0 13.4 15.7 15.8 13.3 13.9 12.9
31 A.timi 13.6–13.8 11.7–13.3 13.1 16.4 13.3 16.0 12.8 13.6 12.1–12.4 14.6 13.9 15.8 11.8 13.3 15.5 12.3 13.3 13.6 14.1
32 A.tranganensis 13.3 11.7–12.1 12.6 15.3 13.9 13.8 11.5 16.8 13.8–14.2 13.1 13.4 16.4 14.2 15.3 16.4 13.3 12.1 11.5 14.7 13.6
33 A.vanhoensis 13.4–13.6 13.0–14.1 12.7 15.5 12.3 15.7 12.2 13.9 11.3–11.7 14.2 13.4 15.6 12.3 11.9 15.5 10.8 12.3 13.7 12.7 4.7 13.0
34 A.yangdatongi 13.7–13.8 12.5–13.6 6.2 16.6 5.6 14.0 12.8 14.4 5.1 14.6 7.3 17.1 13.7 5.9 15.5 11.3 12.6 11.5 14.2 13.1 12.8 11.3
35 A.zugorum 10.4–10.5 12.3–13.4 12.9 15.3 12.8 14.1 12.1 13.3 11.7–12.0 14.1 13.1 15.0 12.9 12.8 15.3 11.0 12.5 13.3 13.3 13.4 11.8 11.8 12.2
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Based on the molecular results above, these specimens are supported to be an unnamed taxon.

Morphological characters

The five newly-collected Achalinus specimens from Hunan Province can be easily distinguished from all other known congeners (Table 3, 4, Figs 3–5). By internasal separated from prefrontal, they differ from A.meiguensis (vs. internasal fused to prefrontal) and A.panzhihuaensis Hou, Wang, Guo, Chen, Yuan & Che, 2021 (vs. internasal fused to prefrontal). By having LSBI vs. LSBP = 1, they differ from A.ater (vs. > 1), A.dabieshanensis (vs. > 1), A.damingensis Xu, Yang, Wu, Gong, Huang & Huang, 2023 (vs. > 1), A.dehuaensis (vs. > 1), A.emilyae Ziegler, Nguyen, Pham, Nguyen, Pham, van Schingen, Nguyen & Le, 2019 (vs. > 1), A.huangjietangi (vs. < 1), A.hunanensis (vs. > 1), A.jinggangensis (Zong & Ma, 1983) (vs. > 1), A.juliani Ziegler, Nguyen, Pham, Nguyen, Pham, van Schingen, Nguyen & Le, 2019 (vs. > 1), A.niger (vs. < 1), A.quangi Pham, Pham, Le, Ngo, Ong, Ziegler & Nguyen, 2023 (vs. > 1), A.rufescens (vs. > 1), A.spinalis (vs. < 1), A.timi Ziegler, Nguyen, Pham, Nguyen, Pham, Van Schingen, Nguyen & Le, 2019 (vs. > 1), A.tranganensis Luu, Ziegler, Ha, Lo, Hoang, Ngo, Le, Tran & Nguyen, 2020 (vs. > 1), A.yangdatongi Hou, Wang, Guo, Chen, Yuan & Che, 2021 (vs. > 1), A.vanhoensis Ha, Ziegler, Sy, Le, Nguyen & Luu, 2022 (vs. > 1) and A.zugorum Miller, Davis, Luong, Do, Pham, Ziegler, Lee, De Queiroz, Reynolds & Nguyen, 2020 (vs. > 1). By loreal separated from prefrontal, they are different from A.formosanuschigirai Ota & Toyama, 1989 (vs. loreal fused to prefrontal), A.f.formosanus Boulenger, 1908 (vs. loreal fused to prefrontal) and A.pingbianensis Li, Yu, Wu, Liao, Tang, Liu & Guo, 2020 (vs. loreal fused to prefrontal). By TaL/TL 0.183 ~ 0.224, they can differ from A.hainanus (vs. 0.258 ~ 0.266), A.ningshanensis (vs. 0.121 ~ 0.161) and A.werneri (vs. 0.250 ~ 0.300). They also can be easily distinguished from their sister taxon A.yunkaiensis by the following morphological characters: (1) relative length of supraocular and upper anterior temporal (supraocular equal to or longer than anterior temporal, SPOL/ATUL 0.99 ~ 1.20 vs. supraocular shorter than anterior temporal, SPOL/ATUL 0.55 ~ 0.83); (2) more ventral scales + subcaudals counts in males (220–225 vs. 200–212); (3) more ventral scales in males (161–170 vs. 150–162); (4) more subcaudals in males (55–61 vs. 49–56); (5) less infralabials (5 (rarely 6) vs. 6); (6) more maxillary teeth in males (24 vs. 20–21); and (7) different uniform dorsal colouration pattern (dark brown vs. brown) (Table 5, Fig. 6).

Table 3.

Main morphological characters of Achalinussheni sp. nov.

Voucher Number ANU20230014 ANU20230012 ANU20230013 ANU20230015 CIB 119043
Holotype Paratype Paratype Paratype Paratype
Sex Adult male Adult male Adult male Subadult male Juvenile male
SVL 292.2 278.8 253.8 208.7 121.8
TaL 79.1 80.3 67.9 56.7 27.2
TL 371.3 359.1 321.7 265.4 149.0
TaL/TL 0.213 0.224 0.211 0.214 0.183
HW 5.13 5.39 4.34 4.24 3.28
HL 10.74 11.28 10.62 9.26 6.96
ED 1.25 1.26 1.17 0.94 0.88
MT – – – – 24
SPL 6/6 6/6 6/6 6/6 6/6
SPL-Eye 4th–5th 4th–5th 4th–5th 4th–5th 4th–5th
IFL 5/5 5/5 5/5 6/5 5/5
Chin 2 2 2 2 2
IFL-1st Chin 1st–3rd 1st–3rd 1st–3rd 1st–3rd 1st–3rd
Loreal 1 1 1 1 1
LorH 0.85 0.93 0.83 0.83 0.69
LorL 1.49 1.71 1.54 1.45 1.29
LorH/LorL 0.57 0.54 0.54 0.57 0.53
LSBI vs. LSBP = = = = =
SPO 1 1 1 1 1
SPOL 1.59 1.52 1.39 1.21 1.64
TMP 2+2+3 2+2+3 2+2+3 2+2+3 2+2+3
ATMP-Eye 2 2 2 2 2
ATUL 1.42 1.48 1.41 1.20 1.42
SPOL/ATUL 1.12 1.03 0.99 1.01 1.16
DSR 23-23-23 23-23-23 23-23-23 23-23-23 23-23-23
V 161 161 166 162 170
SC 60 61 57 58 55
Anal 1 1 1 1 1
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Table 4.

Morphological characters of Achalinus obtained from specimens examined in this study and literature. Int. fus.: internasal fused to prefrontal; Pre fus.: prefrontal fused to loreal; PtO: postoculars.

Species TaL/TL MT Int fus. Pre fus. LorH/LorL LSBI vs. LSBP DSR PtO SPL SPL-Eye IFL IFL-1st Chin TEM aTEM-Eye VEN SC Reference
A.sheni sp. nov. 0.183~0.224 24 0 0 0.53~0.57 =1 23-23-23 0 6 4–5 5–6 1–3 2+2+3 2 161–170 55–61 This study
A.ater 0.190~0.220 – 0 0 0.40 >1 (21–23)-(21–25)-(21–25) 0 6 4–5 5–6 1–3 2+2+3 2 160–170 47–70 Bourret (1935, 1937); Hu et al. (1973); Zhao et al. (1998); Zhao (2006)
A.dabieshanensis 0.168~0.223 – 0 0 0.73~0.83 >1 23-23-23 0 6 4–5 5 1–3 2+2+3(4) 2 141–155 45–55 Zhang et al. (2023)
A.damingensis 0.246 – 0 0 0.65 >1 23-23-23 0 6 4–5 6 1–3 2+2+3 2 162 74 Yang et al. (2023)
A.dehuaensis 0.206~0.286 31–33 0 0 – >1 23-23-23 0 6 4–5 5 1–3 2+2(3)+3(4) 1–2 142–154 63–81 Li et al. (2021)
A.emilyae 0.183~0.203 27–28 0 0 – >1 23-23-23 0 6 4–5 5 1–3 2+2+3 1 157–161 56–63 Ziegler et al. (2019); Hou et al. (2021)
A.formosanuschigirai 0.317 14 0 1 – =1 (25–27)-(25–27)-25 0 6 4–5 5–6 – 2+2 2 161–167 96–97 Ota and Toyama (1989)
A.f.formosanus 0.159 17 0 1(usually) – =1 29-27-25 0 6 4–5 6–7 – 2+2 1 158–184 61–83 Ota and Toyama (1989)
A.hainanus 0.258~0.266 – 0 0 – =1 23-23-23 0 6 4–5 5 1–3 1+2+3(4) 1 165–168 67–69 Koshikawa (1982); Zhao et al. (1998)
A.huangjietangi 0.152~0.232 – 0 0 0.70~0.74 <1 23-23-23 0 6 4–5 5–6 1–3(4) 2+2+3(4) 2 157–170 40–67 Huang et al. (2021); Chen et al. (2022)
A.hunanensis 0.221~0.225 23 0 0 0.62~0.70 >1 23-23-23 0 6 4–5 5–6 1–3(4) 2+2+4 2 163–165 69–72 Ma et al. (2023b)
A.jinggangensis 0.174~0.217 – 0 1 – >1 23-23-23 0 6 4–5 6 1–4 2(1)+2+3(4) 2 156–164 51–64 Zong and Ma (1983); Zhao et al. (1998)
A.juliani 0.224~0.268 28 0 0 – >1 25-23-23 0 6(7) 4–5(5–6) 6 1–3(4) 2+2+4 2 163–179 77–91 Ziegler et al. (2019)
A.meiguensis 0.142~0.238 17 1 0 – – (21–23)-(19–21)-(19–21) 1 6 4–5 6 1–3 2(3)+2(3) 1 146–173 39–60 Hu and Zhao (1966)
A.niger 0.151~0.179 – 0 0 0.67 <1 25-25-23 0 6 4–5 6 1–3(4) 2+2(3) 2 169–185 52–72 Ota and Toyama (1989); Zhao et al. (1998); Zhao (2006)
A.ningshanensis 0.121~0.161 – 0 0 0.45~0.58 =1 23-23-23(21) 0 6 4–5 5 1–2(3) 2+2(3)+3(4) 1–2 159–174 41–46 Yang et al. (2022)
A.panzhihuaensis 0.246 28 1 0 0.67 – 23-23-19 1 6 4–5 6 1–3 2+2+3 1 160 73 Hou et al. (2021)
A.pingbianensis 0.243 – 0 1 – =1 23-23-23 0 7 5–6 6 1–3 2+2+3 1 164 56 Li et al. (2020)
A.quangi 0.219~0.304 27–29 0 0 – >1 (23–25)-23-(21–23) 0 6 4–5 5 1–3 2+2+4 1–2 139–154 69–84 Pham et al. (2023)
A.rufescens 0.191~0.276 23 0 0 0.80~1.00 >1 23-(23–25)-23 0 6 4–5 5 1–3 2(1)+2+3(4) 1–2 132–156 58–82 Boulenger (1888, 1893, 1896); Wang et al. (2019)
A.spinalis 0.150~0.250 16–20 0 0 – <1 (23–25)-(23–25)-(23–25) 0 6 4–5 5–6 1–3 2+2(3) 1–2 138–175 48–67 Zhao et al. (1998); Hou et al. (2021); Ha et al. (2022)
A.timi 0.213 27 0 1 – >1 25-25-23 0 6 4–5 6 1–3 2+2+3 1 170 72 Ziegler et al. (2019)
A.tranganensis 0.254(+) 29 0 0 – >1 25-23-23 0 6 4–5 6 1–3 2+2+3 2 171 73(+) Luu et al. (2020)
A.werneri 0.250~0.300 – 0 0 – =1 ?-(21–23)-? 0 6 4–5 6 – 2+3(4) – 157–191 67–98 Denburgh (1912); Ota and Toyama (1989)
A.yangdatongi 0.180~0.262 24–26 0 0 0.57 >1 23-23-23 0 6 4–5 5–6 1–3 2+2/3+2/3 2 155–171 59–76 Hou et al. (2021); Xu et al. (2023)
A.yunkaiensis 0.156~0.204 20–24 0 0 0.49~0.64 =1 23-23-23 0 6 4–5 6 1–3(4) 2+2+3(4) 2 144–162 49–56 Wang et al. (2019); Yu et al. (2020); Li et al. (2023); Ma et al. (2023a)
A.vanhoensis 0.264 32 0 1 – >1 25-23-23 0 6/7 4–5/5–6 6 1–4 2+2+3 2 176 84 Ha et al. (2022)
A.zugorum 0.229 28 0 1 – >1 25-23-23 0 6 4–5 7 1–3 2+2+3 2 173 70 Miller et al. (2020)
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Figure 3.

Figure 3.

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Holotype (ANU20230014, adult male) of Achalinussheni sp. nov. A dorsolateral view B ventral view C right side of middle body view D light side of head view E right side of head view F dorsal head view G ventral head view. Photos by Yu-Hao Xu.

Figure 5.

Figure 5.

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Paratype (ANU20230013, adult male) of A.sheni sp. nov in life. Photos by Yu-Hao Xu.

Table 5.

Comparisons of main morphological characters of Achalinussheni sp. nov. and A.yunkaiensis.

Species A.sheni sp. nov. A.yunkaiensis
N 5 4 3
Sex ♂ ♂ ♀
SVL 121.8–292.2 188.7–358.5 204–386.3
TaL 27.2–80.3 43.3–63.3 52–72.8
TL 149.0–371.3 232–417.6 256–448.1(+)
TaL/TL 0.183 ~ 0.224 0.185 ~ 0.200 0.156 ~ 0.204
MT 24 20–21 22–24
SPL 6 6 6
SPL-Eye 4th–5th 4th–5th 4th–5th
IFL 5 (rarely 6) 6 6
IFL-1st Chin 1st–3rd 1st–3rd 1st–3rd/4th
Loreal 1 1 1
LorH 0.69–0.93 0.8–1.3 0.74–1.2
LorL 1.29–1.71 1.3–2.2 1.51–2.2
LorH/LorL 0.53 ~ 0.57 0.56 ~ 0.64 0.49 ~ 0.55
LSBI vs. LSBP = = =
SPO 1 1 1
SPOL 1.21–1.59 0.97–1.62 1.26–1.60
TMP 2+2+3 2+2+3/4 2+2+3/4
ATMP-Eye 2 2 2
ATUL 1.20–1.48 1.18–2.18 1.93–2.90
SPOL/ATUL 0.99 ~ 1.16 0.66 ~ 0.83 0.55 ~ 0.65
DSR 23-23-23 23-23-23 23-23-23
V 161–170 151–162 144–156
SC 55–61 49–56 51–55
V + SC 220–225 200–212 195–205
Anal 1 1 1
References This study Wang et al. (2019) Wang et al. (2019); Yu et al. (2020); Ma et al. (2023a)
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Figure 6.

Figure 6.

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Scalation and colouration comparisons between Achalinussheni sp. nov. and A.yunkaiensisAA.sheni sp. nov. (ANU20230014, adult male), A1–A4 photos by Yu-Hao Xu BA.sheni sp. nov. (CIB 119043, juvenile male), B1–B2 photos by Ke-Ji Guo and B3–B4 photos by Sheng-Chao Shi CA.yunkaiensis (SYS r001443, adult male): C1–C4 photos by Shuo Qi. Line illustration (A5, B5 and C5) by Jie-Fang Chen.

Therefore, combining the results of molecular systematics and morphological characters mentioned above, these five specimens, newly collected from Hunan Province, represent a new species and we describe it herein.

Taxonomic account

. Achalinus sheni sp. nov.

903D9271-AA1B-5936-B194-115111BEC5E4

https://zoobank.org/7FBF50AF-C1D8-46C6-8B66-A5805598AFF8

Figs 3 , 4 , 5 , 6

Figure 4.

Figure 4.

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Paratypes of A.sheni sp. nov. A ANU20230012 (adult male) B ANU20230013 (adult male) C ANU20230015 (subadult male) DCIB 119043 (juvenile male). A–C photos by Yu-Hao Xu, D1 and D2 photos by Ke-Ji Guo, D3 and D4 photos by Sheng-Chao Shi.

Chresonymy.

Achalinusspinalis: Li et al. (2010).

Type material.

Holotype. ANU20230014 (field number HSR23019, Fig. 3), an adult male, collected on 21 March 2023 (27°55′11″N, 111°55′3″E; 408 m a. s. l.), Qixingjie Town, Lianyuan City, Hunan Province, China by the team of Song Huang.

Paratypes. Three males, ANU20230012 (field number HSR23011, Fig. 4A), ANU20230013 (field number HSR23012, Figs 4B, 5), ANU20230015 (subadult male, field number HSR23020, Fig. 4C), with the same collecting information as the holotype; CIB 119043, a juvenile male, collected on 20 October 2015 by Bing Zhou and Shanshan Tang from Shumuyuan, Nanyue District, Hunan Province, China (27°15′59″N, 112°43′15″E; 358 m a.s.l., Fig. 4D).

Etymology.

The species name “sheni” is named for the memories of the Chinese herpetologist, Prof. You-Hui Shen (沈猷慧), who worked in Hunan Normal University and made great contributions to the herpetological research of China, particularly in Hunan Province where the new species is found. We suggest “Shen’s Odd-scale Snake” or “Shen’s Burrowing Snake” as its English name and “沈氏脊蛇” (Shěn Shì Jǐ Shé) as its Chinese name.

Diagnosis.

(1) dorsal scales strongly keeled, 23 rows throughout the body, the outmost row smooth and significantly enlarged ; (2) tail relatively short, TaL/TL 0.183 ~ 0.224; (3) the suture between internasals subequal to the suture between prefrontals; (4) loreal one, subrectangular, LorH/LorL 0.53 ~ 0.57; (5) ventrals 161–170, anal entire, subcaudals 55–61, not paired; (6) the length of supraocular equal to or longer than the length of upper anterior temporal; (7) vertebral line inconspicuous and subcaudal streak absent.

Description of holotype.

An adult male with a total length of 371.3 mm (SVL 292.2 mm and TaL 79.1 mm); tail relatively short, Tal/TL 0.213; body slender, cylindrical; head length (HL) 10.74 mm, head width 5.13 mm, HL/HW 2.09, slightly distinct from neck; eye small, ED 1.25 mm, with an oval pupil; maxillary teeth 21. Rostral small, triangular, only the upper tip visible from above. Length of the suture between the internasals (LSBI 1.38 mm) subequal to the length of the suture between the prefrontals (LSBP 1.36 mm). Nostril in the anterior part of the nasal. Loreal one, subrectangular, loreal height (LorH) 0.85 mm, loreal length (LorL) 1.49 mm, LorH/LorL 0.57. Frontal one, pentagonal, pointed backwards, much shorter than the parietals. Parietals paired. No preoculars and postoculars. Supraocular one, length of supraocular (SPOL 1.59 mm) longer than the length of upper anterior temporal (ATUL 1.42 mm, SPOL/ATUL 1.12). Temporals 2+2+3, the anterior two contact the eye, the lower anterior temporal much larger, the upper medium temporal much larger, the upper posterior temporal much larger and separated from the other side one by one scale. Supralabials 6, 4th–5th contact the eye, the last one much elongated. One mental. Two chin shields, the anterior pairs longer than the posterior pairs. Infralabials 5, the first one contact with each other after the mental and before the 1st chin shields, 1st–3rd touch the 1st chin shields.

Dorsal scales strongly keeled, 23 rows throughout the body, the outmost row smooth and significantly enlarged. Ventrals 161; anal entire; subcaudals 60, not paired.

Colouration of holotype in life.

Scales tinged weakly iridescent and metallic lustre. Dorsum dark brown and the five innermost dorsal scale rows a little darker, forming an inconspicuous longitudinal vertebral line. Chin shields are tan. Ventrals generally light brown, darker on both sides, free margins of ventral scales greyish-white. Ventral side of tail brownness.

Colouration of holotype in preservation.

The dorsal surface of the body uniformly brownish-black, slightly tinged with iridescence and the longitudinal vertebral line a little darker. Chin shields light brown. Ventrals generally creamy-brown, darker on both sides, free margins of ventral scales greyish-white. Ventral side of tail light brown.

Variation.

Measurements, body proportions and scale counts are listed in Table 3. All paratypes are very similar to the holotype, except in the following: (1) paratype ANU20230004 has six infralabials on the left side; (2) relatively shorter supraoculars (SPOL/ATUL): ANU20230012: 1.03, ANU 20230013: 0.99, ANU20230004: 1.01; (3) more ventrals: ANU 20230013: 166, CIB 119043: 170; (4) less subcaudals: ANU 20230013: 57, ANU20230015: 58, CIB 119043: 55; (5) dorsum dark brown, venter greyish-white, both sides of ventral scales are taupe and ventral view of tail light grey in both subadult male ANU20230015 and juvenile male CIB 119043.

Distribution and habits.

Achalinussheni sp. nov. is currently only known from Hunan Province, China: Lianyuan City and Nanyue District (350–410 m a.s.l.). The native vegetation in the type locality is subtropical evergreen broad-leaved forests. Areas near the locality where the specimen CIB 119043 was collected is largely covered with artificial coniferous forest dominated by Cryptomeria spp. This new species’ population status requires further investigation. The conservation status for the new species is recommended to rate as data deficient (DD).

Discussion

The description of A.sheni sp. nov. brings the total number of Achalinus known species to 27, with 20 species distributed in China, amongst which 16 species are endemic to China. Amongst these, four Achalinus species have been reported in the Hunan Province, A.hunanensis (the north mountain area in western Hunan Province), A.spinalis (the mountain area in north-western Hunan Province, the west mountainous and hilly areas in southern Hunan Province and the north mountainous and hilly areas in eastern Hunan Province), A.jinggangensis (the east mountainous and hilly areas in southern Hunan Province) and A.yunkaiensis (the southern mountain area in western Hunan Province) (Gao et al. 2022; Ma et al. 2023a) and the description of A.sheni sp. nov. (the hilly area in central Hunan Province) raises this number to five.

Achalinus is a group of poorly-known snakes as many species only have a single voucher specimen: A.damingensis, A.panzhihuaensis, A.pingbianensis, A.timi, A.tranganensis, A.vanhoensis and A.zugorum (Ziegler et al. 2019; Li et al. 2020; Luu et al. 2020; Miller et al. 2020; Hou et al. 2021; Ha et al. 2022; Yang et al. 2023) and several species (e.g. A.hainanus and A.werneri) do not have any sequence data accessioned. Consequently, this lack of adequate taxonomic sampling and genome-scale data results in our current situation where the population status, distribution pattern and evolution history of taxa within this genus are unclear (Miller et al. 2020). Therefore, it is paramount to conduct further survey work in these regions to learn more about these snakes.

Key to species of the genus Achalinus Peters, 1869

1 Internasal absent 2
– Internasal present 3
2 Middle dorsal scale rows 23, subcaudal 39–62 A.meiguensis
– Middle dorsal scale rows 19–21, subcaudal 73 A.panzhihuaensis
3 Loreal absent or usually absent 4
– Loreal present 9
4 Middle dorsal scale rows 23 5
– Middle dorsal scale rows ≥ 25 7
5 Dorsal scale rows 25-23-23 A.vanhoensis
– Dorsal scale rows 23-23-23 6
6 Supralabials 6, internasal suture longer than prefrontal suture A.jinggangensis
– Supralabials 7, internasal suture subequal to prefrontal suture A.pingbianensis
7 Internasal suture shorter than prefrontal suture A.formosanusformosanus
– Internasal suture longer than prefrontal suture 8
8 TaL/TL 0.317, ventrals 161–167, subcaudals 96–97 A.formosanuschigirai
– TaL/TL 0.213, ventrals 170, subcaudals 72 A.timi
9 Anterior dorsal scale rows 25 10
– Anterior dorsal scale rows usually 23 13
10 Dorsal scale rows 25-25-23 A.niger
– Dorsal scale rows 25-23-23 11
11 Infralabials 7 A.zugorum
– Infralabials 6 12
12 Prefrontals 2, ventrals 179 in female A.juliani
– Prefrontals 4, ventrals 171 in female A.tranganensis
13 Internasal suture shorter than prefrontal suture 14
– Internasal suture subequal to or longer than prefrontal suture 15
14 A dark streak in the middle of caudal ventral present A.huangjietangi
– A dark streak in the middle of caudal ventral absent A.spinalis
15 Internasal suture subequal to prefrontal suture 16
– Internasal suture longer than prefrontal suture 20
16 Anterior temporal 1 A.hainanus
– Anterior temporal 2 17
17 TaL/TL 0.250 ~ 0.300, subcaudals 67–98 A.werneri
– TaL/TL less than 0.225, subcaudals less than 61 18
18 The outmost dorsal scale rows keeled A.ningshanensis
– The outmost dorsal scale rows smooth 19
19 Ventrals 150–162, subcaudals 49–56, length of supraocular shorter than the length of upper anterior temporal A.yunkaiensis
– Ventrals 161–170, subcaudals 55–61, length of supraocular subequal to or longer than the length of upper anterior temporal A.sheni sp. nov.
20 Loreal elongate, length twice as height A.ater
– Loreal subquadrate, length longer than height, but the ratio less than two 21
21 Ventrals less than 156 22
– Ventrals more than 155 24
22 Subcaudals less than 55 A.dabieshanensis
– Subcaudals more than 58 23
23 Maxillary teeth 31–33 A.dehuaensis
– Maxillary teeth 27–29 A.quangi
– Maxillary teeth 23 A.rufescens
24 1 anterior temporal touching the eye A.emilyae
– 2 anterior temporals touching the eye 25
25 TaL/TL 0.261 ~ 0.262 in males, ventrals 155 in males, subcaudals 76 in males A.yangdatongi
– TaL/TL 0.246 in male, ventrals 162 in male, subcaudals 74 in male A.damingensis
– TaL/TL 0.221 ~ 0.225 in males, ventrals 163–165 in males, subcaudals 69–72 in males A.hunanensis
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Supplementary Material

XML Treatment for Achalinus sheni

Acknowledgements

We send great thanks to Zhou Bing (Hunan Normal University) for his help in fieldwork. We also sincerely thank Ke-Ji Guo (Central South Inventory and Planning Institute of National Forestry and Grassland Administration), Sheng-Chao Shi and Jie-Fang Chen (Chengdu Institute of Biology, Chinese Academy of Sciences) for their help in this study.

Appendix 1. Specimens examined

Examined Achalinus specimens

A.yunkaiensis (n = 6): China

Xinyi City in Guangdong Province: SYS r001443, SYS r001502, SYS r001503,

SYS r001902, SYS r001903;

Xinning County in Hunan Province: CIB 119041.

Citation

Ma S, Xu Y-H, Qi S, Wang Y-Y, Tang S-S, Huang S, Jiang J-P (2023) Discovery of a new cryptic Achalinus Peters, 1869 (Serpentes, Xenodermidae) species from Hunan Province, China. ZooKeys 1181: 9–27. https://doi.org/10.3897/zookeys.1181.109462

Funding Statement

the National Key Programme of Research and Development, Ministry of Science and Technology (2022YFF1301401)

Contributor Information

Song Huang, Email: snakeman@sinoophis.com.

Jian-Ping Jiang, Email: jiangjp@cib.ac.cn.

Additional information

Conflict of interest

The authors have declared that no competing interests exist.

Ethical statement

No ethical statement was reported.

Funding

The study was supported by the National Key Programme of Research and Development, Ministry of Science and Technology (2022YFF1301401).

Author contributions

Conceptualization: SH, SM, YHX, JPJ. Data curation: SM, SQ, SH, JPJ. Formal analysis: SM. Investigation: SST, YYW, YHX, SQ. Methodology: JPJ, SM. Project administration: JPJ. Resources: SST, JPJ, YYW, SQ, SH, YHX. Software: SM. Supervision: SH, JPJ. Validation: SH, YYW, JPJ. Visualization: SM. Writing - original draft: YHX, SM. Writing - review and editing: YYW, SH, SST, JPJ, SQ, SM, YHX.

Author ORCIDs

Shun Ma https://orcid.org/0009-0003-8611-4550

Yu-Hao Xu https://orcid.org/0000-0001-6094-6680

Shuo Qi https://orcid.org/0000-0002-2924-6093

Shan-Shan Tang https://orcid.org/0009-0007-6582-3859

Song Huang https://orcid.org/0000-0001-6786-8523

Jian-Ping Jiang https://orcid.org/0000-0002-1051-7797

Data availability

All of the data that support the findings of this study are available in the main text.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

XML Treatment for Achalinus sheni
zookeys.1181.109462-treatment1.xml (36.7KB, xml)

Data Availability Statement

All of the data that support the findings of this study are available in the main text.

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