First record of Achalinus hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023 (Serpentes, Xenodermidae) in Guangxi, China, with supplementary morphological information

Biodiversity Data Journal 13: e168622 doi: 10.3897/BDJ.13.e168622 Taxonomy & Inventories First record of Achalinus hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023 (Serpentes, Xenodermidae) in Guangxi, China, with supplementary morphological information Yanyuan Xie , Yuhui Li , Zhengjun Wu , Zening Chen ‡ Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guilin, China § Guangxi Key Laboratory of Rare and Endangered Animal Ecology, Guangxi Normal University, Guilin, China | College of Life Sciences, Guangxi Normal University, Guilin, China, Guilin, China ¶ Authors contributed equally to this work, Guilin, China Corresponding author: Zening Chen ([email protected]) Academic editor: Johannes Penner Received: 13 Aug 2025 | Accepted: 16 Nov 2025 | Published: 27 Nov 2025 Citation: Xie Y, Li Y, Wu Z, Chen Z (2025) First record of Achalinus hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023 (Serpentes, Xenodermidae) in Guangxi, China, with supplementary morphological information. Biodiversity Data Journal 13: e168622. https://doi.org/10.3897/BDJ.13.e168622 Abstract Background The family Xenodermidae comprises six recognised genera: Xenodermus Reinhardt, 1836; Achalinus Peters, 1869; Stoliczkia Jerdon, 1870; Fimbrios Smith, 1921; Parafimbrios Teynié, David, Lottier, Le, Vidal & Nguyen, 2015; and Paraxenodermus Deepak, Lalronunga, Lalhmingliani, Das, Narayanan, Das & Gower, 2021. Amongst these, Achalinus Peters, 1869, is the most species-rich taxon. It is widely distributed across eastern and south-eastern Asia, ranging from northern Vietnam to south-western China and extending partially into Japan. Achalinus hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023 was originally described, based on two male specimens collected from Huaihua City and Changsha City, Hunan ‡,§,|,¶ ‡,§,|,¶ ‡,§,| ‡,§,| © Xie Y et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Province, China. Subsequent surveys also recorded this species in Dushan County, Guizhou Province, marking its first known occurrence there and providing the first description of female specimens. During our herpetological surveys in 2024, three Achalinus specimens were collected from Guangxi Zhuang Autonomous Region, China. Due to severe desiccation, DNA extraction was unsuccessful for specimen GXNU2024090120. However, we analysed mitochondrial DNA sequence data from the remaining two specimens and compared them with all known congeners. Both the morphological and molecular evidence strongly support the identification of the specimens from Jiuwanshan National Nature Reserve as A. hunanensis. Additional morphological data are provided here, based on the examination of three newlycollected individuals. New information In this study, we provide a detailed morphological description of A. hunanensis, based on newly-collected specimens. We also present an updated species diagnosis incorporating additional morphological characters and revise the known distribution of A. hunanensis. Keywords Achalinus hunanensis, morphology, phylogenetics, taxonomy, Guangxi Introduction The genus Achalinus Peters, 1869, which currently comprises 28 recognised species, represents the most diverse genus within the family Xenodermidae and is distributed across northern Vietnam, China and Japan (Uetz et al. 2025). With the expansion of extensive field surveys and advances in molecular techniques, the previously underestimated biodiversity within the genus Achalinus is being increasingly revealed. Since 2019, more than 20 new species have been described within this genus (Peters (1869), Boulenger (1888), Boulenger (1908), Pope (1935), Bourret (1937), Zong and Ma (1983), Ota and Toyama (1989), Zhao et al. (1998), Wang et al. 2019,Ziegler et al. 2019, Li et al. 2020, Miller et al. 2020, Huang et al. 2021, Hou et al. 2021, Pham et al. 2023, Li et al. 2021, Yang et al. 2022, Ma et al. 2023a, Ma et al. 2023c, Xu et al. 2023, Yang et al. 2023, Zhang et al. 2023, Zhang et al. 2023, Li et al. 2024, Huang et al. 2024, Xu et al. 2024). Achalinus are small-sized snakes and characterised by fossorial and secretive habits, typically inhabiting moist microhabitats, such as forest floor leaf litter or beneath decaying logs in mountainous regions. Their activity patterns show strong environmental dependence, with surface activity primarily occurring at night or under rainy conditions. The combination of limited mobility and specialised habitat preferences makes field collection particularly challenging, leading to an extreme scarcity of specimens available for study. The A . hunanensis population identified in Guangxi shows notable morphological divergence from previously reported populations; amongst the three adult 2Xie Y et al specimens examined, two females exhibiting a distinct occipital patch extending across the head and abdomen — a feature absent in males. Given the current scarcity and distinctiveness of available specimens, a systematic and supplementary morphological characterisation of this species is urgently needed. The Hunan odd-scaled snake, Achalinus hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023, was originally described, based on two male specimens. Subsequently, Xu et al. (2025) reported a female specimen from Dushan County, Guizhou Province, thereby extending the known distribution range of this species. Currently, A. hunanensis is documented from Huaihua City and Changsha City in Hunan Province and Dushan County in Guizhou Province, China. It can be distinguished from its congeners primarily by the following combination of morphological characters: (1) dorsal scales strongly keeled, 23 rows throughout the body, the outermost row strongly keeled and substantially enlarged; (2) tail relatively short, TAL/TL ratio 0.22-0.24 in males and 0.17 in females; (3) maxillary teeth 23; (4) length of suture between internasals substantially longer than that between prefrontals, LSBI/LSBP ratio 2.0-2.1; (5) one loreal, subrectangular; (6) six supralabials, the fourth and fifth in contact with the eye; (7) the two anterior temporals in contact with eye; (8) ventrals 163-168 in males and about 169 in females; (9) subcaudals 69-72 in males and about 53 in females, not paired （Xu et al. 2025）. In recent surveys in Guangxi, China, three Achalinus specimens were found in Jiuwanshan National Nature Reserve (Fig. 1). Molecular analyses revealed that the specimens from Rongshui Miao Autonomous County first clustered with the specimens from Guizhou Province and subsequently formed a clade with the type series of A. hunanensis. Morphological examinations further supported these findings. Therefore, we provide supplementary descriptions of the new specimens, an expanded morphological diagnosis and new distribution records for Guangxi. Materials and methods Sampling Three Achalinus specimens were collected in 2024 from the Jiuwanshan National Nature Reserve in Rongshui Miao Autonomous County, Liuzhou, Guangxi, China Fig. 1. The specimens include one adult female GXNU20240905009 (25.21649174°N, 108.68016354°E, 891 m a.s.l.), one adult male GXNU2024102112 (25.22070854°N, 108.6763514°E, 983 m a.s.l.) and one dried roadkill specimen GXNU2024090120 (25.43329212°N, 109.16085809°E, 1281 m a.s.l.), all collected by Li Ding. Specimens were fixed in 80% ethanol and deposited at the School of Life Sciences, Guangxi Normal University. All sampling complied with China's Wild Animal Protection Law and sex was determined via gonadal dissection. Molecular phylogen etic analysis Genomic DNA was extracted from liver tissue using the Hi-Pure Animal Genomic DNA Kit. The partial mitochondrial cytochrome c oxidase 1 (COI) gene was amplified with First record of Achalinus hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023 ... 3 primers RepCOIF and RepCOIR (Nagy et al. 2012). The Polymerase chain reaction (PCR) products were sequenced by Beijing Qingke New Industry Biotechnology Co., Ltd. For phylogenetic analysis, 35 sequences (Table 1) were selected, including 33 sequences obtained from GenBank. These included 30 sequences from 26 Achalinus species and three outgroup sequences from Fimbrios klossi, Parafimbrios lao and Xenodermus javanicus (Luu et al. 2020, Ha et al. 2022). All sequences were aligned with other retrieved sequences from the same gene loci using MEGA 11 (Tamura et al. 2021). Uncorrected pairwise distances (p-distance) were then calculated in MEGA11. Phylogenetic trees were constructed, based on COI gene using Maximum Likelihood (ML) and Bayesian Inference (BI). For the ML analysis, RAxML v.8.2.4 (Stamatakis 2014) was employed with the GTR+GAMMA substitution model and nodal support was assessed through 1000 bootstrap replicates with the rapid bootstrap algorithm. Bayesian analysis was conducted using MrBayes 3.2 (Ronquist et al. 2012) with nucleotide substitution models selected by PartitionFinder 2.1.1 (Lanfear et al. 2012, Lanfear et al. 2017), based on the Bayesian information criterion (BIC), which identified K80+I+G, HKY+I and GTR+G as optimal models for different partitions.The Markov Chain Monte Carlo (MCMC) analysis ran for 20 million generations, sampling every 1000 generations. Meanwhile, uncorrected pairwise genetic distances amongst Figure 1. Distribution of Achalinus hunanensis. The squares indicate the type localities in Hunan, the triangle representing locality in Guizhou and the star marking the sampling site in the present study. Elevation data source: CGIAR-CSI SRTM v.4.1.  4Xie Y et al Achalinus species were calculated in MEGA 11 after excluding outgroups (Kumar et al. 2018) (Table 1). Morphological examination Morphometric data collection, scale enumeration and standardisation of morphological abbreviations all followed the methodologies outlined by Zhao (2006) and Xu et al. (2025). Three key measurements were taken using the Yong Guang Stainless Ruler (00722098) to the nearest mm: snout-vent length (SVL), tail length (TAL) and total length (TL). Other measurements were taken with Deli digital calipers (DL3945) to the nearest 0.1 mm: head length (HL, length from the tip of snout to the posterior margin of mandible; head width (HW, width from the widest part of the head in dorsal view); eye diameter (ED, diameter from the most anterior corner of the eye to the most posterior corner); loreal height (LorH, height from the highest part to the lowest part of the loreal in lateral view); loreal length (LorL, length from the most anterior loreal to the most posterior loreal in lateral view); length of the suture between internasals (LSBI); length of the suture between prefrontals (LSBP). No. Species Voucher Locality GenBank References 1A. hunanensis GXNU20240905009 Rongshui, Liuzhou, Guangxi, China PX048858 This study 2A. hunanensis GXNU2024102112 Rongshui, Liuzhou, Guangxi, China PX048859 This study 3A. hunanensis CIB119040 Ningxiang, Hunan, China OQ848426 Ma et al. (2023b) (4 A. hunanensis CIB119039 Huaihua, Hunan, China OQ848425 Ma et al. (2023b) 5A. hunanensis QHU 2024030 Dushan, Guizhou, China PQ281493 Xu et al. (2024) 6A. niger RN0667 Taiwan, China KU529433 Unpublished 7A. formosanus RN2002 Taiwan, China KU529452 Unpublished 8A. juliani IEBRA.2018.8 HaLang, Cao Bang, Vietnam MK330854 Ziegler et al. (2019) 9A. timi IEBRA.2018.10 ThuanChau, Son La, Vietnam MK330856 Ziegler et al. (2019) 10 A. emilyae IEBR4465 HoanhBo, Quang Ninh, Vietnam MK330857 Ziegler et al. (2019) 11 A. yunkaiensis SYSr001443 Dawuling Forestry Station, Guangdong, China MN380329 Wang et al. (2019) 12 A. ater SYSr00852 Huaping Nature Reserve, Guangxi, China MN380334 Wang et al. (2019) 13 A. rufescens SYSr001866 Hongkong, China MN380339 Wang et al. (2019) Table 1. Localities, voucher information, GenBank accession numbers, and references for the samples used in this study. First record of Achalinus hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023 ... 5 No. Species Voucher Locality GenBank References 14 A. spinalis SYSr001327 Badagong Mountains, Hunan, China MN380340 Wang et al. (2019) 15 A. pingbianensis YBU18273 Honghe, Yunnan, China MT365521 Li et al. (2020) 16 A. huangjietangi HSR18030 Huangshan, Anhui, China MT380191 Huang et al. (2021) 17 A. zugorum IEBR4698 Bac Me, Ha Giang, Vietnam MT502775 Miller et al. (2020) 18 A. tranganensis VNUFR.2018.21 NinhBinh, Vietnam MW023086 Luu et al. (2020) 19 A. dabieshanensis AHU2018EE0710 Fuziling Provincial Reserve, Anhui, China MW316598 Zhang et al. (2023) 20 A. panzhihuaensis KIZ040189 Yanbian, Sichuan, China MW664862 Hou et al. (2021) 21 A. yangdatongi YPX51447 Xichou county,Yunnan,China MW664864 Xu et al. (2023) 22 A. yangdatongi KIZ034327 Wenshan Nature Reserve， Yunnan，China MW664865 Hou et al. (2021) 23 A. meiguensis GP835 Mianyang, Sichuan, China MZ442641 Li et al. (2021) 24 A. dehuaensis YBU13013 Dehua, Fujian, China MZ442642 Li et al. (2021) 25 A. vanhoensis VNUFR.2019.13 VanHo, Son La, Vietnam ON677935 Ha et al. (2022) 26 A. damingensis ANU20220009 Shanglin, Nanning, Guangxi, China OP644487 Yang et al. (2023) 27 A. quangi sp4 Northern Vietnam OQ197471 Pham et al. (2023) 28 A.sheni ANU20230012 Lianyuan,Hunan,China OR178145 Ma et al. (2023c) 29 A. nanshanensis HNNU230902 Nanshan National Park, Hunan, China OR523369 Li et al. (2024) 30 A. nanshanensis HNNU230903 Nanshan National Park, Hunan, China OR523370 Li et al. (2024) 31 A.jinggangensis QHU2023011 Fujian,China PQ507882 Xu et al. (2024) 32 A. jianghuaensis JSUWT005 Jianghua, Hunan, China OR161056 Huang et al. (2024) 33 Fimbrios klossi IEBR3275 Quang Ngai, Vietnam KP410744 Teynie et al. (2015) 34 Paraffmbrios lao MNHN2013.1002 Louangphabang, Laos KP410746 Teynie et al. (2015) 35 Xenodermus javanicus -- Sumatera Barat,Indonesia KP410747 Teynie et al. (2015) The scale features and their abbreviations are as follows: loreals (Lor); supralabials (SL); infralabials (IL); number of chin shield pairs (Chins); infralabials touching the first pair of chin shields (IFL-1st Chin); temporals (TEMP); supraoculars (SPO); dorsal scale rows (DSR) (counted at one-head-length behind the head, at midbody and at one-head-length 6Xie Y et al before the anal), number of anterior temporals that touch the eye (aTEM-Eye) (head bilateral scale counts are given as left/right), ventral scales (VS), cloacal plate (CP), subcaudal (SC). Taxon treatment Achalinus hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023 • GBIF https://doi.org/10.15468/eh9asg Materials a. scientificName: Achalinus hunanensis; order: Squamata; family: Xenodermidae; genus: Achalinus; country: China; stateProvince: Guangxi; county: Rongshui Miao Autonomous; verbatimElevation: 891 m; verbatimCoordinates: 25°12.99'N 108°40.81'E; eventDate: 28-08-2024; individualCount: 1; sex: female; catalogNumber: GXNU20240905009; occurrenceID: 182A6960-3B27-56D2-B35E-40C1433E1BC4 b. scientificName: Achalinus hunanensis; order: Squamata; family: Xenodermidae; genus: Achalinus; country: China; stateProvince: Guangxi; county: Rongshui Miao Autonomous; verbatimElevation: 1281 m; verbatimCoordinates: 25°26.00'N 109°09.65'E; eventDate: 30-08-2024; individualCount: 1; sex: female; catalogNumber: GXNU2024090120; occurrenceID: DCB238DB-23AA-5ABC-AF22-68A659E8E4AB c. scientificName: Achalinus hunanensis; order: Squamata; family: Xenodermidae; genus: Achalinus; country: China; stateProvince: Guangxi; county: Rongshui Miao Autonomous; verbatimElevation: 983 m; verbatimCoordinates: 25°13.24'N 108°40.58'E; eventDate: 15-10-2024; individualCount: 1; sex: male; catalogNumber: GXNU2024102112; occurrenceID: E152E3EE-B346-50C1-83C7-5DDB57E948EB Description The description is based on the specimens from Guangxi. The measurements and scalation characters of A. hunanensis are listed in Table 2. Body slender, cylindrical; head slightly distinct from neck; eye small; triangular, slightly visible from above; length of the suture between the internasal substantially longer than that between prefrontal, with LSBI/LSBP ratios > 1; nostril positioned in anterior part of nasal, deeply concave inwards; prefrontals paired; frontal pentagonal, pointed to the rear, slightly wider than high, much shorter than the parietals; loreal one, subrectangular, with LorH/LorL ratios < 1; supraocularone, Irregularly hexagonal; TEMP 7/7, arranged in three rows (2+2+3 on both sides), the anterior two contact the eye; the upper one smaller, irregularly quadrilateral, the lower one elongated; six supralabials, the fourth and fifth contacting the eye, the last one much elongated; two pairs of chin shields, the anterior pairs almost equal to the posterior pairs (GXNU2024102112 left two scales, right three scales and the second pair on the right side divided into two smaller scales), followed by preventrals; one mental, followed by 5/5 infralabials, the first one contacting with others after the mental and before the 1 chin-shields, 1 -3 touching the first pair of chin-shields. st st rd First record of Achalinus hunanensis Ma, Shi, Xiang, Shu & Jiang, 2023 ... 7 Voucher number GXNU 2024102112 GXNU 20240905009 GXNU 2024090120 QHU 2024030 CIB 20160503 CIB 119039 CIB 119040 Location Liuzhou, Guangxi Liuzhou, Guangxi Liuzhou, Guangxi Dushan, Guizhou Anhua, Hunan Hecheng, Hunan Ningxiang, Hunan Sex ♂ ♀ ♀ ♀ ♂ ♂ ♂ Presence or absence of an occipital patch absence presence presence absence absence absence absence SVL 350 329 290 355 288 255 204 TL 456 401 358 428 379 329 262 TAL 106 72 68 73 91 74 58 TAL/TL 0.23 0.18 0.19 0.17 0.24 0.23 0.22 HL 14.27 12.18 - 12.5 12.7 7.9 6.3 HW 7.67 5.4 - 5.9 4.6 4.8 3.4 SL 3+2+1 3+2+1 - 3+2+1 3+2+1 3+2+1 3+2+1 IL 5/5 5/5 - 6/6 5/5 5/6 5/5 Chins 2* 2 - 2 2 2 2 IL-1stChin 3/3 3/3 - 3/3 3/3 3/4 3/3 Lor 1 1 - 1 1 1 1 LorH 1.35 1.06 - 1.0 1.2 1.0 0.9 LorL 1.78 1.54 - 1.6 1.7 1.5 1.5 LorH/LorL 0.814 0.69 - 0.63 0.71 0.67 0.60 LSBI 2.5 1.43 1.63 1.9 1.8 1.78 1.52 LSBP 1.35 0.85 0.93 0.9 0.9 0.88 0.76 LSBI/ LSBP 1.85 1.68 1.75 2.11 2.00 2.02 2.00 LSBI vs.LSBP > > > > > > > ED 1.41 0.96 - 1.2 1.1 1.4 1.4 TEMP 2+2+3/2+2+3 2+2+3/2+2+3 - 2+2+3/2+2+3 2+3+4/2+3+4 2+2+4/2+2+4 2+2+4/2+2+4 Table 2. Morphological variation of Achalinus hunanensis obtained from specimens examined in this study and Ma et al. (2023b) and Xu et al. 2025. *= left two scales, right three scales and the second pair on the right side divided into two smaller scales. Abbreviations as defined in 'Morphological examination'. 8Xie Y et al Voucher number GXNU 2024102112 GXNU 20240905009 GXNU 2024090120 QHU 2024030 CIB 20160503 CIB 119039 CIB 119040 aTEMPEye 2/2 2/2 - 2/2 2/2 2/2 2/2 SPO 1 1 - 1 1 1 1 DSR 23-23-23 23-23-23 - 23-23-23 23-23-23 23-23-23 23-23-23 VS 163 173 - 169 168 163 165 CP 1 1 1 1 1 1 1 SC 71 61 - 53 69 69 72 Dorsal scales strongly keeled, lanceolate, 23 rows throughout the body, the outermost row strongly keeled and substantially enlarged. Female GXNU20240905009: VS 173, SC 61; Male GXNU2024102112: VS 163, SC 71; anal entire; subcaudals unpaired. In life, specimens display iridescent, uniformly brownish-black dorsal colouration, with a distinctive occipital bright patch extending to the head and abdomen in the two females from Guangxi (absent in males). The first chin shield pair black and second pair brown in the two females (uniformly brownish-black in males). The ventral surface is lighter brownish-black than the dorsum, with the supralabials and infralabials the darker dorsal colouration. Head scales are similar to the body colour. Ventral scale margins are greyish-white. Eyes are completely black with a vertically subelliptic pupil (Fig. 2). Figure 2. 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