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A new species, Achalinus hunanensis sp. nov., is described from middle and western Hunan Province based on the results of molecular systematics and morphological characters. It diverges from known congeners by a significant genetic divergence (p-distance 3.2%–16.9% based on CO1 mitochondrial gene), and it can be distinguished from all known congeners by the following morphological characters: (1) all dorsal scales strongly keeled, 23 rows throughout the body, the outmost one strongly keeled and enlarged; (2) tail relatively short, TaL/TL 0.221 ~ 0.225; (3) maxillary teeth 23; (4) the suture between internasals 2 × as long as that between prefrontals; (5) loreal one, subrectangular, LorH/LorL 0.62 ~ 0.70; (6) supralabials 6, the 4th and 5th touch the eye; (7) the two anterior temporals in contact with eye; (8) ventrals 163–165, subcaudals 69–72, not paired. This raises the number of known species of Achalinus to 24.

Achalinus ningshanensis sp. nov. D.C. Yang, R.Y Huang, K. JIANG, F.T. BURBRINK & S. Huang (Figs. 3–5) Suggested English common name: Ningshan Odd-scaled Snake. Suggested Chinese common name: Ťkḛffi (Bopomofo: Níng Shǎn Jǐ Shé). Holotype. ANU20220001 (field number JK0917, Fig. 3), an adult female, collected in summer of 2008 from Xunyangba Town (33.5434 N, 108.5439 E, 1372 m a. s. l.), Ningshan County, Shaanxi Province, China by the team of Ke Jiang. Paratypes. Six females, JK0918, JK0889, JK0890, JK0891, HSR19131, and HSR19132 (Voucher number: ANU20220002–7), all with the same collecting information as the holotype. Diagnosis. Achalinus ningshanensis sp. nov. can be differentiated from all other members of the genus Achalinus by the following combination of morphological characters:(1) dorsum iridescent and uniformly dark brown in preservative, longitudinal vertebral line absent; (2) brown beneath; (3) dotted black streak in the middle of the subcaudals absent; (4) tail length relatively short, TaL/ToL 12–16% in females; (5) fewer subcaudals, 41–46, in females; (6) dorsal scales 23 rows throughout, strongly keeled, and the outer-most rows on both sides of the body also keeled and slightly enlarged; (7) one loreal; (8) internasal not fused to prefrontal; (9) suture between internasals is similar size when compared to the suture between prefrontals; (10) preocular and postocular absent; (11) 6 supralabials; (12) 5 infralabials, the first 3 (rarely 2) touching the first pair of chin shields; (13) 3 pairs of chin shields. Description of the holotype. An adult female in excellent condition (Figs. 3 & 4). Body slender and subcylindrical, total length 436 mm (SVL 374 mm and Tal 62 mm); tail relatively shorter, TaL/ToL 14%; head slightly distinct from neck dorsally covered with large head scales, head length 13.72 mm; head width 7.16 mm; eyes small with subround pupils. Rostral small, subtriangular in frontal view, barely visible from above. Internasals paired, the suture between internasals (1.94 mm) subequal to that between prefrontals (1.63 mm); prefrontals paired, subrectangular. Frontal shield-shaped, nearly straight anteriorly, pointed backwards, slightly broader than it is long, and much shorter than the parietals. Parietals paired, the parietal suture longer than frontal. Nostril in the anterior part of the nasal. One loreal, rectangular, LorH: 0.97 mm, LorL: 1.90 mm (LorH/LorL: 0.51), extending from the nasal to the eye. One supraocular, in contact with loreal, prefrontals, frontal, parietals, and superior anterior temporals. No preocular or postocular. Temporals 2+3+4, two anterior temporals elongated, the upper one smaller in contact with parietal, the lower one in contact with fifth and sixth supralabials, both in contact with the eye; three elongated middle temporals; four elongated posterior temporals, the uppermost (super-temporal) significantly enlarged, the supertemporal split into two parts on the left, surrounding the parietal; the super-temporals from two sides contacting at the midline. Supralabials six, the first very small, 1–3 contacting the nasal, fourth and fifth contacting the orbit, fourth in narrow contact, fifth in broad contact, and sixth the longest and largest. One mental. Five infralabials, the first pair in contact blocking the mental from contacting an anterior pair of chin shields; first infralabial smallest, increasing in size until the fifth infralabial that is the longest. Three pairs of chin shields followed by ventrals. First three infralabials touching the first pair of chin shields on both sides. Dorsal scale rows 23–23–23, dorsal scales fusiform, not overlapping, distinctly keeled posterior to nape, and outermost dorsal scale row on both sides slightly keeled and enlarged. Ventrals 167; cloacal plate entire; subcaudals 43, uniserial. Coloration of holotype in preservative. Dorsum uniformly dark brown with metallic luster under light, the anterior portion of the head ash black, interstitial skin of dorsal dark brown. Ventral ground color brown, free margins of ventral scales grayish white. Variation. Measurements, body proportions, and scale counts are listed in Table 1. All paratypes are very similar to the holotype except in the following: paratypes JK0889, JK0891, and HSR19132 have two middle temporals; paratypes JK0890 and HSR19131 have two middle temporals and three posterior temporals; paratypes JK0890 have the first two infralabials touching the first pair of chin shields on both sides. The number of anterior temporals that contact the eyes is not a stable trait. Comparisons. Achalinus ningshanensis sp. nov. can be differentiated from all other known species of snakes in the genus Achalinus by a combination of the following morphological characters: infralabials five, three pairs of chin shields, relatively shorter tail length (TaL/ToL 12–16% in females), longitudinal vertebral line absent, and missing a dotted black streak in the middle of the subcaudals. Achalinus ningshanensis sp. nov. differs from all other species in Achalinus except A. spinalis Peters, 1869, A. hainanus Huang, 1975, A. emilyae Ziegler, Nguyen, Pham, Nguyen, Pham, Van Schingen, Nguyen & Le, 2019, A. huangjietangi Huang, Peng, & Huang, 2021, and A. dehuaensis Li, Wu, Xu, Zhu, Ren, Guo & Dong, 2021 by having fewer infralabials (five vs. six). Furthermore, it differs from A. spinalis and A. huangjietangi by having the following characters: absent longitudinal vertebral line, and missing a dotted black streak in the middle of the subcaudals; from A. hainanus by having two anterior temporals (vs. only one), three pairs of chin shields (vs. two pairs), fewer subcaudals in females (41–46 vs. 67–69); from A. emilyae by having fewer subcaudals in females (41–46 vs. 63), three pairs of chin shields (vs. two pairs), outermost dorsal scales rows keeled (vs. outmost rows smooth); from A. dehuaensis by having a relatively shorter tail length (TaL/ToL 12–16% vs. 21–22% in females), fewer subcaudals in females (41–46 vs. 63–65), uniformly dark brown above, light brown beneath (vs. greyish brown above, pale yellow beneath). Achalinus ningshanensis sp. nov. differs from A. werneri Van denburgh, 1912 by having the following characters: absent longitudinal vertebral line, and missing a dotted black streak in the middle of the subcaudals. Achalinus ningshanensis sp. nov. differs from A. yangdatongi by having fewer infralabials (5 vs. 6), different dorsal scale row counts (23–23–23 vs. 23–23–19) and having three pairs of chin shields (vs. two pairs). Achalinus ningshanensis sp. nov. differs from A. ater by the suture between internasals subequal to that between prefrontals (vs. suture between internasals distinctly longer than between prefrontals) and having fewer subcaudals (41–46 vs. 56–63). Achalinus ningshanensis sp. nov. differs from A. juliani by the suture between internasals subequal to that between prefrontals (vs. the suture between internasals distinctly longer than between prefrontals) and having a relatively shorter tail length (TaL/ToL 12–16% vs. 22–37%), fewer subcaudals (41–46 vs. 77–91), different dorsal scale row counts (23–23–23 vs. 25–23–23), and having three pairs of chin shields (vs. two pairs). Achalinus ningshanensis sp. nov. differs from A. rufescens by having six supralabials, the fourth and fifth widely in contact with the eye (vs. five supralabials, third and fourth entering the eye) and being light brown beneath (vs. uniform yellowish beneath). Achalinus ningshanensis sp. nov. differs from A. formosanus Boulenger, 1908, A. jinggangensis (Zong & Ma, 1983), A. timi Ziegler, Nguyen, Pham, Nguyen, Pham, Van Schingen, Nguyen & Le, 2019, A. pingbianensis Li, Yu, Wu, Liao, Tang, Liu & Guo, 2020, A. zugorum Miller, Davis, Luong, Do, Pham, Ziegler, Lee, De Queiroz, Reynolds & Nguyen, 2020, by having a separated loreal (vs. absence). Further it is different from A. formosanus by having fewer midbody dorsal scale rows (23 vs. 27), three pairs of chin shields (vs. two pairs), fewer subcaudals in females (41–46 vs. 61–70); from A. jinggangensis by having fewer infralabials (5 vs. 6), three pairs of chin shields (vs. two pairs), fewer subcaudals in females (41–46 vs. 51); from A. timi by different dorsal scale row counts (23–23–23 vs. 25–25–23), fewer infralabials (5 vs. 6), three pairs of chin shields (vs. two pairs), and the suture between internasals subequal to that between prefrontals (vs. the suture between internasals distinctly longer than between prefrontals); from A. pingbianensis by having fewer infralabials (5 vs. 6), fewer supralabials (6 vs. 7), 3 pairs of chin shields (vs. 2 pairs), and being uniformly dark brown above, light brown beneath (vs. uniform black above and beneath), and from A. zugorum by having fewer infralabials (5 vs. 6), 3 pairs of chin shields (vs. 2 pairs). Achalinus ningshanensis sp. nov. differs from A. meiguensis Hu & Zhao, 1966 and A. panzhihuaensis by having divided internasals (vs. absent), absence of postocular (vs. presence), fewer infralabials (5 vs. 6), mental separated from anterior chin shields (vs. in contact), and the first pair of infralabials in contact (vs. separated). Furthermore, it differs from A. panzhihuaensis by different dorsal scale row counts (23–23–23 vs. 23–23–19). Achalinus ningshanensis sp. nov. differs from A. niger Maki, 1931 by having fewer infralabials (five vs. six), different dorsal scale row counts (23–23–23 vs. 25–25–23), and fewer subcaudals in females (41–46 vs. 52–58). Achalinus ningshanensis sp. nov. differs from A. tranganensis Luu, Ziegler, Ha, Lo, Hoang, Ngo, Le, Tran & Nguyen, 2020 by having fewer infralabials (five vs. six), three pairs of chin shields (vs. two pairs), a relatively shorter tail length (TaL/ToL 12–16% vs. 25%), and fewer subcaudals in females (41–46 vs. 73+). Achalinus ningshanensis sp. nov. differs from A. yunkaiensis Wang, Li & Wang, 2019 by having fewer infralabials (five vs. six), three pairs of chin shields (vs. two pairs), and the outer-most dorsal scales rows keeled (vs. outmost rows smooth). Etymology. The specific epithet refers to the location of type specimens, Ningshan County, Shaanxi Province, China. We suggest Níng Shǎn Jǐ Shé (Ťkḛffi) as Chinese common name, and Ningshan Odd-scaled Snake as English common name. Distribution and habits. Achalinus ningshanensis sp. nov. is currently known only from the type locality Ningshan County, Shaanxi Province, China. All the specimens were found in farmland. The surrounding habitat was composed of secondary conifer/broad-leaved mixed forest. The new species is sympatric with A. cf. spinalis, A. cf. rufescens, Stichophanes ningshaanensis (Yuan, 1983), Euprepiophis mandarinus (Cantor, 1842), Elaphe taeniura (Cope, 1861), E. carinata (Günther, 1864), E. xiphodonta Qi, Shi, Ma, Gao, Bu, Grismer, Li, Wang 2021, Oreocryptophis porphyraceus (Cantor, 1839), Cyclophiops major (Günther, 1858), Lycodon ruhstrati (Fischer, 1886), L. liuchengchaoi Zhang, Jiang, Vogel and Rao, 2011, Pseudoxenodon macrops (Blyth, 1855), Rhabdophis nuchalis (Boulenger, 1891), Zaocys dhumnades (Cantor, 1842), Azemiops kharini Orlov, Ryabov and Nguyen, 2013, Gloydius qinlingensis (Song and Chen, 1985), Protobothrops jerdonii (Günther, 1875), Published as part of Yang, Dian-Cheng, Huang, Ru-Yi, Jiang, Ke, Burbrink, Frank T., Yu, Yan-An Gong Jing, Zhang, Yi, Huang, Tian-Qi & Huang, Song, 2022, A new species of the genus Achalinus (Squamata: Xenodermidae) from Ningshan County, Shaanxi Province, China, pp. 127-140 in Zootaxa 5190 (1) on pages 133-136, DOI: 10.11646/zootaxa.5190.1.5, http://zenodo.org/record/7119993, {"references":["Peters, W. C. H. (1869) Nachtrag zu Uber neue Gattungen und neue oder weniger bekannte Arten von Amphibien (Eremias, Dicrodon, Euprepes, Lygosoma, Typhlops, Eryx, Rhynchonyx, Elapomorphus, Achalinus, Coronella, Dromicus, Xenopholis, Anoplodipsas, Spilotes, Tropidonotus). Monatsberichte der koniglichen Akademie der Wissenschaften zu Berlin, 1869, 445 - 447.","Huang, R. Y., Peng, L. F., Yu, L., Huang, T. Q., Jiang, K., Ding, L., Chang, J. K., Yang, D. C., Xu, Y. H. & Huang, S. (2021) A New Species of the Genus Achalinus from Huangshan, Anhui, China (Squamata: Xenodermidae). Asian Herpetological Research, 12 (2), 178 - 187. https: // doi. org / 10.16373 / j. cnki. ahr. 200075","Li, K., Wu, Y. Y., Xu, R. Y., Zhu, F., Ren, J. L., Guo, P. & Dong, B. J. (2021) A new species of the Achalinus rufescens complex (Xenodermidae: Achalinus) from Fujian Province, China. Zootaxa, 5026 (2), 239 - 254. https: // doi. org / 10.11646 / zootaxa. 5026.2.5","Van Denburgh, J. (1912) Concerning certain species of reptiles and amphibians from China, Japan, the Loo Choo Islands, and Formosa. Proceedings of The California Academy of Sciences, 3, 187 - 258.","Boulenger, G. A. (1908) Description of a new frog and a new snake from Formosa. Annals & Magazine of Natural History, 8 (2), 221 - 222. https: // doi. org / 10.1080 / 00222930808692472","Zong, Y. & Ma, J. (1983) A new species of the genus Achalinopsis from Jiangxi and the restoration of this genus. Acta Herpetologica Sinica, 2 (2), 61 - 63. [in Chinese]","Li, K., Yu, M., Wu, Y. Y., Liao, L. H., Tang, K., Liu, Q. & Guo, P. (2020) A new species of the genus Achalinus (Squamata: Xenodermatidae) from southeastern Yunnan Province, China. Zootaxa, 4860 (1), 116 - 128. https: // doi. org / 10.11646 / zootaxa. 4860.1.6","Hu, S. Q. & Zhao, E. M. (1966) Three new species of reptiles from Szechwan. Acta Zootaxon Sinica, 3 (2), 158 - 164. [In Chinese with English abstract]","Luu, V. Q., Ziegler, T., Van Ha, N., Van Lo, O., Hoang, T. T., Ngo, H. T., Le, M. D., Tran, D. H. & Nguyen, T. Q. (2020) A new species of Achalinus (Squamata: Xenodermidae) from Trang An Landscape Complex, Ninh Binh Province, Vietnam. Zootaxa, 4877 (1), 174 - 184. https: // doi. org / 10.11646 / zootaxa. 4877.1.8","Wang, J., Li, Y., Zeng, Z. C., Lyu, Z. T., Sung, Y. H., Li, Y. Y., Lin, C. Y. & Wang, Y. Y. (2019) A new species of the genus Achalinus from southwestern Guangdong Province, China (Squamata: Xenodermatidae). Zootaxa, 4674 (4), 471 - 481. https: // doi. org / 10.11646 / zootaxa. 4674.4.6","Qi, S., Shi, J. S., Ma, Y. B., Gao, Y. F., Bu, S. H., Grismer, L. L., Li, P. P. & Wang, Y. Y. (2021) A sheep in wolf's clothing: Elaphe xiphodonta sp. nov. (Squamata, Colubridae) and its possible mimicry to Protobothrops jerdonii. ZooKeys 1048, 23 - 47. https: // doi. org / 10.3897 / zookeys. 1048.65650"]}

Achalinus ningshanensis sp. nov. D.C. Yang, R.Y Huang, K. JIANG, F.T. BURBRINK & S. Huang (Figs. 3–5) Suggested English common name: Ningshan Odd-scaled Snake. Suggested Chinese common name: Ťkḛffi (Bopomofo: Níng Shǎn Jǐ Shé). Holotype. ANU20220001 (field number JK0917, Fig. 3), an adult female, collected in summer of 2008 from Xunyangba Town (33.5434 N, 108.5439 E, 1372 m a. s. l.), Ningshan County, Shaanxi Province, China by the team of Ke Jiang. Paratypes. Six females, JK0918, JK0889, JK0890, JK0891, HSR19131, and HSR19132 (Voucher number: ANU20220002–7), all with the same collecting information as the holotype. Diagnosis. Achalinus ningshanensis sp. nov. can be differentiated from all other members of the genus Achalinus by the following combination of morphological characters:(1) dorsum iridescent and uniformly dark brown in preservative, longitudinal vertebral line absent; (2) brown beneath; (3) dotted black streak in the middle of the subcaudals absent; (4) tail length relatively short, TaL/ToL 12–16% in females; (5) fewer subcaudals, 41–46, in females; (6) dorsal scales 23 rows throughout, strongly keeled, and the outer-most rows on both sides of the body also keeled and slightly enlarged; (7) one loreal; (8) internasal not fused to prefrontal; (9) suture between internasals is similar size when compared to the suture between prefrontals; (10) preocular and postocular absent; (11) 6 supralabials; (12) 5 infralabials, the first 3 (rarely 2) touching the first pair of chin shields; (13) 3 pairs of chin shields. Description of the holotype. An adult female in excellent condition (Figs. 3 & 4). Body slender and subcylindrical, total length 436 mm (SVL 374 mm and Tal 62 mm); tail relatively shorter, TaL/ToL 14%; head slightly distinct from neck dorsally covered with large head scales, head length 13.72 mm; head width 7.16 mm; eyes small with subround pupils. Rostral small, subtriangular in frontal view, barely visible from above. Internasals paired, the suture between internasals (1.94 mm) subequal to that between prefrontals (1.63 mm); prefrontals paired, subrectangular. Frontal shield-shaped, nearly straight anteriorly, pointed backwards, slightly broader than it is long, and much shorter than the parietals. Parietals paired, the parietal suture longer than frontal. Nostril in the anterior part of the nasal. One loreal, rectangular, LorH: 0.97 mm, LorL: 1.90 mm (LorH/LorL: 0.51), extending from the nasal to the eye. One supraocular, in contact with loreal, prefrontals, frontal, parietals, and superior anterior temporals. No preocular or postocular. Temporals 2+3+4, two anterior temporals elongated, the upper one smaller in contact with parietal, the lower one in contact with fifth and sixth supralabials, both in contact with the eye; three elongated middle temporals; four elongated posterior temporals, the uppermost (super-temporal) significantly enlarged, the supertemporal split into two parts on the left, surrounding the parietal; the super-temporals from two sides contacting at the midline. Supralabials six, the first very small, 1–3 contacting the nasal, fourth and fifth contacting the orbit, fourth in narrow contact, fifth in broad contact, and sixth the longest and largest. One mental. Five infralabials, the first pair in contact blocking the mental from contacting an anterior pair of chin shields; first infralabial smallest, increasing in size until the fifth infralabial that is the longest. Three pairs of chin shields followed by ventrals. First three infralabials touching the first pair of chin shields on both sides. Dorsal scale rows 23–23–23, dorsal scales fusiform, not overlapping, distinctly keeled posterior to nape, and outermost dorsal scale row on both sides slightly keeled and enlarged. Ventrals 167; cloacal plate entire; subcaudals 43, uniserial. Coloration of holotype in preservative. Dorsum uniformly dark brown with metallic luster under light, the anterior portion of the head ash black, interstitial skin of dorsal dark brown. Ventral ground color brown, free margins of ventral scales grayish white. Variation. Measurements, body proportions, and scale counts are listed in Table 1. All paratypes are very similar to the holotype except in the following: paratypes JK0889, JK0891, and HSR19132 have two middle temporals; paratypes JK0890 and HSR19131 have two middle temporals and three posterior temporals; paratypes JK0890 have the first two infralabials touching the first pair of chin shields on both sides. The number of anterior temporals that contact the eyes is not a stable trait. Comparisons. Achalinus ningshanensis sp. nov. can be differentiated from all other known species of snakes in the genus Achalinus by a combination of the following morphological characters: infralabials five, three pairs of chin shields, relatively shorter tail length (TaL/ToL 12–16% in females), longitudinal vertebral line absent, and missing a dotted black streak in the middle of the subcaudals. Achalinus ningshanensis sp. nov. differs from all other species in Achalinus except A. spinalis Peters, 1869, A. hainanus Huang, 1975, A. emilyae Ziegler, Nguyen, Pham, Nguyen, Pham, Van Schingen, Nguyen & Le, 2019, A. huangjietangi Huang, Peng, & Huang, 2021, and A. dehuaensis Li, Wu, Xu, Zhu, Ren, Guo & Dong, 2021 by having fewer infralabials (five vs. six). Furthermore, it differs from A. spinalis and A. huangjietangi by having the following characters: absent longitudinal vertebral line, and missing a dotted black streak in the middle of the subcaudals; from A. hainanus by having two anterior temporals (vs. only one), three pairs of chin shields (vs. two pairs), fewer subcaudals in females (41–46 vs. 67–69); from A. emilyae by having fewer subcaudals in females (41–46 vs. 63), three pairs of chin shields (vs. two pairs), outermost dorsal scales rows keeled (vs. outmost rows smooth); from A. dehuaensis by having a relatively shorter tail length (TaL/ToL 12–16% vs. 21–22% in females), fewer subcaudals in females (41–46 vs. 63–65), uniformly dark brown above, light brown beneath (vs. greyish brown above, pale yellow beneath). Achalinus ningshanensis sp. nov. differs from A. werneri Van denburgh, 1912 by having the following characters: absent longitudinal vertebral line, and missing a dotted black streak in the middle of the subcaudals. Achalinus ningshanensis sp. nov. differs from A. yangdatongi by having fewer infralabials (5 vs. 6), different dorsal scale row counts (23–23–23 vs. 23–23–19) and having three pairs of chin shields (vs. two pairs). Achalinus ningshanensis sp. nov. differs from A. ater by the suture between internasals subequal to that between prefrontals (vs. suture between internasals distinctly longer than between prefrontals) and having fewer subcaudals (41–46 vs. 56–63). Achalinus ningshanensis sp. nov. differs from A. juliani by the suture between internasals subequal to that between prefrontals (vs. the suture between internasals distinctly longer than between prefrontals) and having a relatively shorter tail length (TaL/ToL 12–16% vs. 22–37%), fewer subcaudals (41–46 vs. 77–91), different dorsal scale row counts (23–23–23 vs. 25–23–23), and having three pairs of chin shields (vs. two pairs). Achalinus ningshanensis sp. nov. differs from A. rufescens by having six supralabials, the fourth and fifth widely in contact with the eye (vs. five supralabials, third and fourth entering the eye) and being light brown beneath (vs. uniform yellowish beneath). Achalinus ningshanensis sp. nov. differs from A. formosanus Boulenger, 1908, A. jinggangensis (Zong & Ma, 1983), A. timi Ziegler, Nguyen, Pham, Nguyen, Pham, Van Schingen, Nguyen & Le, 2019, A. pingbianensis Li, Yu, Wu, Liao, Tang, Liu & Guo, 2020, A. zugorum Miller, Davis, Luong, Do, Pham, Ziegler, Lee, De Queiroz, Reynolds & Nguyen, 2020, by having a separated loreal (vs. absence). Further it is different from A. formosanus by having fewer midbody dorsal scale rows (23 vs. 27), three pairs of chin shields (vs. two pairs), fewer subcaudals in females (41–46 vs. 61–70); from A. jinggangensis by having fewer infralabials (5 vs. 6), three pairs of chin shields (vs. two pairs), fewer subcaudals in females (41–46 vs. 51); from A. timi by different dorsal scale row counts (23–23–23 vs. 25–25–23), fewer infralabials (5 vs. 6), three pairs of chin shields (vs. two pairs), and the suture between internasals subequal to that between prefrontals (vs. the suture between internasals distinctly longer than between prefrontals); from A. pingbianensis by having fewer infralabials (5 vs. 6), fewer supralabials (6 vs. 7), 3 pairs of chin shields (vs. 2 pairs), and being uniformly dark brown above, light brown beneath (vs. uniform black above and beneath), and from A. zugorum by having fewer infralabials (5 vs. 6), 3 pairs of chin shields (vs. 2 pairs). Achalinus ningshanensis sp. nov. differs from A. meiguensis Hu & Zhao, 1966 and A. panzhihuaensis by having divided internasals (vs. absent), absence of postocular (vs. presence), fewer infralabials (5 vs. 6), mental separated from anterior chin shields (vs. in contact), and the first pair of infralabials in contact (vs. separated). Furthermore, it differs from A. panzhihuaensis by different dorsal scale row counts (23–23–23 vs. 23–23–19). Achalinus ningshanensis sp. nov. differs from A. niger Maki, 1931 by having fewer infralabials (five vs. six), different dorsal scale row counts (23–23–23 vs. 25–25–23), and fewer subcaudals in females (41–46 vs. 52–58). Achalinus ningshanensis sp. nov. differs from A. tranganensis Luu, Ziegler, Ha, Lo, Hoang, Ngo, Le, Tran & Nguyen, 2020 by having fewer infralabials (five vs. six), three pairs of chin shields (vs. two pairs), a relatively shorter tail length (TaL/ToL 12–16% vs. 25%), and fewer subcaudals in females (41–46 vs. 73+). Achalinus ningshanensis sp. nov. differs from A. yunkaiensis Wang, Li & Wang, 2019 by having fewer infralabials (five vs. six), three pairs of chin shields (vs. two pairs), and the outer-most dorsal scales rows keeled (vs. outmost rows smooth). Etymology. The specific epithet refers to the location of type specimens, Ningshan County, Shaanxi Province, China. We suggest Níng Shǎn Jǐ Shé (Ťkḛffi) as Chinese common name, and Ningshan Odd-scaled Snake as English common name. Distribution and habits. Achalinus ningshanensis sp. nov. is currently known only from the type locality Ningshan County, Shaanxi Province, China. All the specimens were found in farmland. The surrounding habitat was composed of secondary conifer/broad-leaved mixed forest. The new species is sympatric with A. cf. spinalis, A. cf. rufescens, Stichophanes ningshaanensis (Yuan, 1983), Euprepiophis mandarinus (Cantor, 1842), Elaphe taeniura (Cope, 1861), E. carinata (Günther, 1864), E. xiphodonta Qi, Shi, Ma, Gao, Bu, Grismer, Li, Wang 2021, Oreocryptophis porphyraceus (Cantor, 1839), Cyclophiops major (Günther, 1858), Lycodon ruhstrati (Fischer, 1886), L. liuchengchaoi Zhang, Jiang, Vogel and Rao, 2011, Pseudoxenodon macrops (Blyth, 1855), Rhabdophis nuchalis (Boulenger, 1891), Zaocys dhumnades (Cantor, 1842), Azemiops kharini Orlov, Ryabov and Nguyen, 2013, Gloydius qinlingensis (Song and Chen, 1985), Protobothrops jerdonii (Günther, 1875)

Achalinus yangdatongi sp. nov. (Figs. 6 and 7) Holotype. KIZ 034327, adult male, collected by Kai Xu on 15 April 2018 from Xiaoqiaogou (23.361°N, 104.686°E; 1609 m a.s.l.), Xichou County, Wenshan, Yunnan Province, China. Diagnosis. Achalinus yangdatongi sp. nov. can be distinguished from recognized species of Achalinus by a combination of the following characters: (1) TaL/ToL 26.2% in the male; (2) suture between internasals distinctly longer than that between prefrontals; (3) internasal present; (4) loreal present; (5) supralabials 6; (6) temporals 2+2+3, anterior two temporals in contact with eye; (7) infralabials 6; (8) first pair of infralabials in contact with each other behind mental; (9) dorsal body scales in 23–23–19 rows; (10) scales behind head irregular in shape, smooth; (11) ventrals 161; (12) subcaudals 82, unpaired; (13) precloacal scale entire; (14) maxillary teeth 19; and (15) body surface black above and beneath, iridescent. Description of holotype. Total length 397 mm (SVL 293 mm, TaL 104 mm); tail long, TaL/ToL 26.2%; body slender, cylindrical; head slightly distinct from neck, HL 11.6 mm; eye small, pupil vertically subelliptic. Rostral small, triangular, slightly visible from above; suture between internasals (1.9 mm) longer than that between prefrontals (1.3 mm); nostril in anterior part of nasal; frontal pentagonal, slightly broader than long, pointed backwards, much shorter than parietals; single pair of parietals; loreal rectangle, wider (LeL: 1.4 mm) than the height (HiL: 0.8 mm); single supraocular, in contact with loreal, prefrontals, frontal, parietals and superior anterior temporals; temporals 2+2+4, two anterior temporals all pentagonal and in contact with eye, superioanterior temporals in contact with parietal, inferioanterior temporal in contact with fourth and fifth supralabials; middle temporals elongated, inferior middle temporal in contact with sixth supralabials; four posterior temporals, superioposterior temporals biggest, inferioposterior temporal smallest; supralabials 6, first smallest, fourth and fifth entering orbit, sixth longest; mental in arc shape, separated from anterior chin shields; infralabials 6, first pair of infralabials in contact with each other behind mental; two pairs of chin shields, anterior one semicircle-shape, posterior pair in unequilateral quadrilateral shape; first three infralabials in contact with anterior chin shields; third and fourth infralabials in contact with posterior chin shields. All scales with metallic luster, weakly iridescent; scales behind head irregular in shape, smooth without keeled; dorsal scale rows 23–23–19, scales lanceolate and strongly keeled; ventrals 161; subcaudals 82, unpaired; precloacal entire. Coloration: In preservative, the dorsal surface of the body is black, the anterior portion of the coloration of underside of head is dark brown, and the posterior portion and throat is light brown. The color becomes darken gradually from the throat posteriorly until it becomes black, except the free margin of each ventral scale, which is grayish white. Comparisons. A. yangdatongi sp. nov. is most similar to A. ater, in which both species have a suture between internasals distinctly longer than that between prefrontals, equal number of supralabials and infralabials (both 6), anterior temporals in contact with eyes, first pair of infralabials in contact with each other behind the mental, dorsal scales in 23–23–19 rows, as well as by the presence of internasal and loreal scales. However, the new species can be diagnosed from A. ater by having more subcaudals (SC 82 vs. 47–70), a comparatively longer tail (TaL/ToL 26.2% vs. 19.0%–22.0%), and different coloration of ventral head (the anterior portion dark brown, posterior portion and throat light brown vs. uniformly yellowish-white). Achalinus yangdatongi sp. nov. differs from A. juliani by having fewer ventrals (161 vs. 173–179), fewer DSRH (23 vs. 25), and a distinct coloration (black on both dorsal and ventral surfaces vs. greyish brown dorsally, greyish cream ventrally). Achalinus yangdatongi sp. nov. differs from A. tranganensis by having fewer ventrals (161 vs. 171), by having dorsal scale rows 23–23–19, smooth without keeled (vs. dorsal scales in 25–23–23 rows, keeled), by having temporals 2+2+4 (vs. 2+3). Achalinus yangdatongi sp. nov. differs from A. emilyae and A. rufescens by having more infralabials (6 vs. 5 in both A. emilyae and A. rufescens), distinct body coloration (black on dorsal body and belly vs. dorsum iridescent pale yellowish brown in A. emilyae, and uniform pale reddish or reddish-brown dark grey dorsally in A. rufescens). Furthermore, the new species differ from A. rufescens by having more ventrals in males (161 vs. 131–137) (Table 4). Achalinus yangdatongi sp. nov. differs from A. niger, A. werneri, A. yunkaiensis, and A. spinalis by having suture between the internasals distinctly longer than that between the prefrontals (vs. less than or subequal to), a comparatively longer tail (TaL/ToL 26.2% vs. 15.0%–18.0% in A. niger, 15.0%–25.0% in A. spinalis, and 18.0%–20.0% in A. yunkaiensis), fewer subcaudals in male (SC 82 vs. 89–98 in A. werneri); from A. formosanus, A. jinggangensis, A. pingbianensis, A. timi and A. zugorum by presence of loreal scale (vs. absence), fewer dorsal scale rows (23–23–19 vs. 25–25– 23 in A. timi, and 27–27– 25 in A. formosanus), and more subcaudals (SC 82 vs. 51–64 in A. jinggangensis, 56 in A. pingbianensis and 70 in A. zugorum); from A. meiguensis and A. panzhihuaensis sp. nov. by presence of internasal (vs. absent), absence of postocular (vs. present), as well as by having different state of nasal scales (separated vs. in contact each other behind the rostral), mental separated from anterior chin shields (vs. in contact), and first pair of infralabials in contact with each other (vs. separated); and from A. hainanus by having different temporal formula (2–2–3 vs. 1–2–3), more subcaudals (SC 82 vs. 67–69), and more infralabials (6 vs. 5). Natural history and distribution. The holotype was found on a paved road near a reservoir on a drizzly night. The nearby habitat is characterized by secondary forests and abandoned farmlands (Fig. 7). At the type locality, this species is sympatric with Trimerodytes percarinatus (Boulenger, 1899), Protobothrops mucrosquamatus (Cantor, 1839), and Pareas sp. With the holotype and the genetically identified snake sheds, A. yangdatongi sp. nov. is only known from its type locality at Xiaoqiaogou, Xichou county, Wenshan Prefecture, Yunnan Province, China (Fig. 1). Etymology. The species name, yangdatongi, is a patronym honoring the Chinese herpetologist, Dr. Da-Tong Yang. We name the new species after Dr. Yang in recognition of his great contributions to the herpetological research in Southwestern China, particularly in Yunnan Province where the new species is found. We suggest “Yang’s Odd-scaled Snake” as its common English name, and “ 杨氏ñffi ” (Pinyin: Yang Shi Ji She) as its Chinese common name.

Achalinus panzhihuaensis sp. nov. (Figs. 3 and 4) Holotype. KIZ 040189, adult male, collected by Benfu Miao and Kai Wang on 10 May 2018 from Hongbao Village (27.00��N, 101.53��E), Yanbian County, Panzhihua, Sichuan Province, China. Diagnosis. Achalinus panzhihuaensis sp. nov. can be distinguished from recognized congeners by a combination of the following characters: (1) TaL/ToL 24.6% in the single male; (2) two nasal scales in contact with each other behind the rostral; (3) internasal absent; (4) loreal rectangular; (5) supralabials 6; (6) postocular single and small; (7) temporals 2+2+3, anterior pair elongated, upper one smaller, only uppermost in contact with eye; (8) infralabials 6; (9) mental in contact with first pair of chin shields, fully separating first pair of infralabials; (10) dorsal scales 23���23���19 rows; (11) ventrals 160; (12) subcaudals 73, unpaired; (13) precloacal scale entire; (14) maxillary teeth 28; and (15) all scales iridescent with metallic luster, brown dorsally, with single indigo-colored vertebral line. Description of holotype. Body size small, total length 257 mm (SVL 194 mm, TaL 63 mm); tail long, 24.6% total length; body slender, cylindrical in cross section. Head slightly distinct from neck, HL 7.8 mm; eye small, pupil vertically subelliptic. Rostral small, triangular, invisible from above; nasal divided, each half in contact with each other; internasal absent; prefrontals paired, suture length 2.1 mm; frontal pentagonal, slightly wider than long, pointed posteriorly; single pair of parietals; loreal pentagonal, tip pointing anteriorly, longer (LeL: 1.2 mm) than high (HiL: 0.8 mm), LeL/HiL 150.0%; supraocular single, in contact with loreal, prefrontals, frontal, parietals, and superior anterior temporals. Temporals in three groups, 2+2+3; superior one of anterior most pair triangular, small, inferior one much larger, elongated, in contact with fourth and fifth supralabials and parietal; the middle pair, superior one parallelogram, small, inferior one much larger, elongated, in contact with sixth supralabials and three posterior temporals; superior most one of last trios biggest, size gradually decreases inferiorly; supralabials six, first one smallest, fourth and fifth in contact with eyes, sixth longest. Mental arc-shaped, in contact with first pair of chin shields; three pairs of chin shields, first pair in fan-shaped, remaining ones of second and third pairs in unequilateralquadrilateral shape. Infralabials six, first pair not in contact with each other, first three in contact with anterior-most pair of chin shields, third and fourth infralabials in contact with middle pair. Dorsal scales elliptical, 23���23���19 rows, medial 6���11 rows distinctly keeled, remaining outer rows smooth. Ventrals 160, rounded laterally; subcaudals 73, unpaired; precloacal entire. Coloration: In life, all scales are weakly iridescent with metallic luster. Dorsum is purplish brown. The vertebral and three paravertebral rows of dorsal scales are darker indigo, which form a darker longitudinal vertebral stripe extending from the posterior margin of the parietals to the tip of tail. Ventral surface of the body is greyish white, and the subcaudal region is purplish brown. In preservative, all scales are still iridescent. Coloration becomes darker after preservation. The dorsum becomes dark grey, and the vertebral stripe turns black. The ventral surface of the body becomes greyish brown, and the ventral tail is dark greyish brown. Comparisons. A. panzhihuaensis sp. nov. is most similar to its sister species A. meiguensis, in which both species have divided nasal scales in contact with each other, no internasal, a single postocular, 6 supralabials, 6 infralabials, mental in contact with first pair of chin shields, and fully separated first pair of infralabials. However, the new species can be diagnosed readily from A. meiguensis by having more subcaudals (SC 73 vs. 39���60), more ventrals in male (VEN 160 vs. 146���155), and more DSRM (23 vs. 19���21) (Table 4). Achalinus panzhihuaensis sp. nov. can be easily distinguished from A. ater, A. emilyae, A. formosanus Boulenger, A. hainanus Huang, A. jinggangensis Zong & Ma, A. juliani, A. niger Mahi, A. pingbianensis Li, Yu, Wu, Liao, Tang, Liu & Guo, A. rufescens Boulenger, A. spinalis Peters, A. tranganensis Luu, Ziegler, Ha, Lo, Hoang, Ngo, Le, Tran & Nguyen, A. timi, A. yunkaiensis, A. werneri Van Denburgh and A. zugorum Miller, Davis, Luong, Do, Pham, Ziegler, Lee, De Queiroz, Reynolds & Nguyen, by having divided nasal scales in contact each other behind the rostral (vs. separated), mental in contact with the first pair of chin shields (vs. separated), first pair of infralabials separated from each other (vs. in contact), as well as an absence of internasal (vs. present), and by the presence of a small postocular (vs. absent). Furthermore, the new species differs from A. jinggangensis, A. pingbianensis, A. timi and A. formosanus by having loreal separated from prefrontal (vs. fused); and from A. emilyae, A. hainanus and A. rufecens by having more infralabials (6 vs. 5). Natural history and distribution. The holotype was found on a montane road at night. The surrounding habitat was of secondary forest of evergreen broadleaf forest with shrubs and vines (Fig. 5). According to locals, road-killed individuals are somewhat common in the summer. At the type locality, the species is sympatric with Diploderma swild Wang, Wu, Jiang, Chen, Miao, Siler, Che, 2019, Lycodon cf. gongshan Vogel, Luo, 2011, Hebius yanbianensis Liu, Zhong, Wang, Liu, Guo, 2018, Ptyas nigromarginata (Blyth, 1854), Megophrys platyparietus (Yang, Rao, 1997), and Odorrana sp.. The new species is currently only known from the type locality in Panzhihua, Sichuan Province, China (Fig. 1). Etymology. The specific epithet ��� panzhihuaensis ��� is named after the type locality of the new species, Panzhihua, Sichuan Province, China. We propose ���Panzhihua Odd-scaled Snake��� as its common English name and ��� ������ AE��ffi ��� (Pinyin: Pan Zhi Hua Ji She) as its Chinese common name., Published as part of Hou, Shao-Bing, Wang, Kai, Guo, Peng, Chen, Jin-Min, Yuan, Zhi-Yong & Che, Jing, 2021, Two new species and a new country record of the genus Achalinus (Reptilia Squamata: Xenodermidae) from China, pp. 528-546 in Zootaxa 4950 (3) on pages 535-537, DOI: 10.11646/zootaxa.4950.3.6, http://zenodo.org/record/4650074

Achalinus emilyae Ziegler, Nguyen, Pham, Nguyen, Pham, Van Schingen, Nguyen & Le, 2019 (Figs. 8 and 9) Chinese Name. We suggest ��� ��������ffi ��� (Pinyin: Yue Bei Ji She) as its Chinese common name. Specimen examined. Single adult female (KIZ 022248), road-killed individual collected by Zhiyong Yuan and Jinmin Chen from Dongzhong (21.719�� N, 107.583��E), Fangchenggang County, Guangxi Zhuang A. R., China, on 2 September 2012 (Fig. 1). Description. Total length 453 mm (SVL 361 mm, TaL 92 mm, TaL/ToL 20.3%); body slender, cylindrical; head slightly distinct from neck, dorsally covered with large shields; eye small, with pupil vertically subelliptic. Rostral small, triangular, slightly visible from above; frontal pentagonal, slightly broader than long, pointed backwards, much shorter than parietals; parietal long, more than half length of head; nasal divided, nostril in anterior half; one loreal, wider than high, extending from nasal to eye; single supraocular, in contact with loreal, prefrontals, frontal, parietals, and superior anterior temporals; two anterior temporals, only uppermost in contact with eye; two elongated middle temporals, superior one much larger, inferior one in contact with sixth supralabial; three elongate posterior temporals, most superior one largest, separated from each other behind parietals by one small scale; supralabials six, first smallest, third and fourth in contact with loreal; fourth and fifth in contact with eye, sixth longest; mental in arc shape, separated from anterior chin shields, followed by five infralabials; first pair of infralabials in contact with each other; first three infralabials in contact with anterior chin shields; posterior chin shields smaller, laterally in contact with third and fourth infralabials. Dorsal scales elliptical, keeled from neck region onwards; dorsal scale rows 23���23���23; ventrals 157 (potential preventrals included), rounded laterally; subcaudals 56, unpaired; precloacal entire. Coloration. In life, the dorsal body surfaces of the snake are greyish brown with a dark greyish brown vertebral stripe along the body. The ethanol-preserved specimen is greyish brown above, venter is greyish cream, with the ventral surface of the tail being somewhat darker, and the gular region somewhat paler. Infralabials and chin shields light greyish brown. Comments. The Guangxi specimen matches with most of the diagnosis of A. emilyae, including having (1) TaL/ToL 20.3%; (2) suture between internasals distinctly longer than that between the prefrontals; (3) internasal present; (4) loreal present, wider than high, extending from nasal to eye; (5) supralabials 6; (6) infralabials 5; (7) first pair of infralabials in contact with each other; (8) first three infralabials in contact with anterior chin shields; (9) mental separated from anterior chin shields; (10) temporals 2+2, only the superioanterior one in contact with eye; (11) ventrals 157 in female; (12) subcaudals unpaired; (13) dorsal scale rows 23���23���23; (14) maxillary teeth 28; and (15) dorsum iridescent pale yellowish brown with a dark longitudinal vertebral stripe. The only deviation from the diagnosis of the type series is the number of subcaudal scale (65 for Guangxi specimen vs. 63 for the female paratype). Natural history. The specimen was a road-kill, and its head was found swallowed by a road-killed Bungarus fasciatus (Fig. 9). The nearby habitat consists of secondary forest of broadleaf evergreen forest mixed with shrubs and vines (Provided by Jin-Min Chen, who collected this specimen in the wild). At the type locality, the species is sympatric with Boiga multomaculata (Boie, 1827), Hypsiscopus plumbea (Boie, 1827), Pareas margaritophorus (Jan, 1866), Ptyas dhumnades (Cantor, 1842) and Ptyas multicinctus (Roux, 1907). Distribution. Currently A. emilyae is only known from southern China and northern Vietnam. In China, this species is known from a single locality in Guangxi Zhuang A. R. (Fig. 1)., Published as part of Hou, Shao-Bing, Wang, Kai, Guo, Peng, Chen, Jin-Min, Yuan, Zhi-Yong & Che, Jing, 2021, Two new species and a new country record of the genus Achalinus (Reptilia Squamata: Xenodermidae) from China, pp. 528-546 in Zootaxa 4950 (3) on pages 541-542, DOI: 10.11646/zootaxa.4950.3.6, http://zenodo.org/record/4650074

Key to species of the genus Achalinus Peters, 1869 1a. Internasal absent..................................................................................... 2 1b. Internasal present..................................................................................... 3 2a. Ventrals 146���155 in male; subcaudals 39���60; DSRM 19���21........................................ A. meiguensis 2b. Ventrals 160 in male; subcaudals 73; DSRM 23............................................... A. panzhihuaensis 3a. Loreal absent........................................................................................ 4 3b. Loreal present....................................................................................... 6 4a. Dorsal scale rows 27���27���25................................................................. A. formosanus 4b. Dorsal scale rows 23���23���23............................................................................ 5 5a. Suture between internasals longer than prefrontal suture......................................... A. jinggangensis 5b. Length of suture between internasals subequal to that between prefrontals............................ A.pingbianensis 6a. Anterior temporals single; two superior posterior temporals in contact and overlap greatly posterior to parietal....................................................................................................... A. hainanus 6b. Anterior temporals 2; two superior posterior temporals not in contact with each other posterior to parietal, or in contact but overlap slightly...................................................................................... 7 7a. Suture length between internasals less than or subequal to that between prefrontals................................. 8 7b. Suture length between the internasals much longer than that between prefrontals.................................. 10 8a. Dorsal scale rows 25���25���23...................................................................... A. niger 8b. Middorsal scale rows 23............................................................................... 9 9a. Dorsal color brown in adults, ventral light brown; TaL/ToL 18���20%................................. A. yunkaiensis 9b. Dorsal color black, ventral black brown; TaL/ToL 15���25%............................................ A. spinalis 10a. Infralabials 5....................................................................................... 11 10b. Infralabials 6....................................................................................... 12 11a. Ventrals 157���161 in females; subcaudals 63���65..................................................... A. emilyae 11b. Ventrals 148���158 in females; subcaudals 54���61.................................................... A. rufescens 12a. Subcaudals 47���70; TaL/ToL 19���22%................................................................ A. ater 12b. Subcaudals 82; TaL/ToL 26%............................................................... A. yangdatongi, Published as part of Hou, Shao-Bing, Wang, Kai, Guo, Peng, Chen, Jin-Min, Yuan, Zhi-Yong & Che, Jing, 2021, Two new species and a new country record of the genus Achalinus (Reptilia Squamata: Xenodermidae) from China, pp. 528-546 in Zootaxa 4950 (3) on page 544, DOI: 10.11646/zootaxa.4950.3.6, http://zenodo.org/record/4650074, {"references":["Peters, W. C. H. (1869) s. n. In: Uber neue Gattungen und neue oder weniger bekannte Arten von Amphibien (Eremias, Dicrodon, Euprepes, Lygosoma, Typhlops, Eryx, Rhynchonyx, Elapomorphus, Achalinus, Coronella, Dromicus, Xenopholis, Anoplodipsas, Spilotes, Tropidonotus). Monatsber. k. preuss. Akad. Wiss. Berlin, pp. 432 - 447."]}

Achalinus yangdatongi sp. nov. (Figs. 6 and 7) Holotype. KIZ 034327, adult male, collected by Kai Xu on 15 April 2018 from Xiaoqiaogou (23.361��N, 104.686��E; 1609 m a.s.l.), Xichou County, Wenshan, Yunnan Province, China. Diagnosis. Achalinus yangdatongi sp. nov. can be distinguished from recognized species of Achalinus by a combination of the following characters: (1) TaL/ToL 26.2% in the male; (2) suture between internasals distinctly longer than that between prefrontals; (3) internasal present; (4) loreal present; (5) supralabials 6; (6) temporals 2+2+3, anterior two temporals in contact with eye; (7) infralabials 6; (8) first pair of infralabials in contact with each other behind mental; (9) dorsal body scales in 23���23���19 rows; (10) scales behind head irregular in shape, smooth; (11) ventrals 161; (12) subcaudals 82, unpaired; (13) precloacal scale entire; (14) maxillary teeth 19; and (15) body surface black above and beneath, iridescent. Description of holotype. Total length 397 mm (SVL 293 mm, TaL 104 mm); tail long, TaL/ToL 26.2%; body slender, cylindrical; head slightly distinct from neck, HL 11.6 mm; eye small, pupil vertically subelliptic. Rostral small, triangular, slightly visible from above; suture between internasals (1.9 mm) longer than that between prefrontals (1.3 mm); nostril in anterior part of nasal; frontal pentagonal, slightly broader than long, pointed backwards, much shorter than parietals; single pair of parietals; loreal rectangle, wider (LeL: 1.4 mm) than the height (HiL: 0.8 mm); single supraocular, in contact with loreal, prefrontals, frontal, parietals and superior anterior temporals; temporals 2+2+4, two anterior temporals all pentagonal and in contact with eye, superioanterior temporals in contact with parietal, inferioanterior temporal in contact with fourth and fifth supralabials; middle temporals elongated, inferior middle temporal in contact with sixth supralabials; four posterior temporals, superioposterior temporals biggest, inferioposterior temporal smallest; supralabials 6, first smallest, fourth and fifth entering orbit, sixth longest; mental in arc shape, separated from anterior chin shields; infralabials 6, first pair of infralabials in contact with each other behind mental; two pairs of chin shields, anterior one semicircle-shape, posterior pair in unequilateral quadrilateral shape; first three infralabials in contact with anterior chin shields; third and fourth infralabials in contact with posterior chin shields. All scales with metallic luster, weakly iridescent; scales behind head irregular in shape, smooth without keeled; dorsal scale rows 23���23���19, scales lanceolate and strongly keeled; ventrals 161; subcaudals 82, unpaired; precloacal entire. Coloration: In preservative, the dorsal surface of the body is black, the anterior portion of the coloration of underside of head is dark brown, and the posterior portion and throat is light brown. The color becomes darken gradually from the throat posteriorly until it becomes black, except the free margin of each ventral scale, which is grayish white. Comparisons. A. yangdatongi sp. nov. is most similar to A. ater, in which both species have a suture between internasals distinctly longer than that between prefrontals, equal number of supralabials and infralabials (both 6), anterior temporals in contact with eyes, first pair of infralabials in contact with each other behind the mental, dorsal scales in 23���23���19 rows, as well as by the presence of internasal and loreal scales. However, the new species can be diagnosed from A. ater by having more subcaudals (SC 82 vs. 47���70), a comparatively longer tail (TaL/ToL 26.2% vs. 19.0%���22.0%), and different coloration of ventral head (the anterior portion dark brown, posterior portion and throat light brown vs. uniformly yellowish-white). Achalinus yangdatongi sp. nov. differs from A. juliani by having fewer ventrals (161 vs. 173���179), fewer DSRH (23 vs. 25), and a distinct coloration (black on both dorsal and ventral surfaces vs. greyish brown dorsally, greyish cream ventrally). Achalinus yangdatongi sp. nov. differs from A. tranganensis by having fewer ventrals (161 vs. 171), by having dorsal scale rows 23���23���19, smooth without keeled (vs. dorsal scales in 25���23���23 rows, keeled), by having temporals 2+2+4 (vs. 2+3). Achalinus yangdatongi sp. nov. differs from A. emilyae and A. rufescens by having more infralabials (6 vs. 5 in both A. emilyae and A. rufescens), distinct body coloration (black on dorsal body and belly vs. dorsum iridescent pale yellowish brown in A. emilyae, and uniform pale reddish or reddish-brown dark grey dorsally in A. rufescens). Furthermore, the new species differ from A. rufescens by having more ventrals in males (161 vs. 131���137) (Table 4). Achalinus yangdatongi sp. nov. differs from A. niger, A. werneri, A. yunkaiensis, and A. spinalis by having suture between the internasals distinctly longer than that between the prefrontals (vs. less than or subequal to), a comparatively longer tail (TaL/ToL 26.2% vs. 15.0%���18.0% in A. niger, 15.0%���25.0% in A. spinalis, and 18.0%���20.0% in A. yunkaiensis), fewer subcaudals in male (SC 82 vs. 89���98 in A. werneri); from A. formosanus, A. jinggangensis, A. pingbianensis, A. timi and A. zugorum by presence of loreal scale (vs. absence), fewer dorsal scale rows (23���23���19 vs. 25���25��� 23 in A. timi, and 27���27��� 25 in A. formosanus), and more subcaudals (SC 82 vs. 51���64 in A. jinggangensis, 56 in A. pingbianensis and 70 in A. zugorum); from A. meiguensis and A. panzhihuaensis sp. nov. by presence of internasal (vs. absent), absence of postocular (vs. present), as well as by having different state of nasal scales (separated vs. in contact each other behind the rostral), mental separated from anterior chin shields (vs. in contact), and first pair of infralabials in contact with each other (vs. separated); and from A. hainanus by having different temporal formula (2���2���3 vs. 1���2���3), more subcaudals (SC 82 vs. 67���69), and more infralabials (6 vs. 5). Natural history and distribution. The holotype was found on a paved road near a reservoir on a drizzly night. The nearby habitat is characterized by secondary forests and abandoned farmlands (Fig. 7). At the type locality, this species is sympatric with Trimerodytes percarinatus (Boulenger, 1899), Protobothrops mucrosquamatus (Cantor, 1839), and Pareas sp. With the holotype and the genetically identified snake sheds, A. yangdatongi sp. nov. is only known from its type locality at Xiaoqiaogou, Xichou county, Wenshan Prefecture, Yunnan Province, China (Fig. 1). Etymology. The species name, yangdatongi, is a patronym honoring the Chinese herpetologist, Dr. Da-Tong Yang. We name the new species after Dr. Yang in recognition of his great contributions to the herpetological research in Southwestern China, particularly in Yunnan Province where the new species is found. We suggest ���Yang���s Odd-scaled Snake��� as its common English name, and ��� ��������ffi ��� (Pinyin: Yang Shi Ji She) as its Chinese common name., Published as part of Hou, Shao-Bing, Wang, Kai, Guo, Peng, Chen, Jin-Min, Yuan, Zhi-Yong & Che, Jing, 2021, Two new species and a new country record of the genus Achalinus (Reptilia Squamata: Xenodermidae) from China, pp. 528-546 in Zootaxa 4950 (3) on pages 538-540, DOI: 10.11646/zootaxa.4950.3.6, http://zenodo.org/record/4650074

Achalinus panzhihuaensis sp. nov. (Figs. 3 and 4) Holotype. KIZ 040189, adult male, collected by Benfu Miao and Kai Wang on 10 May 2018 from Hongbao Village (27.00°N, 101.53°E), Yanbian County, Panzhihua, Sichuan Province, China. Diagnosis. Achalinus panzhihuaensis sp. nov. can be distinguished from recognized congeners by a combination of the following characters: (1) TaL/ToL 24.6% in the single male; (2) two nasal scales in contact with each other behind the rostral; (3) internasal absent; (4) loreal rectangular; (5) supralabials 6; (6) postocular single and small; (7) temporals 2+2+3, anterior pair elongated, upper one smaller, only uppermost in contact with eye; (8) infralabials 6; (9) mental in contact with first pair of chin shields, fully separating first pair of infralabials; (10) dorsal scales 23–23–19 rows; (11) ventrals 160; (12) subcaudals 73, unpaired; (13) precloacal scale entire; (14) maxillary teeth 28; and (15) all scales iridescent with metallic luster, brown dorsally, with single indigo-colored vertebral line. Description of holotype. Body size small, total length 257 mm (SVL 194 mm, TaL 63 mm); tail long, 24.6% total length; body slender, cylindrical in cross section. Head slightly distinct from neck, HL 7.8 mm; eye small, pupil vertically subelliptic. Rostral small, triangular, invisible from above; nasal divided, each half in contact with each other; internasal absent; prefrontals paired, suture length 2.1 mm; frontal pentagonal, slightly wider than long, pointed posteriorly; single pair of parietals; loreal pentagonal, tip pointing anteriorly, longer (LeL: 1.2 mm) than high (HiL: 0.8 mm), LeL/HiL 150.0%; supraocular single, in contact with loreal, prefrontals, frontal, parietals, and superior anterior temporals. Temporals in three groups, 2+2+3; superior one of anterior most pair triangular, small, inferior one much larger, elongated, in contact with fourth and fifth supralabials and parietal; the middle pair, superior one parallelogram, small, inferior one much larger, elongated, in contact with sixth supralabials and three posterior temporals; superior most one of last trios biggest, size gradually decreases inferiorly; supralabials six, first one smallest, fourth and fifth in contact with eyes, sixth longest. Mental arc-shaped, in contact with first pair of chin shields; three pairs of chin shields, first pair in fan-shaped, remaining ones of second and third pairs in unequilateralquadrilateral shape. Infralabials six, first pair not in contact with each other, first three in contact with anterior-most pair of chin shields, third and fourth infralabials in contact with middle pair. Dorsal scales elliptical, 23–23–19 rows, medial 6–11 rows distinctly keeled, remaining outer rows smooth. Ventrals 160, rounded laterally; subcaudals 73, unpaired; precloacal entire. Coloration: In life, all scales are weakly iridescent with metallic luster. Dorsum is purplish brown. The vertebral and three paravertebral rows of dorsal scales are darker indigo, which form a darker longitudinal vertebral stripe extending from the posterior margin of the parietals to the tip of tail. Ventral surface of the body is greyish white, and the subcaudal region is purplish brown. In preservative, all scales are still iridescent. Coloration becomes darker after preservation. The dorsum becomes dark grey, and the vertebral stripe turns black. The ventral surface of the body becomes greyish brown, and the ventral tail is dark greyish brown. Comparisons. A. panzhihuaensis sp. nov. is most similar to its sister species A. meiguensis, in which both species have divided nasal scales in contact with each other, no internasal, a single postocular, 6 supralabials, 6 infralabials, mental in contact with first pair of chin shields, and fully separated first pair of infralabials. However, the new species can be diagnosed readily from A. meiguensis by having more subcaudals (SC 73 vs. 39–60), more ventrals in male (VEN 160 vs. 146–155), and more DSRM (23 vs. 19–21) (Table 4). Achalinus panzhihuaensis sp. nov. can be easily distinguished from A. ater, A. emilyae, A. formosanus Boulenger, A. hainanus Huang, A. jinggangensis Zong & Ma, A. juliani, A. niger Mahi, A. pingbianensis Li, Yu, Wu, Liao, Tang, Liu & Guo, A. rufescens Boulenger, A. spinalis Peters, A. tranganensis Luu, Ziegler, Ha, Lo, Hoang, Ngo, Le, Tran & Nguyen, A. timi, A. yunkaiensis, A. werneri Van Denburgh and A. zugorum Miller, Davis, Luong, Do, Pham, Ziegler, Lee, De Queiroz, Reynolds & Nguyen, by having divided nasal scales in contact each other behind the rostral (vs. separated), mental in contact with the first pair of chin shields (vs. separated), first pair of infralabials separated from each other (vs. in contact), as well as an absence of internasal (vs. present), and by the presence of a small postocular (vs. absent). Furthermore, the new species differs from A. jinggangensis, A. pingbianensis, A. timi and A. formosanus by having loreal separated from prefrontal (vs. fused); and from A. emilyae, A. hainanus and A. rufecens by having more infralabials (6 vs. 5). Natural history and distribution. The holotype was found on a montane road at night. The surrounding habitat was of secondary forest of evergreen broadleaf forest with shrubs and vines (Fig. 5). According to locals, road-killed individuals are somewhat common in the summer. At the type locality, the species is sympatric with Diploderma swild Wang, Wu, Jiang, Chen, Miao, Siler, Che, 2019, Lycodon cf. gongshan Vogel, Luo, 2011, Hebius yanbianensis Liu, Zhong, Wang, Liu, Guo, 2018, Ptyas nigromarginata (Blyth, 1854), Megophrys platyparietus (Yang, Rao, 1997), and Odorrana sp.. The new species is currently only known from the type locality in Panzhihua, Sichuan Province, China (Fig. 1). Etymology. The specific epithet “ panzhihuaensis ” is named after the type locality of the new species, Panzhihua, Sichuan Province, China. We propose “Panzhihua Odd-scaled Snake” as its common English name and “ Ẓ枝 AEñffi ” (Pinyin: Pan Zhi Hua Ji She) as its Chinese common name.

Achalinus, commonly known as odd-scaled snakes due to their unique scutellation, are a fascinating group of xenodermid snakes distributed throughout east Asia. Currently, northern Vietnam is known to host six species of Achalinus, three of which are considered endemic. During recent herpetofaunal surveys conducted in the Bac Me District of Ha Giang Province, we collected a single specimen of Achalinus in a lowland region surrounded by secondary forest on karst. We conducted Bayesian and maximum likelihood phylogenetic analyses using multiple mitochondrial protein-coding loci and a ribosomal subunit to ascertain the phylogenetic position of the Ha Giang specimen among currently recognized odd-scaled snake species. The results of those analyses along with morphological differences support this specimen as representing a new species, which we describe as Achalinus zugorum, new species. We provide detailed morphological descriptions and comparisons of the new species as well as brief comments on the biogeography and conservation of Achalinus in northern Vietnam.

Achalinus tranganensis sp. nov. Figs. 2, 3 Holotype. VNUF R.2018.21 (field number TA.18.21), adult female, from limestone forest (20��15.266���N, 105��53.677���E, 9 m a.s.l.), near Tran Temple, Trang An Landscape Complex, Ninh Binh Province, northern Vietnam, collected by V. Q. Luu, O. V. Lo, N. T. Nguyen on 31 May 2018. Diagnosis. Achalinus tranganensis sp. nov is characterized by the following combination of morphological characters: 1) maxillary teeth 29; 2) suture between the internasals distinctly longer than that between the prefrontals; 3) loreal distinctly wider than high, extending from the nasal to the eye; 4) dorsal scales in 25���23���23 rows, keeled; 5) two pairs of prefrontals; 6) supralabials six; 7) infralabials six; 8) temporals 2+3, the two anterior temporals in contact with eye; 9) ventrals 171; 10) subcaudals 73+, entire; 11) cloacal entire; 12) dorsum in preservative reddish to greyish brown above; 13) the lower part of head side and chin region somewhat paler than remaining head; 14) venter greyish cream, with the anterior region of each ventral and subcaudal somewhat darker. Description of the holotype. Total length 448 mm (SVL 334 mm, TailL 114 mm); tail long, tail tip lost, tail length/ total length ratio 0.25; body slender, cylindrical; head length 9.9 mm; head slightly distinct from neck, dorsally covered with large shields; eye small, with vertically subelliptic pupil; left maxilla with 29 equally sized, curved teeth. Rostral small, triangular, not visible from above; suture between internasals (2.3 mm) longer than that between prefrontals (1.6 mm); nostril in anterior part of nasal; frontal heptagonal, heart-shaped, slightly broader than long, pointed backwards, much shorter than parietals; parietal bordered behind by an elongated nuchal, nuchals separated from each other by three small, elongated scales; one loreal, distinctly longer than high, extending from nasal to eye; medial pair of prefrontals elongated, in broad contact with larger lateral prefrontal; lateral prefrontals in contact with nasal, internasal, medial prefrontal, frontal, supraocular, and loreal; one supraocular; two anterior temporals, both touching eye; two large posterior temporals (a minute scale present between upper anterior and posterior temporals on right); supralabials six, first smallest, fourth and fifth in contact with eye, sixth longest; one curved rectangle mental; six infralabials, first pair in contact with each other, first pair of chin shields larger than posterior, in contact with first three infralabials; posterior pair of chin shields smaller, in contact with third and fourth infralabials. Dorsal scales elliptical, keeled from the neck region posteriorly, in 25-23-23 rows; ventrals 171 (no preventrals), approximately 3 times wider than long, laterally rounded; subcaudals 73+, unpaired; cloacal entire. Colouration in preservative. Reddish to greyish brown above with weakly iridescent colouration in all scales; lower sides of head somewhat paler; venter greyish cream, with anterior region of the ventrals and subcaudals somewhat darker; underside of the tail somewhat darker than belly and the chin region somewhat paler than remaining head (Fig. 4). Colouration in life. Dorsum iridescent reddish to greyish brown; underside of head light brown; venter greyish cream; under tail dark brown. Comparisons. The condition of the prefrontals being arranged in two pairs is unique in Achalinus and thus distinguishes the new species from all other congeners and thus is not repeated in the detailed comparisons in the following. At first glance, Achalinus tranganensis sp. nov. resembles A. juliani in color pattern and dorsal scalerow formula. However, A. tranganensis can be distinguished from A. juliani by having fewer ventrals in the female (171 versus 179); from A. ater by having more anterior temporals (3 versus 2), more dorsal scale rows anteriorly (25 versus 23 or 21), and more subcaudals (73+ versus 47���70); from A. emilyae by having more infralabials (6 ver-sus 5), more posterior temporals (3 versus 2), more dorsal scale rows anteriorly (25 versus 23), more ventrals (171 versus 157���161), and more subcaudals (73+ versus 63); from A. formosanus by having more maxillary teeth (29 versus 14���17), the internasal suture distinctly longer than prefrontal suture (versus internasal suture almost as long as prefrontal suture), the loreal unfused with prefrontal (versus fused), fewer dorsal scale rows (25���23���23 versus 25���29��� 25���27���25), more posterior temporals (3 versus 2), and lacking a black mid-dorsal line; from A. jinggangensis Zong & Ma, 1983 by having more maxillary teeth (29 versus 22), loreal unfused with prefrontal (versus fused), more posterior temporals (3 versus 2), more ventrals (171 versus 156���164), and more subcaudals (73+ versus 51���64); from A. hainanus Huang, 1975 by having more infralabials (6 versus 5), more temporals (2+3 versus 1+2), more dorsal scale rows anteriorly (25 versus 23), more ventrals (171 versus 165���168), and more subcaudals (73+ versus 67���69); from A. meiguensis by having more maxillary teeth (29 versus 17), more dorsal scale rows anteriorly and posteriorly (25 versus 21 or 23; 23 versus 19, respectively), and more subcaudals (73+ versus 39���62); from A. niger by having the internasal suture being distinctly longer than that between the prefrontals (versus almost as long as or shorter), fewer midbody scale rows (23 versus 25), more subcaudals in females (73 versus 52���58), and keeled dorsal scales (versus smooth on anterior part of body); from A. pingbianensis by having the loreal unfused with prefrontal (versus fused), more dorsal scale rows anteriorly (25 versus 23), more ventrals (171 versus 164+2), and more subcaudals (73+ versus 56); from A. rufescens by having more infralabials (6 versus 5), more posterior temporals (3 versus 2), more ventrals in females (171 versus 148���158), and more subcaudals (73+ versus 54���61); from A. spinalis by having more maxillary teeth (29 versus 16���20), the internasal suture being distinctly longer than that between the prefrontals (versus as long as or shorter), more posterior temporals (3 versus 2), more dorsal scale rows anteriorly (25 versus 21���24), and more subcaudals (73 versus 39���67); from Achalinus timi by having the loreal unfused with prefrontal (versus fused), more posterior temporals (3 versus 2), and fewer scale rows at midbody (23 versus 25); from A. werneri by the internasal suture being distinctly longer than that between the prefrontals (versus almost as long as), having more posterior temporals (3 versus 2), and by lacking a black mid-dorsal line; from A. yunkaiensis by having more maxillary teeth (29 versus 20���22), the internasal suture being distinctly longer than that between the prefrontals (versus as long as), more posterior temporals (3 versus 1), more dorsal scale rows anteriorly (25 versus 23), more ventrals (171 versus 151���162), and more subcaudals (73+ versus 38���56). Distribution. Achalinus tranganensis sp. nov. is currently known only from the type locality in the Trang An Landscape Complex, Ninh Binh Province, Vietnam (Fig. 4). Etymology: We name this species after its type locality, the Trang An Landscape Complex, where the new Achalinus was discovered and propose the following common names: Trang An Burrowing Snake (English), R���n xe đi���u tr��ng an (Vietnamese). Natural history. The holotype was found at 2045 h, while crawling on a forest path under dry leaves, at an elevation of 9 m a.s.l. The surrounding habitat is secondary karst forest (Fig. 5). The humidity at the time of collection was approximately 78%, and the air temperature was 29 oC. Other amphibians and reptiles were observed and collected in the area such as Theloderma annae Nguyen, Pham, Nguyen, Ngo, and Ziegler; Sylvirana guentheri (Boulenger), Lycodon futsingensis (Pope), L. subcinctus Boie, Oligodon chinensis (G��nther)., Published as part of Luu, Vinh Quang, Ziegler, Thomas, Ha, Nghia Van, Lo, Oanh Van, Hoang, Tuoi Thi, Ngo, Hanh Thi, Le, Minh Duc, Tran, Dung Hoang & Nguyen, Truong Quang, 2020, A new species of Achalinus (Squamata: Xenodermidae) from Trang An Landscape Complex, Ninh Binh Province, Vietnam, pp. 174-184 in Zootaxa 4877 (1) on pages 177-180, DOI: 10.11646/zootaxa.4877.1.8, http://zenodo.org/record/4572461, {"references":["Zong, Y. & Ma, J. (1983) A new species of the genus Achalinopsis from Jiangxi and the restoration of this genus. Acta Herpetologica Sinica, 2 (2), 61 - 63. [in Chinese]"]}

Achalinus tranganensis sp. nov. Figs. 2, 3 Holotype. VNUF R.2018.21 (field number TA.18.21), adult female, from limestone forest (20°15.266’N, 105°53.677’E, 9 m a.s.l.), near Tran Temple, Trang An Landscape Complex, Ninh Binh Province, northern Vietnam, collected by V. Q. Luu, O. V. Lo, N. T. Nguyen on 31 May 2018. Diagnosis. Achalinus tranganensis sp. nov is characterized by the following combination of morphological characters: 1) maxillary teeth 29; 2) suture between the internasals distinctly longer than that between the prefrontals; 3) loreal distinctly wider than high, extending from the nasal to the eye; 4) dorsal scales in 25–23–23 rows, keeled; 5) two pairs of prefrontals; 6) supralabials six; 7) infralabials six; 8) temporals 2+3, the two anterior temporals in contact with eye; 9) ventrals 171; 10) subcaudals 73+, entire; 11) cloacal entire; 12) dorsum in preservative reddish to greyish brown above; 13) the lower part of head side and chin region somewhat paler than remaining head; 14) venter greyish cream, with the anterior region of each ventral and subcaudal somewhat darker. Description of the holotype. Total length 448 mm (SVL 334 mm, TailL 114 mm); tail long, tail tip lost, tail length/ total length ratio 0.25; body slender, cylindrical; head length 9.9 mm; head slightly distinct from neck, dorsally covered with large shields; eye small, with vertically subelliptic pupil; left maxilla with 29 equally sized, curved teeth. Rostral small, triangular, not visible from above; suture between internasals (2.3 mm) longer than that between prefrontals (1.6 mm); nostril in anterior part of nasal; frontal heptagonal, heart-shaped, slightly broader than long, pointed backwards, much shorter than parietals; parietal bordered behind by an elongated nuchal, nuchals separated from each other by three small, elongated scales; one loreal, distinctly longer than high, extending from nasal to eye; medial pair of prefrontals elongated, in broad contact with larger lateral prefrontal; lateral prefrontals in contact with nasal, internasal, medial prefrontal, frontal, supraocular, and loreal; one supraocular; two anterior temporals, both touching eye; two large posterior temporals (a minute scale present between upper anterior and posterior temporals on right); supralabials six, first smallest, fourth and fifth in contact with eye, sixth longest; one curved rectangle mental; six infralabials, first pair in contact with each other, first pair of chin shields larger than posterior, in contact with first three infralabials; posterior pair of chin shields smaller, in contact with third and fourth infralabials. Dorsal scales elliptical, keeled from the neck region posteriorly, in 25-23-23 rows; ventrals 171 (no preventrals), approximately 3 times wider than long, laterally rounded; subcaudals 73+, unpaired; cloacal entire. Colouration in preservative. Reddish to greyish brown above with weakly iridescent colouration in all scales; lower sides of head somewhat paler; venter greyish cream, with anterior region of the ventrals and subcaudals somewhat darker; underside of the tail somewhat darker than belly and the chin region somewhat paler than remaining head (Fig. 4). Colouration in life. Dorsum iridescent reddish to greyish brown; underside of head light brown; venter greyish cream; under tail dark brown. Comparisons. The condition of the prefrontals being arranged in two pairs is unique in Achalinus and thus distinguishes the new species from all other congeners and thus is not repeated in the detailed comparisons in the following. At first glance, Achalinus tranganensis sp. nov. resembles A. juliani in color pattern and dorsal scalerow formula. However, A. tranganensis can be distinguished from A. juliani by having fewer ventrals in the female (171 versus 179); from A. ater by having more anterior temporals (3 versus 2), more dorsal scale rows anteriorly (25 versus 23 or 21), and more subcaudals (73+ versus 47–70); from A. emilyae by having more infralabials (6 ver-sus 5), more posterior temporals (3 versus 2), more dorsal scale rows anteriorly (25 versus 23), more ventrals (171 versus 157–161), and more subcaudals (73+ versus 63); from A. formosanus by having more maxillary teeth (29 versus 14–17), the internasal suture distinctly longer than prefrontal suture (versus internasal suture almost as long as prefrontal suture), the loreal unfused with prefrontal (versus fused), fewer dorsal scale rows (25–23–23 versus 25–29– 25–27–25), more posterior temporals (3 versus 2), and lacking a black mid-dorsal line; from A. jinggangensis Zong & Ma, 1983 by having more maxillary teeth (29 versus 22), loreal unfused with prefrontal (versus fused), more posterior temporals (3 versus 2), more ventrals (171 versus 156–164), and more subcaudals (73+ versus 51–64); from A. hainanus Huang, 1975 by having more infralabials (6 versus 5), more temporals (2+3 versus 1+2), more dorsal scale rows anteriorly (25 versus 23), more ventrals (171 versus 165–168), and more subcaudals (73+ versus 67–69); from A. meiguensis by having more maxillary teeth (29 versus 17), more dorsal scale rows anteriorly and posteriorly (25 versus 21 or 23; 23 versus 19, respectively), and more subcaudals (73+ versus 39–62); from A. niger by having the internasal suture being distinctly longer than that between the prefrontals (versus almost as long as or shorter), fewer midbody scale rows (23 versus 25), more subcaudals in females (73 versus 52–58), and keeled dorsal scales (versus smooth on anterior part of body); from A. pingbianensis by having the loreal unfused with prefrontal (versus fused), more dorsal scale rows anteriorly (25 versus 23), more ventrals (171 versus 164+2), and more subcaudals (73+ versus 56); from A. rufescens by having more infralabials (6 versus 5), more posterior temporals (3 versus 2), more ventrals in females (171 versus 148–158), and more subcaudals (73+ versus 54–61); from A. spinalis by having more maxillary teeth (29 versus 16–20), the internasal suture being distinctly longer than that between the prefrontals (versus as long as or shorter), more posterior temporals (3 versus 2), more dorsal scale rows anteriorly (25 versus 21–24), and more subcaudals (73 versus 39–67); from Achalinus timi by having the loreal unfused with prefrontal (versus fused), more posterior temporals (3 versus 2), and fewer scale rows at midbody (23 versus 25); from A. werneri by the internasal suture being distinctly longer than that between the prefrontals (versus almost as long as), having more posterior temporals (3 versus 2), and by lacking a black mid-dorsal line; from A. yunkaiensis by having more maxillary teeth (29 versus 20–22), the internasal suture being distinctly longer than that between the prefrontals (versus as long as), more posterior temporals (3 versus 1), more dorsal scale rows anteriorly (25 versus 23), more ventrals (171 versus 151–162), and more subcaudals (73+ versus 38–56). Distribution. Achalinus tranganensis sp. nov. is currently known only from the type locality in the Trang An Landscape Complex, Ninh Binh Province, Vietnam (Fig. 4). Etymology: We name this species after its type locality, the Trang An Landscape Complex, where the new Achalinus was discovered and propose the following common names: Trang An Burrowing Snake (English), Rắn xe điếu tràng an (Vietnamese). Natural history. The holotype was found at 2045 h, while crawling on a forest path under dry leaves, at an elevation of 9 m a.s.l. The surrounding habitat is secondary karst forest (Fig. 5). The humidity at the time of collection was approximately 78%, and the air temperature was 29 oC. Other amphibians and reptiles were observed and collected in the area such as Theloderma annae Nguyen, Pham, Nguyen, Ngo, and Ziegler; Sylvirana guentheri (Boulenger), Lycodon futsingensis (Pope), L. subcinctus Boie, Oligodon chinensis (Günther).

Achalinus pingbianensis sp. nov. (Figures 1, 3–5) Holotype. YBU 18273, an adult male, collected by K. Li, M. Yu, L. H. Liao, and K. Tang at night on July 12, 2019 in Dawei Mountain Nature Reserve, Pingbian County (N 103°42′01.02″, E 22°55′02.78″), southeastern Yunnan Province, China, at an elevation of 1, 968 m above sea level. Diagnosis. A new species of Achalinus having the combination of (1) dorsal scales strongly keeled, 23 rows throughout; (2) tail relatively short, TaL/TL 24.3%; (3) length of suture between internasals subequal to that between prefrontals; (4) nasal divided into two sections by nasal cleft; (5) loreal fused with prefrontal, with the prefrontal extending towards the supralabials; (6) supralabials 7, the fifth and sixth widely in contact with eye; (7) infralabials 6, the first three touching the first pair of chin shields; (8) temporals 2+2+3 on right side and 2+2 on left side, the uppermost anterior temporal in contact with eye; (9) ventrals 164+2, subcaudals 56, arranged in single row; (10) anal entire; (11) uniform black, tinged weakly iridescent; (12) light black beneath. Description of holotype. An adult male with a total length of 429 mm (SVL 345 mm and TaL 84 mm), TaL/TL 24.3%. Body slender, cylindrical; head slightly distinct from neck; eye small, with vertically oval pupil; rostral small, triangular, slightly visible from above. LSBI subequal to LSBP. Nostril in the anterior part of the nasal, posterior margin of nostril with a distinct nostril cleft, the posterior section of nasal vertically rectangular. Frontal pentagonal, slightly broader than long, pointed backwards, much shorter than the parietals; each parietal bordered by an elongated nuchal. Nuchals separated from each other behind parietals by one small scale; the second pair of nuchals about 2/3 the size as the first pair. Loreal lacking, prefrontals stretch towards the SPL. Preocular and postocular absent. A single SPO. Two aTMP, elongated, upper one smaller, only uppermost in contact with eye, four elongated pTMP on right side, and pTMP of the left side nondescript. SPL 7, the first smallest, fifth and sixth in contact with the eye, seventh longest. One mental, followed by six IFL, the first pair of IFL in contact with each other; the first three IFL touching the first pair of chin shields; posterior pair of chin shields larger, length of the suture between the first pair equal to that between the second pair, laterally in contact with third to fifth IFL. Dorsal scales lanceolate and strongly keeled, in 23-23-23 rows, those of the most outer rows on both sides significantly enlarged and smooth. VS 164 (plus two preventrals), distinctly rounded laterally; SC 56, not paired; anal entire. Coloration of holotype in life. Uniform black above, vertebral line unseen. All scales tinged iridescent and margin of scales greyish white. Uniform light black beneath. The ventral tail dark brown, the dorsal tail surface iridescent black (Figs. 3 and 4). Coloration of holotype in preservation. All scales tinged weakly iridescent. Uniform black, margin of all scales dark grey. Etymology. The specific name refers to the type locality of this species, Dawei Mountain Nature Reserve, Pingbian County, Southeastern Yunnan, China. We suggest the common names as Ping Bian Ji She (DZṈṘẘ) in Chinese and Pingbian odd-scaled snake in English. Distribution and habits. Currently, Achalinus pingbianensis sp. nov. is known only from its type locality at Dawei Mountain Nature Reserve, Pingbian County, southeastern Yunnan Province, China (Fig. 1). The specimen was found at 9:00 PM on the road with moss and leaf litters in well-preserved montane evergreen broadleaf forest on both sides. Comparisons. Achalinus pingbianensis sp. nov. differs from all other species of Achalinus, except A. jinggangensis and A. timi, by the absence of a loreal. Achalinus pingbianensis sp. nov. further differs from A. jinggangensis, A. timi, A. ater, A. hainanus, A. rufescens, A. emilyae, A. yunkaiensis, and A. juliani by having length of suture between internasals subequal to that between prefrontals (vs. distinctly longer than that between prefrontals). Achalinus pingbianensis sp. nov. can be easily distinguished from A. formosanus (mDSR 25–27), A. meiguensis (mDSR 19–21), A. timi (mDSR 25), and A. niger (mDSR 27) by having mDSR 23, and from A. hainanus and A. meiguensis by the presence of internasals. In addition, the new species can be differentiated from some congeners in VS, SC, and Tal/TL ratio. Comparisons between the new species and its congeners are summarized in Table 4. ......continued on the next page, Published as part of Li, Ke, Yu, Min, Wu, Ya-Yong, Liao, Lin-Hong, Tang, Kui, Liu, Qin & Guo, Peng, 2020, A new species of the genus Achalinus (Squamata: Xenodermatidae) from southeastern Yunnan Province, China, pp. 116-128 in Zootaxa 4860 (1) on pages 121-123, DOI: 10.11646/zootaxa.4860.1.6, http://zenodo.org/record/4537645, {"references":["Van Denburgh, J. (1912) Concerning certain species of reptiles and amphibians from China, Japan, the Loo Choo Islands, and Formosa. Proceedings of The California Academy of Sciences, 3, 187 - 258. https: // doi. org / 10.1016 / S 1631 - 0691 (02) 01509 - 3","Pope, C. H. (1935) The reptiles of China. Turtles, crocodilians, snakes, lizards. Natural History of central Asia. Vol. X. American Museum of Natural History, New York, 604 pp.","Bourret, R. L. (1935) Notes herpetologiques sur l'Indochine francaise. VIII. Sur les Achalinus d'Indochine. Bulletin Generale de l'Instruction Publique, Hanoi, 15 (5), 101 - 104","Bourret, R. (1937) Notes herpetologiques sur l Indochine francaise. XV. Lezards et serpents recus au Laboratoire des Sciences Naturelles de l' Universite au cours de l' annee 1937. Descriptions de deux especes et de deux varietes nouvelles. Bulletin general de l Instruction Publique, Hanoi, 17 (4), 57 - 80.","Smith, M. A. (1943) The fauna of British India, including Ceylon and Burma. Reptilia and Amphibia. Vol. III. Serpentes. Taylor & Francis Ltd., London, 583 pp.","Koshikawa, A. (1982) Three new species of reptiles from Hainan Island, Guangdong Province. Smithsonian Herpetological Information Service, 53, 1 - 10. https: // doi. org / 10.5479 / si. 23317515.53.1","Karsen, S. J., Lau, M. W. & Bogadek, A. (1986) Hong Kong amphibians and reptiles. Urban Council, Hong Kong, 136 pp.","Ota, H. & Toyama, M. (1989) Taxonomic re-definition of Achalinus formosanus Boulenger (Xenoderminae: Colubridae: Ophidia), with description of a new subspecies. Copeia, 1989 (3), 597 - 602. https: // doi. org / 10.2307 / 1445485.","Zhao, E. M. (2006) Snakes of China. Anhui Science and Technology Publishing House, Hefei, 372 (texts) + 279 pp. (photos). [in Chinese]","Das, I. (2010) A field guide to the reptiles of Southeast Asia. New Holland Publishers (UK) Ltd, London, Cape Town, Sydney and Auckland, 376 pp.","Ziegler, T., Nguyen, T. Q., Pham, C. T., Nguyen, T. T., Pham, A. V., Schingen, V. S., Nguyen, T. T. & Le, M. D. (2019) Three new species of the snake genus Achalinus from Vietnam (Squamata: Xenodermatidae). Zootaxa, 4590 (2), 249 - 269. https: // doi. org / 10.11646 / zootaxa. 4590.2.3","Wang, J., Li, Y., Zeng, Z. C., Lyu, Z. T., Sung, Y. H., Li, Y. Y., Lin, C. Y. & Wang, Y. Y. (2019) A new species of the genus Achalinus from southwestern Guangdong Province, China (Squamata: Xenodermatidae). Zootaxa, 4674 (4), 471 - 481. https: // doi. org / 10.11646 / zootaxa. 4674.4.6","Zong, Y. & Ma, J. (1983) A new species of the genus Achalinopsis from Jiangxi and the restoration of this genus. Acta Herpetologica Sinica, 2 (2), 61 - 63. [in Chinese]"]}

Achalinus pingbianensis sp. nov. (Figures 1, 3–5) Holotype. YBU 18273, an adult male, collected by K. Li, M. Yu, L. H. Liao, and K. Tang at night on July 12, 2019 in Dawei Mountain Nature Reserve, Pingbian County (N 103°42′01.02″, E 22°55′02.78″), southeastern Yunnan Province, China, at an elevation of 1, 968 m above sea level. Diagnosis. A new species of Achalinus having the combination of (1) dorsal scales strongly keeled, 23 rows throughout; (2) tail relatively short, TaL/TL 24.3%; (3) length of suture between internasals subequal to that between prefrontals; (4) nasal divided into two sections by nasal cleft; (5) loreal fused with prefrontal, with the prefrontal extending towards the supralabials; (6) supralabials 7, the fifth and sixth widely in contact with eye; (7) infralabials 6, the first three touching the first pair of chin shields; (8) temporals 2+2+3 on right side and 2+2 on left side, the uppermost anterior temporal in contact with eye; (9) ventrals 164+2, subcaudals 56, arranged in single row; (10) anal entire; (11) uniform black, tinged weakly iridescent; (12) light black beneath. Description of holotype. An adult male with a total length of 429 mm (SVL 345 mm and TaL 84 mm), TaL/TL 24.3%. Body slender, cylindrical; head slightly distinct from neck; eye small, with vertically oval pupil; rostral small, triangular, slightly visible from above. LSBI subequal to LSBP. Nostril in the anterior part of the nasal, posterior margin of nostril with a distinct nostril cleft, the posterior section of nasal vertically rectangular. Frontal pentagonal, slightly broader than long, pointed backwards, much shorter than the parietals; each parietal bordered by an elongated nuchal. Nuchals separated from each other behind parietals by one small scale; the second pair of nuchals about 2/3 the size as the first pair. Loreal lacking, prefrontals stretch towards the SPL. Preocular and postocular absent. A single SPO. Two aTMP, elongated, upper one smaller, only uppermost in contact with eye, four elongated pTMP on right side, and pTMP of the left side nondescript. SPL 7, the first smallest, fifth and sixth in contact with the eye, seventh longest. One mental, followed by six IFL, the first pair of IFL in contact with each other; the first three IFL touching the first pair of chin shields; posterior pair of chin shields larger, length of the suture between the first pair equal to that between the second pair, laterally in contact with third to fifth IFL. Dorsal scales lanceolate and strongly keeled, in 23-23-23 rows, those of the most outer rows on both sides significantly enlarged and smooth. VS 164 (plus two preventrals), distinctly rounded laterally; SC 56, not paired; anal entire. Coloration of holotype in life. Uniform black above, vertebral line unseen. All scales tinged iridescent and margin of scales greyish white. Uniform light black beneath. The ventral tail dark brown, the dorsal tail surface iridescent black (Figs. 3 and 4). Coloration of holotype in preservation. All scales tinged weakly iridescent. Uniform black, margin of all scales dark grey. Etymology. The specific name refers to the type locality of this species, Dawei Mountain Nature Reserve, Pingbian County, Southeastern Yunnan, China. We suggest the common names as Ping Bian Ji She (DZṈṘẘ) in Chinese and Pingbian odd-scaled snake in English. Distribution and habits. Currently, Achalinus pingbianensis sp. nov. is known only from its type locality at Dawei Mountain Nature Reserve, Pingbian County, southeastern Yunnan Province, China (Fig. 1). The specimen was found at 9:00 PM on the road with moss and leaf litters in well-preserved montane evergreen broadleaf forest on both sides. Comparisons. Achalinus pingbianensis sp. nov. differs from all other species of Achalinus, except A. jinggangensis and A. timi, by the absence of a loreal. Achalinus pingbianensis sp. nov. further differs from A. jinggangensis, A. timi, A. ater, A. hainanus, A. rufescens, A. emilyae, A. yunkaiensis, and A. juliani by having length of suture between internasals subequal to that between prefrontals (vs. distinctly longer than that between prefrontals). Achalinus pingbianensis sp. nov. can be easily distinguished from A. formosanus (mDSR 25–27), A. meiguensis (mDSR 19–21), A. timi (mDSR 25), and A. niger (mDSR 27) by having mDSR 23, and from A. hainanus and A. meiguensis by the presence of internasals. In addition, the new species can be differentiated from some congeners in VS, SC, and Tal/TL ratio. Comparisons between the new species and its congeners are summarized in Table 4. ......continued on the next page

Achalinus timi sp. nov. (Figs. 6–7) Holotype. IEBR A.2018.10 (Field no. PA.180), adult male, from forest within the Copia Nature Reserve, near Hua Ty Village (21°20.105’N, 103°35.860’E), Co Ma Commune, Thuan Chau District, Son La Province, northern Vietnam, collected by A.V. Pham on 12 May 2014 at an elevation of ca. 1470 m above sea level. Diagnosis. A species of the genus Achalinus, characterized by a combination of the following characters: 1) maxillary teeth 27; 2) suture between the internasals distinctly longer than that between the prefrontals; 3) loreal fused with prefrontal on each side, with the prefrontal extending towards the supralabials; 4) dorsal scales in 25–25–23 rows, keeled; 5) ventrals 170+1; 6) subcaudals 72, unpaired; 7) a total length of at least 177.9 mm in males (with a tail length of 37.9 mm and a tail/total length ratio of 0.21); 8) dorsum in preservative reddish to greyish brown above, with wide portion of the vertebral region being distinctly darker; the lower head sides are somewhat paler; infralabial and chin shields light greyish brown; venter greyish cream, with the underside of the tail being somewhat darker and the chin region somewhat paler. Description of holotype. Total length 177.9 mm (SVL 140 mm, TaL 37.9 mm); tail long, tail/total length ratio 0.21; body slender, cylindrical; head length 7.8 mm (from tip of snout to posterior margin of parietal); head slightly distinct from neck, dorsally covered with large shields; eye small, with vertically subelliptic pupil; left maxilla with at least 27 equally sized and curved teeth. Rostral small, triangular, not visible from above; suture between the internasals (1.7 mm) longer than that between the prefrontals (0.8 mm); nostril in the anterior part of the nasal; frontal pentagonal, slightly broader than long, pointed backwards, much shorter than the parietals; parietals bordered each by an elongated nuchal, nuchals separated from each other behind parietals by two small scales; second pair of nuchals about half the size than first pair; loreal lacking, prefrontals stretch towards the supralabials; one supraocular; two anterior temporals, only the smaller, upper one in contact with eye, and two elongated posterior temporals; supralabials six, the first smallest, fourth and fifth in contact with the eye, sixth longest; one mental, followed by six infralabials; first pair of infralabials in contact with each other; first three infralabials in contact with the first pair of chin shields; posterior pair of chin shields smaller, laterally in contact with fourth and fifth infralabials. Dorsal scales elliptical, keeled from the neck region onwards, in 25 rows at the anterior part of the body (one head length behind head), 25 scale rows at midbody, the outer row enlarged, and 23 rows at posterior body (one head length before vent); ventrals 170 (plus one preventral) distinct, laterally rounded; subcaudals 72, unpaired; cloacal entire. The ethanol-preserved holotype is reddish to greyish brown above, with a wide portion of the vertebral region being distinctly darker; the lower head sides somewhat paler; venter greyish cream, with the underside of the tail being somewhat darker and the chin region somewhat paler; infralabial and chin shields light greyish brown. Comparisons. Achalinus timi sp. nov. lacks a separate loreal scale, which is fused with the prefrontal on each side, with the prefrontal extending towards the supralabials; all remaining Achalinus species known at time to occur in Vietnam (A. ater, A. juliani, A. rufescens, and A. spinalis) have a loreal being separated from the prefrontal by a suture, which is also the case in most other Achalinus species (A. hainanus, A. meiguensis, A. niger, and A. werneri) which thus can be easily distinguished from Achalinus timi sp. nov. Achalinus timi sp. nov. further differs from A. formosanus, A. jinggangensis, A. meiguensis, A. rufescens, and A. spinalis by having more maxillary teeth. For details and further distinguishing characters see Table 5. Besides different maxillary teeth counts, Achalinus timi sp. nov. can be distinguished from the two subspecies of A. formosanus as follows: from A. f. formosanus by having the internasal suture distinctly longer than prefrontal suture (versus internasal suture almost as long as prefrontal suture) and 25–25–23 versus 29–27–25 dorsal scale rows; and from A. f. chigirai by 23 versus 25 dorsal scale rows at posterior body and by having more ventrals and less subcaudals (170 versus 161–167 ventrals; 72 versus 96–97 subcaudals). Furthermore, Achalinus timi sp. nov. can be distinguished from A. jinggangensis by having 25 versus 23 dorsal scale rows at midbody, more ventrals and subcaudals (170 versus 156–164 ventrals; 72 versus 51–64 subcaudals, respectively). Etymology. We name this species after Tim N. Ziegler. As common name we propose Tim’s Burrowing Snake. Distribution. The new species currently is only known from the type locality in Son La Province, northwestern Vietnam (Fig. 12). Natural history. The male holotype of Achalinus timi sp. nov. was discovered at 10: 15 in the morning, as a road kill specimen. The surrounding habitat was secondary evergreen forest. Air temperature at the site was 25–30 o C and relative humidity 70–75%., Published as part of Ziegler, Thomas, Nguyen, Truong Quang, Pham, Cuong The, Nguyen, Tao Thien, Pham, Anh Van, Schingen, Mona Van, Nguyen, Tham Thi & Le, Minh Duc, 2019, Three new species of the snake genus Achalinus from Vietnam (Squamata: Xenodermatidae), pp. 249-269 in Zootaxa 4590 (2) on pages 258-260, DOI: 10.11646/zootaxa.4590.2.3, http://zenodo.org/record/2651878

Achalinus juliani sp. nov. (Figs. 2–5) Holotype. IEBR A.2018.8 (Field no. CB 2014.18), an adult male, from forest of Duc Quang Commune (22°43.084’N, 106°39.653’E, at an elevation of 477 m above sea level), Ha Lang District, Cao Bang Province, northern Vietnam, collected by C.T. Pham on 14 June 2014. Paratypes. IEBR A.2018.9 (Field no. CB 2014.19), a female, from Phia Oac-Phia Den National Park (22°36.147’N, 105°52.726’E, at an elevation of 1461 m above sea level), Nguyen Binh District, Cao Bang Province, northern Vietnam, collected by T.H. Pham on 24 May 2014; VNMN 0 6924 (Field no. TAO 766), an adult male, from forest of Thanh Cong Commune within Phia Oac-Phia Den National Park (22°60.556’N, 105°87.530’E, at an elevation of 1590 m above sea level), Nguyen Binh District, Cao Bang Province, northern Vietnam, collected by T.T. Nguyen on 10 May 2010. Diagnosis. A species of the genus Achalinus, characterized by a combination of the following characters: 1) maxillary teeth 28; 2) suture between internasals distinctly longer than that between the prefrontals; 3) internasal not fused to prefrontal; 4) loreal not fused with prefrontal; 5) infralabials 6; 6) mental separated from anterior chin shields; 7) two elongated anterior temporals, in contact with eye, and two posterior temporals; 8) dorsal scales in 25–23–23 rows, keeled; 9) ventrals 173–179; 10) subcaudals 77–91, unpaired; 11) a total length of at least 413 mm (with a maximum tail length of 109 mm, and a tail/total length ratio of 0.22–0.37); 12) dorsum in preservative reddish to greyish brown above, the lower and posterior head sides paler; venter greyish cream, with the underside of the tail being somewhat darker. Description of holotype. Total length 355 mm (SVL 260 mm and TaL 95 mm); tail long, tail/total length ratio 0.365; body slender, cylindrical; head length 8.9 mm (from tip of snout to posterior margin of parietal); head slightly distinct from neck, dorsally covered with large shields; eye small, with vertically subelliptic pupil; left maxilla with 28 equally sized and curved teeth. Rostral small, triangular, slightly visible from above; suture between the internasals (1.4 mm) longer than that between the prefrontals (0.9 mm); nostril in the anterior part of the nasal; frontal pentagonal, slightly broader than long, pointed backwards, much shorter than the parietals; each parietal bordered by an elongated nuchal; nuchals separated from each other behind parietals by two small scales; second pair of nuchals about half the size than first pair; one loreal, distinctly wider than high, extending from the nasal to the eye; one supraocular; two anterior temporals, elongated, upper one smaller, both in contact with eye, and two elongated posterior temporals; supralabials six, the first smallest, fourth and fifth in contact with the eye, sixth longest; third and fourth in contact with the loreal; one mental, followed by six infralabials; first pair of infralabials in contact with each other; first four infralabials in contact with the first pair of chin shields; posterior pair of chin shields smaller, laterally in contact with fourth and fifth infralabials. Dorsal scales elliptical, keeled from the neck region onwards, 23 scale rows at midbody, those of the outer row enlarged, 25 scales round the anterior part of the body (one head length behind head), and 23 dorsal scale rows at posterior body (one head length before vent); ventrals 169 (plus one preventral), distinctly rounded laterally; subcaudals 91, unpaired, plus tail tip; cloacal entire. The ethanol-preserved holotype greyish brown above, the lower and posterior head sides being paler; venter greyish cream, with the underside of the tail being somewhat darker and the chin region somewhat paler; infralabial and chin shields light greyish brown. Ventrals and subcaudals anteriorly and laterally darker. Variation. For scalation details of the paratypes see Table 3. In addition, the nuchals of the female paratype IEBR A.2018.9 are separated from each other behind the parietals by four small scales and those of the male paratype VNMN 0 6924 by two large, two medium sized and a small scale. Furthermore, in the paratype VNMN 0 6924 the posterior pair of chin shields on the left side is in contact with third and fourth infralabials laterally. The hemipenes are basally everted in the specimen VNMN 0 6924. Comparisons. Achalinus juliani sp. nov. can be differentiated from the remaining Achalinus representatives from Vietnam by having more subcaudals, more dorsal scale rows on anterior part of the body, more ventrals, more infralabials, and a longer internasal suture (see Tables 3, 5). Achalinus juliani sp. nov. differs from A. ater in having more dorsal scale rows in the anterior part of the body (25 versus 21–23) and more subcaudals (77–91 versus 47–70). Achalinus juliani sp. nov. differs from A. rufescens by having more infralabials (6 versus 5), more ventrals (163–179 versus 131–158), more subcaudals (77–91 versus 54–82), and more maxillary teeth. Achalinus juliani sp. nov. differs from A. spinalis by the internasal suture being distinctly longer than that between the prefrontals (versus as long as or shorter), more dorsal scale rows in the anterior part of the body (25 versus 21–24), more subcaudals (77–91 versus 39–67), by lacking a black mid-dorsal line, and by having more maxillary teeth. Achalinus juliani sp. nov. differs from A. formosanus by having the internasal suture distinctly longer than prefrontal suture (versus internasal suture almost as long as prefrontal suture), by the loreal not being fused with prefrontal, fewer dorsal scale rows (25–23–23 versus 25–29 – 25–27–25), more maxillary teeth (28 versus 14–17), and by lacking a black mid-dorsal line; in addition, Achalinus juliani sp. nov. can be distinguished from A. f. formosanus by having more subcaudals (77–91 versus 61–83), and from A. f. chigirai by having fewer subcaudals (77–91 versus 96–97). Achalinus juliani sp. nov. differs from A. hainanus by having 6 versus 5 infralabials, 2 versus 1 anterior temporal, more dorsal scale rows in the anterior part of the body (25 versus 23), and more subcaudals (77–91 versus 67–69). Achalinus juliani sp. nov. differs from A. jinggangensis by loreal not being fused with prefrontal, having more ventrals (163–179 versus 156–164), more subcaudals (77–91 versus 51–64), and more maxillary teeth. Achalinus juliani sp. nov. differs from A. meiguensis by mental being separated from anterior chin shields, internasal not fused to prefrontal, by different dorsal scale row counts (25–23–23 versus 21–23 – 19–23 – 19), by having more subcaudals (77–91 versus 39–62), and by having more maxillary teeth. Achalinus juliani sp. nov. differs from A. niger by the internasal suture being distinctly longer than that between the prefrontals (versus almost as long as or shorter), fewer midbody dorsal scale rows (23 versus 25), more subcaudals (77–91 versus 52–72), and keeled body scales (versus smooth on anterior part of body). Achalinus juliani sp. nov. differs from A. werneri by the internasal suture being distinctly longer than that between the prefrontals (versus almost as long as), and by lacking a black mid-dorsal line and a dark subcaudal streak. Etymology. We name this species after Julian L. Ziegler. As common name we propose Julian’s Burrowing Snake. Distribution. The new species currently is only known from two localities within Cao Bang Province, northeastern Vietnam (Fig. 12). Natural history. Specimens were found between 20:00 and 22:00 h on forest paths. The surrounding habitat was secondary forest of large, medium and small hardwoods mixed with shrubs and vines. Air temperature at the sites were 25.4–32.6 o C and relative humidity 65–80%. The new species was found in different habitat types: lowland forest in Phia Oac-Phia Den National Park and limestone karst forest in Ha Lang District, at elevations from 470 to 1460 m above sea level., Published as part of Ziegler, Thomas, Nguyen, Truong Quang, Pham, Cuong The, Nguyen, Tao Thien, Pham, Anh Van, Schingen, Mona Van, Nguyen, Tham Thi & Le, Minh Duc, 2019, Three new species of the snake genus Achalinus from Vietnam (Squamata: Xenodermatidae), pp. 249-269 in Zootaxa 4590 (2) on pages 253-255, DOI: 10.11646/zootaxa.4590.2.3, http://zenodo.org/record/2651878

Achalinus juliani sp. nov. (Figs. 2–5) Holotype. IEBR A.2018.8 (Field no. CB 2014.18), an adult male, from forest of Duc Quang Commune (22°43.084’N, 106°39.653’E, at an elevation of 477 m above sea level), Ha Lang District, Cao Bang Province, northern Vietnam, collected by C.T. Pham on 14 June 2014. Paratypes. IEBR A.2018.9 (Field no. CB 2014.19), a female, from Phia Oac-Phia Den National Park (22°36.147’N, 105°52.726’E, at an elevation of 1461 m above sea level), Nguyen Binh District, Cao Bang Province, northern Vietnam, collected by T.H. Pham on 24 May 2014; VNMN 0 6924 (Field no. TAO 766), an adult male, from forest of Thanh Cong Commune within Phia Oac-Phia Den National Park (22°60.556’N, 105°87.530’E, at an elevation of 1590 m above sea level), Nguyen Binh District, Cao Bang Province, northern Vietnam, collected by T.T. Nguyen on 10 May 2010. Diagnosis. A species of the genus Achalinus, characterized by a combination of the following characters: 1) maxillary teeth 28; 2) suture between internasals distinctly longer than that between the prefrontals; 3) internasal not fused to prefrontal; 4) loreal not fused with prefrontal; 5) infralabials 6; 6) mental separated from anterior chin shields; 7) two elongated anterior temporals, in contact with eye, and two posterior temporals; 8) dorsal scales in 25–23–23 rows, keeled; 9) ventrals 173–179; 10) subcaudals 77–91, unpaired; 11) a total length of at least 413 mm (with a maximum tail length of 109 mm, and a tail/total length ratio of 0.22–0.37); 12) dorsum in preservative reddish to greyish brown above, the lower and posterior head sides paler; venter greyish cream, with the underside of the tail being somewhat darker. Description of holotype. Total length 355 mm (SVL 260 mm and TaL 95 mm); tail long, tail/total length ratio 0.365; body slender, cylindrical; head length 8.9 mm (from tip of snout to posterior margin of parietal); head slightly distinct from neck, dorsally covered with large shields; eye small, with vertically subelliptic pupil; left maxilla with 28 equally sized and curved teeth. Rostral small, triangular, slightly visible from above; suture between the internasals (1.4 mm) longer than that between the prefrontals (0.9 mm); nostril in the anterior part of the nasal; frontal pentagonal, slightly broader than long, pointed backwards, much shorter than the parietals; each parietal bordered by an elongated nuchal; nuchals separated from each other behind parietals by two small scales; second pair of nuchals about half the size than first pair; one loreal, distinctly wider than high, extending from the nasal to the eye; one supraocular; two anterior temporals, elongated, upper one smaller, both in contact with eye, and two elongated posterior temporals; supralabials six, the first smallest, fourth and fifth in contact with the eye, sixth longest; third and fourth in contact with the loreal; one mental, followed by six infralabials; first pair of infralabials in contact with each other; first four infralabials in contact with the first pair of chin shields; posterior pair of chin shields smaller, laterally in contact with fourth and fifth infralabials. Dorsal scales elliptical, keeled from the neck region onwards, 23 scale rows at midbody, those of the outer row enlarged, 25 scales round the anterior part of the body (one head length behind head), and 23 dorsal scale rows at posterior body (one head length before vent); ventrals 169 (plus one preventral), distinctly rounded laterally; subcaudals 91, unpaired, plus tail tip; cloacal entire. The ethanol-preserved holotype greyish brown above, the lower and posterior head sides being paler; venter greyish cream, with the underside of the tail being somewhat darker and the chin region somewhat paler; infralabial and chin shields light greyish brown. Ventrals and subcaudals anteriorly and laterally darker. Variation. For scalation details of the paratypes see Table 3. In addition, the nuchals of the female paratype IEBR A.2018.9 are separated from each other behind the parietals by four small scales and those of the male paratype VNMN 0 6924 by two large, two medium sized and a small scale. Furthermore, in the paratype VNMN 0 6924 the posterior pair of chin shields on the left side is in contact with third and fourth infralabials laterally. The hemipenes are basally everted in the specimen VNMN 0 6924. Comparisons. Achalinus juliani sp. nov. can be differentiated from the remaining Achalinus representatives from Vietnam by having more subcaudals, more dorsal scale rows on anterior part of the body, more ventrals, more infralabials, and a longer internasal suture (see Tables 3, 5). Achalinus juliani sp. nov. differs from A. ater in having more dorsal scale rows in the anterior part of the body (25 versus 21–23) and more subcaudals (77–91 versus 47–70). Achalinus juliani sp. nov. differs from A. rufescens by having more infralabials (6 versus 5), more ventrals (163–179 versus 131–158), more subcaudals (77–91 versus 54–82), and more maxillary teeth. Achalinus juliani sp. nov. differs from A. spinalis by the internasal suture being distinctly longer than that between the prefrontals (versus as long as or shorter), more dorsal scale rows in the anterior part of the body (25 versus 21–24), more subcaudals (77–91 versus 39–67), by lacking a black mid-dorsal line, and by having more maxillary teeth. Achalinus juliani sp. nov. differs from A. formosanus by having the internasal suture distinctly longer than prefrontal suture (versus internasal suture almost as long as prefrontal suture), by the loreal not being fused with prefrontal, fewer dorsal scale rows (25–23–23 versus 25–29 – 25–27–25), more maxillary teeth (28 versus 14–17), and by lacking a black mid-dorsal line; in addition, Achalinus juliani sp. nov. can be distinguished from A. f. formosanus by having more subcaudals (77–91 versus 61–83), and from A. f. chigirai by having fewer subcaudals (77–91 versus 96–97). Achalinus juliani sp. nov. differs from A. hainanus by having 6 versus 5 infralabials, 2 versus 1 anterior temporal, more dorsal scale rows in the anterior part of the body (25 versus 23), and more subcaudals (77–91 versus 67–69). Achalinus juliani sp. nov. differs from A. jinggangensis by loreal not being fused with prefrontal, having more ventrals (163–179 versus 156–164), more subcaudals (77–91 versus 51–64), and more maxillary teeth. Achalinus juliani sp. nov. differs from A. meiguensis by mental being separated from anterior chin shields, internasal not fused to prefrontal, by different dorsal scale row counts (25–23–23 versus 21–23 – 19–23 – 19), by having more subcaudals (77–91 versus 39–62), and by having more maxillary teeth. Achalinus juliani sp. nov. differs from A. niger by the internasal suture being distinctly longer than that between the prefrontals (versus almost as long as or shorter), fewer midbody dorsal scale rows (23 versus 25), more subcaudals (77–91 versus 52–72), and keeled body scales (versus smooth on anterior part of body). Achalinus juliani sp. nov. differs from A. werneri by the internasal suture being distinctly longer than that between the prefrontals (versus almost as long as), and by lacking a black mid-dorsal line and a dark subcaudal streak. Etymology. We name this species after Julian L. Ziegler. As common name we propose Julian’s Burrowing Snake. Distribution. The new species currently is only known from two localities within Cao Bang Province, northeastern Vietnam (Fig. 12). Natural history. Specimens were found between 20:00 and 22:00 h on forest paths. The surrounding habitat was secondary forest of large, medium and small hardwoods mixed with shrubs and vines. Air temperature at the sites were 25.4–32.6 o C and relative humidity 65–80%. The new species was found in different habitat types: lowland forest in Phia Oac-Phia Den National Park and limestone karst forest in Ha Lang District, at elevations from 470 to 1460 m above sea level.

Achalinus timi sp. nov. (Figs. 6–7) Holotype. IEBR A.2018.10 (Field no. PA.180), adult male, from forest within the Copia Nature Reserve, near Hua Ty Village (21°20.105’N, 103°35.860’E), Co Ma Commune, Thuan Chau District, Son La Province, northern Vietnam, collected by A.V. Pham on 12 May 2014 at an elevation of ca. 1470 m above sea level. Diagnosis. A species of the genus Achalinus, characterized by a combination of the following characters: 1) maxillary teeth 27; 2) suture between the internasals distinctly longer than that between the prefrontals; 3) loreal fused with prefrontal on each side, with the prefrontal extending towards the supralabials; 4) dorsal scales in 25–25–23 rows, keeled; 5) ventrals 170+1; 6) subcaudals 72, unpaired; 7) a total length of at least 177.9 mm in males (with a tail length of 37.9 mm and a tail/total length ratio of 0.21); 8) dorsum in preservative reddish to greyish brown above, with wide portion of the vertebral region being distinctly darker; the lower head sides are somewhat paler; infralabial and chin shields light greyish brown; venter greyish cream, with the underside of the tail being somewhat darker and the chin region somewhat paler. Description of holotype. Total length 177.9 mm (SVL 140 mm, TaL 37.9 mm); tail long, tail/total length ratio 0.21; body slender, cylindrical; head length 7.8 mm (from tip of snout to posterior margin of parietal); head slightly distinct from neck, dorsally covered with large shields; eye small, with vertically subelliptic pupil; left maxilla with at least 27 equally sized and curved teeth. Rostral small, triangular, not visible from above; suture between the internasals (1.7 mm) longer than that between the prefrontals (0.8 mm); nostril in the anterior part of the nasal; frontal pentagonal, slightly broader than long, pointed backwards, much shorter than the parietals; parietals bordered each by an elongated nuchal, nuchals separated from each other behind parietals by two small scales; second pair of nuchals about half the size than first pair; loreal lacking, prefrontals stretch towards the supralabials; one supraocular; two anterior temporals, only the smaller, upper one in contact with eye, and two elongated posterior temporals; supralabials six, the first smallest, fourth and fifth in contact with the eye, sixth longest; one mental, followed by six infralabials; first pair of infralabials in contact with each other; first three infralabials in contact with the first pair of chin shields; posterior pair of chin shields smaller, laterally in contact with fourth and fifth infralabials. Dorsal scales elliptical, keeled from the neck region onwards, in 25 rows at the anterior part of the body (one head length behind head), 25 scale rows at midbody, the outer row enlarged, and 23 rows at posterior body (one head length before vent); ventrals 170 (plus one preventral) distinct, laterally rounded; subcaudals 72, unpaired; cloacal entire. The ethanol-preserved holotype is reddish to greyish brown above, with a wide portion of the vertebral region being distinctly darker; the lower head sides somewhat paler; venter greyish cream, with the underside of the tail being somewhat darker and the chin region somewhat paler; infralabial and chin shields light greyish brown. Comparisons. Achalinus timi sp. nov. lacks a separate loreal scale, which is fused with the prefrontal on each side, with the prefrontal extending towards the supralabials; all remaining Achalinus species known at time to occur in Vietnam (A. ater, A. juliani, A. rufescens, and A. spinalis) have a loreal being separated from the prefrontal by a suture, which is also the case in most other Achalinus species (A. hainanus, A. meiguensis, A. niger, and A. werneri) which thus can be easily distinguished from Achalinus timi sp. nov. Achalinus timi sp. nov. further differs from A. formosanus, A. jinggangensis, A. meiguensis, A. rufescens, and A. spinalis by having more maxillary teeth. For details and further distinguishing characters see Table 5. Besides different maxillary teeth counts, Achalinus timi sp. nov. can be distinguished from the two subspecies of A. formosanus as follows: from A. f. formosanus by having the internasal suture distinctly longer than prefrontal suture (versus internasal suture almost as long as prefrontal suture) and 25–25–23 versus 29–27–25 dorsal scale rows; and from A. f. chigirai by 23 versus 25 dorsal scale rows at posterior body and by having more ventrals and less subcaudals (170 versus 161–167 ventrals; 72 versus 96–97 subcaudals). Furthermore, Achalinus timi sp. nov. can be distinguished from A. jinggangensis by having 25 versus 23 dorsal scale rows at midbody, more ventrals and subcaudals (170 versus 156–164 ventrals; 72 versus 51–64 subcaudals, respectively). Etymology. We name this species after Tim N. Ziegler. As common name we propose Tim’s Burrowing Snake. Distribution. The new species currently is only known from the type locality in Son La Province, northwestern Vietnam (Fig. 12). Natural history. The male holotype of Achalinus timi sp. nov. was discovered at 10: 15 in the morning, as a road kill specimen. The surrounding habitat was secondary evergreen forest. Air temperature at the site was 25–30 o C and relative humidity 70–75%.