Research Article |
Corresponding author: Thomas Ziegler ( ziegler@koelnerzoo.de ) Academic editor: Johannes Penner
© 2023 Trung My Phung, Cuong The Pham, Truong Quang Nguyen, Hoa Thi Ninh, Huy Quoc Nguyen, Marta Bernardes, Son Thanh Le, Thomas Ziegler, Tao Thien Nguyen.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Phung TM, Pham CT, Nguyen TQ, Ninh HT, Nguyen HQ, Bernardes M, Le ST, Ziegler T, Nguyen TT (2023) Southbound – the southernmost record of Tylototriton (Amphibia, Caudata, Salamandridae) from the Central Highlands of Vietnam represents a new species. ZooKeys 1168: 193-218. https://doi.org/10.3897/zookeys.1168.96091
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A new species of the genus Tylototriton is described from Ngoc Linh Mountain, Kon Tum Province, in the Central Highlands of Vietnam based on integrative taxonomy, namely by combining molecular and morphological evidence. Tylototriton ngoclinhensis sp. nov. differs from all other congeners based on morphological data, allopatric distribution, and molecular divergence. In terms of genetic divergence, Tylototriton ngoclinhensis sp. nov. distinctly differs from the sister species T. panhai (6.77%) and from T. ngarsuensis (12.36%) based on the mitochondrial NADH dehydrogenase subunit 2 (ND2) gene. Tylototriton ngoclinhensis sp. nov. is a moderate sized and robust salamander species with large cephalic edges, parotoids, and vertebral ridge orange in coloration. The new taxon differs from its congeners by a combination of the following morphological characteristics: size medium (SVL 60.8–66.5 mm, TL 57.6–61.8 mm in males, and SVL 72.5–75.6 mm, TL 62.9–67.9 mm in females); head longer than wide; parotoids very prominent and enlarged, projecting backwards; tail length shorter than snout-vent length; vertebral ridge large, high and glandular in appearance; 14 large and distinct dorsolateral glandular warts; gular fold present; tips of fore and hind limbs overlapping when adpressed along the body; tips of fingers reaching between eye and nostril when foreleg is laid forward; dorsal surface and lateral sides of the head, upper and lower lips, dorsolateral glandular warts, vertebral ridge, the peripheral area of the cloaca and the ventral edge of the tail orange in coloration; the presence of a distinct black line extending from the posterior end of the eye towards the shoulder. Tylototriton ngoclinhensis sp. nov. is restricted to evergreen montane forests near water bodies on Ngoc Linh Mountain. We suggest that the new species should be classified as Endangered (EN) in the IUCN Red List. This new important discovery represents the eighth Tylototriton taxon described from Vietnam, and at the same time constitutes the southernmost distributional record for the whole genus in Asia.
Crocodile newt, ND2 gene, Ngoc Linh Mountain, Salamandridae, taxonomy, Tylototriton ngoclinhensis sp. nov.
The salamandrid genus Tylototriton Anderson, 1871, commonly known as crocodile newts, currently contains 38 species inhabiting montane forest areas throughout the Asian monsoon climate zone and is distributed across Asia, from eastern Himalayas, eastern Nepal, northern India, Bhutan, Myanmar, central to southern China (including Hainan Island), and southwards through Laos, Thailand, and Vietnam (
Remarkably, 15 new species have been described in the past five years (
In Vietnam, six species and seven taxa are currently known, Tylototriton anguliceps Le, Nguyen, Nishikawa, Nguyen, Pham, Matsui, Bernardes & Nguyen, 2015; T. pasmansi pasmansi Bernardes, Le, Nguyen, Pham, Pham, Nguyen & Ziegler, 2020; T. pasmansi obsti Bernardes, Le, Nguyen, Pham, Pham, Nguyen & Ziegler, 2020; T. sparreboomi Bernardes, Le, Nguyen, Pham, Pham, Nguyen & Ziegler, 2020; T. thaiorum Poyarkov, Nguyen & Arkhipov, 2021; T. vietnamensis Böhme, Schöttler, Nguyen & Köhler, 2005; and T. ziegleri Nishikawa, Matsui & Nguyen, 2013 (
During recent fieldwork in May 2022 a new Tylototriton population was discovered in Ngoc Linh Mountain, Kon Tum Province, Central Vietnam resembling the T. panhai phenotype I from Phu Luang Wildlife Sanctuary and Phu Ruea National Park, Loei Province, northeastern Thailand (see
A field survey was conducted in Ngoc Linh Nature Reserve, Kon Tum Province of the Central Highlands, Vietnam, on 22nd of May 2022. Crocodile newts were found on the forest floor between 9:00 and 16:00. After having been photographed in life, six specimens were anaesthetized and euthanized in a closed vessel with a piece of cotton wool containing ethyl acetate (
DNA from tissue samples of the preserved specimens were extracted using the Dneasy blood and tissue kit, Qiagen (California, USA). A fragment of a mitochondrial gene, the NADH dehydrogenase subunit 2 (ND2), was amplified by PCR master mix (Fermentas, Burlington, ON, Canada) using the primer pair, Sal_Nd2_F1 (5’- AAGCTTTTGGGCCCATACC-3’), Sal_Nd2_R1 (5’-GTTATAAATATGGAKLARGTTA-3’) (
For the phylogenetic analyses, 53 sequences of species of the genus Tylototriton were used in combination with a sequence of Pleurodeles waltl and Echinotriton chinhaiensis as outgroups according to
Samples of the Tylototriton species and other species used for DNA analyses in this study.
No. | Scientific name | Voucher number | Locality | GenBank number | Reference |
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1. | Tylototriton ngoclinhensis sp. nov. | IEBR A.5131 | Kon Tum Prov., Vietnam | LC575223 | This study |
2. | Tylototriton ngoclinhensis sp. nov. | IEBR A.5130 | Kon Tum Prov., Vietnam | LC575221 | This study |
3. | Tylototriton ngoclinhensis sp. nov. | IEBR A.5133 | Kon Tum Prov., Vietnam | LC575222 | This study |
4. | T. anguliceps | NUOL 00420 | Viengphoukha, Luang Namtha, Laos | KT304301 |
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5. | T. anhuiensis | CIB 08042905-3 | Yuexi Co. Anhui Prov., China | KY800854 |
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6. | T. anhuiensis | CIB 08042905-4 | Yuexi Co. Anhui Prov., China | KY800855 |
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7. | T. asperrimus | CIB GX20080714 | Jinxiu Co., Guangxi Prov., China | KY800819 |
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8. | T. broadoridgus | CIB 200084 | Sangzhi Co., Hunan Prov., China | KY800837 |
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9. | T. dabienicus | HNNU1004-024 | Shangcheng Co., Henan Prov., China | KC147812 |
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10. | T. dabienicus | HNNU 1004-015 | Shangcheng Co., Henan Prov., China | KC147811 |
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11. | T. dabienicus | HNNU 1004-026 | Shangcheng Co., Henan Prov., China | KY800869 |
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12. | T. daloushanensis | GZNU 20060626002 | Suiyang Co., Guizhou Prov., China | JF825872 |
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13. | T. daloushanensis | GZNU 20060626001 | Suiyang Co., Guizhou Prov., China | FJ415600 |
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14. | T. hainanensis | CIB 20081048 | Mt. Diaoluo, Hainan Prov., China | KC147817 |
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15. | T. himalayanus | CIB 201406246 | Mai Pokhari, Illam, Mechi, Nepal | KT765173 |
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16. | T. kweichowensis | CIB Wg20080818014 | Bijie City, Guizhou Prov., China | KY800823 |
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17. | T. liuyangensis | CIB 110601F06 | Liuyang City, Hunan Prov., China | KY800875 |
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18. | T. maolanensis | CIB ML20180427003 | Libo Co., Guizhou Prov., China | MK820701 |
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19. | T. maolanensis | CIB ML20180427004 | Libo Co., Guizhou Prov., China | MK820702 |
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20. | T. maolanensis | GZNU 200706050101 | Leishan Co., Guizhou Prov., China | FJ415596 |
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21. | T. maolanensis | GZNU 200706050102 | Leishan Co., Guizhou Prov., China | JF825868 |
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22. | T. ngarsuensis | LSUHC13762 | Shan State, Myanmar | MH836585 |
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23. | T. notialis | FMNH: HERP:271120 | Boualapha, Khammouan, Laos | HM462061 |
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24. | T. panhai | NUOL 00424 | Botene, Xaignabouli, Laos | KT304309 |
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25. | T. panhai | NUOL 00425 | Botene, Xaignabouli, Laos | KT304311 |
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26. | T. panhai | NUOL 00421 | Botene, Xaignabouli, Laos | KT304310 |
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27. | T. pasmansi | IEBR 4466 (Holotype) | Da Bac, Hoa Binh Prov., Vietnam | MT210166 |
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28. | T. pasmansi | IEBR:4467 | Da Bac, Hoa Binh Prov., Vietnam | MT210167 |
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29. | T. podichthys | NCSM 77725 | Phoukhoun, Luang Phabang, Laos | KT304295 |
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30. | T. pseudoverrucosus | CIB WCG2012003 | Ningnan Co., Liangshanyizu State, Sichuan Prov., China | KY800861 |
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31. | T. pulcherrimus | KUHE:46406 | Pet Trade | KY800880 |
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32. | T. shanjing | CIB 980004 | Baoshan City, Yunnan Prov., China | KY800831 |
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33. | T. shanorum | KUHE 42348 | Shan State, Myanmar | AB769544 |
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34. | T. sini | SYS a008354 | Mt Yunkai, Guangdong Prov., China | OK539836 |
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35. | T. sparreboomi | IEBR 4477 | Sin Ho, Lai Chau Prov., Vietnam | MT210163 |
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36. | T. taliangensis | CIB GG200110183 | Shimian Co., Yan’an City, Sichuan Prov., China | KC147819 |
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37. | T. thaiorum | ZMMU A-7577 | Pu Hoat NR, Nghe An Prov., Vietnam | MW883478 |
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38. | T. tongziensis | CIB WB2020081511 | Tongzi Co., Guizhou Prov., China | OK349411 |
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39. | T. tongziensis | CIB TZ20160714002 | Tongzi Co., Guizhou Prov., China | OK349413 |
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40. | T. tongziensis | TZ20160714010 | Tongzi Co., Guizhou Prov., China | OK349414 |
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41. | T. tongziensis | CIB WB2020202 | Tongzi Co., Guizhou Prov., China | OK349415 |
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42. | T. uyenoi | KUHE:19147 | Doi Suthep, Chiang Mai Prov., Thailand | AB830733 |
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43. | T. verrucosus | CIB-TSHS1 | Longchuan Co., Dehong State, Yunnan Prov., China | KY800847 |
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44. | T. wenxianensis | CIB 2010123101 | Pingwu Co., Gansu Prov., China | KY800867 |
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45. | T. wenxianensis | CIB 2010123102 | Pingwu Co., Gansu Prov., China | KY800868 |
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46. | T. yangi | KUHE:42282 | Pet Trade | KY800887 |
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47. | T. ziegleri | VNMN 3390 | Quan Ba, Ha Giang Prov., Vietnam | KY800889 |
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48. | T. liuyangensis | CSUFT20100108 | Liuyang City, Hunan Prov., China | KJ205598 |
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49. | T. phukhaensis | CUMZ-A-7717 | DPKNP, Nan Prov., Thailand | MN912573 |
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50. | T. sparreboomi | IEBR 4477 | Sin Ho, Lai Chau Prov., Vietnam | MT210163 |
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51. | T. vietnamensis | IEBR A.2014.44 | Mau Son, Loc Binh, Lang Son Prov., Vietnam | KX609962 |
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52. | T. vietnamensis | IEBR A.2014.43 | Hoanh Bo, Quang Ninh Prov., Vietnam | KX609961 |
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53. | T. vietnamensis | IEBR A.0701 | Mau Son, Lang Son Prov., Vietnam | KY800873 |
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54. | Echinotriton chinhaiensis | CIB ZHJY2 | Zhenhai Co., Zhejiang Prov., China | KY800892 |
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55. | Pleurodeles waltl | - | Cadiz, Andalusia, Spain | EU880330 |
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CHROMAS PRO software (Technelysium Pty Ltd., Tewantin, Australia) was used to edit the sequences, which were aligned using MAFFT v. 7 (
A total of 27 morphological characters were measured following
Morphological comparisons between the new taxon and its congeners were based on the specimens examination and the following literature:
Aligned, combined sequences yielded a total of 1,035 characters. Of 1,035 nucleotide sites, 416 were variable and 336 were parsimony informative within the in-group. The ML and Bayesian analyses produced topologies with -lnL = 7442.0236 and 7521.862, respectively. Phylogenetic analyses employing ML and BI methods yielded slightly different topologies only among referenced species, and only the ML tree is presented in Fig.
Monophyly of Tylototriton with respect to the outgroup species was fully supported (each 100% support in ML bootstrap value and Bayesian posterior probability) and samples were split into four major clades named A, B, C, and D.
Monophyly of clade A, including T. maolanensis Li, Wei, Cheng, Zhang & Wang, 2020; T. wenxianensis Fei, Ye & Yang, 1984; T. anhuiensis Qian, Sun, Li, Guo, Pan, Kang, Wang, Jiang, Wu & Zhang, 2017; T. dabienicus Chen, Wang & Tao, 2010; T. tongziensis Li, Liu, Shi, Wei & Wang, 2022; T. broadoridgus Shen, Jiang & Mo, 2012 T. daloushanensis Zhou, Xiao, and Luo, 2022; and T. liuyangensis Yang, Jiang, Shen, and Fei, 2014, was well supported (100% and 92% support).
The undescribed species of Tylototriton from Kon Tum Province, Vietnam was clustered in clade B with T. panhai Nishikawa, Khonsue, Pomchote & Matsui, 2013 from Laos and T. vietnamensis from Vietnam, but the support was not significant, particularly for Bayesian posterior probability (0.83 and 60%) (Table
Mean uncorrected (p) distance (%) among 1,035 bp fragments of ND2 of the genus Tylototriton and related taxa.
1. | 2. | 3. | 4. | 5. | 6. | 7. | 8. | 9. | 10. | 11. | 12. | 13. | 14. | 15. | 16. | 17. | 18. | 19. | 20. | 21. | 22. | 23. | 24. | 25. | 26. | 27. | 28. | 29. | 30. | 31. | 32. | ||
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1. |
Tylototriton ngoclinhensis
sp. nov. |
0.00–0.31 | |||||||||||||||||||||||||||||||
2. | T. anguliceps | 10.08–11.55 | - | ||||||||||||||||||||||||||||||
3. | T. anhuiensis | 10.19–10.64 | 10.82 | - | |||||||||||||||||||||||||||||
4. | T. asperrimus | 9.88–10.64 | 11.30 | 8.31 | - | ||||||||||||||||||||||||||||
5. | T. broadoridgus | 9.54–9.73 | 10.92 | 3.67 | 8.50 | - | |||||||||||||||||||||||||||
6. | T. dabienicus | 9.23–10.03 | 11.88–12.08 | 3.86–3.96 | 8.99–9.08 | 3.38–3.48 | 0.10–0.29 | ||||||||||||||||||||||||||
7. | T. daloushanensis | 9.54–9.73 | 11.69 | 4.64 | 9.28 | 4.25 | 4.44–4.45 | - | |||||||||||||||||||||||||
8. | T. hainanensis | 7.72–8.21 | 9.95 | 7.83 | 5.02 | 7.63 | 8.79–8.89 | 9.18 | - | ||||||||||||||||||||||||
9. | T. himalayanus | 8.64–9.12 | 6.86 | 10.82 | 11.50 | 10.43 | 11.01–11.21 | 11.01 | 9.76 | - | |||||||||||||||||||||||
10. | T. kweichowensis | 8.64–9.12 | 6.18 | 9.86 | 10.14 | 8.99 | 10.24–10.34 | 10.63 | 8.60 | 5.31 | - | ||||||||||||||||||||||
11. | T. liuyangensis | 8.62–9.12 | 10.14–10.24 | 7.25–7.34 | 8.70–8.79 | 7.05–7.15 | 7.25–7.44 | 7.44–7.54 | 7.73–7.83 | 10.05–10.14 | 9.47–9.57 | 0.10 | |||||||||||||||||||||
12. | T. maolanensis | 9.57–11.55 | 10.72–11.40 | 3.48–3.57 | 8.60 | 2.80–3.00 | 3.38–3.67 | 4.35–4.44 | 8.21–8.31 | 10.63–11.11 | 9.66–9.95 | 7.05–7.25 | 0.00–2.13 | ||||||||||||||||||||
13. | T. ngarsuensis | 12.04–12.36 | 7.74 | 12.05 | 12.34 | 11.56 | 12.34–12.54 | 12.44 | 10.97 | 6.46 | 6.95 | 11.36–11.46 | 11.46–11.85 | - | |||||||||||||||||||
14. | T. notialis | 9.26–9.73 | 10.63 | 8.50 | 4.93 | 8.41 | 9.18–9.28 | 9.47 | 4.83 | 10.63 | 9.86 | 8.70–8.79 | 8.60–8.70 | 11.75 | - | ||||||||||||||||||
15. | T. panhai | 6.77–6.99 | 12.95 | 9.57 | 11.11 | 8.37 | 9.47–9.57 | 10.24 | 9.66 | 12.27 | 10.72 | 9.37–9.47 | 9.86–10.14 | 13.22 | 10.34 | 0.00 | |||||||||||||||||
16. | T. pasmansi | 9.57–10.33 | 10.40–10.69 | 8.41–8.50 | 3.38–3.48 | 8.31–8.41 | 9.28–9.37 | 9.57–9.66 | 4.83 | 11.21–11.69 | 9.95–10.24 | 8.31–8.41 | 8.89–9.08 | 12.44–12.93 | 4.64–4.93 | 10.43–10.53 | 0.48 | ||||||||||||||||
17. | T. phukhaensis | 11.11–11.38 | 4.29 | 11.40 | 11.99 | 11.11 | 11.89–12.09 | 12.28 | 10.62 | 7.02 | 6.34 | 10.33–10.43 | 11.11–11.89 | 9.01 | 11.01 | 12.87 | 12.09–12.38 | ||||||||||||||||
18. | T. podichthys | 9.88–10.15 | 5.31 | 9.86 | 10.82 | 9.95 | 10.63–10.82 | 10.14 | 10.14 | 6.76 | 6.09 | 10.05–10.14 | 10.05–10.43 | 8.33 | 10.72 | 12.27 | 11.21–11.50 | 6.24 | |||||||||||||||
19. | T. pseudoverrucosus | 9.26–9.54 | 8.50 | 9.47 | 9.66 | 9.28 | 9.47–9.66 | 9.66 | 8.50 | 7.05 | 5.99 | 9.80–9.18 | 9.28–9.86 | 8.72 | 9.28 | 10.43 | 9.37–9.86 | 8.38 | 7.25 | ||||||||||||||
20. | T. pulcherrimus | 9.73–10.15 | 3.96 | 9.55–9.95 | 10.92 | 9.86 | 10.34–10.53 | 12.24 | 9.47 | 6.18 | 5.41 | 9.76–9.86 | 9.76–10.14 | 6.95 | 10.24 | 12.08 | 10.50–11.20 | 4.39 | 3.67 | 6.67 | |||||||||||||
21. | T. shanjing | 11.25–11.69 | 4.35 | 10.43 | 11.40 | 10.24 | 10.82–11.01 | 10.63 | 10.24 | 6.28 | 5.99 | 10.53–10.63 | 9.95–10.72 | 7.35 | 11.01 | 12.66 | 12.08–11.79 | 5.36 | 4.25 | 7.73 | 2.51 | ||||||||||||
22. | T. shanorum | 9.88–10.33 | 6.67 | 10.82 | 11.30 | 10.14 | 10.92–11.11 | 11.40 | 9.76 | 5.02 | 5.89 | 10.24–10.34 | 10.24–10.63 | 1.76 | 10.63 | 12.37 | 11.21–11.69 | 7.60 | 7.44 | 7.92 | 6.18 | 6.57 | |||||||||||
23. | T. sini | 7.72–8.81 | 9.57 | 8.21 | 5.22 | 8.60 | 8.99–9.08 | 8.79 | 3.19 | 9.47 | 8.89 | 7.83–7.92 | 8.31–8.6 | 10.77 | 5.51 | 10.34 | 5.12–5.60 | 10.62 | 9.66 | 8.50 | 9.28 | 10.24 | 9.57 | ||||||||||
24. | T. sparreboomi | 8.64–10.03 | 10.72–10.92 | 7.92–8.12 | 4.15 | 8.02–8.21 | 8.50–8.70 | 9.28–9.47 | 4.44–4.64 | 10.53–10.72 | 9.57–9.76 | 8.60–8.79 | 8.50–8.79 | 11.95–12.14 | 4.73 | 9.95–10.14 | 3.96–4.25 | 11.31–11.50 | 10.92–11.11 | 9.08–9.28 | 10.34–10.53 | 11.40–11.59 | 10.53–10.72 | 4.83–5.02 | 0.19 | ||||||||
25. | T. taliangensis | 9.42–9.85 | 8.41 | 8.99 | 9.28 | 9.28 | 9.08–9.28 | 9.47 | 8.60 | 7.54 | 6.47 | 8.99–9.08 | 8.89–9.57 | 9.11 | 9.47 | 10.53 | 9.76–10.05 | 8.58 | 7.73 | 2.71 | 7.25 | 7.34 | 8.12 | 8.79 | 9.28–9.47 | ||||||||
26. | T. thaiorum | 8.64–9.12 | 10.72 | 8.21 | 5.31 | 7.92 | 8.70–8.79 | 8.99 | 4.64 | 10.53 | 9.95 | 8.50–8.60 | 8.12–8.21 | 12.05 | 2.80 | 10.24 | 4.64–4.93 | 10.82 | 10.72 | 8.89 | 10.24 | 11.01 | 10.92 | 5.89 | 4.64–4.83 | 9.08 | |||||||
27. | T. tongziensis | 8.33–9.12 | 10.05–10.14 | 2.80–2.90 | 7.83–7.92 | 2.61–2.71 | 2.61–2.80 | 3.67 | 7.44–7.54 | 9.95–10.05 | 8.99–9.08 | 6.47–6.67 | 2.42–2.80 | 10.87–10.97 | 7.92–8.02 | 9.18–9.28 | 8.12–8.21 | 10.43–10.53 | 9.37–9.47 | 8.12–8.21 | 9.08–9.18 | 9.86–9.95 | 9.66–9.76 | 7.44–7.54 | 7.73–8.02 | 8.02–8.12 | 7.44–7.54 | 0.00–0.10 | |||||
28. | T. uyenoi | 12.96–13.23 | 7.25 | 12.75 | 12.85 | 12.75 | 13.04–13.14 | 13.24 | 12.46 | 8.50 | 8.02 | 12.56–12.66 | 12.56–12.75 | 10.09 | 13.04 | 14.40 | 13.04–13.33 | 7.21 | 8.21 | 9.95 | 6.76 | 7.25 | 9.08 | 12.27 | 13.62–13.82 | 9.95 | 12.66 | 11.59–11.69 | |||||
29. | T. verrucosus | 10.94–11.08 | 4.35 | 10.63 | 11.50 | 10.24 | 10.82–11.01 | 10.82 | 10.24 | 6.47 | 5.70 | 10.24–10.34 | 9.95–10.72 | 6.95 | 11.01 | 12.56 | 11.79–12.08 | 4.97 | 4.06 | 7.54 | 2.13 | 1.16 | 6.18 | 10.05 | 11.40–11.59 | 7.44 | 11.01 | 9.86–9.95 | 7.25 | ||||
30. | T. vietnamensis | 11.11–11.38 | 13.04–13.17 | 10.64–10.84 | 10.82–11.04 | 10.84–10.92 | 10.44–10.92 | 11.14–11.21 | 10.72–10.94 | 12.36–12.75 | 11.65–11.98 | 10.64–10.94 | 10.53–11.14 | 12.97–13.17 | 11.35–11.55 | 10.54–11.24 | 11.59–12.75 | 13.48–13.74 | 12.95–13.07 | 11.45–11.65 | 11.79–12.06 | 12.57–12.66 | 11.85–12.06 | 11.01–11.45 | 10.54–10.82 | 10.94–11.14 | 11.55–11.75 | 9.83–10.14 | 14.78–14.99 | 12.08–12.06 | 0.00 | ||
31. | T. wenxianensis | 9.88–10.33 | 10.72 | 4.15 | 8.70 | 4.25 | 4.73–4.83 | 3.77 | 8.70 | 10.53 | 9.76 | 6.96–7.05 | 4.15–4.25 | 12.05 | 8.89 | 10.14 | 9.47–9.57 | 11.11 | 9.57 | 9.28 | 9.08 | 9.86 | 11.11 | 9.08 | 9.08–9.28 | 8.60 | 8.60 | 3.57–3.67 | 12.46 | 9.66 | 10.23–10.24 | 0.00 | |
32. | T. yangi | 11.73–12.00 | 4.15 | 10.14 | 10.14 | 10.05 | 10.82–11.01 | 10.43 | 9.57 | 6.57 | 6.18 | 9.37–9.47 | 9.57–10.34 | 7.35 | 10.24 | 12.46 | 10.53–10.82 | 5.56 | 5.12 | 7.44 | 3.77 | 4.35 | 6.38 | 8.79 | 9.95–10.14 | 7.83 | 10.34 | 9.18–9.28 | 7.54 | 3.96 | 11.96–12.16 | 9.66 | |
33. | T. ziegleri | 8.95–9.73 | 10.82 | 8.12 | 4.44 | 7.92 | 8.79–8.89 | 9.28 | 4.35 | 10.92 | 9.18 | 8.41–8.50 | 8.41–8.50 | 12.05 | 4.93 | 9.95 | 4.83–5.12 | 11.21 | 10.72 | 9.28 | 10.43 | 11.21 | 10.92 | 5.22 | 4.35 | 9.47 | 4.83 | 7.54–7.63 | 13.33 | 11.21 | 10.94–11.21 | 8.79 | 10.05 |
Monophyly of clade C, including T. pasmansi; T. sparreboomi; T. asperrimus Unterstein, 1930; T. thaiorum; T. notialis Stuart, Phimmachak, Sivongxay & Robichaud, 2010; T. sini Lyu, Wang, Zeng, Zhou, Qi, Wan & Wang, 2021; T. hainanensis Fei, Ye & Yang, 1984 and T. ziegleri, was well supported (100% and 98% support).
Monophyly of clade D, including T. verrucosus Anderson, 1871; T. shanjing Nussbaum, Brodie & Yang, 1995; T. podichthys Phimmachak, Aowphol & Stuart, 2015; T. pulcherrimus Hou, Zhang, Li & Lu, 2012; T. uyenoi Nishikawa, Khonsue, Pomchote & Matsui, 2013; T. phukhaensis Pomchote, Khonsue, Thammachoti, Hernandez, Peerachidacho, Suwannapoom, Onishi & Nishikawa, 2020; T. anguliceps; T. yangi Hou, Zhang, Zhou, Li & Lu, 2012; T. shanorum Nishikawa, Matsui & Rao, 2014; T. ngarsuensis Grismer, Wood, Quah, Thura, Espinoza, Grismer, Murdoch & Lin, 2018; T. himalayanus Khatiwada, Wang, Ghimire, Vasudevan, Paudel & Jiang, 2015; T. kweichowensis Fang & Chang, 1932; T. taliangensis Liu, 1950 and T. pseudoverrucosus Hou, Gu, Zhang, Zeng & Lu, 2012, was also strongly supported (100% and 97% support).
There is a clear genetic distance between clade A and the remaining clades B, C, and D: from 8.33% (Tylototriton sp. from Kon Tum Province, Vietnam and T. tongziensis) to 11.55% (Tylototriton sp. from Kon Tum Province, Vietnam and T. maolanensis); from 7.44% (T. sini and T. tongziensis) to 9.66% (T. pasmansi and T. daloushanensis); from 8.02 (T. daloushanensis and T. uyenoi) to 13.24% (T. tongziensis and T. taliangensis), respectively. The genetic distance between clade B and the two clades C and D ranges from 7.72% (Tylototriton sp. from Kon Tum Province, Vietnam and T. thaiorum) to 11.79% (T. vietnamensis and T. thaiorum); from 8.64% (Tylototriton sp. from Kon Tum Province, Vietnam and T. pseudoverrucosus) to 14.99% (T. vietnamensis and T. uyenoi) and clear genetic distances between clades C and D: from 8.5% (T. hainanensis and T. pseudoverrucosus) to 13.82 (T. sparreboomi and T. uyenoi).
The Tylototriton population from Kon Tum Provice, Vietnam exhibited distinct genetic distances from the thirty-three examined species of Tylototriton, with uncorrected p-distance of 6.77% (compared to T. panhai from Laos) to 12.36% (compared to T. ngarsuensis), being higher than that between some pairs of sister species, for example, T. verrucosus vs T. shanjing (1.16%), and T. maolanensis vs T. tongziensis (2.42%).
Furthermore, the population of Tylototriton sp. from Kon Tum Province, Vietnam was also clearly separated morphologically from all the other congeners, including its sister species T. panhai, which is in congruence with the genetic separation. Thus, we describe the new Tylototriton population from Kon Tum Province, Vietnam as a new species.
Holotype. IEBR A.5130 (Field No KT 2022.02), an adult male collected by T. M. Phung on 22 May 2022 in the montane evergreen forests of Ngoc Linh Natural Reserve, Dak Glei District, Kon Tum Province, Central Vietnam at 1.854 m a.s.l. Paratypes. IEBR A.5131, A.5132 (Field No KT 2022.01, KT 2022.5), two adult males and IEBR A.5133, A.5134 (Field No KT2022.03, KT 2022.6), two adult females, collected by T. M. Phung; IEBR A.5135 (Field No KT 2022.4), an adult female, collected by S. T. Le on 20 May 2022, the same collection data as the holotype.
The specific epithet ngoclinhensis refers to the type locality of the new species, Ngoc Linh Mountain in the Central Highlands of Vietnam. As common names, we suggest Ngoc Linh Crocodile Newt (English), Cá cóc sần ngọc linh (Vietnamese).
The new species is assigned to the genus Tylototriton and the subgenus Yaotriton based on the results of the molecular phylogenetic analyses and the following combination of morphological attributes: rough skin covered with fine warts, the presence of dorsolateral bony ridges on the head; the presence of dorsolateral glandular warts on the body; quadrate spine absent (
A medium-sized male (SVL 66.5 mm, TL 59.5 mm). Head longer than wide (HW/HL 81.6%); head slightly concave on the top; snout short, truncate in dorsal view, slightly angular shaped in profile and protruding beyond lower jaw; nostril closer to the snout tip than to the eye; upper lip thick, fleshy and overlapping lower lip under the eye region; dorsolateral bony ridges on head prominent, moderately protruding, from above eye to above anterior end of parotoid, posterior ends relatively thick and scrolled inside; mid-dorsal ridge on head distinct and thin; parotoids enlarged, projecting backwards; tongue oval, attached to anterior floor of mouth, free laterally and posteriorly; vomerine teeth series in an inverted V-shape, converging anteriorly and reaching choanae; glandular vertebral ridge large, high, segmented tuberculate, extending from top of head to base of tail; rib nodules large, forming knob-like warts, distinctly isolated from each other, 14 on each side of body from axilla to base of tail; gular fold present.
Limbs comparatively long, and slender; length of forelimbs approximately equal to hind limbs; relative length of forelimb FORE/SVL ratio 39.0%, relative length of hind limb HIND/SVL ratio 38.1%; tips of forelimb and hind limb overlapping when adpressed along the body; tips of fingers reaching between eye and nostril when foreleg is laid forward; fingers and toes well developed, free of webbing; fingers four, comparative finger lengths 1FL<4FL<2FL<3FL; toes five, comparative toe lengths 1TL<5TL<2TL<4TL<3TL.
Tail length shorter than the snout-vent length (TL/SVL 89.5%); tail compressed laterally, the base relatively broad, tapering posteriorly, tail tip pointed; tail height less than the width at the tail base; dorsal fin fold relatively high; ventral side smooth. In general, the appearance of the tail is relatively low and flat.
Dorsal skin very rough, with small granules and larger warts on dorsal surfaces of head and dorsum, lateral sides of body and tail; ventral skin with tubercles shaped like transverse wrinkles; throat with numerous tiny flat tubercles; surfaces of head ridges and middorsal vertebral ridge rough; limbs dorsally with numerous tiny tubercles, volar and plantar surfaces of hands and feet with tiny grooves forming reticulated pattern; flattened outer metacarpal and metatarsal tubercles distinct on palms and soles, respectively. Cloacal region slightly swollen, vent as a longitudinal slit, vent edges with numerous small transverse folds.
In life, ground color of dorsal and ventral surfaces black; dorsal surface and lateral sides of head and lower lips to jaw angles, rib nodules, vertebral ridge, the peripheral area of the cloaca and the ventral edge of the tail orange; tips of fingers, toes and elbow orange-brown.
The specimen in preservative is blackish brown. The orange coloration in life has faded to pale yellow.
Males are probably smaller than females but sample size was small (n = 3) and thus needs confirmation based on further records in the future. The female cloacal slit is short and its inner cloacal walls have no papilla. The male has papilla on its inner cloacal wall and its cloaca presents a long slit.
The new species is currently known only from the Ngoc Linh Nature Reserve, Kon Tum Province, in the Central Highlands of Vietnam (Fig.
All specimens were collected during the day on the forest floor, under rotten trees or under moss, near a small rocky stream (Figs
Morphometric measurements of Tylototriton ngoclinhensis sp. nov. examined in this study are given in Table
Morphometric measurements (mm) of Tylototriton ngoclinhensis sp. nov. examined in this study.
Voucher | IEBR A.5130 Holotype | IEBR A.5131 Paratype | IEBR A.5132 Paratype | IEBR A.5133 Paratype | IEBR A.5134 Paratype | IEBR A.5135 Paratype |
---|---|---|---|---|---|---|
Sex | ♂ | ♂ | ♂ | ♀ | ♀ | ♀ |
SVL | 66.5 | 65.7 | 60.8 | 75.6 | 74.8 | 72.5 |
HL | 20.6 | 19.9 | 18.9 | 23.8 | 22.2 | 21.5 |
HW | 16.8 | 15.6 | 16.3 | 18.6 | 17.5 | 17.4 |
MHW | 18.5 | 18.4 | 17.9 | 20.1 | 19.5 | 19.4 |
PL | 11.5 | 11.4 | 11.2 | 13.5 | 12.1 | 12.4 |
PW | 5.7 | 5.8 | 5.3 | 5.9 | 5.9 | 5.8 |
PH | 5.9 | 6.3 | 5.2 | 6.5 | 6.2 | 6.1 |
EL | 4.8 | 4.4 | 4.4 | 5.2 | 4.9 | 4.9 |
EN | 4.2 | 4 | 3.9 | 4.8 | 4.6 | 4.5 |
IN | 5.5 | 5.7 | 5.4 | 6.4 | 6.6 | 6.2 |
IE | 8.4 | 8.2 | 8.5 | 9.8 | 9.5 | 9.4 |
LJL | 14.1 | 13.6 | 13.7 | 17.1 | 16.1 | 16.6 |
UEL | 2.5 | 2.6 | 2.2 | 2.8 | 2.5 | 2.6 |
HUM | 9.2 | 8.4 | 8.7 | 9.5 | 9.4 | 9.3 |
RAD | 16.7 | 15.6 | 15.8 | 17.6 | 17.3 | 17.2 |
FEM | 8.7 | 8.2 | 8.3 | 8.8 | 8.9 | 8.6 |
TIB | 16.6 | 15.9 | 16.8 | 17.8 | 18.1 | 17.2 |
FORE | 25.9 | 24 | 24.5 | 27.1 | 26.7 | 26.5 |
HIND | 25.3 | 24.1 | 25.1 | 26.6 | 27 | 26.2 |
TL | 59.5 | 57.6 | 61.8 | 67.9 | 62.9 | 66.2 |
TH | 7.2 | 7 | 7.5 | 8.2 | 7.2 | 7.6 |
CIL | 7.4 | 6.9 | 6.7 | 5.9 | 5.5 | 5.8 |
CIW | 4.9 | 4.6 | 4.3 | 3.7 | 3.5 | 3.5 |
WVr | 4.2 | 4.5 | 3.8 | 4.4 | 4.2 | 4.1 |
L5W | 3.2 | 3.1 | 2.7 | 3.5 | 3.3 | 3.4 |
AG | 35.4 | 34.5 | 31.7 | 41.4 | 39.4 | 37.8 |
TkL | 49.7 | 49.3 | 45.5 | 58.7 | 55.7 | 53.8 |
ToL | 126 | 123.3 | 122.6 | 143.5 | 137.7 | 138.7 |
We compared the new species with other members of the genus Tylototriton based on data obtained from the literature (Table
Morphological comparisons between Tylototriton ngoclinhensis sp. nov. with other members of the subgenus Yaotriton (morphological data obtained from
Species | TOL of males | TOL of females | Gular fold | Reach of finger tips when forelimbs stretched forward | Reach of tips of fore-and hind limbs when adpressed along body | Rib nodules shape | Vertebral ridge | Orange markings on the parotoid | Orange coloration on the rib nodules |
---|---|---|---|---|---|---|---|---|---|
Tylototriton ngoclinhensis sp. nov. | 122.6–126.0 | 137.7–143.5 | present | between the eye and nostril | overlapping | knob-like | segmented tuberculate | present | present |
T. anhuiensis | 118.9–145.7 | 103.8–165.4 | present | / | meeting | slightly flattened | not segmented | absent | absent |
T. asperrimus | 118.0-138.0 | 149.0–202.0 | present | reaching to the nostril or eye | meeting or overlapping | knob-like | not segmented | absent | absent |
T. broadoridgus | 110.4–140.3 | 138.9–162.5 | absent | anterior corner of eye | not touched | slightly flattened | not segmented | absent | absent |
T. dabienicus | 120.3–135.3 | 134.9–155.5 | present | anterior corner of eye | not touched | slightly flattened | not segmented | absent | absent |
T. daloushanensis | / | / | present | eyes to nostrils | overlapping | slightly flattened | not segmented | absent | absent |
T. hainanensis | 137.0–148.0 | 125.0–140.0 | present | eye | meeting or overlapping | slightly flattened | not segmented | absent | absent |
T. liuyangensis | 110.1–146.5 | 138.6–154.2 | present | eye | not touched | slightly flattened | not segmented | absent | absent |
T. lizhenchangi | 145.6–173.0 | 150.0–156.5 | present | Tip of snout | overlapping | slightly flattened | not segmented | absent | absent |
T. maolanensis | 151.0–172.0 | 142.7–170.5 | present | beyond the snout | overlapping | knob-like | not segmented | absent | absent |
T. notialis | 109.1–130.4 | 141.8 | present | / | / | knob-like | not segmented | absent | present |
T. panhai | 129.9–1603 | 160.0–166.8 | present | / | / | knob-like | not segmented | present | present |
T. pasmansi | / | 160.0 | present | eye | / | knob-like | not segmented | absent | absent |
T. sini | 118.4–124.5 | 144.5 | present | / | overlapping | knob-like | not segmented | absent | absent |
T. sparreboomi | / | / | present | nostril | / | knob-like | not segmented | absent | absent |
T. thaiorum | 116.1–138.0 | / | present | / | overlapping | knob-like, in irregular series | not segmented | absent | absent |
T. tongziensis | 120.5–135.1 | 123.5–127.6 | present | beyond the snout | overlapping | slightly flattened | not segmented | absent | absent |
T. vietnamensis | 113.0–121.8 | / | absent | / | / | slightly flattened | not segmented | absent | absent |
T. wenxianensis | 126.0–133.0 | / | present | nostril | meeting or overlapping | slightly flattened | not segmented | absent | absent |
T. ziegleri | / | / | present | / | overlapping | knob-like | segmented tuberculate | absent | absent |
Tylototriton ngoclinhensis sp. nov. differs from T. anhuiensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and tips of fore-and hind limbs overlapping when adpressed along the body (vs meeting); from T. asperrimus by having a smaller size in females (TOL 137.7–143.5 mm vs 149.0–202.0 mm), head longer than wide (vs head wider than long), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. broadoridgus by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and tips of fore and hind limbs overlapping when adpressed along the body (vs separated from each other); from T. dabienicus by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), tips of fore-and hind limbs overlapping when adpressed along the body (vs separated from each other), and finger tips reaching between eye and nostril when foreleg is laid forward (vs reaching anterior corner of eye); from T. daloushanensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on dorsolateral glandular warts (vs absent); from T. hainanensis by having a smaller size in males (TOL 122.6–126.0 mm vs 137.4–148.0 mm), head longer than wide (vs head wider than long), different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange marking on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and finger tips reaching between eye and nostril when foreleg laid forward (vs reaching eye); from T. joe by having larger size (TOL 122.6–126.0 mm vs 108–115 mm in males and 137.7–143.5 mm vs 121–128 mm in females), ventral edge of the tail orange, and tip of fingers, toes and elbow orange-brown (vs whole body dark brown but brownish tip of toes and tip of tail in some individuals); from T. liuyangensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), tips of fore-and hind limbs overlapping when adpressed along body (vs separated from each other), and finger tips reaching between eye and nostril when foreleg laid forward (vs reaching eye); from T. lizhenchangi by having a smaller size (TOL 122.6–126.0 mm vs 145.6–173.0 mm in males, TOL 137.7–143.5 mm vs 150.0–156.5 mm in females), different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange coloration on the dorsolateral glandular warts (vs absent), tips of fingers reaching between eyes and nostrils when foreleg laid forward (vs reaching to tip of snout), and the presence of orange markings on the parotoids (vs absent); from T. maolanensis by having a smaller size (TOL 122.6–126.0 mm vs 151.0–172.0 mm in males, TOL 137.7–143.5 mm vs 142.7–170.5 mm in females), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. notialis by different color pattern on head and vertebral ridge (orange vs dark brown), lower lip with orange marking (vs brown), and dorsolateral glandular warts and vertebral ridge distinctively large (vs small); from T. panhai by having a different ground color (black vs dark brown to brown), the presence of a distinct black line extending from the back of the eye towards the shoulder (vs less evident brownish line to absent line), dorsal edges of tail black (vs yellow, orange to reddish brown). Since T. panhai is the closest known taxon to Tylototriton ngoclinhensis sp. nov., additional morphological comparisons were made between the two species, especially between topotypic T. panhai type I and type II from Laos. Tail height was the only character (with n ≥ 3) that showed variation, presenting higher values both in males and in females (Fig.
Comparison of average tail heights (mm) between Tylototriton ngoclinhensis sp. nov and T. panhai. The left side shows data for males (A) of Tylototriton ngoclinhensis sp. nov. (n = 3; own data) and T. panhai (n = 15; taken from
The new species is distinguished from T. pasmansi by having rib nodules distinctively large (vs small), the presence of orange markings on the parotoid (vs absent), and the presence of orange colorations of the dorsolateral glandular warts (vs absent); from T. sini by different color pattern on head and vertebral ridge (orange vs dark brown), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and dorsolateral glandular warts distinct and large (vs small); from T. sparreboomi by different color pattern on head and vertebral ridge (orange vs dark brown), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and tips of fingers reaching between eye and nostril when foreleg laid forward (vs reaching nostril); from T. thaiorum by having head longer than wide (vs head wider than long), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. tongziensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. vietnamensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and the presence of gular fold (vs absent); from T. wenxianensis by different shape of dorsolateral glandular warts (knob-like vs slightly flattened), the presence of orange markings on the parotoids (vs absent), the presence of orange coloration on the dorsolateral glandular warts (vs absent), and finger tips reaching to between eyes and nostrils (vs reaching nostril); from T. ziegleri by having head longer than wide (vs head wider than long), different color pattern on head and vertebral ridge (orange vs dark brown), the presence of orange markings on the parotoids (vs absent), and the presence of orange coloration on the dorsolateral glandular warts (vs absent); from T. anguliceps, T. himalayanus, T. kachinorum, T. ngarsuensis, T. panwaensis, T. phukhaensis, T. podichthys, T. pulcherrimus, T. pseudoverrucosus, T. shanorum, T. shanjing, T. uyenoi, T. umphangensis, and T. verrucosus by having limbs and tail edges dark brown except for the orange digits, palms, and soles (vs limbs and tail edges uniformly orange or pale brown in the latter), the presence of a black line extending from the back of the eye towards the shoulder (vs absent); and from T. kweichowensis and T. yangi by different color pattern on tail (black vs uniformly orange in the latter), and ventral side dark brown (vs ventrolateral sides yellow in the latter).
New species are being continuously described within the genus Tylototriton. A total of 12 new species has been recorded during the last three years alone, from China, Thailand and northern Vietnam (
This is also the first time that a crocodile newt species is recorded from the Central Highlands of Vietnam. Occurring at an elevation more than 1,800 m, this discovery sets an altitudinal record for the genus in the country, with former ranges distributed between 250 m (for T. vietnamensis) and 1,740 m (for T. anguliceps). Furthermore, this discovery represents the southernmost distribution range of the genus known to date. The new species is located approximately 370 air km distant from the nearest T. notialis population from Khammouan Province, Laos. Ngoc Linh Mountain is located on the northwestern border of the Kon Tum Massif and is the highest peak in Central Vietnam with 2,598 m (
Ngoc Linh Nature Reserve has been established in 1986 with an initial protected area of 41,424 hectares and represents a key biodiversity area for the threatened Golden-winged Laughingthrush, Trochalopteron ngoclinhense, listed as Endangered in the IUCN Red List, as well as for other rare species like the Truong Son Muntjac, Muntiacus truongsonensis, Rhesus Macaque, Macata mulatta, and the Stump-tailed Macaque, Macaca arctoides (
Together with T. panhai, T. ngoclinhensis is the only known species within the subgenus Yaotriton to present characteristic colorful markings on the body. Although there is a high phenotypic variation recorded for T. panhai (types I, II, and III from
Tylototriton species so far have been documented as having little dispersal abilities due to limitations in vagility and their specific habitat requirements (
Due to the aforementioned reasoning and given that Tylototriton ngoclinhensis sp. nov. is currently known only from Ngoc Linh Mountain, implying a limited distribution range composed of a single small isolated mountain population, is distinct evidence for a high threat potential. In addition to its special zoogeographic situation and rarity, the particular colorful appearance of the new crocodile newt species is very likely to draw the interest of illegal collectors. Therefore, this species should be provisionally considered to be listed as Endangered (EN) under IUCN Red List criteria B1ab(i,iii), as it is known only from Ngoc Linh Mountain in Kon Tum Province; the estimated extent of occurrence (EOO) is less than 500 km2; and the species' habitat is currently being degraded due to human impacts, for example forest product exploitation, tourism development and agricultural cultivation. All species of the genus Tylototriton are listed in the Appendices of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (
We are grateful to the directorates of the Ngoc Linh Nature Reserve and the Forest Protection Department of Kon Tum Province for support of our field work and issuing relevant permits. We thank Duy D.T. (Kon Tum Forest Ranger), Mai N.T.T, Anh D.N.H, Lam P.N.T (Ho Chi Minh City) for their assistance in the field. For constructive comments on a previous version of the manuscript we thank L. Lee Grismer, Axel Hernandez and Bryan Stuart. For the fruitful cooperation within joint research projects, we cordially thank Nguyen S.V. (IEBR, Hanoi), as well as T. Pagel and C. Landsberg (Cologne Zoo).
The authors have declared that no competing interests exist.
No ethical statement was reported.
This research was supported by the Vietnam Academy of Science and Technology (Project Code: ĐLSĐ00.01/20-23).
Field survey: Trung My Phung and Son Thanh Le; conceptualization: Tao Thien Nguyen, Truong Quang Nguyen, Thomas Ziegler; methodology: Marta Bernardes, Tao Thien Nguyen; data analysis: Cuong The Pham, Hoa Thi Ninh, Huy Quoc Nguyen, Marta Bernardes; writing, review and editing: all authors.
Trung My Phung https://orcid.org/0000-0001-7086-8110
Cuong The Pham https://orcid.org/0000-0001-5158-4526
Truong Quang Nguyen https://orcid.org/0000-0002-6601-0880
Huy Quoc Nguyen https://orcid.org/0000-0003-3171-1561
Marta Bernardes https://orcid.org/0009-0008-2847-8862
Thomas Ziegler https://orcid.org/0000-0002-4797-609X
Tao Thien Nguyen https://orcid.org/0000-0002-5640-4536
All of the data that support the findings of this study are available in the main text or Supplementary Information.