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Trimerodytes aequifasciatus (BARBOUR, 1908)

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Higher TaxaColubridae (Natricinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common NamesE: Asiatic Annulate Keelback, Asiatic Water Snake
Chinese: “Huan Wen Hua You She” ( 环纹华游蛇 ) 
SynonymNatrix aequifasciata BARBOUR 1908: 317
Natrix aequifasciata — MELL 1931 [1929]
Sinonatrix aequifasciata — ROSSMAN & EBERLE 1977
Sinonatrix aequifasciata — VOGEL et al. 2004
Sinonatrix aquaefasciata
Sinonatrix aequifasciata — NGUYEN et al. 2009
Sinonatrix aequifasciata — WALLACH et al. 2014: 677
Trimerodytes aequifasciata — REN et al. 2019
Trimerodytes aequifasciata — FRANCIS 2021 
DistributionChina (Guangxi, Guangdong, Hong Kong, Hainan, Fujian, Guizhou, Hunan, Jiangxi, Sichuan, Zhejiang),
N Vietnam (Hoa Binh, Vinh Phuc, Lao Cai, Ha Giang, Cao Bang southwards to Nghe An, Ha Tinh), Laos

Type locality: “Mt. Wuchi”, now Mt. Wuzhi, Hainan Island, People’s Republic of China).  
TypesHolotype: MCZ 7101 
DiagnosisDescription.- Body stout, cylindrical; head oval, strongly elongate, rather narrow, barely distinct from neck; snout long, accounting for 29.2 % of total head length, 2.0 as long as horizontal diameter of eye, slightly flattened, narrowing at its tip which is nearly blunt when seen from above, rounded seen from side, with no defined canthus rostralis; nostril dorsolateral, directed upwards; eye large, its diameter much greater than distance between its inferior margin and upper lip edge; pupil rounded; tail long, cylindrical and clearly progressively tapering. Maxillary teeth 23, gradually enlarged posteriorly. Snout-vent length 485 mm; tail length 152 mm; total length 637 mm. Ventrals (3 preventrals) + 149 ; subcaudals 78, all paired; anal divided. Dorsal scale rows 19-19-17, strongly keeled except those in outermost row which are smooth. Dorsal scale rows reduction:
left: 3rd + 4th -> 3rd (ventral 89)
right: 3rd + 4th -> 3rd (ventral 90)
Rostral twice as wide as high; internasals subtriangular, longer than wide, distinctly anteriorly narrowed; prefrontals only slightly larger than internasals, reaching loreal; one large, undivided supraocular on each side; nasal rectangular, much longer than high, divided into two parts, with a dorsolateral nostril piercing upwards near upper edge of the limit between nostril parts; one subrectangular, gothic-shaped loreal; 9/9 supralabials, 5th entering orbit, 4th and 6th separated from orbit by only a small scale, 7th largest; 1/1 preocular; no subocular; 3/3 postoculars; 2 + 2 + 3 temporals on both sides; 10/9 infralabials.
In life and preservative, dorsal and upper tail surfaces are dark grey, marked on each side of body with 21 and on each side of tail with 13 wide, regular, distinct vertical black bands encircling body, which are strongly constricted in their middle at mid-height of flanks; wider lower and upper parts of each band marked with an oval blotch of dorsum ground colour, giving the appearance of conspicuous, broad rounded X-shaped markings on each flank, the X more or less contacting each other by their upper branches on the vertebral line; bands immediately behind head and towards the tail end indistinct. Head uniformly dark olive grey, without any marking. Venter dirty whitish yellow, darker towards tail, marked with irregular double (sometimes single) black bands coming from lateral X-shaped markings, separated by a more or less wide amount of venter ground colour [from VOGEL et al. 2004]. 
CommentSpecimens from Yunnan have been redescribed as S. yunnanensis. 
  • Barbour, THOMAS 1908. Some new reptiles and amphibians. Bull. Mus. Comp. Zool. Harvard 51 (12): 315-325 - get paper here
  • Barbour, Thomas 1909. Notes on Amphibia and Reptilia from Eastern Asia. Proc. New England zool. Club 4: 53-78, 2 plates - get paper here
  • Francis, A. 2021. A field guide to the snakes of Hong Kong. Regal Printing, Hong Kong - get paper here
  • Hecht, Vera L.; Cuong T. Pham, Tao T. Nguyen, Truong Q. Nguyen, Michael Bonkowski & Thomas Ziegler 2013. First report on the herpetofauna of Tay Yen Tu Nature Reserve, northeastern Vietnam. Biodiversity Journal 4 (4): 507–552
  • Le, Dzung Trung; Anh Van Pham, Cuong The Pham, Son Lan Hung Nguyen, Thomas Ziegler, Truong Quang Nguyen 2015. Review of the Genus Sinonatrix in Vietnam with a New Country Record of Sinonatrix yunnanensis Rao et Yang, 1998. Russ. J. Herpetol. 22 (2): 84-88
  • Mell,R. 1931. List of Chinese snakes. Lingnan Sci. Jour., Canton, 8 [1929]: 199-219.
  • Nguyen, S.V., Ho, C.T. and Nguyen, T.Q. 2009. Herpetofauna of Vietnam. Chimaira, Frankfurt, 768 pp.
  • Nguyen, Truong Quang; Tan Van Nguyen, Cuong The Pham, An Vinh Ong & Thomas Ziegler 2018. New records of snakes (Squamata: Serpentes) from Hoa Binh Province, northwestern Vietnam. Bonn zoological Bulletin 67 (1): 15–24 - get paper here
  • Rao, DING QI & D. T. YANG. 1998. A new species of Sinonatrix (Serpentes: Colubridae) of China with preliminary survey on Sinonatrix. Russ. J. Herpetol. 5 (1): 70-73. - get paper here
  • REN, Jinlong; Kai WANG, Peng GUO, Yingyong WANG, Tao Thien NGUYEN, and Jiatang LI 2019. On the Generic Taxonomy of Opisthotropis balteata (Cope, 1895) (Squamata: Colubridae: Natricinae): Taxonomic Revision of Two Natricine Genera. Asian Herpetological Research 10 (2): 105–128; DOI: 10.16373/j.cnki.ahr.180091 - get paper here
  • Stuart, B.L. & Heatwole, H. 2008. Country records of snakes from Laos. Hamadryad 33: 97–106
  • Thinh, Bui Bao; <br />Trinh Thi Hong; <br />Hoang Ngoc Thao; Bui Bao Thien 2018. Initial building the sample sets of amphibians and reptiles in the Hong Duc University (Viet Nam). Постулат. 2018. No12 УДК 597.6 + 598.1 - get paper here
  • Vogel, Genot; Patrick David, Olivier S. G. Pauwels and Norbert Brachtel 2004. On the occurence of the watersnake Sinonatrix aequifasciata (Barbour, 1908) (Serpentes, Colubridae, Natricinae) in Vietnam. Hamadryad 29 (1): 110 – 114
  • Wallach, Van; Kenneth L. Williams , Jeff Boundy 2014. Snakes of the World: A Catalogue of Living and Extinct Species. [type catalogue] Taylor and Francis, CRC Press, 1237 pp.
  • Wang, Kai; Jinlong Ren, Hongman Chen, Zhitong Lyu, Xianguang Guo Ke Jiang, Jinmin Chen, Jiatang Li, Peng Guo, Yingyong Wang, Jing Che 2020. The updated checklists of amphibians and reptiles of China. Biodiversity Science 28 (2): 189-218 - get paper here
  • Zhao, E.M. 2006. The snakes of China [in Chinese]. Hefei, China, Anhui Sience & Technology Publ. House, Vol. I, 372 pp., Vol. II (color plates), 280 pp.
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