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Xenochrophis bellulus (Stolickza, 1871) was described as Tropidonotus bellulus based on a single specimen collected from Myanmar in the late 19th century. Since then the holotype has been lost, and the species has been transferred to several genera in the subfamily Natricinae including Natrix, Sinonatrix and finally Xenochrophis based on one museum specimen matching the original description. Herpetofaunal surveys of the Moyingyi Wildlife Sanctuary and vicinity, Bago Region, Myanmar revealed three individuals obtained in 2001 and 2003 that match the type description of X. bellulus. This small series of newly collected specimens allows us to redescribe this species based on all known material, provide a description of the hemipenis, designate a neotype and comment on its taxonomic status.

Sinonatrix yapingi sp. nov. Figs. 3���7 Holotype: YBU 15296, adult female, from Jingdong (24.53��N, 100.94��E), Yunnan Province, China, at an elevation of 1500 m a.s.l.; collected by F. Zhu and Z.Q. Zhang in August 2015. Diagnosis: 1) Large body size (maximum total length more than 795 mm); 2) dorsal scales in 19-19-17 rows, moderately keeled except outer four; 3) prefrontal single; 4) ventral scales 149, subcaudals 55, paired; 5) cloaca divided; 6) body bands 30; 7) belly milk-white, without speckles or bands; 8) reduction of dorsal scale rows from 19 to 17 anterior to 90 th ventral scale; 9) reduction of caudodorsal scales rows from 8 to 6 anterior to 12 th subcaudal and from 6 to 4 anterior to 38 th subcaudal; 10) postorbital bones not in contact with frontals, with weak parietal ridge; end of supratemporal bones extending beyond braincase; maxillary teeth 25, last two not enlarged; dentary teeth 26. In addition, the genetic distances between the new species and each Sinonatrix representative range from 14.6% to 15.0%. Description of holotype: Adult female. Total length 795 mm, tail length 160 mm. Body stout, cylindrical. Head elongated and narrow, about twice as long as wide; slightly flattened, snout blunt. Eye moderate. Rostral 1.5 times as broad as deep, just visible from above; nasal completely divided; nostril dorsolateral. Internasals much longer than broad, narrowed anteriorly, longer than prefrontal; single prefrontal, 1.6 times as broad as long, extending downward on both sides and touching loreals, preoculars, and nasals. Frontal shield-like, 1.5 times as long as broad, as long as distance from end of snout; parietal large, 1.7 times as long as broad. Supraoculars narrow and long, about twice as long as broad, slightly shorter than frontal. Loreals square, slightly longer than broad; one preocular; three or four postoculars, lowest one extending beyond eye. Six temporals, arranged 2+4 on left and 1/(1+1) +3 on right (anterior one long above 2 short + 2 posterior temporals). Nine supralabials, fifth entering eye, seventh largest; ten infralabials, first five in contact with anterior chin-shields. Dorsal scales in 19-19- 17 rows, all moderately keeled except outer four. Reduction of dorsal scale rows from 19 to 17 at 90 th ventral scale. Ventrals 149+1. Cloaca divided. Subcaudals 55, paired; reduction of dorsal scale rows on tail from 8 to 6 and from 6 to 4 at 12 th and 38 th subcaudals, respectively. Nasals small and triangular, prefrontals broad, frontals about twice as long as broad. Postorbitals large, not touching frontals. Parietal ridge Y-shaped and strong; posterior end of supratemporal bones slender, extending beyond braincase. Quadrates broad. Maxillary teeth 25, last two not enlarged. Dentary teeth 26. Dorsal surface gray-brown. Thirty black, irregular bands on both sides of vertebral line; bands arranged alternatively on both sides and contacting each other (single marking on vertebral line close to neck). V-shaped speckles occurring on both sides of body and close to ventral scales, connecting and constituting W-shaped markings from anterior to posterior. Dorsal surface of head uniformly dark without markings; belly and ventral surface of head uniformly yellowish white, infralabials gray dark outside. Ventral surface of tail gray-white with some blackish spots. Ecological notes. The specimen was collected in a rice field close to an evergreen forest at 21:00 pm on 13 August 2015 (Fig. 7). No data on its diet or reproductive behavior are currently available. Etymology. The species is named after Dr. Yaping Zhang, a Chinese academician, in recognition of his great contribution to Chinese herpetological research. We suggest the following common names: ��� �������ńĸ ��� (Chinese) and Jingdong Water Snake (English). Distribution. This species is currently known only from the type locality, Jingdong, Yunnan Province, China (Fig. 1). Since the first specimen was collected, no addition specimens have been found, although the type locality has been visited several times., Published as part of Guo, Peng, Zhu, Fei & Liu, Qin, 2019, A new member of the genus Sinonatrix (Serpentes: Colubridae) from western China, pp. 535-544 in Zootaxa 4623 (3) on pages 538-539, DOI: 10.11646/zootaxa.4623.3.5, http://zenodo.org/record/3258638

A new member of the natricine snake genus Sinonatrix Rossman & Eberle, 1977 is described from Yunnan Province, southwestern China, based on a single female specimen. The new species, Sinonatrix yapingi sp. nov., is distinguished from its congeners and related species by the following combination of characters: 1) large body size (maximum total length more than 795 mm); 2) dorsal scales in 19-19-17 rows, moderately keeled except outer four; 3) prefrontal single; 4) ventral scales 149, subcaudals 55, paired; 5) cloaca divided; 6) body bands 30; 7) belly milk-white, without speckles or bands; 8) reduction of dorsal scale rows from 19 to 17 anterior to 90th ventral scale; 9) reduction of caudodorsal scale rows from 8 to 6 anterior to 12th subcaudal and from 6 to 4 anterior to 38th subcaudal; 10) postorbital bones not in contact with frontals, with weak parietal ridge; end of supratemporal bones extending beyond braincase; maxillary teeth 25, last two not enlarged; and, dentary teeth 26. In addition, the genetic distances between the new species and other representatives of Sinonatrix ranged from 14.6% to 15.0%.

The Asian water snake genus Trimerodytes (formerly Sinonatrix) is endemic to East and Southeast Asia. Although several species have been included in various phylogenetic studies previously, the evolution and relationships among members of this genus as a whole remain unexplored. In this study, we report the sequencing two protein-coding mitochondrial gene fragments (MTCYB and ND2) and three nuclear genes (c-mos, NT3, and Rag1), reconstruct interspecific phylogeny, and explore biogeography for the genus Trimerodytes. Both Bayesian inference and maximum likelihood analyses consistently recover the monophyly of Trimerodytes with strong support, with T. yapingi the sister-group to the remaining species. The divergence date and ancestral area estimation suggest that Trimerodytes likely originated in Hengduan Mountains (eastern Tibetan Plateau) in western China at 23.93 Ma (95% HPD: 17.09–31.30), and intraspecific divergence began at about 4.23 Ma (95% HPD: 2.74–6.10). Analyses support the validity of T. yunnanensis.

Based on the first molecular phylogenetic analyses of samples from northeast India, specimens referred to Rhabdops from this region are more closely related to the southeast and east Asian natricine genera Opisthotropis Günther, 1872 and Sinonatrix Rossman & Eberle, 1977 (as well as to New World and western Palearctic natricines) than to peninsular Indian (true) Rhabdops. Morphologically, these northeast Indian populations differ from other natricines by having a single (‘fused’ or unpaired) internasal shield and a single prefrontal shield. Given the morphological and phylogenetic distinctiveness of these northeast Indian populations, we refer them to a new genus, Smithophis gen. nov., and transfer Rhabdops bicolor (Blyth, 1854) to Smithophis bicolor comb. nov. Based on morphological and molecular variation within our northeast Indian sample, we additionally describe Smithophis atemporalis sp. nov. from the state of Mizoram.