Natricinae

Ren, Jin-Long, Wang, Kai, Nguyen, Tao Thien, Hoang, Chung Van, Zhong, Guang-Hui, Jiang, Ke, Guo, Peng & Li, Jia-Tang, 2018, Taxonomic re-evaluation of the monotypic genus Pararhabdophis Bourret, 1934 (Squamata: Colubridae: Natricinae) with discovery of its type species, P. chapaensis, from China, Zootaxa 4486 (1), pp. 31-56 : 51-52

Key to the genera of Natricinae in China and Vietnam (modified from Zhao [2006] and Smith [1943])

1 Internasal single.............................................................................. Rhabdops

- Internasals 2–3...................................................................................... 2

2 Internasals 2–3; prefrontals 2–4; nostril valvular...................................................... Atretium

- Internasals paired; prefrontal single or paired; nostril valvular or not............................................ 3

3 Total length less than 370 mm; subcaudals 25–44................................................. Trachischium

- Total length more than 370 mm; subcaudals usually more than 44.............................................. 4

4 Head somewhat triangular shaped; temporals stongly keeled...................................... Macropisthodon

- Head not triangular shaped; temporals not keeled........................................................... 5

5 Prefrontal single or mostly single, much broader than long.................................................... 6

- Prefrontal paired, normal sized.......................................................................... 8

6 Head barely distinct from neck; maxillary teeth subequal; nostrils directed upwards...................... Opisthotropis

- Head distinct or moderately distinct from neck; maxillary teeth enlarged posteriorly; nostrils directed dorsolaterally...... 7

7 Dorsal scale rows 19 at midbody; nostrils valvular; last 3 or 4 maxillary teeth slightly enlarged............ Paratapinophis

- Dorsal scale rows 17 or 15 at midbody; nostrils not valvular; last 2 maxillary teeth moderately enlarged....... Parahelicops

8 Hemipenis forked, sulcus spermaticus of hemipenis forked or not.............................................. 9

- Hemipenis not forked, sulcus spermaticus of hemipenis not forked............................................ 11

9 Sulcus spermaticus of hemipenis not forked........................................................ Sinonatrix

- Sulcus spermaticus of hemipenis forked................................................................. 10

10 Neck with nuchal gland or not; last two maxillary teeth distinctly enlarged and curved, with diastema........ Rhabdophis

- Neck without nuchal gland; maxillary teeth gradually enlarged in a continuous series or abruptly enlarged posteriorly............................................................................................... Xenochrophis

11 Maxillary teeth gradually enlarged in a continuous series, without diastema; nostrils directed dorsolaterally......... Natrix

- Maxillary teeth gradually enlarged posteriorly or last two distinctly enlarged, often with diastema; nostrils directed more or less laterally........................................................................................ 12

12 Maxillary teeth more than 37; 2 vertical white stripes present on both preoculars and postoculars......... Amphiesmoides

- Maxillary teeth less than 37; preocular and postocular color pattern not as such................................... 13

13 Dorsal scale rows 19:19:17; internasals distinctly truncated anteriorly.......................................... 14

- Dorsal scale rows 19:19:17 or 17:17:17; internasals broad anteriorly; maxillary teeth in continuous series, gradually enlarged posteriorly in the series or the last two teeth abruptly enlarged............................................ Hebius

14 Ventrals 142–157; subcaudal 41–82.............................................................. Amphiesma - Ventrals 172–217; subcaudal 69–107............................................................ Herpetoreas