Rhabdophis nuchalis (Boulenger, 1891)

Nguyen, Tan Van, Keetapithchayakul, Tosaphol Saetung, Lathrop, Amy, Orlov, Nikolai L., Nguyen, Duc Trong, Poyarkov, Nikolay A. & David, Patrick, 2025, Molecular and morphological evidences for considering Rhabdophis guangdongensis Zhu, Wang, Takeuchi & Zhao, 2014 a junior synonym of Rhabdophis angeli (Bourret, 1934) (Squamata: Natricidae), Zootaxa 5706 (1), pp. 1-35 : 15

Based on the available literature (Nguyen & David 2023; Liu et al. 2023) and our own material, we here propose the following provisional identification key to the species of the Rhabdophis nuchalis group species:

1a. Dorsal scale rows 15–15–15............................................................................. 3

1b. Dorsal scale rows 17–17 (15, 16)–15..................................................................... 2

2a. Ventrals 136–151; infralabials 7; temporals 1+2; maxillary teeth 25................................... R. hmongorum

2b. Ventrals 151–157; infralabials 8; temporals 1+1; maxillary teeth 19.............................. R. leonardi complex

3a. Usually supralabials 5.................................................................................. 4

3b. Usually supralabials 6.................................................................................. 5

4a. Dorsum green; venter pale............................................................. R. pentasupralabialis

4b. Dorsum brown; venter dark...................................................................... R. chiwen

5a. Black line present below the eye and extending onto the last two supralabials..................................... 6

5b. Black line absent below eye and on last two supralabials.......................................... R. kaiyuanensis

6a. Distinct mark present on nape........................................................................... 7

6b. Nape without V-shaped black patches............................................................. R. nuchalis

7a. TEM usually 1+1; VEN 118–127; SC 38–47; nape grey with an orange V-shaped zone behind the black collar; faint dorsolateral cross-bars present............................................................................ .. R. angeli

7b. TEM usually 1+2; VEN 124–165; SC 44–74; nape reddish-brown before the black collar, without an orange V-shaped zone; dorsolateral cross-bars absent.................................................................. R. swinhonis