Key to the species of the genus Tonkinaphaenops Deuve, 2013

1. The 1 st humeral pore of marginal umbilicate series located before the 2 nd pore...................................... 2

- The 1 st humeral pore of marginal umbilicate series located behind the 2 nd pore........................ T. marinae Deuve

2. Elytra with very little marked shoulders; the 3 rd pore of marginal umbilicate series much closer to the 2 nd than to the 4 th ......................................................................................... T. jingxicus sp. nov.

- Elytra with quite distinct and very marked shoulders......................................................... 3

3. The 3 rd pore of marginal umbilicate series equidistant from the 2 nd and the 4 th ..................... T. yinquanicus sp. nov.

- The 3 rd pore of marginal umbilicate series closer to the 2 nd than to the 4 th .......................................... 4

4. Elytra convex, amygdaloid; posterior pronotal setae lacking................................. T. impunctatus sp. nov.

- Elytra long, poorly convex and subparallel, slightly narrowed backwards; posterior pronotal setae present.................................................................................................... T. anthonyi sp. nov.