Key to species of Alainthesius n. gen.

1. Dorsal surface of carapace almost smooth (Figs. 20 C, D; 27D). G1 conspicuously short, stout (Fig. 83 A, B) [Madagascar]......................................................................................... A. signatus n. sp.

- Dorsal surface of carapace covered with small flattened granules (Figs. 20 E–H; 27E, F). G1 relatively slender, with distal half elongated (Fig. 83 D–G) [Papua New Guinea; New Caledonia; Fiji]................................ A. bertrandi n. sp.