Riotintobolus Wesener & Enghoff & Sierwald 2009

Key to the Riotintobolus species:

1 Tarsal pads absent (Fig. 27F). Eyes with 20 or less ocelli (Figs 26A, 27E). Anal valves with a deep groove between anterior half and sharp-edged lips (Figs 26B, 27G)......................................................................................... 2

– At least male legs 3–7 with tarsal pads (Fig. 29C). Eyes with more than 25 ocelli. Anal valves with neither a groove, nor sharp-edged lips (Figs 28A, 29A).......................................................................................................... 3

2 Specimens 35–43 mm long. Colour laterally black, dorsally with a thick, light brown stripe (Fig. 24A). Telopodite of posterior gonopod laterally with one large and second small finger-shaped process (Fig. 26M)........ R. mandenensis sp. n.

– Specimens shorter than 25 mm. Colour laterally black, dorsally with a thick, red stripe (Fig. 27A). Telopodite of posterior gonopod laterally with two large finger-shaped processes of equal size (Fig. 27K)................. R. minutus sp. n.

3 Telson with an elongated, protruding preanal process, lips on anal valves well-developed (Fig. 28A). Only male legs 3–7 with tarsal pads. Apical mem- brane on posterior gonopod weakly developed (Fig. 28G). Telopodite at mesal margin with a suspicious horn (Fig. 28F). Colour brown-blackish with a conspicuously wide light brown stripe.................................. R. aridus sp. n.

– Telson preanal process not protruding, lips on anal valves weakly developed (Fig. 29A). Male legs three and beyond with tarsal pads (Fig. 29C). Apical membrane on posterior gonopod large, widely protruding (Fig. 29F). Colour light grey, posterior margin of rings dark grey, dorsally with a conspicuous, wide blood-red stripe..................................................... R. anomalus sp. n.