Key to species of Acanthocyrtus

1 Tenent hair chavate (Fig. 8E); Australian species............................................................ 2

- Tenent hair pointed; African species................................................ A. marginalis Salmon, 1956

2 Prelabral chaetae ciliate................................................................................ 3

- Prelabral chaetae smooth............................................................................... 4

3 Head with 7 sutural mac; Th II–III respectively with 9 and 7 mac in p1–3 complex; Abd I with 4 mac; Abd IV with 19 central mac.......................................................................... A. lineatus Womersley, 1934

- Head with 5 sutural mac; Th II–III respectively with 4 and 5 mac in p1–3 complex; Abd I with 2 mac; Abd IV with 15 central mac............................................................................ A. spinosus (Schött, 1917)

4 Labral papillae present (Figs 3E, 9C)..................................................................... 5

- Labral papillae absent.................................................................................. 6

5 Head and Abd III–IV with lateral spots (Fig. 2); labral inner papillae conical, outer papillae reduced to a small rounded projection (Fig. 3E); labial papilla E l.p. surpass the base of a.a. (Fig. 4A); manubrium ventro-distally with 3 inner chaetae (Fig. 7B) A. necropolitanus sp. nov.

- Head and trunk depigmented (Fig. 8); labral inner papillae with 3 projections and outer papillae with 4 projections (Fig. 9C); labial papilla E l.p. not reach the base of a.a. (Fig. 9E); manubrium ventro-distal with 2 inner chaetae (Fig. 11F)................................................................................................ A. pallidus sp. nov.

6 Ant IV apical bulb bilobed; Th II with 24 mac in p1–3 complex; Abd III with 5 lateral mac; Abd IV with 20 central mac; mucronal proximal tooth clearly smaller than distal, mucronal basal spine surpassing the proximal tooth........................................................................... A. barrowensis Zhang, 2009 (in: Zhang et al. 2009)

- Ant IV apical bulb absent; Th II with 17 or less mac in p1–3 complex; Abd III with 4 lateral mac; Abd IV with 15 or less central mac; mucronal teeth subequal, mucronal spine reaching the apex of proximal tooth................................. 7

7 Head S1 and S4 mac present and Pe5 absent; labial basomedian field with 3 smaller chaetae (M2, R and RS); Th II with 6 and 17 mac respectively in m2 and p3 complex; unguis a.t. absent............ A. loftyensis Zhang, 2009 (in: Zhang et al. 2009)

- Head S1 and S4 mac absent and Pe5 present; labial basomedian field with 1 smaller chaetae (M2, RS absent); Th II with 5 and 15 mac respectively in m2 and p3 complex; unguis a.t. present............. A. yolngui Zhang, 2009 (in: Zhang et al. 2009)