Key to identification of Monospilus species of the world

1. Carapace with lateral projections.................................... M. daedalus (Kotov & Sinev 2011) —East Asia

- Carapace without lateral projections.......................................................................2

2. Postabdominal claw armed with distalmost basal spine robust, while proximalmost basal spine short and thin............3

- Postabdominal claw armed with both distalmost and proximalmost basal spine robust.......... M. dispar —Cosmopolitan?

3. Postabdominal claw on the postabdomen armed with two pectens...............................................4

- Postabdominal claw with a single saw-shaped pecten......................... M. macroerosus sp. nov. — Central Brazil

4. Postabdominal claw with not sharp tip; proximalmost basal spine length about 1/5 of the length of the distalmost basal spine; labral keel with three rows of setulae.................................... .. M. brachyspinus sp. nov. — Central Brazil

- Postabdominal claw with sharp tip; proximalmost basal spine longer than half of distalmost spine length; labral keel with one row of setulae....................................................... Monospilus sp. —Southern South America