The North American genus Ammonaios Irwin and Lyneborg is revised, and the three new species, A. confusus sp. n., A. mexicanus sp. n., and A. sabulosus sp. n., are described. The limits of the genus are redefined; a key to the species, descriptions of the pupae of three species, and distribution maps are provided. A cladistic analysis provides hypotheses of phylogenetic relationships within the genus, and the monophyly of Ammonaios was affirmed when tested with respect to species within its putatively closely related genera.