A revision of the genus Anthonaeus Horn is provided as the initial step of a multiphase project to completely revise the entire New World Kateretidae fauna. Anthonaeus, a previously monospecific genus of short-winged flower beetles, was formerly known from the type species Anthonaeus agavensis (Crotch). This species is a specialist on flowers of Hesperoyucca (Engelm.) Baker (Agavaceae) in southern California, USA. Anthonaeus bajaensis, new species, is described from Baja California, Mexico, and a redescription of A. agavensis is provided for comparative morphology. The larva of A. agavensis is described for the first time and the relationship of Anthonaeus to other New and Old World Kateretidae genera is discussed in the context of both larval and adult morphology.