The description of new taxa of small minnow mayflies (Insecta : Ephemeroptera : Baetidae) includes the following. Cryptonympha copiosa n. gen. and n.sp., from Brazil, is distinguished by long, robust, pilose setae on the medial margin of the prosthecae ; apically narrow glossae and paraglossae ; absence of hindwingpads ; and long, basally narrow gill 1. Rivudiva n. gen., including R. minantenna n.sp., from Brazil, and R. trichobasis n.sp., from Brazil and Paraguay, is distinguished by a broad lingua and relatively narrow superlinguae ; broad glossae with a distomedial row of long, robust, falcate, simple setae ; and tarsal claws with minute denticles arranged in an ellipse. Spiritiops silvudus n.gen. and n. sp., from Brazil and French Guyana, is distinguished by a long, robust, pilose seta arising from the medial margin of the right prostheca and tarsal claws with two rows of denticles and lateral long, fine, simple seta. Varipes lasiobrachius n. gen. and n. sp., from Colombia and Ecuador, is distinguished by the reduced right prostheca and U-shape arrangement of denticles on the tarsal claws. Zelusia principalis n. gen. and n. sp., from Brazil and Colombia, is distinguished by a medially raised labrum, bifid right prostheca, and long, slender maxillary palps.