Alfaroa Standl. has five species with a total of 10 taxa ranging from southern Mexico to northern Colombia, although Costa Rica has the most (four), including the type species A. costaricensis Standl. A taxonomic treatment of the Juglandaceae for Flora Mesoamericana recognizes the new subspecies A. costaricensis subsp. septentrionalis D. E. Stone from Mexico and Guatemala as a northern variant. Review of A. guanacastensis D. E. Stone reduces the species to synonomy under A. manningii J. León. The widespread southeastern Asian genus Alfaropsis Iljinsk. ( =  Engelhardia roxburghiana Wall.) is monotypic while possessing several morphological and molecular characters somewhat intermediate between New World Alfaroa and Oreomunnea Oerst., on the one hand, and Old World Engelhardia Lesch. ex Blume on the other. Although Alfaropsis was proposed in 1993, the generic name was not generally recognized until the phylogeny of extant and fossil Juglandaceae was examined by Manos et al. in 2007.