A cladistic analysis including for the first time all taxa of Anulocaulis, five species and four varieties, is presented. Sixteen potentially related taxa classified within Boerhavia, Commicarpits, Cyphomeris, Nyctaginia, and Okenia were used as outgroup to test the monophyly and phylogenetic position of Anulocaulis; Mirabilis glabrifolia was used to root the tree. Forty-one characters were included in the matrix, which was analyzed using the parsimony criterion. Our results are in partial agreement with previous studies using molecular data. Here, the monophyly of Anulocaulis is corroborated, but the sister group remains ambiguous depending on whether the multistate characters are treated as additive or nonadditive. In the first case, Anulocaulis is sister to Nyctaginia-Okenia, while in the second it is sister to Boerhavia anisophylla. The morphological characters which have been used in the traditional taxonomy and classification of the genus are analyzed and discussed under a phylogenetic context. Species recognition, infraspecific taxa and infrageneric classification for Anulocaulis are discussed. A taxonomic synopsis for this xerophytic genus including keys and descriptions based on our cladistic results is presented.