Aoplonema lopidium sp. nov. is described from the Mexican states of Guerrero and Oaxaca, representing the first records of this genus from mainland Mexico. A summary of the hypothesized phylogenetic species relationship is (A. princeps (A. lopidium (A. rubrum A. nigrum))). A biogeographical analysis proposes that the Sierra Madre del Sur is the sister area to the rest of the areas occupied by the other species of Aoplonema.