Cyathodium foetidissimum Schiffn., an Asiatic species is reported for the first time for the Neotropics. The species is distinguished by the presence of a central multistratose area of cells; oil cells with a single oil body; strongly dimorphic rhizoids; large ventral scales; monoicous condition with an apical, male receptacle flanked by archegonia in undulate laminar involucres; an operculum of 12 cells; upper cells of the capsule with bar-like thickenings; elaters with three bands; and verrucose spores. The closest relative in habit is Cyathodium spruceanum Prosk., but plants of this species lack a “midrib” and have oil bodies and chloroplasts in the thallus cells; it is dioicous and the spores are lamellate-reticulate. Mature male plants of Cyathodium foetidissimum have been found along with bisexual thalli. This is the first report of both types of gametophytes occurring simultaneously in monoicous species of neotropical Cyathodium.