Ditrichanthus was separated from Palicourea based on its unusual pyrene form, and included one species. This pyrene form was determined to be anomalous within two similar genera, Palicourea and Psychotria based on an apparently original broad survey of Neotropical species of Palicourea, Psychotria subg. Heteropsychotria, and Psychotria s. str. (Borhidi et al., 2015). This survey referenced the work on pre-formed germination slits (PGS's) by Robbrecht & Piesschaert, and concluded that all Neotropical species of both Palicourea and Psychotria (both it subgenera) have a single longitudinal ventral PGS. This is however not what was found by Piesschaert in his 2001 survey, where Psychotria s. str. worldwide was found to lack PGS's. The survey by Borhidi et al. did not collect data on presence or form of PGS's, and the South American species of Psychotria studied here included species of both subgenera without separate denotation, thus the species of selected genera of two tribes sensu Razafimandimbison and Robbrecht & Manen or two subclades of Psychotrieae sensu Bremer & Eriksson were mixed without survey of related genera. Additionally the fruit illustrated as "the common form in the Palicourea and Psychotria genera" (Borhidi et al., 2015: 242, fig. 1) is misidentified as to genus. Ditrichanthus was classified formally in "Sect. Palicoureeae", which presumably is intended to refer to either Tribe Palicoureeae unless the authors intended to provide a name for the subclade that contained Palicourea in the analysis of Bremer & Eriksson. Borhidi et al. (2015) also considered Ditrichanthus related to Mexocarpus, and separated these two genera by characters of the inflorescences and corollas that are all found in numerous species of Palicourea.
The pyrenes of Ditrichantus are unusual but not dissimilar to those of other species of Palicourea, as noted by Borhidi et al. (2015) who included another species with rather similar pyrenes in another monotypic genus, Mexocarpus. These pyrenes were previously noted as unusual but not unique in Palicourea by Taylor (1997), who found its single species agrees with the characters of Palicourea.