Apomuria was described by Bremekamp as a segregate of Psychotria that he distinguished by seed and pyrene characters. Bremekamp noted that this genus included species from East Africa, but he only formally named species from Madagascar (12 endemic species) and the Comores (1 otherwise East African species). These seed and pyrene characters are variable within clades of Psychotria, however, and Apomuria was clearly a heterogeneous assemblage. In particular Apomuria punctata and the other species with leaf nodules from East African nodulated group appear to be related to the African Psychotria subg. Tetramerae rather than the Madagascar core Psychotria. Apomuria bullata appears to be related to the other Madagascar Psychotria species with bacterial leaf nodules, rather than the non-nodulated species; Apomuria moramangensis appears to be related to several Psychotria species of humid vegetation on the eastern escarpment of Madagascar; and the remaining Apomuria species may be mostly or all related to each other and perhaps Psychotria boenyana. Bremekamp distinguished the individual species of Apomuria mainly by leaf characters and details of pubescence, and several of them may not be distinct. He also recognized two varieties of several Apomuria species, and distinguished the varieties by details of the pubescence; in most cases now that the species are better documented the pubescence variation seems to be continuous, however the plants included in Apomuria angustifolia var. angustifolia and its var. pubescens may actually not be conspecific, with the var. pubescens similar to several other species that were classified in Apomuria but var. angustifolia more closely related to species now classified in Psychotria.
Razafimandimbison et al. (2014) studied Apomuria with molecular data and concluded that it is in fact a heterogeoneous group of species that are each more closely related to species of Psychotria, and they synonymized Apomuria with that genus.
For more information about Apomuria including detailed outlines of the species that were included and their putative relationships, see the genus page in the TROPICOS Rubiaceae Project (in the upper right corner of the web page, click on "Choose Project" and then "Rubiaceae"). Species of Apomuria are similar in aspect to, and frequently confused with: Triainolepis, which differs in its ovaries with 2 ovules in each locule and subglobose multilocular fruits; the species formerly included in Pyragra, which differ in their ovate, flattened, schizocarpous fruits with carpophores that persist after the mericarps have fallend and are now included in Psychotria; and some species that were formerly included in Cremocarpon, which have ellipsoid schizocarpous fruits that also have persistent carpophores and are now included in Psychotria. Also similar to some of the species included in Apomuria are several species described in Psychotria, which differ in their yellow corollas and fruits that become white then blue or black; particularly similar here are Psychotria boenyana, Psychotria ambongensis, and Psychotria rubropedicellata.