Imprecise descriptions of Martius ex Masters led to redundant descriptions as Sacco, Feuillet & Cremers, Holm-Nielsen & Lawesson and Escobar.

was incompletely described by Masters, who cited specimens of Martius and Spruce. While , the unique syntype with an observable corona, exhibits a reduced outermost series of filaments, the accompanying iconography represents two equal outer series. Later descriptions have neither added significant information nor corrected the inconsistency in the corona description, so that four closely related species have been distinguished on the basis of traits not properly documented for : (unequal outer series of filaments), (bract color), (flower size and sepal awn length), and (hypanthium pubescence and shape). The present study compares (i) the descriptions of the above-mentioned taxa and (ii) 43 associated vouchers, as well as live specimens from two associated populations. These and other specimens were georeferenced for a comparison of their distribution and habitat. Of the five descriptions found in floras, only that of the Flora of Ecuador appears clearly divergent, corresponding in fact to . Those of the four other taxa only differ by unequal corona filaments (except for ) and the pubescence of floral parts. However, 22 vouchers associated with all these descriptions (including 16 for ), as well as the live specimens, share both these traits; the other 21 vouchers were uninformative and/or could not be assigned to any of the five species. The wider sample of 62 specimens indicates no significant differences in either geographic or in climatic distribution (lowlands of the Amazon basin), and a marked preference for riparian habitats. Thus, their very close morphology and ecology justify the placement of , , and as synonyms of , designating as epitype. The most similar species, (20 specimens mapped), differs in corolla and bract color, as well as a distribution centered along the tropical Andes of South America and in Central America, in more diverse habitats.