Ledermanniella s.l. (Podostemaceae) occurs in western Africa, where species are commonly localized to single rapids or waterfalls. Recent collecting efforts in this region have led to the discovery of new species diversity; however, molecular phylogenetic analyses estimate the genus as polyphyletic and associated with at least nine other genera. Here, we describe a new species of Ledermanniella s.l. while addressing the problem of describing a species into a polyphyletic genus with a phylogenetic approach. We sampled species diversity for molecular and morphological data and combined them with morphological data only from the new species, which we were unable to sequence because of non-optimal DNA preservation or other reasons. We tested and rejected the monophyly of Ledermanniella s.l. and L. subgenus Ledermanniella with the Shimodaira-Hasegawa test, and found support for a monophyletic L. subgenus Phyllosoma, which was recently treated at the genus level as Inversodicraea. Based on Bayesian phylogenetic inference, we describe Inversodicraea achoundongii, which we infer in a clade with I. cristata, I. ntemensis (combined here), and I. annithomae. The morphological and phylogenetic consequences of these results are discussed, including leaf homologies, along with a description of the ecological, distributional, and conservation implications of the new species and western African Ledermanniella s.l.