Background – Botanical exploration of the Sapo National Park in Liberia resulted in the discovery of a new species, which, after DNA investigation, was identified as belonging to Soyauxia of the small family Peridiscaceae. Methods – Normal practices of herbarium taxonomy and DNA sequence analysis have been applied. All the relevant herbarium material has been studied, mainly at BR, K, P, and WAG. The presented phylogenetic relationships of the new Soyauxia species is based on rbcL gene sequence comparison, inferred by a RAxML analysis including 100 replicates fast bootstrapping. The distribution maps have been produced using Map Maker Pro. Relevant collection data are stored in the NHN (Nationaal Herbarium Nederland) database. Key results – The new species Soyauxia kwewonii and an imperfectly known species are treated in the framework of a synopsis with the six other species of the genus. rbcL sequence comparison followed by RAxML analyses yielded a well-supported match of S. kwewonii with the Soyauxia clade. Its conservation status according to the IUCN red list criteria is assessed as Endangered. Its distribution as well as the distribution areas of the genus and of the remaining species are mapped. Soyauxia ledermannii is neotypified and the most common species in Gabon, S. glabrescens, is also illustrated.

LIBERIA; MEDUSANDRACEAE; NEW SPECIES; PERIDISCACEAE; SOYAUXIA; TAXONOMIC SYNOPSIS; TROPICAL AFRICA