Cryptacanthus: a new genus of Acanthaceae from the Guineo-Congolian forests of tropical Africa

Summary The new genus Cryptacanthus I.Darbysh. & Kiel (Acanthaceae: Acanthoideae: Justicieae: Justiciinae) is described from the Guineo-Congolian forests of West and Central Africa based on a combination of molecular phylogenetic data and macro- and micro-morphological studies. Previously referred to informally as the “ Rhinacanthus virens Clade”, it comprises three species currently placed in either Justicia L. or Rhinacanthus Nees, namely J. tenuipes S.Moore, R. obtusifolius (Heine) I.Darbysh. and R. virens (Nees) Milne-Redh. for which new combinations are made, plus three species endemic to Cameroon, all of which are newly described here, namely Cryptacanthus bakossii I.Darbysh., C. ebo Cheek and C. obovatus I.Darbysh. With the exception of the widespread R. virens, for which recent accounts already exist, descriptions and illustrations are provided for all of the species, and notes on their habitat preferences, distribution and extinction risk status are provided. The new species are all considered to be Critically Endangered based upon current evidence.