We describe two new species of Adiantum (Pteridaceae): A. nodosum and A. pseudocajennense. These species occur in the lowland rainforests of the Amazon Basin at 100–350 m in elevation. Both species have laminae 2-pinnate and grow on waterlogged soil in tall swamp forests, but they differ in the rhizome diameter and degree of incision of the pinnule margins. Currently available information suggests that A. pseudocajennense may be endemic to Ecuador, whereas A. nodosum has a wider distribution and is known from Brazil, Colombia and Peru. For both species we present descriptions, distribution statements, comments and illustrations.

Version of record first published online on 13 November 2017 ahead of inclusion in December 2017 issue.