Background - Cyclodium is a neotropical fern genus comprising about ten species. Most species are found in northern South America, and the foothills of the Guiana Shield is an important region for species diversification. Our phylogenetic and taxonomic studies of the genus demonstrated the need to describe a new species and to recognize a variety at species level. Methods - This study is based on herbarium specimens from CAY, HUA, INPA, MBM, NY, P, RB, UC, UFP, UPCB, and US. Morphological characters were analyzed using standard procedures. The indumentum and spores of the new species were studied using a scanning electron microscope. Species delimitation is proposed based on our preliminary phylogenetic studies, as well as on morphology and geographical distribution. Key results - Cyclodium alansmithii Bohn & Labiak is recognized as a new species, described, and illustrated. The most similar species is Cyclodium inerme (Fee) A.R.Sm., from which it differs by ovate-lanceolate and bicolored scales, reduced fronds, truncate pinna bases, and non-ciliate indusia. Cyclodium alansmithii is currently assessed as Endangered (EN) using IUCN criteria, but more fieldwork and herbarium studies are necessary to establish a more accurate conservation assessment. Cyclodium trianae (Mett.) A.R.Sm. var. chocoense A.R.Sm. is here elevated to species rank. A key to species of Cyclodium with free veins is provided.
