Fifteen taxa have been listed for the genus Fossombronia Raddi in North America, north of Mexico. The difficulty in delimiting species based on gametophyte morphology has led the majority of bryologists to identify species of Fossombronia using characters of the distal spore wall architecture. Attempts to compare these data with other morphological and ecological data are lacking, leading to a total misunderstanding of the species within this genus. Also, many reports were based on previous literature rather than on a thorough evaluation of type material. As part of a complete revision of the genus for Europe and North America, north of Mexico, a character set generated from light and SEM analysis of type collections, supplemented with other collections and live material, was compared in a phylogenetic framework and used to generate parallel descriptions of all accepted taxa. Common garden experiments were conducted to assess morphological plasticity of the gametophyte and spore wall characters through successive generations. Based on specimen evaluation, common garden results and taxonomic reduction, a total of ten species are here recognized for North America, north of Mexico.

Key words: common garden, Fossombronia, morphology, North America, revision