The Gyalectaceae are a family of lichenized ascomycetes of worldwide distribution from temperate to tropical regions that share a general type of hemiangiocarpous ascoma ontogeny and apothecia having a pseudoparenchymatic excipulum proprium. The genus Coenogonium (including Dimerella) has been included in the Gyalectaceae, but varies from the remaining species of this family in apothecial ontogeny and anatomy, spore size and septation, thallus and pycnidial anatomy, and ascus ultrastructure. To determine the relationships between Coenogonium and other genera in the family, ascoma ontogeny and various anatomical characters were investigated in detail. Although the ontogeny of both the genus Coenogonium and the Gyalectaceae s. str. is hemiangiocarpous, the development of the apothecia of Coenogonium and the resulting apothecial anatomy are remarkably different. Ontogenetic, anatomical, and morphological evidence supports the re-establishment of the monogeneric family Coenogoniaceae (Fr.) Stizenb.