Cystopteridaceae
Cystopteridaceae is a family of ferns in the order Polypodiales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), the family is placed in the suborder Aspleniineae of the order Polypodiales, and includes three genera. Alternatively, it may be treated as the subfamily Cystopteridoideae of a very broadly defined family Aspleniaceae. Cystopteridaceae are small or medium-sized ferns in forests and crevices. They generally have thin laminae, and small, round, naked sori. Genera. Three genera are accepted in the PPG I classification, and by the "Checklist of Ferns and Lycophytes of the World" : "Cystopteris chinensis" has been placed  in a separate genus, "Cystoathyrium", but the genus is not accepted by recent sources. Phylogenetic relationships. The following diagram for the Aspleniineae (eupolypods II), based on Lehtonen, 2011, and Rothfels & al., 2012, shows a likely phylogenic relationship between the Cystopteridaceae and the other families of the clade. "Gymnocarpium" and "Cystopteris" have been found to be sister to the remaining Aspleniineae.