Pellaea lyngholmii is an apogamous tetraploid that arose through hybridization between P . atropurpurea and P . truncata (M. D. Windham 1993). It is most often confused with P . atropurpurea , from which P . lyngholmii differs in having sparsely villous rachises, smaller and more numerous ultimate segments, and spores usually more than 62 µm in diameter.