Athyrium distentifolium subsp. americanum (Butters) Hultén
Athyrium distentifolium subsp. americanum (Butters) Hultén is a synonym sensu FNA Ed. Comm., 1993 of:
Athyrium distentifolium var. americanum (Butters) B. Boivin, an accepted variety name sensu Baldwin et al., 2012.