In Athyrium the correct name of the Alpine Lady-fern is A. distentifolium and not A. alpestre, even though the latter name is older. Hoppe’s epithet dates from 1799, when he described Polypodium alpestre. Athyrium distentifolium Tausch ex Opiz dates from 1820. The problem is that an Athyrium alpestre was described by Clairv. in 1811 but examination of its type shows it to be A. filix-foemina and therefore his A. alpestre becomes a synonym of A. filix-foemina. The epithet is thus not available for Hoppe’s plant to be transferred into Athyrium and the next earliest name is used – distentifolium. This however is not a problem for the transfer of alpestre to Pseudathyrium and Wei et al. (2018*) are right to use it when resurrecting the genus Pseudathyrium.
The endemic late-snow bed ecotype that was once recognised as Athyrium flexile has a valid published name under Pseudathyrium – P. alpestre var. flexile (Newman) Rouy.
Currently no valid name exists for the hybrids between Athyrium and Pseudathyrium. I would suggest × Apseudathyrium Rumsey with Apseudathyrium × cassum (Chiovenda) Rumsey : Basionym Athyrium × cassum Chiovenda Fl. Alp. Lep. Occid. 2 :46 (1929) = Athyrium filix-foemina × Pseudathyrium alpestre but this name would require valid publication.

*Wei, Ebihara, Zhu, Zhao, Hennequin & Zhang (2018)