The distinction between this species, L. alpina var. major Rosenst., and L. laxa Copel., are not clear to me at this time. Leptopteris wilkesiana (Brack.) Christ, which is more broadly distributed, is also very similar. Further taxonomic revision is needed.
On looking at this amazing species, another filmy-like fern Hymenophyllopsis dejecta is also very strange to me. I think Leptopteris is very similar to Todea in the shape of leaves. Does Leptopteris live in a dark and rheophytic habitat?
It does live on slopes in dense forest. I have not seen it as a rheophyte, but I have only encountered it a few times.