It can be distinguished from other Cheilanthes species within its range (Ch. maderensis, Ch. guanchica) by its fimbriated pseudoindusia and habitat (limestone).
Gymnocarpium dryopteris, separated from G. robertianum by its rachis glabrous and lowermost pinnae as large as the rest of the blade. Photos taken in Kaunas, Lithuania, in a spruce forest.