Fern identification usually requires the use of mature sporophytes, since attempts to identify juveniles using morphological traits often provides unsatisfactory results. Here we examined young sporophytes found among boulders in a river basin of a xeric valley in central Peru. Attempts to identify these sporophytes first pointed to four different genera, two in Pteridaceae (Anogramma and Pityrogramma), and the others in Aspleniaceae (Asplenium) and Cystopteridaceae (Cystopteris). Here, we resolved this puzzle combining morphology and sequences of DNA (rbcL and trnG-R) that point to Pityrogramma trifoliata of Pteridaceae.