Mycopteris attenutissima is distinguished by the dense and evenly distributed erect reddish setae on the lower leaf surface. Mycopteris alsopteris is similar, but differs by having glabrous pinna margins. The pinna margins of M. attenuatissima are setose. In these photographs you can see the black clavate ascomes (fruiting bodies) of Acrospermum, the epibiotic ascomycete that inhabits the leaves of nearly all Mycopteris.