Megalastrum Holttum, Gard. Bull.

Kessler, Michael, Moran, Robbin C., Mickel, John T., Matos, Fernando B. & Smith, Alan R., 2018, Prodromus of a fern flora for Bolivia. XXXV. Dryopteridaceae, Phytotaxa 353 (1), pp. 448-450 : 448-450

Megalastrum Holttum, Gard. Bull. Singapore 39(2): 161. 1986.

Megalastrum was relatively recently named and described by Holttum (1986), who separated it from Ctenitis . It differs from Ctenitis by its coarse, hyaline, septate, strigose, or spreading hairs with pointed tips on the adaxial and sometimes abaxial surfaces of the axes. Ctenitis and related genera have fine, usually blunt, often reddish, erect to spreading adaxial hairs that characteristically have adjacent cells twisted in opposite directions (catenate) when dried. In Megalastrum , the basal basiscopic veinlets of the distal pinnules arise from the costae (not from the costules as in Ctenitis ) and the basiscopic lobes of the distal pinnules are therefore broadly adnate to the costae. Further, in Megalastrum the veins end before the margins in conspicuous clavate tips, as viewed adaxially. Other characters of the genus include pinnate-pinnatifid to often much more dissected, decompound blades; petiole bases and blades scales often with marginal, curved teeth; exindusiate sori in most species (in Bolivia, all species except two; Smith & Moran 1988); and x = 41. Macrothelypteris also resembles some species of Megalastrum , but has two vascular bundles in the petioles (vs. four or more in Megalastrum ).

A genus of about 90 species, most of these in the Neotropics, 15 in Bolivia; three species occur in Africa, Madagascar, and the Mascarenes ( Rouhan & Moran 2011), and a few are on southern islands of the Pacific and Indian Oceans ( Sundue et al. 2010). The Bolivian species were treated by Kessler & Smith (2006), and all Andean species were more recently revised by Moran et al. (2014a, b). The following treatment incorporates elements from both studies.