Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Pteridaceae
Genus Description - Terrestrial, less commonly epipetric; rhizomes short-creeping to erect, compact, with scales at apices; fronds medium-sized to very large, clumped, monomorphic; stipes usually glabrous; blades pinnate to several times pinnate, often with basal pinnae exaggerated basiscopically, blades often pentagonal to pedate; laminae chartaceous to coriaceous, minor axes mostly glabrous, generally with slender, antrorse awns on the adaxial axes at base of pinnae (rachis awns), pinnules, and ultimate segments (pinna awns); veins free or netted, without included veinlets; sori marginal, protected by differentiated recurved margins (false indusia), mostly continuous except at sinuses and segment apices; paraphyses usually present, mixed with sporangia; spores each generally with an equatorial ridge, perispore lacking; x =29.
Lectotype (first chosen by J. Sm.?, Hist. Fil. 295. 1875): Pteris longifolia L.
Litobrochia C. Presl, Suppl. Tent. Pterid. 148. 1836. Type: Litobrochia ampla (Kunze) C. Presl [= Pteris ampla Kunze] = Pteris grandifolia L.
Pteris is a pantropical genus of about 250 species, of which only about 60 are American. It is distinguished by its generally large fronds, marginal sori, and spores with an equatorial flange. Awns, which occur adaxially on the blade axes of many species of Pteris, are most conspicuous in the more laminated parts of the blades. Molecular studies (Cranfill, unpubl.) suggest that the genus is polyphyletic. In particular, P. longifoliia and P. vittata are not closely related to the rest of Pteris, and probably not congeneric with the remaining Mexican species