Argyrochosma (J.Sm.) Windham, Amer. Fern J.

Kessler, Michael, Smith, Alan R. & Prado, Jefferson, 2017, Prodromus of a fern flora for Bolivia. XXVII. Pteridaceae, Phytotaxa 332 (3), pp. 201-250 : 205

Argyrochosma (J.Sm.) Windham, Amer. Fern J. 77(2): 38. 1987.

= Notholaena sect. Argyrochosma J.Sm., J. Bot. (Hooker) 4: 50. 1841.

Argyrochosma is monophyletic ( Sigel et al. 2011) and closely related to a clade comprising Paragymnopteris , Pellaea , and Astrolepis ( Wang et al. 2015) ; the species have frequently been included in one of those genera, or, more often, in the New World genus Notholaena (e.g., by Tryon 1956). In Bolivia, Argyrochosma is recognized by 2-to 3-pinnate blades with petiolulate, ovate ultimate segments, farinose abaxial pinnae surfaces (except for A. tenera ), lack of hairs or scales on the blades, very dark reddish to atropurpureous petioles and rachises, concolorous rhizome scales; and a base chromosome number of x = 27, unique in the family ( Sigel et al. 2011). A largely New World genus of about 20 species ( Windham 1987), concentrated in the arid subtropical regions of southwestern U.S.A. and northern Mexico ( Mickel & Smith 2004); three closely related species are known from Bolivia, and these have sometimes been considered conspecific, e.g., by Tryon (1964) and by Tryon & Stolze (1989). Remarkably, a single species, A. connectens (C.Chr.) G.M.Zhang , has recently been documented in central China ( Wang et al. 2015).