Myriopteris Fée

Kessler, Michael, Smith, Alan R. & Prado, Jefferson, 2017, Prodromus of a fern flora for Bolivia. XXVII. Pteridaceae, Phytotaxa 332 (3), pp. 201-250 : 214

Myriopteris Fée , emend. Grusz & Windham (2013), Mém. Foug. 5: 148. 1852.

Myriopteris comprises ca. 45 species and at least two recognized hybrids ( Grusz & Windham 2013), ranging from the United States to South America (to northern Argentina); much of the diversity is in Mexico ( Mickel & Smith 2004). One species, M. rawsonii (Mett. ex Kuhn) Grusz & Windham , is known from South Africa ( Eiserhardt et al. 2011). By far the greatest number of species occurs in southwestern U.S.A. and Mexico, and only five species occur in South America, all of these wide-ranging.

Grusz & Windham (2013) discussed the paucity of synapomorphies distinguishing Myriopteris from other cheilanthoid genera and the fact that homoplasy is rampant in the cheilanthoid lineage (as it is in Notholaena ; see Rothfels et al. 2008). One interesting difference exhibited by Myriopteris is that all species produce 64 small spores or 32 large spores per sporangium (vs. 32 small spores or 16 large spores in Cheilanthes s.s.); this difference relates to the fact that there is one more cell division (as in most higher leptosporangiate fern families and genera) in the lineages of cells prior to meiosis in Myriopteris compared to Cheilanthes s.s.; apomicts in both genera have the lower spore number, with spores invariably larger than in sexual species. In addition, the spores of Myriopteris spp. are mostly cristate or rugulose (vs. echinate, granulose, or verrucate in Cheilanthes s.s.). There is also a lack of obvious vein endings near the margins of ultimate segments (vs. prominent hydathodes). A further distinction is in the ranges of the two genera: Myriopteris is predominantly a genus of North America, while Cheilanthes comprises spp. from South America, and (primarily) the southern hemisphere of the Old World (Australasia, southern Africa). Other characters of Myriopteris include the compact to long-creeping, scale-tipped rhizomes, the scales concolorous, tan to dark brown, or bicolorous with a darker (blackish) central stripe; leaves in some species non-circinate; petioles castaneous to black, scaly and/or pubescent (rarely almost glabrous); rachises terete, flattened, or grooved adaxially, with indument similar to the petioles; blades usually 2-to 4-pinnate, lanceolate to ovate-deltate; abaxial surfaces usually scaly or pubescent; ultimate segments round to oblong, often very small (ca. 1 mm); veins obscure; segment margins usually recurved, only weakly differentiated, the sporangia partly to completely covered by the recurved margins; sporangia clustered at vein tips; and x = 29, 30 (many species apomictic).

Myriopteris is sister to the pellaeid clade, which includes Pellaea , Argyrochosma , and Astrolepis , among other genera (Schuettpeltz et al. 2007, Rothfels et al. 2008, Windham et al. 2009).