Cyclosorus Link, Hort. Berol.

Smith, Alan R. & Kessler, Michael, 2017, Prodromus of a fern flora for Bolivia. XXX. Thelypteridaceae, Phytotaxa 331 (1), pp. 1-34 : 21

Cyclosorus Link, Hort. Berol. 2: 128. 1833.

= Thelypteris subg. Cyclosorus (Link) C.V.Morton, Amer. Fern J. 53(4): 153. 1963.

The narrow circumscription of Cyclosorus used here has previously been adopted by some authors (e.g., Pichi Sermolli 1977, Holttum 1971, 1982). This clade (pantropical, with two species, only one of which, C. interruptus , occurs in the neotropics) is supported as monophyletic by Almeida et al. (2016). The native species previously placed in Thelypteris subg. Cyclosorus in some floras ( Mickel & Beitel 1988, Mickel & Smith 2004, Proctor 1977, 1985, 1989, Salino & Semir 2002, Smith 1981a, b, 1983, 1988, 1992, 1995a, b) are now treated in the genus Christella , as done by Pichi Sermolli (1977) and Holttum (1974, 1982).

Cyclosorus s.s. is characterized by having very long-creeping, nearly naked rhizomes; blades not reduced proximally (proximal pinnae the largest, or nearly so); veins from adjacent segments uniting below the sinuses and producing an excurrent vein that runs to the sinus; broadly ovate, tan scales on the costae abaxially; indusiate sori; sporangial stalks bearing stalked, globose, reddish glands; and a chromosome base number of x = 36. Plants typically grow in sunny freshwater swamps. Phylogenetic studies show it to be related to two Old World genera, Mesophlebion (ca. 17 spp.) and Ampelopteris (monotypic), with these three genera forming a clade sister to Meniscium .