Pellaea zygophylla, a new combination for a distinctive and well-known but neglected fern

Pellaea ovata is a widespread species, sexual diploid in Texas and northeastern Mexico but an apogamous triploid in northwestern Mexico, south to northern Argentina, and on Hispaniola. The type belongs to the southern, apogamous triploid form. Although these two forms have been discussed repeatedly in the literature, morphological distinctions between them have been overlooked and they have not been recognized taxonomically. However, they are distinct. Pellaea ovata s.s. has puberulent rachides and costae; pinnae usually 2-pinnate with a well-defined main axis and pinnules borne singly; fertile pinnules ovate, cordate basally and rounded apically. The sexual diploid form has rachides and costae glabrous; pinnae pseudo-dichotomously branched and pinnules usually paired; fertile pinnules narrowly rounded-trapeziform, obliquely truncate to cordate basally and truncate apically. Riddell named the sexual diploid form Pteris zygophylla, from which I give it the new combination Pellaea zygophy...