Stems compact to short-creeping; stem scales uniformly chestnut brown or with lighter margin, to 6 mm, margins ciliate-dentate. Leaves 11--130 cm. Blade pinnate-pinnatifid, pinna pairs 30--60. Pinnae deltate to ovate, largest 7--35 mm, symmetrically lobed, lobes 6--14 often acute, separated by deep sinuses; abaxial scales concealing surface, lanceolate, usually 1--1.5 mm, ciliate-dentate with delicate marginal projections; adaxial scales sparse, deciduous, elongate, stellate, attached at base, body 1--2 cells wide, attached at base. Sporangia containing 32 or 64 spores. Astrolepis sinuata comprises two cytotypes that tend to occupy different ranges and are treated here as subspecies. Sexual diploid populations (subsp. mexicana ) are widely distributed in Mexico, but in the flora they are apparently confined to the Davis and Chisos mountains of Texas and to southeast New Mexico. The range of the apogamous triploid (subsp. sinuata ) extends from Argentina to the southwestern United States, with a disjunct population in Georgia. Isozyme studies suggest that subsp. sinuata was derived from the diploid subsp. mexicana through autopolyploidy (D. M. Benham 1989).