Stems long-creeping, 1--3 mm diam.; scales uniformly brown or slightly darker at base, linear-lanceolate, straight to slightly contorted, loosely appressed, persistent. Leaves usually scattered, 8--40 cm; vernation noncircinate. Petiole black, rounded adaxially. Blade lanceolate to linear-oblong, 2-pinnate-pinnatifid to 3-pinnate at base, 1.5--6 cm wide; rachis rounded adaxially, lacking scales, with dimorphic pubescence, abaxially sparsely hirsute, adaxially covered with tortuous, appressed hairs. Pinnae not articulate, dark color of stalk continuing into pinna base, basal pair often slightly larger than adjacent pair, ± equilateral, appearing glabrous or sparsely pubescent adaxially. Costae black adaxially for most of length; abaxial scales absent. Ultimate segments narrowly elliptic to elongate-deltate, not beadlike, the largest 3--7 mm, abaxially and adaxially sparsely hirsute to glabrescent. False indusia marginal to obscurely inframarginal, somewhat differentiated, 0.1--0.4 mm wide. Sori somewhat discontinuous, often concentrated on interrupted lateral lobes. Sporangia containing 64 spores. 2 n = 116.
Sporulating summer--fall. Calcareous rock outcrops and shell mounds; 0--100 m; Fla.; Mexico; West Indies; Central America; South America.
In the flora, the primarily Caribbean Cheilanthes microphylla is known from a small number of localities on the Florida peninsula. This restricted distribution, combined with its smaller stems, mostly black costae, and 64-spored sporangia, helps to separate Cheilanthes microphylla from the closely related C . alabamensis .