Roots proliferous. Stems erect, unbranched; scales brown throughout, broadly linear, 1--2 × 0.7--1.1 mm, margins shallowly and widely dentate. Leaves monomorphic. Petiole green to black, dull, 2--10(--12) cm, 1/3--1/2 length of blade; indument absent. Blade narrowly deltate, 1--2-pinnate, 4--20(--30) × 1.8--12(--18) cm, thick, nearly glabrous; base not tapered; apex gradually tapered, not rooting. Rachis green to black, dull, abaxially glabrous. Pinnae in 10--22 pairs, linear-deltate, medial pinnae 1--4(--9) × 0.3--1(--2.5) cm; base with acroscopic auricle or pinnule enlarged, excavated in proximal 1/5--1/4; margins mostly 1--2-dentate-serrate, or lobed or pinnate proximally or in proximal 2/3; apex blunt in some 1-pinnate forms, gradually reduced to attenuate in strongly 2-pinnate forms; pinnules narrow, not auriculate. Veins free, evident. Sori 4--9(--10) pairs per pinna, subcostal, nearly parallel to costae on both basiscopic and acroscopic sides. Spores 64 per sporangium.

Mainly epiphytic on old sloping tree trunks in shady forests; 0--50 m; Fla.; Mexico; West Indies in the Antilles; Central America; South America.

In the flora Asplenium auritum is evidently confined to Florida, where it is rare, occurring primarily on live oaks ( Quercus virginiana Miller). The species is highly variable. Juvenile plants, less than 2 cm, tend to be 2-pinnate. In mature plants all stages between 1-pinnate and 2-pinnate leaves are found, but 1-pinnate are more common.