It is a small fern with pinnate fronds, growing in erect tufts, with a shiny black stipe and rachis (stem and leaf axis).

[4] It is round in cross-section but slightly flattened adaxially and has indistinct wings 0.1 to 0.3 millimeters (0.0039 to 0.012 in) on either side,[4][7] or lacks them entirely.

[3][5] Unlike the related Palmer's spleenwort (A. palmeri), it does not form proliferating buds at the tip;[5] however, the pinnatifid is often deciduous, leaving behind a naked rachis.

The members of this group all share dark, lustrous stipes and lack prominent hydathodes on the surface of the blade,[11] the latter characteristic distinguishing them from single-sorus spleenwort (A. monanthes) and others.

[12] Among the group, A. resiliens has a slightly more leathery leaf texture than the rest, lacks distinct teeth on the pinna margins, and tends to have once-forked, rather than simple, fertile veins.

[13][14] Stolze noted that specimens with leaf texture so thick as to obscure the veins may be identified as A. resiliens, as A. heterochroum and A. palmeri very rarely become this leathery.

The pinnae of A. resiliens are more widely spaced than those of A. trichomanes, which also lack the upward-pointing auricle,[2] the texture of the leaf tissue is more leathery,[13] and the stipe darker.

[22] Oliver Atkins Farwell transferred it to a segregate genus as Chamaefilix resiliens in 1931,[24] but this name was never widely accepted.

Alston described material from Argentina, previously identified with A. trichomanes, as a new species, A. lealii, which he named for its collector, Adrián Ruiz Leal.

A global phylogeny of Asplenium published in 2020 divided the genus into eleven clades,[26] which were given informal names pending further taxonomic study.

Members of the clade grow on rocks and have once-pinnate leaf blades with slender, chestnut- to dark-brown stalks.

[28] Within this group, a study based on nuclear and plastid genetic markers, using material from the United States, Mexico, and Costa Rica, showed that A. resiliens forms a clade with A. palmeri and specimens resembling A. heterochroum.

This suggests that A. resiliens developed by reticulate evolution, i.e., as the descendant of a hybrid between two taxa, each parental taxon carrying one of the two groups of plastid and nuclear makers.

[5][4] Within the United States, it is found from Florida west to Arizona and southern Nevada and north to south-central Pennsylvania.

[31] It is found on or at the base of cliffs or sinkholes, on limestone or other alkaline rocks,[3][4][7] although specimens have also been reported from crevices in granite[32] and sandstone.

[3][6] Plants at the higher altitudes (3,000 meters (9,800 ft) and above) are stunted and more compact than usual, with leaves 4 to 10 centimeters (2 to 4 in) long and overlapping pinnae a few millimeters in length.

These differences (observed in Guatemalan and Peruvian material) are believed to be due to environmental factors rather than any taxonomic distinction.

[35] While globally secure (G5), it is considered an endangered species in many of the states at the northern edge of its North American range.

[1] It has become extinct in Louisiana since the limestone caprock of a salt dome at Winnfield, the only location for the fern in the state, was quarried away.