From the Greek. Thelys means female, + pteris, the word for ferns in general.
Rhizome: long-creeping, triangular scales.
Frond: deciduous, monomorphic or somewhat dimorphic.
Stipe: scaly, vascular bundles: 2, crescent-shaped.
Blade: 1-pinnate to pinnate-pinnatifid, lanceolate to ovate, transparent needlelike hairs, sometimes glandular.
costae grooved above, discontinuous with the rachis, veins free.
Sori: round or oblong, medial to supramedial or elongate along veins, indusium: reniform, occasionally ephemeral, at a sinus.
Members of the genus are pinnate with deeply lobed pinnae, have two vascular bundles, sori with a kidney-shaped, short-lived indusium, and needle-like, translucent or white hairs on the lamina, rachis, stipe.