This thinness generally necessitates a permanently humid habitat, and makes the fronds somewhat translucent.

“Filmy ferns” in the taxa Hymenophyllaceae grow in constantly wet environments.

The Pteridophyte Phylogeny Group classification of 2016 (PPG I) accepts the genus as one of eight in the subfamily Trichomanoideae, saying that there are about 60 species.

T. ankersii Parker T. tuerckheimii Christ T. hostmannianum (Klotzsch) Kunze T. pinnatum Hedw.

T. holopterum Kunze (Entire-winged bristle fern) T. roraimense Jenman T. lucens Sw. T. trigonum Desv.

T. crispiforme Alston T. vandenboschii P.G.Windisch T. accedens C.Presl T. egleri P.G.Windisch T. pilosum Raddi Species formerly placed in this genus include: