Abrodictyum elongatum is a fern of the family Hymenophyllaceae. In addition to the characteristics of the genus, the stipe as well as the rachis is bare and the blade of the fronds is divided twice. The sori are numerous and regularly arranged on the lower limb, often in double rows. The style of the sori carries few capsules at its base; it extends more than three times the length of the campanulate indusie. This very long length is the characteristic that served to forge the specific epithet. The species, like those of the genus, has 33 pairs of chromosomes.