Greek diploos, twofold, +pteron, wing, + idion, a diminutive suffix; the pinnae of the fronds resemble wings.
Plants medium to large-sized, terrestrial. Rhizomes long-creeping, scales dark, with a few scattered marginal cilia. Fronds with indeterminate growth, sometimes very long and scandent. Stipes erect, sometimes climbing, hemispheric in cross-section or with wide, shallow, adaxial U-shaped grooves, scales sparse at bases, changing to white fibrils distally. Blades 2-pinnatepinnatisect, scaly, growing indeterminately (without forking) by repeated growth from intermittently dormant buds between most distal pinnae, apical buds covered by dark, linear-triangular scales with lighter-colored, ciliate margins. Pinnae opposite, large, up to 1.2 m long. Pinnules pectinate. Ultimate segments short. Veins once forked. Sori exindusiate, with 2-6 sporangia.
A genus of about twenty-five species ranging from northern India, southern China, the western Pacific from Japan to Australia, and Polynesia, with one species in South America.
Represented in Hawai'i by a single indigenous species.