Name honors Harold Lloyd Lyon (1879-1957), American botanist at Hawaiian Sugar Planters' Association; later a director of Foster Botanical Garden and Manoa Arboretum (the latter subsequently renamed Harold L. Lyon Arboretum).

Plants small to medium-sized. Rhizomes decumbent, short with several persistent dead stipes, and 7-20 fronds clustered at tips. Fronds 10-25 cm long, arranged in a flattened rosette. Stipes usually 1/3-1/4 frond length, deeply grooved adaxially, dark brown to black. Blades 1-pinnate at base, pinnatifid distally, lanceolate; rachises deeply grooved. Pinnae, usually only basal 1-2 pairs short-stalked. Ultimate segments slightly falcate, margins toothed. Sori short, 1-2 mm long, parallel and close to or touching midrib, almost always in 1 row, very close and often overlapping, elongate. Indusia large, often overlapping, with scattered fine hairs.

Seldom seen but locally common in its restricted habitat under dark, moist, over-hanging banks or vegetation, near streambeds, 490-880 m, on Kaua'i (one site in Koai'e Canyon), O'ahu, Maui, and historically also from Hawai'i.

Doodia lyonii differs from D. kunthiana in having smaller, narrower, more lanceolate fronds, and sori close to or touching the midrib, almost always in one row and very close to overlapping. It grows on dark, damp streamsides with overhanging banks and vegetation.