Mankyua is a recently discovered plant, a single species in its own genus. It is a fern in the Ophioglossales. Its only species, M. chejuense, grows only on a small Korean island, Cheju Island. While this plant is clearly ophioglossoid in the broad sense, its precise cladistic position is uncertain. It has a fused sporangial structure similar to Ophioglossum, but a vegetative structure, with palmately-radiating pinnae, reminiscent of Helminthostachys. It may be a basal offshoot of the ophioglossoid clade sensu strictu.