Mankyua is a recently-discovered plant, a single species in its own genus. It is a fern in the Ophioglossales

Ophioglossales

Ophioglossales are a small group of pteridophyte plants. Traditionally they are included in the division Pteridophyta, the ferns, originally as a family and later as the order 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

Ophioglossum

Ophioglossum is a genus of about 25-30 species of Ophioglossales in the family Ophioglossaceae, with a cosmopolitan but primarily tropical and subtropical distribution. The name Ophioglossum comes from the Greek, and means "snake-tongue".Adders-tongues are so-called because the spore-bearing stalk...

, but a vegetative structure, with palmately-radiating pinnae, reminiscent of Helminthostachys

Helminthostachys

Helminthostachys zeylanica is a terrestrial, herbaceous, fern-like plant of southeastern Asia and Australia, commonly known as Kamraj and tunjuk-langit...

. It may be a basal offshoot of the ophioglossoid clade sensu strictu.