Some sources include two Asian species, "M. orientalis" and "M. intermedia", but molecular data shows that "M. struthiopteris" is more closely related to "Onocleopsis" and "Onoclea" (sensitive fern) than it is to "M. orientalis" and "M. intermedia", and so the latter should be moved to a genus "Pentarhizidium" which contains those two species.