|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
|H. W. Pfefferkorn et al. 1971||M. arnoldi has a pinnately divided frond; free sporangia cover the pinnules on the abaxial side. M. arnoldi has the largest sporangia and pinnules so far known in the genus, but is otherwise similar to M. angelica, M. monomakhoffi and M. permica.|