What is "marattiidae"

Marattiidae is a subclass of Equisetopsida in the sense used by Mark W. Chase and James L. Reveal in their 2009 article "A phylogenetic classification of the land plants to accompany APG III." This subclass comprises a single fern order, Marattiales, and family, Marattiaceae. It is equivalent to the class Marattiopsida in previous treatments, including Smith et al., 2006.