Marattiaceae, the giant fern family, the only family of the fern order Marattiales. The family contains four genera and some 150 modern species of large tropical and subtropical ferns with stout, erect stems. The leaves (fronds) may be very large in some species, such as Angiopteris evecta, which may have a stem 60 to 180 cm (2 to 6 feet) in height and leaves 4.5 metres (15 feet) or more in length.
Genera are distinguished mainly by the disposition of the spore-producing structures (sporangia), which occur on the lower side of the leaves. Angiopteris, with one species (including some 200 microspecies), has separate sporangia. Marattia (60 species) has the sporangia united in clusters called synangia, which are paired along each side of certain leaf veins and open toward the leaflet axis in this genus. Danaea (30 species) has single synangia, sometimes extending from the midrib of the leaflet to the margin and open at the terminal end. The genus Christensenia (one species) has the synangia circular in outline, rather than oval.
The genus of extinct ferns Psaronius, from Carboniferous and Permian times (roughly 360 to 250 million years ago), is considered to be either a member of the Marattiaceae or very closely related to it. The Marattiaceae generally are considered to be one of the most primitive extant families of ferns.