Monotypic plant orders

REDIRECT Pleuromeiaceae

REDIRECT Selaginella

The Caytoniales are an extinct order of seed plants known from fossils spanning from the Middle Triassic (Anisian) to the Late Cretaceous (Campanian). They are regarded as "seed ferns" because they are seed-bearing plants with fern-like leaves. Although at one time considered angiosperms because of their berry-like cupules, that hypothesis was later disproven. Nevertheless, many authorities consider them likely ancestors or close relatives of angiosperms. The origin of angiosperms remains unclear, and they cannot be linked with any known seed plants groups with certainty.

REDIRECT Calamopityaceae