The order
Cyatheales, which includes the
tree ferns, is a
taxonomic division of the
fern class,
Polypodiopsida. No clear
morphological features characterize all of the Cyatheales, but
DNA sequence data indicate the order is
monophyletic. Some species in the Cyatheales have tree-like growth forms, but others have
rhizomes. Some species have scales on the stems and leaves, while others have hairs. However, most plants in the Cyatheales are
tree ferns and have trunk-like stems up to tall. It is unclear how many times the tree form has evolved and been lost in the order.