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Division Polypodiophyta
Division Polypodiophyta
In a modern sense, ferns are plants with frond-like leaves and underground rhizomatous stems. Early ferns, during the Devonian Period, did not possess these features and were "leafless" with a wide range of morphologies. Anatomically, fern-like plants possess complex anatomy, with permanent protoxylem strands restricted to the periphery of the protoxylem sections (Beck & Stein, 1993). This specific anatomical feature unites all living and extinct "ferns", sometimes called the monilophytes. Notice that the horsetails and the psilophytes, which don't look like ferns, are also in this clade.
Diversity
Diversity
Approx. 12,000 species of living (extant) ferns
Very successful spore-bearing group
The Polypodiophyta or Pteridophyta are "ferns" sensu lato (in the loose sense)
This clade is sometimes called the Monilophytes
Living and extinct fern (monilophyte) groups, include:
- Ophioglossidae
Psilophytes (Psilotales)
Ophioglossoid ferns (Ophioglossales)
Osmundaceae
Guaireaceae †
Botryopteridaceae †
Anachoropteridaceae †
Kaplanopteridaceae †
Psalixochlaenaceae †
Sermayaceae †
Tedeleaceae †
Skaaripteridaceae †
Tempskyaceae †
Schizaeaceae
Hymenophyllaceae
Gleicheniaceae
Dicksoniaceae
Cyatheaceae
Matoniaceae
Loxsomataceae
Dipteridaceae
Above: Anatomy of several extinct and living monilophytes (ferns) showing the permanent protoxylem strands in the tips of the xylem lobes (A=Asteropteris, B=Calamophyton, C=Equisetum)
Ecology & Form
Ecology & Form
Stems
Stems
Vascular tissue present, but no secondary xylem (except in fossil groups)
A synapomorphy for this group is protoxylem permanently in the lobes of the vascular stele
Maturation of the xylem is mesarch
Leaves
Leaves
Wide range of simple and compound leaves in derived forms
Although compound leaves are a feature that most people attribute to ferns, the basal groups in the fern clade were leafless
e.g., Members with absent or reduced leaves: stauropterids, rhacophytes, and psilophytes(?)
Roots
Roots
Roots adventitious, born from rhizomes
Roots absent in the psilophytes
Reproductive structures
Reproductive structures
Sporangia are born abaxially on leaves in ferns
Sporangia are born on lateral stalks in psilophytes and equisetophytes
Additional Resources
Additional Resources
Leaf arrangement steers vascular pattern evolution in ferns (Phys.org 27Oct2025)
└Fern vascular architecture reveals how developmental constraint can generate novel morphology (Suissa, 2025)
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