Fossil Ferns and Seed Plants

Fossil ferns, seed ferns, and gymnosperms record the great Paleozoic and Mesozoic forests and the origin of the seed, a key reproductive innovation.

Definition

Fossil ferns and seed plants comprise the spore-bearing vascular plants and the early seed-bearing plants whose fossils document forest ecosystems before the rise of flowering plants.

Scope

This topic covers the fossil record of ferns and fern allies such as lycophytes and sphenophytes, the seed ferns, and the gymnosperms including conifers, cycads, and ginkgoes, addressing their anatomy, reproduction, and roles in ancient forests and coal swamps.

Core questions

• How did the seed habit evolve and why was it advantageous?
• What plants built the Carboniferous coal forests?
• How are fern and gymnosperm fossils distinguished and reconstructed?
• How did gymnosperms dominate Mesozoic vegetation?

Key concepts

• Spore-bearing vascular plants
• The seed habit and ovules
• Coal-swamp floras
• Gymnosperm diversification

Key theories

Origin of the seed

The evolution of seeds in seed ferns freed plant reproduction from water and is documented by transitional ovule-bearing fossils.

Coal-forest ecosystems

Giant lycophytes, sphenophytes, and ferns built the Carboniferous wetland forests whose burial formed major coal deposits.

Clinical relevance

These plants formed the great coal forests whose preserved biomass is a major fossil fuel, and their fossils reconstruct the structure and climate of pre-angiosperm terrestrial ecosystems.

History

Fossil ferns and seed ferns were central to the study of Carboniferous coal floras from the nineteenth century, and the recognition of seed ferns resolved how the seed habit arose. Detailed anatomy from coal balls clarified the biology of these ancient plants.

Debates

Relationships among early seed plants

The branching relationships of seed ferns, conifers, cycads, and other gymnosperms remain debated as new fossils and analyses appear.

Key figures

• Gar W. Rothwell
• Thomas N. Taylor
• William G. Chaloner

Seminal works

• taylor2009
• stewart1993

Frequently asked questions

What are seed ferns?

Seed ferns are extinct plants with fern-like foliage that reproduced by seeds rather than spores, documenting an early stage in the evolution of seed plants.

What plants made coal?

Much coal formed from the buried remains of Carboniferous wetland forests dominated by giant lycophytes, horsetails, and ferns.