Progymnosperm
Extinct woody plants ancestral to seed plants and first trees.
Progymnosperms are an extinct group of woody, spore-bearing plants that evolved from the trimerophytes and eventually gave rise to the spermatophytes, the ancestors of both gymnosperms and angiosperms (flowering plants). They have been treated formally at the rank of division Progymnospermophyta or class Progymnospermopsida. They are considered a paraphyletic grade of plants.
- classification
- Extinct group of woody, spore-bearing plants
- stratigraphic_range
- Middle Devonian to end of Permian
- earliest_known_order
- Aneurophytales (Middle Devonian)
- latest_surviving_group
- Noeggerathiales (until end of Permian)
- key_characteristics
- Vascular cambium with unlimited growth potential; xylem and phloem; strong monopodial growth; pycnoxylic wood in Archaeopteridales and Noeggerathiales
- spore_type
- Aneurophytales homosporous; remaining groups heterosporous
Lore & Background
During Late Devonian times, the aneurophytaleans are presumed to have given rise to the pteridosperm order Lyginopteridales. Also in the Late Devonian, another group of progymnosperms gave rise to the first really large trees known as Archaeopteris. The latest surviving group of progymnosperms is the Noeggerathiales, which persisted until the end of the Permian.
Reader's Guide
Progymnosperms hold a pivotal position in plant evolutionary history as the paraphyletic grade that bridges trimerophytes and seed plants. They are significant as the ancestors of the earliest seed plants (spermatophytes) and as the first true trees, with Archaeopteris representing the first really large trees. Their vascular cambium with unlimited growth potential and production of xylem and phloem allowed for substantial woody growth. The transition from homospory in Aneurophytales to heterospory in later groups marks a key step toward seed plant reproduction. The presence of pycnoxylic wood in both Archaeopteridales and Noeggerathiales indicates advanced wood anatomy. Their eventual decline and extinction by the end of the Permian closed a chapter that laid the foundation for the dominance of seed plants in terrestrial ecosystems.
Did You Know?
- Progymnosperms are a paraphyletic grade, not a monophyletic group.
- The earliest known progymnosperms are from the Middle Devonian order Aneurophytales.
- Archaeopteris, a Late Devonian progymnosperm, represents the first really large trees.
- The latest surviving progymnosperms, the Noeggerathiales, persisted until the end of the Permian.
More in Conifers And Gymnosperms 1-24
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