Plants leave the water for good
What happened
Rock from the Ordovician Period carries the first evidence that plants had begun colonizing dry land, in the form of microscopic spores called cryptospores, distinct from anything a marine alga produces. The U.S. National Park Service notes that the first unquestioned plant fossils come slightly later, from the Late Silurian, but the earlier Ordovician spore evidence points to the same slow migration: plant ancestors most likely evolved first in the sea, moved into fresh water, and only then, gradually, onto land itself.
Why it matters
Before this, dry land was mineral and rock, nothing more. Plants were the first to build soil, hold moisture, and create shade, terraforming the continents into a place animals could later follow, which is exactly what happens through the rest of this timeline.
How we know
The evidence is cryptospores, recovered by dissolving Ordovician and Silurian rock and examining the microscopic residue, whose distinctive wall structure marks them as land-plant spores rather than the very differently structured spores of algae. Their features resemble the spores of modern liverworts, the site of the earliest land plants uncontested lineage.
Sources
- U.S. National Park Service. Plant Fossils · Reputable sourcenps.gov · The domain "nps.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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Related timelines
- The Cambrian Explosion → · Picks up where the Cambrian explosion's ocean-bound story leaves off