The Devonian Era from 416 million years ago to 359 million years ago. Most of the planet remains under water. Land masses continue to drift away from the south pole. Much of the land is near the equator, the world is warm.
Plants develop true leaves during this era, but the veins carrying water through them are rather haphazard. At 380 million years back the leaves, microphylls, have a single vein, same as they do on horse tails today. The dramatic CO2 drop has been linked to the evolution of leaves on plants.
By 350 million years back, we have megaphylls, which are the types of leaves we see on modern plants. The veins are more like webbing than modern day vein patterns.
Horsetail plants are common, we usually call them rush now. Ferns show up and give us the first seed bearing plant. Spores need the male and female parts to get wet so they can move and get together. Seed bearing plants do not need water for fertilization.
Plants get larger and many develop stronger woodier stems. Some of these plants reach as high as 60′. Forests begin to cover the land and life moves further from the water’s edges.
Insects also appear, centipedes, scorpions, and plant eating mites.
Most plants reproduce asexually but seed bearing plants are gaining ground. Plants are getting sexy, and they are providing some starting food with the seeds.
One of the most important developments for plants during this era is soil. Earlier plants grew on rock and sand. While early lichens were working their hearts out creating soil, the first real organic soil appears at this time. As soil deepens in this era plant root systems evolve to make use of this new soil. As soil spreads so do our forests. The soil also likely drew down CO2.
At the end of this era we have a major extinction likely due to global cooling.
Terrestrial±marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events
Plants kick-started Earth’s oxygenation
Devonian Times – Plants and soils
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