Land Plants get complicated!
During the Silurian and Early Devonian, land plants evolved a wide variety of new shapes, increasing in size and complexity as different solutions to living on land were explored. Many groups of plants could now grow up (rather than just along the ground) and branch out, which allows gathering more sunlight and producing more spores. The tallest plants reached 3 feet (1 meter) or more.
Early Devonian plant communities contained many different plants of different shapes and sizes.
Early lycophytes and distant relatives of ferns and horsetails appeared. Interestingly, liverworts, hornworts and mosses—which we would expect to find on the basis of relationships and known fossil spores—have not been found as large fossils in Silurian and early Devonian rocks.
Can I find Silurian-Early Devonian plants in Oklahoma?
No. Unfortunately, Oklahoma was still under the ocean during this period.