Molecular phylogenetic studies of land plant (embryophyte) origins have begun to tease apart those evolutionary contributions derived from prior algal genes and those de novo genes that evolved during a charophyte–embryophyte transition. Applying the concept of genomic assembly in plant evolution to the fossil record leads to a paradigm shift in the interpretation of the Ordovician record of land plants. Traditional phylogenetic thinking requires fossil species taxa to occupy nodes on a phylogeny. An evo-devo approach can view character evolution separately from species taxa, freeing up fossil spores and tissue fragments to become clues to underlying developmental pathways or gene regulatory networks. This results in a re-assessment of what is meant by the presence of land plants in the Ordovician landscape. The new model helps to reconcile discrepancies between molecular time-trees and the “missing” record of fossil plants during the Ordovician Period.
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