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Summary The advent of embryophytes (land plants) is among the most important evolutionary breakthroughs in Earth history. It irreversibly changed climates and biogeochemical processes on a global scale; it allowed all eukaryotic terrestrial life to evolve and to invade nearly all continental environments. Before this work, the earliest unequivocal embryophyte traces were late Darriwilian (late Middle Ordovician; c. 463–461 million yr ago (Ma)) cryptospores from Saudi Arabia and from the Czech Republic (western Gondwana). Here, we processed Dapingian (early Middle Ordovician, c. 473–471 Ma) palynological samples from Argentina (eastern Gondwana). We discovered a diverse cryptospore assemblage, including naked and envelope‐enclosed monads and tetrads, representing five genera. Our discovery reinforces the earlier suggestion that embryophytes first evolved in Gondwana. It indicates that the terrestrialization of plants might have begun in the eastern part of Gondwana. The diversity of the Dapingian assemblage implies an earlier, Early Ordovician or even Cambrian, origin of embryophytes. Dapingian to Aeronian (Early Silurian) cryptospore assemblages are similar, suggesting that the rate of embryophyte evolution was extremely slow during the first c. 35–45 million yr of their diversification. The Argentinean cryptospores predate other cryptospore occurrences by c. 8–12 million yr, and are currently the earliest evidence of plants on land.

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The advent of wood (secondary xylem) is a major event of the Paleozoic Era, facilitating the evolution of large perennial plants. The first steps of wood evolution are unknown. We describe two small Early Devonian (407 to 397 million years ago) plants with secondary xylem including simple rays. Their wood currently represents the earliest evidence of secondary growth in plants. The small size of the plants and the presence of thick-walled cortical cells confirm that wood early evolution was driven by hydraulic constraints rather than by the necessity of mechanical support for increasing height. The plants described here are most probably precursors of lignophytes.

A database of all reported Ordovician–Silurian land plant megafossil and dispersed spore assemblages has been assembled. For each assemblage a list of taxa has been prepared and its location plotted on new palaeocontinental reconstructions. These new data compilations are analysed with respect to palaeophytogeographical differentiation and various patterns of taxon diversity and morphological disparity that emerged during the origin, adaptive radiation and geographical spread of land plants. Our analyses include new quantitative assessments.Supplementary material:Appendix consisting of an abridged version of our dispersed spore database is available at:http://www.geolsoc.org.uk/SUP18680

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