Devonian Period

An age of land plant diversification

The Devonian Period (419-359 Ma) is in the Paleozoic Era, occurring after the Silurian Period and before the Carboniferous Period.

Geologic Age

  • 419.2–358.9 million years ago

Eon / Era / Period


What happened during this time?


Trends over time...

  • Major radiation of land plants during this time, in which plants are relatively small at the start of the period and become 100 foot trees by the end

  • In Early Devonian, land plants small and restricted to the water's edge and moist, lowland habitats.

    • Changes in stelar arrangement of the vascular system of plants made them more drought-resistant, which opened up new landscapes for exploration (Bouda et al. 2022)

      • The cylinder-shaped arrangement in the earliest land plants had initially served them well in their early watery habitats.

      • As plants moved onto land with fewer water resources, the plants had to overcome drought-induced air bubbles.

      • Early land plants did this by reconfiguring the ancestral, cylindrical-shaped xylem into more complex shapes that prevented air bubbles from spreading.

    • The origin of roots in the zosterophylls, and woody growth in the euphyllophytes appears at this time

    • Plants probably evolve heterospory in the early Emsian, in which there are large "female" spores, and smaller "male" spores (e.g. Aarabia)

  • By Middle Devonian plants become increasing larger with the evolution of leaves and complex vascular tissue

    • Plants became tree-like (Eospermatopteris) during the Eifelian, and early forests ecosystems formed by the Givetian (e.g. Gilboa, NY)

    • Seed-like structures or proto-seeds appear (e.g. Runcaria), but are not true seeds since they have an incomplete integument

  • By the Late Devonian, true trees (i.e. Archaeopteris) had evolved and dominated flood plain environments.

    • In addition, early lycophyte trees grew in stands in swamp-like conditions

    • The earliest evidence of true seeds appear in the Late Devonian



  • Diversification of land invertebrates

  • Amphibians originate

Image from Berry (2019), on the ecology and appearance of known early forests throughout the Devonian Period.

  • By the early Middle Devonian (Eifelian), there are forests of Cladoxylopsids, including the earliest known tree-like plant, Eospermatopteris

  • The late Middle Devonian (Givetian), these Cladoxylopsid forests also had vine-like aneurophytes and smaller lycophyte trees intermixed

  • The Late Devonian, saw a change to forests with true trees, such as the progymnosperm Archaeopteris. Other forests were dominated with lycophyte trees, such as Guangdedendron (Wang et al. 2019)


  • Oxygen levels begin at 20% of the atmosphere, and then steadily increase to 27.5%

  • Carbon dioxide levels begin at ~4,200 ppm and drop to 2,900 ppm in the Middle Devonian, then increasing to ~3,500 ppm by the Period's end

    • The colonization of land by plants led to the following changes in carbon dioxide and oxygen (Dahl & Arens 2020):

      1. Atmospheric CO2 decline and climatic cooling (permanent transition)

      2. Atmospheric O2 rise and ocean oxygenation (potentially permanent transition)

      3. Ocean fertilization and anoxia (temporary perturbations, ~1 Myr)

  • Significant changes in the world's geography took place during the Devonian

  • Earth was divided into two supercontinents, Gondwana and Euramerica.

    • These vast landmasses lay relatively near each other in a single hemisphere, while a vast ocean covered the rest of the globe.

    • These supercontinents were surrounded on all sides by subduction zones.

    • With the development of the subduction zone between Gondwana and Euramerica, a major collision was set in motion that would bring the two together to form the single world-continent Pangea in the Permian.

  • In addition to global patterns of change, many important regional activities also occurred.

  • In the Middle Devonian, the continents of North America and Europe collided, resulting in massive granite intrusions and the raising of the Appalachian Mountains of eastern North America (Acadian Orogeny).

    • Vigorous erosion of these newly uplifted mountains yielded great volumes of sediment, which were deposited in vast lowlands and shallow seas nearby.

  • During Late Devonian environmental conditions change causing large faunal extinction event

  • "Biotic crisis" decimates tropical marine environments (Algeo and Scheckler 1998)

    • Land plants may have increased weathering of rocks and soils, producing an influx of minerals to the marine env't

    • Both an increase in root depth and penetration as well as the ability of seed plants to conoloize drier, upland env'ts may have contributed to increased soil formation (pedogenesis)

    • Increased nutrient input on rivers creates eutrophic conditions in epicontinental seaways, "resulting in algal blooms, widespread bottom water anoxia, and high sedimentary organic carbon fluxes".

    • Increase in plant biomass causes a draw-down of atmospheric CO2, and results in global cooling and glaciation.

Additional Resources