Ecosystems during the Devonian Period

Hemicyclaspis

Ichthyostega

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  The first amphibians, such as Ichthyostega, appeared towards the end of the Devonian period.


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  Both freshwater and marine fishes show a great proliferation of forms, with many heavily armoured fishes including the Pteraspids, and the Cephalaspids such as Hemicyclaspis.


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  The evolutionary trends of the Silurian period continued during the Devonian period, with plants and vertebrate animals showing spectacular advances.
  

Geography during the Devonian Period

• As we approach the Late Devonian, Pangea is beginning to take shape.
• As the pressure on the Laurentian plate increased, huge mountain ranges were thrust up around the periphery of the continent.
• In addition, the Late Devonian saw the evolution of large trees with deep root systems
  
  

Climate during the Devonian Period

• The Devonian has been regarded as largely warm and equable, with a disastrous drop in temperatures in the Late Devonian leading to the Frasnian-Famennian "mass extinction".
• The climate of the Early Devonian is rather strongly zonal.
• In the Late Devonian, the southern "cool temperate" zone expands, with indications of glacial ice in parts of far western Gondwana (northern South America).
• However, the northern temperate zone appears to retreat before a subtropical zone which extends almost to 60° N.
  
  

Introduction to the Devonian Period

• The Age of Fishes
• A time of great transition. In the sea ammonoids and fish evolve and quickly diversify. On land trees and forests appear for the first time. The first insects, spiders, and tetrapods evolve.

Geography during the Silurian Period

• The early Paleozoic saw the continents clustered around the equator, with Gondwanaland continues it's slow southern drift
• Siberia, Laurentia and Baltica converge at the equator.
• By the end of the Silurian, these colliding continents had began to raise mountains and forge a new supercontinent, Laurussia.
  

Climate during the Paleozoic Era

• The Early Paleozoic climatewas also strongly zonal.
• The Early Paleozoic ended, rather abruptly, with the short, but apparently severe, Late Ordovician Ice Age.
• The Middle Paleozoic was a time of considerable stability.
• Baltica (Northern Europe and Russia) and Laurentia (eastern North America and Greenland) remained in the tropical zone.
  
  

Flora and fauna during the Silurian Period

lTropical reefs are common in the shallow seas of this period.

lJawless fish invade brackish and fresh water, as do eurypterids, xiphosurids, scorpions, which may have been semi-aquatic.