The Devonian: Age of Fishes

• In search of our origins
  • Records of past life
    • The notion of geologic time
    • The history of the Devonian System
  • Witnesses to evolution
  • A lost world
    • Tectonic context
    • Paleogeography
    • Climate
    • A Devonian day
  • Life in crisis
    • The Late Devonian extinction event
• The plant world
  • The conquest of land
  • The first forests
  • The plants of Miguasha
    • Protobarinophyton
    • Archaeopteris
    • Spermasporites
    • Spores by the millions
• The animal world
  • Life in the sea
  • The diversification of fish
  • Toward the first tetrapods
  • The animals of Miguasha
    • A window through time
      • Representativity
      • Fossil quality
      • Specimens by the thousands
    • The food chain
      • Of predators and prey
      • Stomach contents
      • Coprolites
    • Invertebrates
      • The aquatic environment
      • Land-based communities
    • Vertebrates
      • Jawless fish
        • Anaspids
        • Osteostracans
      • Jawed fish
        • Placoderms
          • Antiarchs
          • Arthrodires
        • Acanthodians
        • Actinopterygians
        • Sarcopterygians
          • Actinistians
          • Porolepiforms
          • Dipnoi
          • Osteolepiforms
          • Elpistostegalians

Climate

During most of the Devonian Period, the climate was relatively mild and the continent of Euramerica, which straddled the equator at the time, set the scene for the spread of tropical and equatorial forests. The position of this land mass also meant that many communities of vertebrate animals were concentrated near the equator where the warm climate encouraged their growth and evolution.

(56 kb)But the end of the Devonian was marked by a period of global cooling, and severe glaciations caused the extinction of many species. This cooler period lasted for 100 million years until the beginning of the Triassic Period, when dinosaurs rose up to reign over the world.

The cooling episode may be partly explained by the emergence of photosynthetic plants in Earth’s first forests. Photosynthetic plants remove carbon dioxide – a greenhouse gas – from the atmosphere, and this may have contributed to the lower temperatures. But the “big chill” can also be explained by the positions of the continents themselves. With the major remodelling of a landmass like that involved in the formation of Pangea, oceans are closed and water currents drastically modified. (40 kb)Ocean currents are important temperature regulators because they redistribute heat around the planet, so a change in ocean current circulation inevitably leads to a change in the climate.

Miguasha: A story written in stone

• The Gaspé Peninsula: A world of oceans and mountains
  • The birth of the Appalachians
  • The closing of an ocean
  • A sea of fossils
  • Faunal realms
  • Devonian lands in the Gaspé Peninsula
• The Miguasha Group
  • The Fleurant Formation
  • The Escuminac Formation
    • Geological characteristics
    • Localization systems
    • Biostratigraphy
    • An ancient estuary
    • An environment of exceptional preservation
• Of cliffs and men
  • The Seigniory of Shoolbred
  • A World Heritage Site
  • Miguasha fossils around the world
  • The geology craze of the 19th century
  • The first discoveries
  • Scientists come to Miguasha
  • Links to Scotland
  • Local fossil hunters
  • Erik Jarvik and the Prince of Miguasha
  • The birth of the Miguasha project
  • The 1991 International Symposium
• Le Parc national de Miguasha
  • Protecting a unique heritage
  • Fossil digs and research
  • The on-site museum

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Climate
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© Miguasha National Park 2007

Title: Atmospheric carbon curve
Author: François Bienvenue
Sources: Parc national de Miguasha
Year: 2007

Description:
Variations in temperatures and atmospheric concentrations of carbon through geological time. A marked drop in the concentration of atmospheric carbon and rapid cooling characterized the end of the Devonian and the onset of the Carboniferous.

Title: Miguasha under the tropics!
Author: François Bienvenue
Sources: C.R. Scotese (Paleomap Project, http://scotese.com).
Year: 2007

Description:
Major climatic domains of the Upper Devonian. The region of Miguasha was situated south of the equator and benefited from a relatively warm climate. An ice cap associated with an overall decrease in temperatures formed at the South Pole at the end of the Devonian. Position of the paleocontinents by C.R. Scotese (Paleomap Project, http://scotese.com).