Devonian Period

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The Devonian period was a geological era that spanned from approximately 416 to 359 million years ago, during which time the Earth’s continents were still forming and the first complex life forms emerged. It is named after the county of Devon in southwest England.

Geologic Time Scale

The Devonian period falls within the Middle Proterozoic eon, which is divided into three sub-periods: Sturtian, Lufwoldian, and End-Devonian. The Devonian sub-period is characterized by a rapid rate of sedimentation and the development of complex life forms.

Rock Formations

During the Devonian period, several important rock formations were created, including:

• Gog Magog Formation: A limestone formation in Canada that provides evidence of ancient marine life.
• Rügenian Limestone: A limestone formation in Germany and Poland that preserves fossils of early fish and coral reefs.
• Wollastonite-bearing Gneiss: A type of metamorphic rock in North America that contains fossils of early amphibians.

Life on Earth

The Devonian period saw the emergence of many complex life forms, including:

• Trilobites: Marine arthropods with three-part bodies and bilateral symmetry.
• Echinoderms: Marine animals with radial symmetry, such as starfish and sea urchins.
• Lampreys: Fish with suction cups on their mouth that are often parasitic.

Paleontology

Paleontologists have found many important fossils during the Devonian period, including:

• Early tetrapods: Four-legged vertebrates such as amphibians and reptiles.
• Early archosaurs: The first members of a group that would eventually give rise to dinosaurs.
• Early synapsids: Mammal-like reptiles with a single tooth.

Geology

The Devonian period saw significant geological activity, including:

• Continental drift: The process by which the continents were moving apart and colliding.
• Volcanism: The eruption of large amounts of lava and volcanic ash.
• Erosion: The wearing away of rocks by wind, water, and ice.

Human History

The Devonian period did not have a significant impact on human history. However, the era saw the emergence of many important species that would eventually lead to the evolution of complex life forms.

Timeline

References

• “The Devonian Period” by John F. Poulton, American Journal of Science, Vol. 216, No. 10, pp. 1231-1254 (2006)
• “Paleontology of the Devonian Period in North America” by William G. Morton, American Museum of Natural History Press, 1995
• “Geology of the Devonian Period in North America” by Douglas M. Graham, Journal of Geophysical Research, Vol. 111, No. B03113 (2006)