Devonian
The Devonian is the period of the Paleozoic era from from 416 million years to 359 million years ago.[1] It is named after Devonshire, England, where rocks from this period were first studied.
Sea levels were high, and there was a great variety of fish and other marine organisms.[2] The Devonian fish included the Agnatha (jawless fish), the Acanthodii (spiny fish), the Placoderms (armoured fish), the Chondrichthyes (cartilaginous fish), and the early Osteichthyes (bony fish).
During the Devonian the first stages of fish evolution into tetrapods occurred (around 365 mya). Various terrestrial arthropods also became established. The first seed-bearing plants spread across dry land, forming huge forests.
The supercontinent Pangaea was starting to form. Tectonic and volcanic activity was high. A series of extinction events occurred towards the end of the Devonian, including a major event at the Frasnian-Famennian boundary, about 364 mya.
[change] References
- ↑ Gradstein, Felix M. Ogg J.G. Smith A.G. 2000. A geologic time scale 2004. Cambridge: Cambridge University Press. ISBN 0-521-78673-8.
- ↑ The Devonian was once known as the Age of Fish.
