Devonian
| Eon | Era | Period | Epoch | Start Million years ago |
|---|---|---|---|---|
| Phanerozoic | Mesozoic | Triassic | Lower Triassic | 252.17 |
| Palaeozoic | Permian | 298.9 | ||
| Carboniferous | Pennsylvanian | 323.2 | ||
| Mississippian | 358.9 | |||
| Devonian | 419.2 | |||
| Silurian | 443.4 | |||
| Ordovician | 485.4 | |||
| Cambrian | 541 | |||
| Proterozoic | Neoproterozoic | Ediacaran | 635 | |
The Devonian is the period of the Paleozoic era from 419.2 million years to about 359 million years ago.[1][2] 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.[3] 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.
References [change]
- ↑ International Stratigraphic Chart. [1]
- ↑ 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.
| Precambrian (4.567 gya – 541 mya) | |
|---|---|
| In the left column are Eons, bold are Eras, not bold are Periods. gya = billion years ago, mya = million years ago | |
| Hadean (4.567 gya – 4 gya) | |
| Archaean (4 gya – 2.5 gya) | |
| Proterozoic (4 gya – 2.5 gya) | Palaeoproterozoic (2.5 gya – 1.6 gya)
Mesoproterozoic (1.6 gya – 1 gya) Neoproterozoic (1 gya - 541 mya) Tonian (1 gya – 850 mya) Cryogenian (850 mya – 635 mya) Ediacaran (635 mya – 541 mya) |
| Source | International Chronostratigraphic Chart 2013. International Commission on Stratigraphy, retrieved 8 April 2013. Divisions of geologic time – major chronostratigraphic and geochronologic units USGS, retrieved 8 April 2013. |
