Devonian

This period is part of the Paleozoic era.

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

The Devonian is a geologic period that extends from about 360 to 408.5 million years before the present.

As with most older geologic periods, the rock beds that define the start and end are well identified, but the exact dates of the end of the period is uncertain by 5-15 million years.

The Devonian is named for England's Devonshire area where Devonian outcrops are common. The Devonian follows the Silurian period and precedes the Mississippian subperiod of the Carboniferous.

Devonian subdivisions

The Devonian is usually broken into Lower, Middle, and Upper subdivisions. The Faunal stages from youngest to oldest are:

• Famennian/Chautauquan/Canadaway/Conneaut/Conneautan/Conewango/Conewangan (Upper)
• Frasnian/Senecan/Sonyea/Sonyean/West Falls (Upper)

• Cazenovia/Cazenovian (Middle)
• Givetian/Erian/Senecan/Tioughniogan/Tioughnioga/Taghanic/Taghanican/Genesee/Geneseean (Middle)
• Eifelian/Southwood (Middle)

• Helderberg (Lower)
• Emsian/Sawkill/Deer Park (Lower)
• Pragian/Siegenian (Lower)
• Lochkovian/Gedinnian (Lower)

Devonian rocks are oil and gas producers in some areas.

Devonian palaeogeography

The southern continents remained tied together into the Supercontinent Gondwana. In equatorial regions, North America and Europe formed a continent. The remainder of modern Eurasia lay in the Northern Hemisphere.

During this time period, the subcontinent of Euramerica was home to all of the new things that the Devonian brought. Sea levels were high world wide. Much of the land lay under underneath shallow seas, where tropical reef organisms lived. A huge, deep ocean covered the rest of the planet

The Devonian was called the “greenhouse age.” Widespread reefs indicated that the climate was mild and warm, as well as generally dry.

Devonian fauna

Marine biota

Sea levels in the Devonian were generally high. Marine faunas continued to be dominated by bryozoa, diverse and abundant brachiopods and corals. Trilobites were still fairly common, but less diverse than in earlier periods. The ostracoderms were joined in the mid-Devonian by the first jawed fishes, the great armored placoderms, as well as the first sharks and ray-finned fish. (The first shark to appear in the oceans was Cladoselache, during the Devonion period.) They became abundant and diverse. In the Late Devonian the lobe-finned fish appeared, giving rise to the first tetrapods toward the end of the period.

Devonian reefs

A great barrier reef, now left high and dry in the sink, and atmospheric levels of this greenhouse gas may have dropped, cooling the climate and leading to a massive extinction event.

Both vertebrates and arthropods were solidly established on the land.