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| Middle Devonian | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 393.47 ± 0.99 – 382.31 ± 1.36Ma | |||||||||||||||||
.png) A map of Earth as it appeared 390 million years ago during the Middle Devonian Epoch, Eifelian Age | |||||||||||||||||
| Chronology | |||||||||||||||||
| |||||||||||||||||
| Etymology | |||||||||||||||||
| Name formality | Formal | ||||||||||||||||
| Usage information | |||||||||||||||||
| Celestial body | Earth | ||||||||||||||||
| Regional usage | Global (ICS) | ||||||||||||||||
| Time scale(s) used | ICS Time Scale | ||||||||||||||||
| Definition | |||||||||||||||||
| Chronological unit | Epoch | ||||||||||||||||
| Stratigraphic unit | Series | ||||||||||||||||
| Time span formality | Formal | ||||||||||||||||
| Lower boundary definition | Fad of theConodontPolygnathus costatus partitus | ||||||||||||||||
| Lower boundary GSSP | Wetteldorf Richtschnitt, Eifel hills,Germany 50°08′59″N6°28′18″E / 50.1496°N 6.4716°E /50.1496; 6.4716 | ||||||||||||||||
| Lower GSSP ratified | 1985 | ||||||||||||||||
| Upper boundary definition | FAD of theConodontAncyrodella rotundibola | ||||||||||||||||
| Upper boundary GSSP | Col du Puech de la Suque,Montagne Noire,France 43°30′12″N3°05′12″E / 43.5032°N 3.0868°E /43.5032; 3.0868 | ||||||||||||||||
| Upper GSSP ratified | 1986 | ||||||||||||||||
In thegeological timescale, theMiddle Devonian epoch (from 393.47 ± 0.99 million years ago to 382.31 ± 1.36 million years ago) occurred during theDevonian period, after the end of theEmsian age.
The Middle Devonian epoch is subdivided into two stages:Eifelian andGivetian.
In the middle Devonian the armored jawless fish known asostracoderms were declining in diversity and instead the jawed fish were thriving and increasing in diversity in both the oceans and freshwater. The shallow, warm, oxygen-depleted waters of Devonian inland lakes, surrounded by primitive plants, provided the environment necessary for certain early fish to develop essential characteristics such as well developed lungs, ability to crawl out of the water and onto the land for short periods of time, possibly in search of food which would be developed by the tetrapods later in theLate Devonian which are descendents of these early fish.
The earliestforest grew in the Middle Devonian (Eifelian) time. This new environment was formed bycladoxylopsid trees includingCalamophyton.[5]
TheTaghanic event took place near the end of the Middle Devonian.
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