Middle Devonian

393.3 ± 1.2 – 382.7 ± 1.6 Ma

PreЄ

Chronology

Devonian Graphical Timeline

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-420 --

-415 --

-410 --

-405 --

-400 --

-395 --

-390 --

-385 --

-380 --

-375 --

-370 --

-365 --

-360 --

Mississippian

Přídolí

Early M

Lochkovian

Pragian

Emsian

Eifelian

Givetian

Frasnian

Famennian

Rhynie chert[1]

Hangenberg event

Kellwasser event(s)[2]

Widespread[3]
shrubs & trees

S. America
glaciation begins

Hunsrück fauna

Subdivision of the Devonian according to the ICS, as of 2021.[4]
Vertical axis scale: millions of years ago.

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 the Conodont Polygnathus costatus partitus
Lower boundary GSSP| Wetteldorf Richtschnitt, Eifel hills, Germany
[ ⚑ ] 50°08′59″N 6°28′18″E﻿ / ﻿50.1496°N 6.4716°E﻿ / 50.1496; 6.4716
GSSP ratified| 1985
Upper boundary definition| FAD of the Conodont Ancyrodella rotundibola
Upper boundary GSSP| Col du Puech de la Suque, Montagne Noire, France
[ ⚑ ] 43°30′12″N 3°05′12″E﻿ / ﻿43.5032°N 3.0868°E﻿ / 43.5032; 3.0868
GSSP ratified| 1986

In the geological timescale, the Middle Devonian epoch (from 397.5 ± 2.7 million years ago to 385.3 ± 2.6 million years ago) occurred during the Devonian period, after the end of the Emsian age.

The Middle Devonian epoch is subdivided into two stages: Eifelian and Givetian.

## Life in the middle Devonian

In the middle Devonian the armored jawless fish known as ostracoderms 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 the Late Devonian which are descendents of these early fish.

The Taghanic event took place near the end of the Middle Devonian.

## References

1. ↑ Parry, S. F.; Noble, S. R.; Crowley, Q. G.; Wellman, C. H. (2011). "A high-precision U–Pb age constraint on the Rhynie Chert Konservat-Lagerstätte: time scale and other implications". Journal of the Geological Society (London: Geological Society) 168 (4): 863–872. doi:10.1144/0016-76492010-043. http://jgs.lyellcollection.org/content/168/4/863.abstract.
2. ↑ Kaufmann, B.; Trapp, E.; Mezger, K. (2004). "The numerical age of the Upper Frasnian (Upper Devonian) Kellwasser horizons: A new U-Pb zircon date from Steinbruch Schmidt(Kellerwald, Germany)". The Journal of Geology 112 (4): 495–501. doi:10.1086/421077. Bibcode: 2004JG....112..495K.
3. ↑ Algeo, T. J. (1998). "Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events". Philosophical Transactions of the Royal Society B: Biological Sciences 353 (1365): 113–130. doi:10.1098/rstb.1998.0195.
4. ↑ "Chart/Time Scale". International Commission on Stratigraphy. http://www.stratigraphy.org/index.php/ics-chart-timescale.

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