Early Devonian Explained

Early Devonian
Color:Early Devonian
Time Start:419.2
Time Start Uncertainty:3.2
Time End:393.3
Time End Uncertainty:0.4
Caption Map:Map of Earth as it appeared 400 million years ago during the early Devonian, Emsian stage
Image Outcrop:Rhynie chert.jpg
Caption Outcrop:Sample from the Lower Devonian Rhynie chert
Timeline:Devonian
Chrono Name:Early Devonian
Strat Name:Lower Devonian
Name Formality:Formal
Celestial Body:earth
Usage:Global (ICS)
Timescales Used:ICS Time Scale
Chrono Unit:Epoch
Strat Unit:Series
Timespan Formality:Formal
Lower Boundary Def:FAD of the graptolite Monograptus uniformis
Lower Gssp Location:Klonk, Czech Republic
Lower Gssp Accept Date:1972[1]
Upper Boundary Def:FAD of the conodont Polygnathus costatus partitus
Upper Gssp Location:Wetteldorf Richtschnitt section, Wetteldorf, Eifel, Germany
Upper Gssp Accept Date:1985[2]

The Early Devonian is the first of three epochs comprising the Devonian period, corresponding to the Lower Devonian series. It lasted from and began with the Lochkovian Stage, which was followed by the Pragian from and then by the Emsian, which lasted until the Middle Devonian began, .[3] During this time, the first ammonoids appeared, descending from bactritoid nautiloids. Ammonoids during this time period were simple and differed little from their nautiloid counterparts. These ammonoids belong to the order Agoniatitida, which in later epochs evolved to new ammonoid orders, for example Goniatitida and Clymeniida. This class of cephalopod molluscs would dominate the marine fauna until the beginning of the Mesozoic Era.

Notes and References

  1. Chlupáč . Ivo . Hladil . Jindrich . The global stratotype section and point of the Silurian-Devonian boundary . CFS Courier Forschungsinstitut Senckenberg . January 2000 . 1–8 . 7 December 2020.
  2. Ziegler . W. . Klapper . G. . Stages of the Devonian System . Episodes . June 1985 . 8 . 2 . 104–109 . 10.18814/epiiugs/1985/v8i2/006 . 18 December 2020. free .
  3. Cohen. K.M.. Finney. S.C.. Gibbard. P.L.. Fan. J.-X. . 2013 . The ICS International Chronostratigraphic Chart. Episodes. 36. 3. 199–204 . 10.18814/epiiugs/2013/v36i3/002. 7 January 2021. free.