early Devonian

{{Short description|First epoch/series of the Devonian}}

{{Infobox geologic timespan

| name = Early Devonian

| color = Early Devonian

| top_bar =

| time_start = 419.2

| time_start_uncertainty = 3.2

| time_end = 393.3

| time_end_uncertainty = 0.4

| image_map = Mollweide Paleographic Map of Earth, 405 Ma (Emsian Age).png

| caption_map = A map of Earth as it appeared 405 million years ago during the Early Devonian Epoch, Emsian Age

| image_outcrop = Rhynie chert.jpg

| caption_outcrop = Sample from the Lower Devonian Rhynie chert

| image_art =

| caption_art =

| timeline = Devonian

| chrono_name = Early Devonian

| strat_name = Lower Devonian

| name_formality = Formal

| name_accept_date =

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| celestial_body = earth

| usage = Global (ICS)

| timescales_used = ICS Time Scale

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| chrono_unit = Epoch

| strat_unit = Series

| proposed_by =

| timespan_formality = Formal

| lower_boundary_def = FAD of the graptolite Monograptus uniformis

| lower_gssp_location = Klonk, Czech Republic

| lower_gssp_coords = {{Coord|49.8550|N|13.7920|E|display=inline}}

| lower_gssp_accept_date = 1972{{cite journal |last1=Chlupáč |first1=Ivo |last2=Hladil |first2=Jindrich |title=The global stratotype section and point of the Silurian-Devonian boundary |journal=CFS Courier Forschungsinstitut Senckenberg |date=January 2000 |pages=1–8 |url=https://www.researchgate.net/publication/260135817 |access-date=7 December 2020}}

| upper_boundary_def = FAD of the conodont Polygnathus costatus partitus

| upper_gssp_location = Wetteldorf Richtschnitt section, Wetteldorf, Eifel, Germany

| upper_gssp_coords = {{Coord|50.1496|N|6.4716|E|display=inline}}

| upper_gssp_accept_date = 1985{{cite journal |last1=Ziegler |first1=W. |last2=Klapper |first2=G. |title=Stages of the Devonian System |journal=Episodes |date=June 1985 |volume=8 |issue=2 |pages=104–109 |doi=10.18814/epiiugs/1985/v8i2/006 |url=https://stratigraphy.org/gssps/files/eifelian.pdf |access-date=18 December 2020|doi-access=free }}

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The Early Devonian is the first of three epochs comprising the Devonian period, corresponding to the Lower Devonian series. It lasted from {{period span|Early devonian}} and began with the Lochkovian Stage {{period span|Lochkovian}}, which was followed by the Pragian from {{period span|Pragian}} and then by the Emsian, which lasted until the Middle Devonian began, {{ma|middle devonian|error=show}}.{{cite journal |last1=Cohen| first1= K.M.| last2= Finney|first2 = S.C.|last3 = Gibbard| first3 = P.L.| last4 =Fan|first4 = J.-X. |year=2013 |title=The ICS International Chronostratigraphic Chart| journal = Episodes|volume = 36| issue =3| pages= 199–204 | doi= 10.18814/epiiugs/2013/v36i3/002|url=https://stratigraphy.org/ICSchart/Cohen2013_Episodes.pdf |access-date=7 January 2021|doi-access= free}}

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.