Editing Devonian (section)

{{Short description|Fourth period of the Paleozoic Era}}
{{about|the geological period|the residents of the UK county|Devon|other uses}}
{{Use dmy dates|date=April 2022}}
{{Infobox geologic timespan
| name                         = Devonian
| color                        = Devonian
| top_bar                      =
| time_start                   = 419.2
| time_start_uncertainty       = 3.2
| time_end                     = 358.9
| time_end_uncertainty         = 0.4
| image_map                    = Mollweide Paleographic Map of Earth, 390 Ma (Eifelian Age).png
| caption_map                  = A map of Earth as it appeared 390 million years ago during the Middle Devonian Epoch
| image_outcrop                =
| caption_outcrop              =
| image_art                    =
| caption_art                  =
<!--Chronology-->  
| timeline                     = Devonian
<!--Etymology-->
| name_formality               = Formal
| name_accept_date             =
| alternate_spellings          =
| synonym1                     =
| synonym1_coined              =
| synonym2                     =
| synonym2_coined              =
| synonym3                     =
| synonym3_coined              =
| nicknames                    = Age of Fishes
| former_names                 =
| proposed_names               =
<!--Usage Information--> 
| celestial_body               = earth
| usage                        = Global ([[International Commission on Stratigraphy|ICS]])
| timescales_used              = ICS Time Scale
| formerly_used_by             =
| not_used_by                  =
<!--Definition-->
| chrono_unit                  = Period
| strat_unit                   = System
| proposed_by                  =
| timespan_formality           = Formal
| lower_boundary_def           = [[First appearance datum|FAD]] of the [[Graptolite]] ''[[Monograptus|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<ref>{{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}}</ref>
| upper_boundary_def           = FAD of the [[Conodont]] ''[[Siphonodella|Siphonodella sulcata]]'' (discovered to have biostratigraphic issues as of 2006).<ref>{{cite journal |last1=Kaiser |first1=Sandra |title=The Devonian/Carboniferous boundary stratotype section (La Serre, France) revisited |journal=Newsletters on Stratigraphy |date=1 April 2009 |volume=43 |issue=2 |pages=195–205 |doi=10.1127/0078-0421/2009/0043-0195 |bibcode=2009NewSt..43..195K |url=https://www.schweizerbart.de/papers/nos/detail/43/72810/The_Devonian_Carboniferous_boundary_stratotype_section_La_Serre_France_revisited?af=search |access-date=7 December 2020|url-access=subscription }}</ref>
| upper_gssp_location          = [[La Serre]], [[Montagne Noire]], [[France]]
| upper_gssp_coords            = {{Coord|43.5555|N|3.3573|E|display=inline}}
| upper_gssp_accept_date       = 1990<ref>{{cite journal |last1=Paproth |first1=Eva |last2=Feist |first2=Raimund |last3=Flajs |first3=Gerd |title=Decision on the Devonian-Carboniferous boundary stratotype |journal=Episodes |date=December 1991 |volume=14 |issue=4 |pages=331–336 |doi=10.18814/epiiugs/1991/v14i4/004 |url=https://stratigraphy.org/gssps/files/tournaisian.pdf |archive-url=https://web.archive.org/web/20200609143827/https://stratigraphy.org/gssps/files/tournaisian.pdf |archive-date=2020-06-09 |url-status=live|doi-access=free }}</ref>
<!--Atmospheric and Climatic Data-->
| sea_level                    = Relatively steady around 189&nbsp;m, gradually falling to 120&nbsp;m through period<ref>{{cite journal | author = Haq, B. U.| year = 2008| doi = 10.1126/science.1161648 | title = A Chronology of Paleozoic Sea-Level Changes | journal = Science | volume = 322 | pages = 64–68 | pmid = 18832639 | last2 = Schutter | first2 = SR | issue = 5898 |bibcode = 2008Sci...322...64H | s2cid = 206514545}}</ref>
}}

The '''Devonian''' ({{IPAc-en|d|ə|'|v|oʊ|n|i|.|ən|,_|d|ɛ|-}} {{Respell|də|VOH|nee|ən|,_|deh-}})<ref>{{cite book |last=Wells |first=John |author-link=John C. Wells |title=Longman Pronunciation Dictionary |publisher=Pearson Longman |edition=3rd |date=3 April 2008 |isbn=978-1-4058-8118-0}}</ref><ref>{{dictionary.com|Devonian}}</ref> is a [[period (geology)|geologic period]] and [[system (stratigraphy)|system]] of the [[Paleozoic]] [[era (geology)|era]] during the [[Phanerozoic]] [[eon (geology)|eon]], spanning 60.3&nbsp;million years from the end of the preceding [[Silurian]] period at {{Period start|Devonian}} [[million years ago]] ([[Megaannum|Ma]]), to the beginning of the succeeding [[Carboniferous]] period at {{Period end|Devonian}} Ma. It is the fourth period of both the Paleozoic and the Phanerozoic.<ref name="ICS 2004">{{cite book |title=A Geologic Time Scale 2004 |last1=Gradstein |first1=Felix M. |last2=Ogg |first2=James G. |last3=Smith |first3=Alan G. |year=2004 |publisher=Cambridge University Press |location=Cambridge |isbn=978-0521786737 }}</ref> It is named after [[Devon]], [[South West England]], where rocks from this period were first studied.

The first significant [[evolutionary radiation]] of [[history of life#Colonization of land|life on land]] occurred during the Devonian, as free-[[spore|sporing]] [[land plant]]s ([[pteridophyte]]s) began to spread across [[dry land]], forming extensive [[coal forest]]s which covered the continents. By the middle of the Devonian, several groups of [[vascular plant]]s had evolved [[leaf|leaves]] and true [[root]]s, and by the end of the period the first [[seed]]-bearing plants ([[Pteridospermatophyta|pteridospermatophyte]]s) appeared. This rapid evolution and colonization process, which had begun during the Silurian, is known as the [[Silurian-Devonian Terrestrial Revolution]]. The earliest [[land animal]]s, predominantly [[arthropod]]s such as [[myriapod]]s, [[arachnid]]s and [[Hexapoda|hexapod]]s, also became well-established early in this period, after beginning their colonization of land at least from the [[Ordovician]] period.<!--Arthropods had been on the land since the Silur/Ordovician. See Tumblagooda sandstone.-->

[[Fish]]es, especially [[jawed fish]], reached substantial diversity during this time, leading the Devonian to be called the '''Age of Fishes'''. The [[armour (anatomy)|armor]]ed [[placoderm]]s began [[dominance (ecology)|dominating]] almost every known aquatic environment. In the oceans, [[cartilaginous fish]]es such as primitive [[shark]]s became more numerous than in the Silurian and [[Ordovician#Subdivisions|Late Ordovician]]. [[Tetrapodomorph]]s, which include the ancestors of all four-[[limb (anatomy)|limb]]ed vertebrates (i.e. [[tetrapod]]s), began diverging from [[freshwater fish|freshwater]] [[lobe-finned fish]] as their more robust and muscled [[pectoral fin|pectoral]] and [[pelvic fin]]s gradually evolved into [[forelimb]]s and [[hindlimb]]s, though they were not fully established for life on land until the [[Late Carboniferous]].<ref>{{cite news |last1=Amos |first1=Jonathan |title=Fossil tracks record 'oldest land-walkers' |url=http://news.bbc.co.uk/1/hi/sci/tech/8443879.stm |access-date=24 December 2016 |work=BBC News}}</ref>

The first [[ammonite]]s, a subclass of [[cephalopod]] [[mollusc]]s, appeared. [[Trilobite]]s, [[brachiopod]]s and the great [[coral reef]]s were still common during the Devonian. The [[Late Devonian extinction]], which started about 375&nbsp;Ma,<ref>{{cite web |last=Newitz |first=Annalee |title=How do you have a mass extinction without an increase in extinctions? |url=https://www.theatlantic.com/technology/archive/2013/06/how-do-you-have-a-mass-extinction-without-an-increase-in-extinctions/276836/ |website=The Atlantic |date=2013-06-13 |df=dmy-all}}</ref> severely affected marine life, killing off most of the reef systems, most of the jawless fish, the placoderms, and nearly all trilobites save for a few species of the order [[Proetida]]. The subsequent [[end-Devonian extinction]], which occurred at around 359&nbsp;Ma, further impacted the ecosystems and completed the [[extinction]] of all [[calcite]] [[sponge reef]]s and placoderms.

Devonian [[palaeogeography]] was dominated by the [[supercontinent]] [[Gondwana]] to the south, the small continent of [[Siberia (continent)|Siberia]] to the north, and the medium-sized continent of [[Laurussia]] to the east. Major tectonic events include the closure of the [[Rheic Ocean]], the separation of [[South China]] from Gondwana, and the resulting expansion of the [[Paleo-Tethys Ocean]]. The Devonian experienced several major mountain-building events as Laurussia and Gondwana approached; these include the [[Acadian Orogeny]] in North America and the beginning of the [[Variscan Orogeny]] in Europe. These early collisions preceded the formation of the single supercontinent [[Pangaea]] in the Late Paleozoic.