View source for Devonian

{{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.

==History ==
[[File:Lummaton Quarry 1.JPG|thumb|The rocks of Lummaton Quarry in [[Torquay]] in [[Devon]] played an early role in defining the Devonian Period|left]]
The period is named after [[Devon]], a county in southwestern England, where a controversial argument in the 1830s over the age and structure of the rocks found throughout the county was resolved by adding the Devonian Period to the geological timescale. [[The Great Devonian Controversy]] was a lengthy debate between [[Roderick Murchison]], [[Adam Sedgwick]] and [[Henry De la Beche]] over the naming of the period. Murchison and Sedgwick won the debate and named it the Devonian System.<ref>{{harvtxt|Gradstein|Ogg|Smith|2004}}</ref><ref>{{cite book |last=Rudwick |first=M.S.J. |date=1985 |title=The great Devonian controversy: The shaping of scientific knowledge among gentlemanly specialists |url=https://archive.org/details/greatdevoniancon0000rudw |url-access=registration |location=Chicago |publisher=University of Chicago Press |isbn=978-0226731025}}</ref>{{efn|text= Sedgwick and Murchison coined the term "Devonian system" in 1840:<ref>{{cite encyclopedia |first1=Adam |last1=Sedgwick |first2=Roderick Impey |last2=Murchison |year=1840 |title=On the physical structure of Devonshire, and on the subdivisions and geological relations of its older stratified deposits, etc. Part I and Part II |encyclopedia=Transactions of the Geological Society of London |series=Second series |volume=5 part&nbsp;II |url=https://books.google.com/books?id=QknWzPRnVRQC&pg=PA701 |page=701}}</ref> "We propose therefore, for the future, to designate these groups collectively by the name ''Devonian system''". Sedgwick and Murchison acknowledged William Lonsdale's role in proposing, on the basis of fossil evidence, the existence of a Devonian stratum between those of the Silurian and Carboniferous periods:{{sfn|Sedgwick|Murchison|1840|p=690}} "Again, Mr.&nbsp;Lonsdale, after an extensive examination of the fossils of South Devon, had pronounced them, more than a year since, to form ''a group intermediate between those of the Carboniferous and Silurian systems''".

William Lonsdale stated that in December 1837 he had suggested the existence of a stratum between the Silurian and Carboniferous ones:<ref>{{cite encyclopedia |first1=William |last1=Lonsdale |date=1840 |url=https://books.google.com/books?id=QknWzPRnVRQC&pg=PA721 |title=Notes on the age of limestones from south Devonshire |encyclopedia=Transactions of the Geological Society of London |series=Second series |volume=5 part&nbsp;II |page=724}}</ref> "Mr.&nbsp;Austen's communication [was] read December&nbsp;1837 ...&nbsp;. It was immediately after the reading of that paper ... that I formed the opinion relative to the limestones of Devonshire being of the age of the old red sandstone; and which I afterwards suggested first to Mr.&nbsp;Murchison and then to Prof.&nbsp;Sedgwick".}}

While the [[stratum|rock bed]]s that define the start and end of the Devonian Period are well identified, the exact dates are uncertain. According to the [[International Commission on Stratigraphy]],{{sfn|Gradstein|Ogg|Smith|2004}} the Devonian extends from the end of the Silurian {{Period end|Silurian}} Ma, to the beginning of the [[Carboniferous]] {{Period start|Carboniferous}} Ma – in [[North America]], at the beginning of the [[Mississippian (geology)|Mississippian subperiod]] of the Carboniferous.

In 19th-century texts, the Devonian has been called the "Old Red Age", after the red and brown terrestrial deposits known in the United Kingdom as the [[Old Red Sandstone]] in which early fossil discoveries were found. Another common term is "Age of the Fishes",<ref>{{cite web |url=http://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookPaleo4.html#The%20Devonian |title=Paleobiology: The Late Paleozoic: Devonian |last=Farabee |first=Michael J. |website=The Online Biology Book |publisher=Estrella Mountain Community College |date=2006}}</ref> referring to the evolution of several major groups of [[fish]] that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian, and Farlovian stages, the latter three of which are placed in the Devonian.<ref>{{cite encyclopedia |last1=Barclay |first1=W.J. |date=1989 |title=Geology of the South Wales Coalfield Part&nbsp;II, the country around Abergavenny |edition=3rd |series=Memoir for 1:50,000 geological sheet (England and Wales) |number=232 |pages=18–19 |isbn=0-11-884408-3}}</ref>

The Devonian has also erroneously been characterised as a "greenhouse age", due to [[sampling bias]]: most of the early Devonian-age discoveries came from the [[stratum|strata]] of [[Western Europe]] and eastern [[North America]], which at the time straddled the [[Equator]] as part of the supercontinent of Euramerica where [[fossil]] signatures of widespread reefs indicate tropical [[climate]]s that were warm and moderately humid. In fact, the climate in the Devonian differed greatly during its [[geologic time scale|epochs]] and between geographic regions. For example, during the Early Devonian, arid conditions were prevalent through much of the world including Siberia, Australia, North America, and China, but Africa and [[South America]] had a warm [[temperate climate]]. In the Late Devonian, by contrast, arid conditions were less prevalent across the world and [[temperate climate]]s were more common.{{Citation needed|date=December 2017}}

==Subdivisions==
The Devonian Period is formally broken into Early, Middle and Late subdivisions. The rocks corresponding to those [[series (stratigraphy)|epoch]]s are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System.

=== Early Devonian ===
[[File:Mollweide Paleographic Map of Earth, 405 Ma (Emsian Age).png|thumb|A map of Earth in the [[Emsian]] stage of the Early Devonian (405 million years ago)]]
The [[Early Devonian]] lasted from {{period start|Early devonian}} to {{period end|Early devonian}} Ma. It began with the [[Lochkovian]] Stage from {{period start|Lochkovian}} to {{period end|Lochkovian}} Ma, which was followed by the [[Pragian]] from {{period start|Pragian}} to {{period end|Pragian}} Ma and then by the [[Emsian]], which lasted until the Middle Devonian began at {{period start|Middle devonian}} Ma.<ref name=ICSC>{{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 |archive-url=https://web.archive.org/web/20150913145806/http://www.stratigraphy.org/ICSchart/Cohen2013_Episodes.pdf |archive-date=2015-09-13 |url-status=live |access-date=7 January 2021|doi-access= free}}</ref>
During this time, the first [[Ammonoidea|ammonoids]] appeared, descending from [[Bactritida|bactritoid]] [[Nautiloidea|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 [[Goniatite|Goniatitida]] and [[Clymeniida]]. This class of [[cephalopod]] molluscs would dominate the marine fauna until the beginning of the [[Mesozoic]] Era.

=== Middle Devonian ===
The [[Middle Devonian]] comprised two subdivisions: first the [[Eifelian]], which then gave way to the [[Givetian]] at {{period start|Givetian}} Ma. During this time, the jawless [[agnathan]] fishes began to decline in diversity in freshwater and marine environments partly due to drastic environmental changes and partly due to the increasing competition, predation, and diversity of [[gnathostomata|jawed fishes]]. The shallow, warm, oxygen-depleted waters of Devonian inland lakes, surrounded by primitive plants, provided the environment necessary for certain early fish to develop such essential characteristics as well developed lungs and the ability to crawl out of the water and onto the land for short periods of time.<ref>{{Cite journal|last=Clack|first=Jennifer|date=13 August 2007|title=Devonian climate change, breathing, and the origin of the tetrapod stem group|url=https://academic.oup.com/icb/article/47/4/510/632798|journal=Integrative and Comparative Biology|volume=47|issue=4|pages=510–523|doi=10.1093/icb/icm055|pmid=21672860|quote=Estimates of oxygen levels during this period suggest that they were unprecedentedly low during the Givetian and Frasnian periods. At the same time, plant diversification was at its most rapid, changing the character of the landscape and contributing, via soils, soluble nutrients, and decaying plant matter, to anoxia in all water systems. The co-occurrence of these global events may explain the evolution of air-breathing adaptations in at least two lobe-finned groups, contributing directly to the rise of the tetrapod stem group.|doi-access=free}}</ref>

=== Late Devonian ===
[[File:Mollweide Paleographic Map of Earth, 370 Ma (Famennian Age).png|thumb|250px|right|A map of Earth in the [[Famennian]] stage of the Late Devonian (370 million years ago)]]
Finally, the Late Devonian started with the [[Frasnian]], from {{period start|Frasnian}} to {{period end|Frasnian}} Ma, during which the first forests took shape on land. The first tetrapods appeared in the fossil record in the ensuing [[Famennian]] subdivision, the beginning and end of which are marked with extinction events. This lasted until the end of the Devonian at {{period end|Devonian}} Ma.<ref name=ICSC/>

==Climate==
The Devonian was a relatively warm period, although significant [[glacier]]s may have existed during the Early and Middle Devonian.<ref>{{cite journal |last1=Elrick |first1=Maya |last2=Berkyová |first2=Stana |last3=Klapper |first3=Gilbert |last4=Sharp |first4=Zachary |last5=Joachimski |first5=Michael M. |last6=Frýda |first6=Jiří |date=15 May 2009 |title=Stratigraphic and oxygen isotope evidence for My-scale glaciation driving eustasy in the Early–Middle Devonian greenhouse world |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018209000984 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=276 |issue=1–4 |pages=170–181 |doi=10.1016/j.palaeo.2009.03.008 |bibcode=2009PPP...276..170E |access-date=3 August 2023|url-access=subscription }}</ref> The temperature gradient from the equator to the poles was not as large as it is today. The weather was also very arid, mostly along the equator where it was the driest.<ref name="Joachim Kia 2009"/> Reconstruction of tropical [[sea surface temperature]] from [[conodont]] [[apatite]] implies an average value of {{convert|30|C|4=0|abbr=on}} in the Early Devonian.<ref name="Joachim Kia 2009"/> Early Devonian mean annual surface temperatures were approximately 16 °C.<ref>{{Cite journal |last1=Nardin |first1=E. |last2=Godderis |first2=Yves |last3=Donnadieu |first3=Yannick |last4=Le Hir |first4=Guillaume |last5=Blakey |first5=R. C. |last6=Puceat |first6=E. |last7=Aretz |first7=M. |date=1 May 2011 |title=Modeling the early Paleozoic long-term climatic trend |url=https://www.researchgate.net/publication/233986372 |journal=[[Geological Society of America Bulletin]] |language=en |volume=123 |issue=5–6 |pages=1181–1192 |doi=10.1130/B30364.1 |bibcode=2011GSAB..123.1181N |issn=0016-7606 |access-date=14 December 2023 |via=Research Gate}}</ref> {{Co2}} levels dropped steeply throughout the Devonian Period. The newly evolved forests drew carbon out of the atmosphere, which were then buried into sediments. This may be reflected by a Mid-Devonian cooling of around {{convert|5|C-change|4=0|abbr=on}}.<ref name="Joachim Kia 2009"/> The Late Devonian warmed to levels equivalent to the Early Devonian; while there is no corresponding increase in {{co2}} concentrations, continental weathering increases (as predicted by warmer temperatures); further, a range of evidence, such as plant distribution, points to a Late Devonian warming.<ref name="Joachim Kia 2009">{{Cite journal |first1=M. M. |last1=Joachimski |first2=S. |last2=Breisig |first3=W. F. |last3=Buggisch |first4=J. A. |last4=Talent |first5=R. |last5=Mawson |first6=M. |last6=Gereke |first7=J. R. |last7=Morrow |first8=J. |last8=Day |first9=K. |last9=Weddige |title=Devonian climate and reef evolution: Insights from oxygen isotopes in apatite |journal=[[Earth and Planetary Science Letters]] |volume=284 |issue=3–4 |pages=599–609 |date=July 2009 |doi=10.1016/j.epsl.2009.05.028 |bibcode=2009E&PSL.284..599J}}</ref> The climate would have affected the dominant organisms in [[reef]]s; [[Microorganism|microbes]] would have been the main reef-forming organisms in warm periods, with corals and [[Stromatoporoidea|stromatoporoid]] sponges taking the dominant role in cooler times. The warming at the end of the Devonian may even have contributed to the extinction of the stromatoporoids. At the terminus of the Devonian, Earth rapidly cooled into an [[Greenhouse and icehouse Earth|icehouse]], marking the beginning of the [[Late Paleozoic icehouse]].<ref>{{cite book |last1=Rosa |first1=Eduardo L. M. |last2=Isbell |first2=John L. |editor-last1=Alderton |editor-first1=David |editor-last2=Elias |editor-first2=Scott A. |date=2021 |chapter=Late Paleozoic Glaciation |chapter-url=https://www.sciencedirect.com/science/article/pii/B9780081029084000631 |title=Encyclopedia of Geology |edition=2nd |publisher=Academic Press |pages=534–545 |doi=10.1016/B978-0-08-102908-4.00063-1 |isbn=978-0-08-102909-1|s2cid=226643402 }}</ref><ref name="McClungEtAl2013">{{cite journal |last1=McClung |first1=Wilson S. |last2=Eriksson |first2=Kenneth A. |last3=Terry Jr. |first3=Dennis O. |last4=Cuffey |first4=Clifford A. |date=1 October 2013 |title=Sequence stratigraphic hierarchy of the Upper Devonian Foreknobs Formation, central Appalachian Basin, USA: Evidence for transitional greenhouse to icehouse conditions |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=387 |pages=104–125 |doi=10.1016/j.palaeo.2013.07.020 |bibcode=2013PPP...387..104M |doi-access=free }}</ref>

==Paleogeography==
The Devonian world involved many continents and ocean basins of various sizes. The largest continent, [[Gondwana]], was located entirely within the [[Southern Hemisphere]]. It corresponds to modern day [[South America]], [[Africa]], [[Australia]], [[Antarctica]], and [[India]], as well as minor components of [[North America]] and [[Asia]]. The second-largest continent, Laurussia, was northwest of Gondwana, and corresponds to much of modern-day [[North America]] and [[Europe]]. Various smaller continents, [[microcontinents]], and [[terrane]]s were present east of Laurussia and north of Gondwana, corresponding to parts of Europe and Asia. The Devonian Period was a time of great [[plate tectonics|tectonic]] activity, as the major continents of [[Laurussia]] and [[Gondwana]] drew closer together.<ref name="Cocks-2016">{{Citation |title=Devonian |date=2016 |url=https://www.cambridge.org/core/books/earth-history-and-palaeogeography/devonian/56EB82A628FA7B830FEB1F9A8E5DF77F |work=Earth History and Palaeogeography |pages=138–158 |editor-last=Cocks |editor-first=L. Robin M. |place=Cambridge |publisher=Cambridge University Press |doi=10.1017/9781316225523.009 |isbn=978-1-316-22552-3 |access-date=2022-07-24 |editor2-last=Torsvik |editor2-first=Trond H.|url-access=subscription }}</ref><ref name="Golonka-2020">{{Cite journal |last=Golonka |first=Jan |date=2020-03-01 |title=Late Devonian paleogeography in the framework of global plate tectonics |url=https://www.sciencedirect.com/science/article/pii/S0921818120300187 |journal=Global and Planetary Change |language=en |volume=186 |pages=103129 |doi=10.1016/j.gloplacha.2020.103129 |bibcode=2020GPC...18603129G |s2cid=212928195 |issn=0921-8181|url-access=subscription }}</ref>

Sea levels were high worldwide, and much of the land lay under shallow seas, where tropical [[reef]] organisms lived. The enormous "world ocean", [[Panthalassa]], occupied much of the [[Northern Hemisphere]] as well as wide swathes east of Gondwana and west of Laurussia. Other minor oceans were the [[Paleo-Tethys Ocean]] and [[Rheic Ocean]].<ref name="Cocks-2016" /><ref name="Golonka-2020" />

=== Laurussia ===
[[File:Laurussia Euramerica.svg|thumb|263x263px|Continental boundary of [[Laurussia]] (Euramerica) and its constituents, superimposed onto modern coastlines]]
By the early Devonian, the continent Laurussia (also known as [[Euramerica]]) was fully formed through the collision of the continents [[Laurentia]] (modern day North America) and [[Baltica]] (modern day northern and eastern Europe). The tectonic effects of this collision continued into the Devonian, producing a string of mountain ranges along the southeastern coast of the continent. In present-day eastern North America, the [[Acadian orogeny|Acadian Orogeny]] continued to raise the [[Appalachian Mountains]]. Further east, the collision also extended the rise of the [[Caledonian orogeny|Caledonian Mountains]] of [[Great Britain]] and [[Scandinavia]]. As the Caledonian Orogeny wound down in the later part of the period, [[orogenic collapse]] facilitated a cluster of granite intrusions in Scotland.<ref name="Cocks-2016" />

Most of Laurussia was located south of the equator, but in the Devonian it moved northwards and began to rotate counterclockwise towards its modern position. While the most northern parts of the continent (such as [[Greenland]] and [[Ellesmere Island]]) established tropical conditions, most of the continent was located within the natural dry zone along the [[Tropic of Capricorn]], which (as nowadays) is a result of the convergence of two great air-masses, the [[Hadley cell]] and the [[Ferrel cell]]. In these near-deserts, the [[Old Red Sandstone]] sedimentary beds formed, made red by the oxidised iron ([[hematite]]) characteristic of drought conditions. The abundance of red sandstone on continental land also lends Laurussia the name "the Old Red Continent".<ref>{{Cite encyclopedia |url=https://www.britannica.com/science/Devonian-Period |title=Devonian Period |series=geochronology |encyclopedia=Encyclopedia Britannica |access-date=2017-12-15 |df=dmy-all |language=en}}</ref> For much of the Devonian, the majority of western Laurussia (North America) was covered by subtropical [[Inland sea (geology)|inland seas]] which hosted a diverse ecosystem of reefs and marine life. Devonian marine deposits are particularly prevalent in the [[Midwestern United States|midwestern]] and [[Northeastern United States|northeastern]] United States. Devonian reefs also extended along the southeast edge of Laurussia, a coastline now corresponding to southern [[England]], [[Belgium]], and other mid-latitude areas of Europe.<ref name="Cocks-2016" />

In the Early and Middle Devonian, the west coast of Laurussia was a passive margin with broad coastal waters, deep silty embayments, river deltas and estuaries, found today in [[Idaho]] and [[Nevada]]. In the Late Devonian, an approaching volcanic [[island arc]] reached the steep slope of the continental shelf and began to uplift deep water deposits. This minor collision sparked the start of a mountain-building episode called the [[Antler orogeny]], which extended into the Carboniferous.<ref name="Cocks-2016" /><ref>{{cite web |url=http://jan.ucc.nau.edu/~rcb7/devpaleo.html |archive-url=https://web.archive.org/web/20100415135733/http://jan.ucc.nau.edu/~rcb7/devpaleo.html |title=Devonian Paleogeography, Southwestern US |archive-date=April 15, 2010 |last=Blakey |first=Ron C. |website=jan.ucc.nau.edu |url-status=dead |publisher=Northern Arizona University |df=dmy-all}}</ref> Mountain building could also be found in the far northeastern extent of the continent, as minor tropical island arcs and detached Baltic terranes re-join the continent. Deformed remnants of these mountains can still be found on Ellesmere Island and [[Svalbard]]. Many of the Devonian collisions in Laurussia produce both mountain chains and [[foreland basin]]s, which are frequently fossiliferous.<ref name="Cocks-2016" /><ref name="Golonka-2020" />

=== Gondwana ===
[[File:Early-Middle Devonian chasmataspids paleogeography.png|left|thumb|306x306px|The Early-Middle Devonian world, with major continents Gondwana (Go), Euramerica/Laurussia (Eu), and Siberia (Si)]]
Gondwana was by far the largest continent on the planet. It was completely south of the equator, although the northeastern sector (now Australia) did reach tropical latitudes. The southwestern sector (now South America) was located to the far south, with [[Brazil]] situated near the [[South Pole]]. The northwestern edge of Gondwana was an [[active margin]] for much of the Devonian, and saw the [[Accretion (geology)|accretion]] of many smaller land masses and island arcs. These include [[Chilenia]], [[Cuyania]], and [[Chaitenia]], which now form much of [[Chile]] and [[Tectonic evolution of Patagonia|Patagonia]].<ref name="Cocks-2016" /><ref name="Herve2018">{{cite journal |last1=Hervé |first1=Francisco|author-link1=Francisco Hervé |last2=Calderón |first2=Mauricio |last3=Fanning |first3=Mark |last4=Pankhurst |first4=Robert|author-link4=Robert John Pankhurst |last5=Rapela |first5=Carlos W. |last6=Quezada |first6=Paulo |year=2018 |title=The country rocks of Devonian magmatism in the North Patagonian Massif and Chaitenia |url=http://www.andeangeology.cl/index.php/revista1/article/view/V45n3-3117 |journal=[[Andean Geology]] |volume=45 |issue=3 |pages=301–317 |doi=10.5027/andgeoV45n3-3117|doi-access=free |bibcode=2018AndGe..45..301H |hdl=11336/81577 |hdl-access=free }}</ref> These collisions were associated with [[volcanic activity]] and [[plutons]], but by the Late Devonian the tectonic situation had relaxed and much of South America was covered by shallow seas. These south polar seas hosted a distinctive brachiopod fauna, the Malvinokaffric Realm, which extended eastward to marginal areas now equivalent to South Africa and Antarctica. Malvinokaffric faunas even managed to approach the South Pole via a tongue of Panthalassa which extended into the [[Paraná Basin]].<ref name="Cocks-2016" />

The northern rim of Gondwana was mostly a passive margin, hosting extensive marine deposits in areas such as northwest Africa and [[Tibet]]. The eastern margin, though warmer than the west, was equally active. Numerous mountain building events and [[granite]] and [[kimberlite]] intrusions affected areas equivalent to modern day eastern [[Australia]], [[Tasmania]], and Antarctica.<ref name="Cocks-2016" />

=== Asian terranes ===
[[File:380 Ma plate tectonic reconstruction.png|thumb|200px|The earth at 380 Ma, centered on the [[Paleo-Tethys Ocean]], which fully opened during the Devonian]]Several island microcontinents (which would later coalesce into modern day Asia) stretched over a low-latitude [[archipelago]] to the north of Gondwana. They were separated from the southern continent by an oceanic basin: the [[Paleo-Tethys Ocean|Paleo-Tethys]]. Although the western Paleo-Tethys Ocean had existed since the Cambrian, the eastern part only began to rift apart as late as the Silurian. This process accelerated in the Devonian. The eastern branch of the Paleo-Tethys was fully opened when [[South China craton|South China]] and [[Annamia block|Annamia]] (a [[terrane]] equivalent to most of [[Indochina]]), together as a unified continent, detached from the northeastern sector of Gondwana. Nevertheless, they remained close enough to Gondwana that their Devonian fossils were more closely related to Australian species than to north Asian species. Other Asian terranes remained attached to Gondwana, including [[Sibumasu]] (western Indochina), Tibet, and the rest of the [[Cimmeria (continent)|Cimmerian]] blocks.<ref name="Cocks-2016" /><ref name="Golonka-2020" />
[[File:Nostolepis distribution Early Devonian paleogeography.png|left|thumb|288x288px|World map at 400 Ma (Early Devonian), showing continents and [[terrane]]s with modern continent borders superimposed]]
While the South China-Annamia continent was the newest addition to the Asian microcontinents, it was not the first. [[North China craton|North China]] and the [[Tarim Block]] (now northwesternmost China) were located westward and continued to drift northwards, powering over older oceanic crust in the process. Further west was a small ocean (the Turkestan Ocean), followed by the larger microcontinents of [[Kazakhstania]], [[Siberia (continent)|Siberia]], and [[Amurian Plate|Amuria]]. Kazakhstania was a volcanically active region during the Devonian, as it continued to assimilate smaller island arcs.<ref name="Cocks-2016" /> The island arcs of the region, such as the Balkhash-West Junggar Arc, exhibited biological endemism as a consequence of their location.<ref>{{Cite journal |last1=Wang |first1=Z. H. |last2=Becker |first2=R. T. |last3=Aboussalam |first3=Z. S. |last4=Hartenfels |first4=S. |last5=Joachimski |first5=Michael M. |last6=Gong |first6=Y. M. |date=15 April 2016 |title=Conodont and carbon isotope stratigraphy near the Frasnian/Famennian (Devonian) boundary at Wulankeshun, Junggar Basin, NW China |url=https://www.sciencedirect.com/science/article/pii/S0031018215007646 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |series=Ecosystem evolution in deep time: evidence from the rich Palaeozoic fossil records of China |volume=448 |pages=279–297 |doi=10.1016/j.palaeo.2015.12.029 |bibcode=2016PPP...448..279W |issn=0031-0182 |access-date=11 November 2023|url-access=subscription }}</ref>

Siberia was located just north of the equator as the largest landmass in the Northern Hemisphere. At the beginning of the Devonian, Siberia was inverted (upside down) relative to its modern orientation. Later in the period it moved northwards and began to twist clockwise, though it was not near its modern location. Siberia approached the eastern edge of Laurussia as the Devonian progressed, but it was still separated by a seaway, the [[Ural Ocean]]. Although Siberia's margins were generally tectonically stable and ecologically productive, rifting and deep [[mantle plume]]s impacted the continent with [[flood basalt]]s during the Late Devonian. The [[Altai-Sayan region]] was shaken by volcanism in the Early and Middle Devonian, while Late Devonian magmatism was magnified further to produce the [[Vilyuy Traps]], flood basalts which may have contributed to the Late Devonian Mass Extinction. The last major round of volcanism, the Yakutsk Large Igneous Province, continued into the Carboniferous to produce extensive kimberlite deposits.<ref name="Cocks-2016" /><ref name="Golonka-2020" />

Similar volcanic activity also affected the nearby microcontinent of Amuria (now [[Manchuria]], [[Mongolia]] and their vicinities). Though certainly close to Siberia in the Devonian, the precise location of Amuria is uncertain due to contradictory [[Paleomagnetism|paleomagnetic]] data.<ref name="Cocks-2016" />

=== Closure of the Rheic Ocean ===
The Rheic Ocean, which separated Laurussia from Gondwana, was wide at the start of the Devonian, having formed after the drift of [[Avalonia]] away from Gondwana. It steadily shrunk as the period continued, as the two major continents approached near the [[equator]] in the early stages of the assembly of [[Pangaea]]. The closure of the Rheic Ocean began in the Devonian and continued into the Carboniferous. As the ocean narrowed, endemic marine faunas of Gondwana and Laurussia combined into a single tropical fauna. The history of the western Rheic Ocean is a subject of debate, but there is good evidence that Rheic oceanic crust experienced intense [[subduction]] and [[metamorphism]] under Mexico and Central America.<ref name="Cocks-2016" /><ref name="Golonka-2020" />

The closure of the eastern part of the Rheic Ocean is associated with the assemblage of central and southern Europe. In the early Paleozoic, much of Europe was still attached to Gondwana, including the terranes of [[Iberia]], [[Armorican terrane|Armorica]] (France), [[Palaeo-Adria]] (the western Mediterranean area), [[Bohemia]], [[Franconia]], and [[Saxothuringian Zone|Saxothuringia]]. These continental blocks, collectively known as the Armorican Terrane Assemblage, split away from Gondwana in the Silurian and drifted towards Laurussia through the Devonian. Their collision with Laurussia leads to the beginning of the [[Variscan orogeny|Variscan Orogeny]], a major mountain-building event which would escalate further in the Late Paleozoic. Franconia and Saxothuringia collided with Laurussia near the end of the Early Devonian, pinching out the easternmost Rheic Ocean. The rest of the Armorican terranes followed, and by the end of the Devonian they were fully connected with Laurussia. This sequence of rifting and collision events led to the successive creation and destruction of several small seaways, including the Rheno-Hercynian, Saxo-Thuringian, and Galicia-Moldanubian oceans. Their sediments were eventually compressed and completely buried as Gondwana fully collided with Laurussia in the Carboniferous.<ref name="Cocks-2016" /><ref name="Golonka-2020" /><ref>{{Cite journal |last1=Franke |first1=Wolfgang |last2=Cocks |first2=L. Robin M. |last3=Torsvik |first3=Trond H. |date=2017 |title=The Palaeozoic Variscan oceans revisited |url=https://linkinghub.elsevier.com/retrieve/pii/S1342937X17301399 |journal=Gondwana Research |language=en |volume=48 |pages=257–284 |doi=10.1016/j.gr.2017.03.005|bibcode=2017GondR..48..257F |url-access=subscription }}</ref>

==Life==

===Marine biota===
[[File:Fish evolution.png|thumb|300px|right|Spindle diagram for the evolution of vertebrates<ref>{{cite book |last=Benton |first=M. J. |date=2005 |url=https://books.google.com/books?id=VThUUUtM8A4C&q=Benton+2005+%22%27Vertebrate+Palaeontology%22 |title=Vertebrate Palaeontology |publisher=John Wiley |edition=3rd |isbn=9781405144490 |page=14}}</ref>]]
{{see also|Evolution of fish#Devonian: Age of fishes}}

Sea levels in the Devonian were generally high. Marine faunas continued to be dominated by [[conodonts]],<ref>{{Cite journal |last1=Corradini |first1=Carlo |last2=Corriga |first2=Maria G. |last3=Pondrelli |first3=Monica |last4=Suttner |first4=Thomas J. |date=1 July 2020 |title=Conodonts across the Silurian/Devonian boundary in the Carnic Alps (Austria and Italy) |url=https://www.sciencedirect.com/science/article/pii/S0031018218301718 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |series=Global Events impacting COnodont evolution |volume=549 |pages=109097 |doi=10.1016/j.palaeo.2019.02.023 |bibcode=2020PPP...54909097C |issn=0031-0182 |access-date=11 November 2023|url-access=subscription }}</ref> [[bryozoa|bryozoans]],<ref name="InfluenceAtrypid">{{cite journal |last1=Bose |first1=Rituparna |last2=Schneider |first2=Chris L. |last3=Leighton |first3=Lindsey R. |last4=Polly |first4=P. David |date=1 October 2011 |title=Influence of atrypid morphological shape on Devonian episkeletobiont assemblages from the lower Genshaw formation of the Traverse Group of Michigan: A geometric morphometric approach |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018211004305 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=310 |issue=3–4 |pages=427–441 |doi=10.1016/j.palaeo.2011.08.004 |bibcode=2011PPP...310..427B |access-date=4 April 2023|url-access=subscription }}</ref> diverse and abundant [[brachiopod]]s,<ref>{{cite journal |last1=Chen |first1=Zhong-Qiang |date=2 September 2023 |title=Devonian–Carboniferous brachiopod zonation in the Tarim Basin, northwest China: implications for biostratigraphy and biogeography |url=https://onlinelibrary.wiley.com/doi/10.1002/gj.967 |journal=[[Geological Journal]] |volume=39 |issue=3–4 |pages=431–458 |doi=10.1002/gj.967 |s2cid=129628791 |access-date=4 April 2023|url-access=subscription }}</ref> the enigmatic [[hederellid]]s,<ref>{{cite journal |last1=Michal |first1=Mergl |year=2021 |title=Dead or alive? Brachiopods and other shells as substrates for endo- and sclerobiont activity in the Early Devonian (Lochkovian) of the Barrandian |url=https://otik.uk.zcu.cz/handle/11025/46568 |journal=Bulletin of Geosciences |volume=96 |issue=4 |pages=401–429 |access-date=4 April 2023}}</ref> [[microconchida|microconchids]],<ref name="InfluenceAtrypid" /> and [[coral]]s.<ref>{{cite journal |last1=Zapalski |first1=Mikołaj K. |last2=Baird |first2=Andrew M. |last3=Bridge |first3=Tom |last4=Jakubowicz |first4=Michał |last5=Daniell |first5=James |date=4 February 2021 |title=Unusual shallow water Devonian coral community from Queensland and its recent analogues from the inshore Great Barrier Reef |journal=Coral Reefs |volume=40 |issue=2 |pages=417–431 |doi=10.1007/s00338-020-02048-9 |s2cid=234012936 |doi-access=free }}</ref><ref>{{cite journal |last1=Zatoń |first1=Michał |last2=Borszcz |first2=Tomasz |last3=Berkowski |first3=Błażej |last4=Rakociński |first4=Michał |last5=Zapalski |first5=Mikołaj K. |last6=Zhuravlev |first6=Andrey V. |date=15 April 2015 |title=Paleoecology and sedimentary environment of the Late Devonian coral biostrome from the Central Devonian Field, Russia |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018215000772 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=424 |pages=61–75 |doi=10.1016/j.palaeo.2015.02.021 |bibcode=2015PPP...424...61Z |access-date=4 April 2023|url-access=subscription }}</ref> Lily-like [[crinoid]]s (animals, their resemblance to flowers notwithstanding) were abundant, and [[trilobite]]s were still fairly common. [[Bivalvia|Bivalves]] became commonplace in deep water and outer shelf environments.<ref name=" Nagel-Myers2022">{{cite journal |last1=Nagel-Myers |first1=Judith |date=5 August 2021 |title=An updated look at the taxonomy, stratigraphy, and palaeoecology of the Devonian bivalve genus Ontario Clarke, 1904 (Cardiolidae, Bivalvia) |url=https://link.springer.com/article/10.1007/s12549-021-00491-2? |journal=Palaeobiodiversity and Palaeoenvironments |volume=102 |issue=3 |pages=541–555 |doi=10.1007/s12549-021-00491-2 |s2cid=236921239 |access-date=8 November 2022|url-access=subscription }}</ref> The first ammonites also appeared during or slightly before the early Devonian Period around 400&nbsp;Ma.<ref>{{cite web |title=Palaeos Paleozoic: Devonian: The Devonian Period – 1|url=http://palaeos.com/paleozoic/devonian/devonian.html|website=Palaeos|last1=Kazlev|first1=M. Alan|date=May 28, 1998|access-date=24 January 2019}}</ref> [[Bactritida|Bactritoids]] make their first appearance in the Early Devonian as well; their radiation, along with that of ammonoids, has been attributed by some authors to increased environmental stress resulting from decreasing oxygen levels in the deeper parts of the water column.<ref>{{cite journal |last1=Klug |first1=Christian |last2=Kroeger |first2=Bjoern |last3=Korn |first3=Dieter |last4=Ruecklin |first4=Martin |last5=Schemm-Gregory |first5=Mena |last6=De Baets |first6=Kenneth |last7=Mapes |first7=Royal H. |date=April 2008 |title=Ecological change during the early Emsian (Devonian) in the Tafilalt (Morocco), the origin of the Ammonoidea, and the first African pyrgocystid edrioasteroids, machaerids and phyllocarids |url=https://research-information.bris.ac.uk/en/publications/ecological-change-during-the-early-emsian-devonian-in-the-tafilal |journal=Palaeontographica Abteilung A |volume=283 |issue=4–6 |pages=83–U58 |doi=10.1127/pala/283/2008/83 |bibcode=2008PalAA.283...83K |access-date=8 November 2022|url-access=subscription }}</ref> Among vertebrates, jawless armored fish ([[ostracoderm]]s) declined in diversity, while the jawed fish (gnathostomes) simultaneously increased in both the sea and [[fresh water]]. Armored placoderms were numerous during the early ages of the Devonian Period and became extinct in the Late Devonian, perhaps because of competition for food against the other fish species. Early cartilaginous ([[Chondrichthyes]]) and bony fishes ([[Osteichthyes]]) also become diverse and played a large role within the Devonian seas. The first abundant genus of cartilaginous fish, ''[[Cladoselache]]'', appeared in the oceans during the Devonian Period. The great diversity of fish around at the time has led to the Devonian being given the name "The Age of Fishes" in popular culture.<ref>{{cite journal |last1=Dalton |first1=Rex |title=Hooked on fossils |journal=Nature |date=January 2006 |volume=439 |issue=7074 |pages=262–263 |doi=10.1038/439262a|pmid=16421540 |s2cid=4357313 |doi-access=free }}</ref>

[[File:Gessetal2023_environment_reconstruction.png|thumb|The Devonian period saw the development of early sharks, armoured [[placoderm]]s and various [[lobe-finned fish]]es including the [[Rhipidistia|tetrapod transitional species]]]]

[[File:Diorama of a Devonian seafloor - corals, coiled cephalopod, gastropod, crinoids (44933262614).jpg|thumb|Diorama of a Devonian seafloor]]

The Devonian saw significant expansion in the diversity of [[nekton]]ic marine life driven by the abundance of planktonic microorganisms in the free water column as well as high ecological competition in benthic habitats, which were extremely saturated; this diversification has been labeled the ''Devonian Nekton Revolution'' by many researchers.<ref>{{cite journal |last1=Klug |first1=Christian |last2=Kröger |first2=Björn |last3=Kiessling |first3=Wolfgang |last4=Mullins |first4=Gary L. |last5=Servais |first5=Thomas |last6=Frýda |first6=Jiří |last7=Korn |first7=Dieter |last8=Turner |first8=Susan |date=26 October 2010 |title=The Devonian nekton revolution |url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1502-3931.2009.00206.x |journal=Lethaia |volume=43 |issue=4 |pages=465–477 |doi=10.1111/j.1502-3931.2009.00206.x |bibcode=2010Letha..43..465K |access-date=3 September 2022|url-access=subscription }}</ref> However, other researchers have questioned whether this revolution existed at all; a 2018 study found that although the proportion of biodiversity constituted by nekton increased across the boundary between the Silurian and Devonian, it decreased across the span of the Devonian, particularly during the Pragian, and that the overall diversity of nektonic taxa did not increase significantly during the Devonian compared to during other geologic periods, and was in fact higher during the intervals spanning from the Wenlock to the Lochkovian and from the Carboniferous to the Permian. The study's authors instead attribute the increased overall diversity of nekton in the Devonian to a broader, gradual trend of nektonic diversification across the entire Palaeozoic.<ref>{{cite journal |last1=Whalen |first1=Christopher D. |last2=Briggs |first2=Derek E. G. |date=18 July 2018 |title=The Palaeozoic colonization of the water column and the rise of global nekton |journal=Proceedings of the Royal Society B |volume=285 |issue=1883 |pages=1–9 |doi=10.1098/rspb.2018.0883 |pmid=30051837 |pmc=6083262 }}</ref>

===Reefs===
A now-dry barrier reef, located in present-day [[Kimberley (Western Australia)|Kimberley Basin]] of northwest [[Australia]], once extended {{cvt|350|km}}, fringing a Devonian continent.<ref>{{cite journal |last1=Tyler |first1=Ian M. |last2=Hocking |first2=Roger M. |last3=Haines |first3=Peter W. |title=Geological evolution of the Kimberley region of Western Australia |journal=Episodes |date=1 March 2012 |volume=35 |issue=1 |pages=298–306 |doi=10.18814/epiiugs/2012/v35i1/029|doi-access=free }}</ref> Reefs are generally built by various [[carbonate]]-secreting organisms that can erect wave-resistant structures near sea level. Although modern reefs are constructed mainly by corals and calcareous [[algae]], Devonian reefs were either microbial reefs built up mostly by [[autotrophic]] [[cyanobacteria]] or coral-stromatoporoid reefs built up by coral-like [[Stromatoporoidea|stromatoporoids]] and tabulate and [[Rugosa|rugose corals]]. Microbial reefs dominated under the warmer conditions of the early and late Devonian, while coral-stromatoporoid reefs dominated during the cooler middle Devonian.<ref>{{cite journal |last1=Joachimski |first1=M.M. |last2=Breisig |first2=S. |last3=Buggisch |first3=W. |last4=Talent |first4=J.A. |last5=Mawson |first5=R. |last6=Gereke |first6=M. |last7=Morrow |first7=J.R. |last8=Day |first8=J. |last9=Weddige |first9=K. |title=Devonian climate and reef evolution: Insights from oxygen isotopes in apatite |journal=Earth and Planetary Science Letters |date=July 2009 |volume=284 |issue=3–4 |pages=599–609 |doi=10.1016/j.epsl.2009.05.028|bibcode=2009E&PSL.284..599J }}</ref>

===Terrestrial biota===
[[File:Prototaxites milwaukeensis.jpg|thumb|150px|''Prototaxites milwaukeensis'', a large fungus, initially thought to be a marine alga, from the Middle Devonian of Wisconsin]]
By the Devonian Period, life was well underway in its colonization of the land. The [[moss]] forests and [[bacteria]]l and algal mats of the Silurian were joined early in the period by primitive rooted plants that created the first stable [[soil]]s and harbored arthropods like [[mite]]s, [[scorpion]]s, [[Trigonotarbida|trigonotarbids]]<ref>{{cite journal |last1=Garwood |first1=Russell J. |last2=Dunlop |first2=Jason |date=July 2014 |title=The walking dead: Blender as a tool for paleontologists with a case study on extinct arachnids |url=https://www.academia.edu/7625529 |journal=[[Journal of Paleontology]] |volume=88 |issue=4 |pages=735–746 |doi=10.1666/13-088 |bibcode=2014JPal...88..735G |s2cid=131202472 |issn=0022-3360 |access-date=2015-07-21}}</ref> and [[Myriapoda|myriapods]] (although arthropods appeared on land much earlier than in the Early Devonian<ref name="Garwood">{{cite journal |last1=Garwood |first1=Russell J. |last2=Edgecombe |first2=Gregory D. |date=September 2011 |title=Early Terrestrial Animals, Evolution, and Uncertainty |journal=Evolution: Education and Outreach |volume=4 |issue=3 |pages=489–501 |doi=10.1007/s12052-011-0357-y |df=dmy-all|doi-access=free }}</ref> and the existence of fossils such as ''[[Protichnites]]'' suggest that amphibious arthropods may have appeared as early as the [[Cambrian]]). By far the largest land organism at the beginning of this period was the enigmatic ''[[Prototaxites]]'', which was possibly the fruiting body of an enormous fungus,<ref>{{cite journal |last1=Hueber |first1=Francis M. |title=Rotted wood-alga fungus: The history and life of ''Prototaxites'' Dawson 1859 |journal=Review of Palaeobotany and Palynology |year=2001 |volume=116 |issue=1–2 |pages=123–159 |doi=10.1016/s0034-6667(01)00058-6|bibcode=2001RPaPa.116..123H }}</ref> rolled liverwort mat,<ref>{{cite journal |last1=Graham |first1=Linda E. |last2=Cook |first2=Martha E. |last3=Hanson |first3=David T. |last4=Pigg |first4=Kathleen B. |last5=Graham |first5=James M. |title=Rolled liverwort mats explain major ''Prototaxites'' features: Response to commentaries |journal=American Journal of Botany |year=2010 |volume=97 |issue=7 |pages=1079–1086 |doi=10.3732/ajb.1000172 |pmid=21616860|doi-access=free |bibcode=2010AmJB...97.1079G }}</ref> or another organism of uncertain affinities<ref>{{cite journal |last1=Taylor |first1=Thomas N. |last2=Taylor |first2=Edith L. |last3=Decombeix |first3=Anne-Laure |last4=Schwendemann |first4=Andrew |last5=Serbet |first5=Rudolph |last6=Escapa |first6=Ignacio |last7=Krings |first7=Michael |title=The enigmatic Devonian fossil ''Prototaxites'' is not a rolled-up liverwort mat: Comment on the paper by Graham et al.(AJB 97: 268–275) |journal=American Journal of Botany |year=2010 |volume=97 |issue=7 |pages=1074–1078 |doi=10.3732/ajb.1000047 |pmid=21616859|doi-access=free |bibcode=2010AmJB...97.1074T |hdl=11336/97957 |hdl-access=free }}</ref> that stood more than {{convert|8|metres|feet}} tall, and towered over the low, carpet-like vegetation during the early part of the Devonian. Also, the first possible fossils of [[insect]]s appeared around 416&nbsp; Ma, in the Early Devonian. Evidence for the earliest [[tetrapod]]s takes the form of trace fossils in shallow lagoon environments within a marine carbonate platform/shelf during the Middle Devonian,<ref>{{cite journal |last1=Niedźwiedzki |year=2010 |title=Tetrapod trackways from the early middle Devonian period of Poland |journal=[[Nature (journal)|Nature]] |volume=463 |issue=7277 |pages=43–48 |doi=10.1038/nature08623 |bibcode=2010Natur.463...43N |pmid=20054388|s2cid=4428903 }}</ref> although these traces have been questioned and an interpretation as fish feeding traces (''[[Piscichnus]]'') has been advanced.<ref>{{cite journal |last1=Lucas |year=2015 |title=Thinopus and a Critical Review of Devonian Tetrapod Footprints |journal=[[Ichnos (journal)|Ichnos]] |volume=22 |issue=3–4 |pages=136–154 |doi=10.1080/10420940.2015.1063491|bibcode=2015Ichno..22..136L |s2cid=130053031 }}</ref>

====The greening of land====
{{main|Devonian explosion}}
[[File:Devonianscene-green.jpg|thumb|The Devonian Period marks the beginning of extensive land colonization by [[plant]]s. With large land-dwelling [[herbivore]]s not yet present, large forests grew and shaped the landscape.]]
Many [[List of Early Devonian land plants|Early Devonian plants]] did not have true roots or leaves like extant plants, although vascular tissue is observed in many of those plants. Some of the early land plants such as ''[[Drepanophycus]]'' likely spread by vegetative growth and spores.<ref>{{cite journal |last1=Zhang |first1=Ying-ying |last2=Xue |first2=Jin-Zhuang |last3=Liu |first3=Le |last4=Wang |first4=De-ming |title=Periodicity of reproductive growth in lycopsids: An example from the Upper Devonian of Zhejiang Province, China |journal=Paleoworld |year=2016 |volume=25 |issue=1 |pages=12–20 |doi=10.1016/j.palwor.2015.07.002}}</ref> The earliest land plants such as ''[[Cooksonia]]'' consisted of leafless, [[Dichotomous branching|dichotomous]] axes with terminal sporangia and were generally very short-statured, and grew hardly more than a few centimetres tall.<ref>{{cite journal |last1=Gonez |first1=Paul |last2=Gerrienne |first2=Philippe |title=A new definition and a lectotypification of the genus ''Cooksonia'' Lang 1937 |journal=International Journal of Plant Sciences |year=2010 |volume=171 |issue=2 |pages=199–215 |doi=10.1086/648988|bibcode=2010IJPlS.171..199G |s2cid=84956576 }}</ref> Fossils of ''[[Armoricaphyton|Armoricaphyton chateaupannense]]'', about 400 million years old, represent the oldest known plants with [[wood]]y tissue.<ref name="Chateau">{{cite web | url=https://www.lightsource.ca/news/details/analyzing_the_worlds_oldest_woody_plant_fossil.html | title=Analyzing the World's Oldest Woody Plant Fossil | publisher=[[Canadian Light Source]] | date=28 August 2019 | access-date=19 May 2021 | last=MacPherson | first=C. | archive-date=14 April 2021 | archive-url=https://web.archive.org/web/20210414132810/https://www.lightsource.ca/news/details/analyzing_the_worlds_oldest_woody_plant_fossil.html | url-status=dead }}</ref> By the Middle Devonian, shrub-like forests of primitive plants existed: [[Lycopodiophyta|lycophytes]], [[Equisetales|horsetails]], [[fern]]s, and [[progymnosperm]]s evolved. Most of these plants had true roots and leaves, and many were quite tall. The earliest-known trees appeared in the Middle Devonian.<ref>{{cite news |url=http://www.timesonline.co.uk/tol/news/uk/science/article1674051.ece |archive-url=https://web.archive.org/web/20080704130342/http://timesonline.co.uk/tol/news/uk/science/article1674051.ece |url-status=dead |archive-date=4 July 2008 |newspaper=The Times |location=London |title=Fossil from a forest that gave Earth its breath of fresh air |first=Lewis |last=Smith |date=April 19, 2007 |access-date=May 1, 2010 |df=dmy-all}}</ref> These included a lineage of lycopods and another arborescent, woody vascular plant, the [[Cladoxylopsida|cladoxylopsids]] and progymnosperm ''[[Archaeopteris]]''.<ref>{{cite encyclopedia |first1=C. Michael |last1=Hogan |date=2010 |url=http://www.eoearth.org/article/Fern?topic=49480 |title=Fern |encyclopedia=Encyclopedia of Earth |editor-first1=Saikat |editor-last1=Basu |editor-first2=C. |editor-last2=Cleveland |publisher=National Council for Science and the Environment |location=Washington DC}}</ref> These [[tracheophyte]]s were able to grow to large size on dry land because they had evolved the ability to biosynthesize [[lignin]], which gave them physical rigidity and improved the effectiveness of their vascular system while giving them resistance to pathogens and herbivores.<ref>{{cite journal |last1=Weng |first1=Jing-Ke |last2=Chapple |first2=Clint |title=The origin and evolution of lignin biosynthesis: Tansley review |journal=New Phytologist |date=July 2010 |volume=187 |issue=2 |pages=273–285 |doi=10.1111/j.1469-8137.2010.03327.x|pmid=20642725 |doi-access=free }}</ref> In [[Eifelian]] age, cladoxylopsid trees formed the first forests in Earth history.<ref>{{cite journal|author=Davies, Neil S., McMahon, William J. and Berry, Christopher M.|year=2024|url=https://orca.cardiff.ac.uk/id/eprint/166971/1/davies-et-al-2024-earth-s-earliest-forest-fossilized-trees-and-vegetation-induced-sedimentary-structures-from-the.pdf|title=Earth's earliest forest: fossilized trees and vegetation-induced sedimentary structures from the Middle Devonian (Eifelian) Hangman Sandstone Formation, Somerset and Devon, SW England|journal=Journal of the Geological Society|volume=181 |issue=4 |doi=10.1144/jgs2023-204|bibcode=2024JGSoc.181..204D |archive-url=https://web.archive.org/web/20240309154116/https://orca.cardiff.ac.uk/id/eprint/166971/1/davies-et-al-2024-earth-s-earliest-forest-fossilized-trees-and-vegetation-induced-sedimentary-structures-from-the.pdf|archive-date=2024-03-09|url-status=live}}</ref> By the end of the Devonian, the first seed-forming plants had appeared. This rapid appearance of many plant groups and growth forms has been referred to as the Devonian Explosion or the Silurian-Devonian Terrestrial Revolution.<ref name="SilurianDevonianTerrestrialRevolution">{{cite journal |last1=Capel |first1=Elliot |last2=Cleal |first2=Christopher J. |last3=Xue |first3=Jinzhuang |last4=Monnet |first4=Claude |last5=Servais |first5=Thomas |last6=Cascales-Miñana |first6=Borja |date=August 2022 |title=The Silurian–Devonian terrestrial revolution: Diversity patterns and sampling bias of the vascular plant macrofossil record |journal=[[Earth-Science Reviews]] |volume=231 |page=104085 |doi=10.1016/j.earscirev.2022.104085 |bibcode=2022ESRv..23104085C |s2cid=249616013 |doi-access=free |hdl=20.500.12210/76731 |hdl-access=free }}</ref>

The 'greening' of the continents acted as a [[carbon sink]], and [[Atmosphere of Earth|atmospheric concentrations]] of [[carbon dioxide]] may have dropped. This may have cooled the climate and led to a massive [[extinction event]]. (''See'' [[Late Devonian extinction]]).

{{gallery
|align=center
|width=200
|height=180
|File: Lycopod axis.jpg|Lycopod axis (branch) from the Middle Devonian of Wisconsin
|File: Cladoxylopsid bark.jpg|Bark (possibly from a cladoxylopsid) from the Middle Devonian of Wisconsin
}}

====Animals and the first soils====
Primitive arthropods co-evolved with this diversified terrestrial vegetation structure. The evolving co-dependence of insects and seed plants that characterized a recognizably modern world had its genesis in the Late Devonian Epoch. The development of soils and plant root systems probably led to changes in the speed and pattern of [[erosion]] and sediment deposition. The rapid evolution of a terrestrial ecosystem that contained copious animals opened the way for the first [[vertebrate]]s to seek terrestrial living. By the end of the Devonian, arthropods were solidly established on the land.<ref>{{cite journal |last1=Gess |first1=R.W. |year=2013 |title=The earliest record of terrestrial animals in Gondwana: A scorpion from the Famennian (Late Devonian) Witpoort Formation of South Africa |url=http://africaninvertebrates.org/ojs/index.php/AI/article/view/284 |archive-url=https://web.archive.org/web/20130906073206/http://africaninvertebrates.org/ojs/index.php/AI/article/view/284 |url-status=usurped |archive-date=6 September 2013 |journal=[[African Invertebrates]] |volume=54 |issue=2 |pages=373–379 |doi=10.5733/afin.054.0206|bibcode=2013AfrIn..54..373G |doi-access=free }}</ref>

===Gallery===
<gallery mode="packed">
File:Dunkleosteus terrelli 2024 reconstruction.jpg|''[[Dunkleosteus]]'', one of the largest armoured fish ever to roam the planet, lived during the Late Devonian
File:Titanichthys clarki (2024).png|''[[Titanichthys]]'', a [[Planktivore|planktivorous]] [[Arthrodira|arthrodire]] from the [[Famennian]] of the [[Cleveland Shale]] of [[Ohio]].
File:Eastmanosteus pustulosus.jpg|Lower jaw of ''[[Eastmanosteus]] pustulosus'' from the Middle Devonian of Wisconsin
File:Onychodus.jpg|Tooth of the lobe-finned fish ''[[Onychodus]]'' from the Middle Devonian of Wisconsin
File:Bothriolepis canadensis (2024).png|''[[Bothriolepis]]'', a diverse [[Antiarchi|antiarch]] [[genus]] that lived from the Mid to Late Devonian.
File:Devonianfishes ntm 1905 smit 1929.gif|Shark-like ''[[Cladoselache]]'', several [[Sarcopterygii|lobe-finned fishes]], including ''[[Eusthenopteron]]'' that was an early marine tetrapodomorph, and the placoderm ''[[Bothriolepis]]'' in a painting from 1905
File:Melocrinites nodosus spinosus.jpg|''Melocrinites nodosus spinosus'', a spiny, stalked [[crinoid]] from the Middle Devonian of [[Wisconsin]]
File:PhacopidDevonian.jpg|Enrolled phacopid [[trilobite]] from the Devonian of Ohio
File:AuloporaDevonianSilicaShale.jpg|The common tabulate coral ''[[Aulopora]]'' from the Middle Devonian of Ohio – view of colony encrusting a [[brachiopod]] valve
File:Tropidoleptus carinatus.jpg|''Tropidoleptus carinatus'', an orthid brachiopod from the Middle Devonian of New York
File:Pleurodictyum americanum Kashong.jpg|''[[Pleurodictyum|Pleurodictyum americanum]]'', a unique [[Tabulata|Tabulate]] coral, Kashong Shale, Middle Devonian of New York
File:HederelloidSEM.jpg|SEM image of a [[Hederellid|hederelloid]] from the Devonian of Michigan (largest tube diameter is 0.75&nbsp;mm)
File:HederellaOH3.jpg|Devonian spiriferid brachiopod from [[Ohio]] which served as a host substrate for a colony of hederelloids
File:Prototaxites Dawson1888.PNG|''[[Prototaxites]]'', an 8-meter genus of [[fungus]].
</gallery>

==Late Devonian extinction==
{{Main|Late Devonian extinction}}
[[File:Extinction Intensity.svg|thumb|The Late Devonian is characterised by three episodes of extinction ("Late D")]]The [[Late Devonian extinction]] is not a single event, but rather is a series of pulsed extinctions at the Givetian-Frasnian boundary, the Frasnian-Famennian boundary, and the Devonian-Carboniferous boundary.<ref name="Becker-2020">{{Citation|last1=Becker|first1=R. T.|title=Chapter 22 - The Devonian Period|date=2020-01-01|url=https://www.sciencedirect.com/science/article/pii/B978012824360200022X|work=Geologic Time Scale 2020|pages=733–810|editor-last=Gradstein|editor-first=Felix M.|publisher=Elsevier|language=en|doi=10.1016/b978-0-12-824360-2.00022-x|isbn=978-0-12-824360-2|access-date=2021-03-19|last2=Marshall|first2=J. E. A.|last3=Da Silva|first3=A. -C.|last4=Agterberg|first4=F. P.|last5=Gradstein|first5=F. M.|last6=Ogg|first6=J. G.|s2cid=241766371|editor2-last=Ogg|editor2-first=James G.|editor3-last=Schmitz|editor3-first=Mark D.|editor4-last=Ogg|editor4-first=Gabi M.|url-access=subscription}}</ref> Together, these are considered one of the "[[Extinction event#The "Big Five" mass extinctions|Big Five]]" mass extinctions in Earth's history.<ref>{{Cite journal|last1=Raup|first1=D. M.|last2=Sepkoski|first2=J. J.|date=1982-03-19|title=Mass Extinctions in the Marine Fossil Record|url=https://www.science.org/doi/10.1126/science.215.4539.1501|journal=Science|language=en|volume=215|issue=4539|pages=1501–1503|doi=10.1126/science.215.4539.1501|pmid=17788674|bibcode=1982Sci...215.1501R|s2cid=43002817|issn=0036-8075|url-access=subscription}}</ref> The Devonian extinction crisis primarily affected the marine community, and selectively affected shallow warm-water organisms rather than cool-water organisms. The most important group to be affected by this extinction event were the reef-builders of the great Devonian reef systems.<ref>{{Cite book|last=McGhee|first=George R.|url=https://www.worldcat.org/oclc/33010274|title=The Late Devonian mass extinction : the Frasnian/Famennian crisis|date=1996|publisher=Columbia University Press|isbn=0-231-07504-9|location=New York|oclc=33010274}}</ref>

Amongst the severely affected marine groups were the brachiopods, trilobites, ammonites, and [[acritarch]]s, and the world saw the disappearance of an estimated 96% of vertebrates like [[conodont]]s and [[Osteichthyes|bony fishes]], and all of the ostracoderms and placoderms.<ref name="Becker-2020" /><ref>[https://carlzimmer.com/after-a-mass-extinction-only-the-small-survive-80/ After a Mass Extinction, Only the Small Survive | Carl Zimmer]</ref> Land plants as well as freshwater species, such as our tetrapod ancestors, were relatively unaffected by the Late Devonian extinction event (there is a counterargument that the Devonian extinctions nearly wiped out the tetrapods<ref>{{cite book |last=McGhee |first=George R. |year=2013 |title=When the invasion of land failed: The legacy of the Devonian extinctions |location=New York |publisher=Columbia University Press |isbn=9780231160568}}</ref>).

The reasons for the Late Devonian extinctions are still unknown, and all explanations remain speculative.<ref>{{Cite journal|last1=Carmichael|first1=Sarah K.|last2=Waters|first2=Johnny A.|last3=Königshof|first3=Peter|last4=Suttner|first4=Thomas J.|last5=Kido|first5=Erika|date=2019-12-01|title=Paleogeography and paleoenvironments of the Late Devonian Kellwasser event: A review of its sedimentological and geochemical expression|url=https://www.sciencedirect.com/science/article/pii/S0921818118306258|journal=Global and Planetary Change|language=en|volume=183|pages=102984|doi=10.1016/j.gloplacha.2019.102984|bibcode=2019GPC...18302984C|s2cid=198415606|issn=0921-8181}}</ref><ref>{{Cite journal|last1=Lu|first1=Man|last2=Lu|first2=YueHan|last3=Ikejiri|first3=Takehitio|last4=Sun|first4=Dayang|last5=Carroll|first5=Richard|last6=Blair|first6=Elliot H.|last7=Algeo|first7=Thomas J.|last8=Sun|first8=Yongge|date=2021-05-15|title=Periodic oceanic euxinia and terrestrial fluxes linked to astronomical forcing during the Late Devonian Frasnian–Famennian mass extinction|journal=Earth and Planetary Science Letters|language=en|volume=562|pages=116839|doi=10.1016/j.epsl.2021.116839|bibcode=2021E&PSL.56216839L|s2cid=233578058|issn=0012-821X|doi-access=free}}</ref><ref>{{Cite journal|last1=Kaiser|first1=Sandra Isabella|last2=Aretz|first2=Markus|last3=Becker|first3=Ralph Thomas|date=2015-11-11|title=The global Hangenberg Crisis (Devonian–Carboniferous transition): review of a first-order mass extinction|url=https://doi.org/10.1144/SP423.9|journal=Geological Society, London, Special Publications|volume=423|issue=1|pages=387–437|doi=10.1144/sp423.9|s2cid=131270834|issn=0305-8719|url-access=subscription}}</ref><ref>{{Citation|last=Racki|first=Grzegorz|title=Chapter 2Toward understanding Late Devonian global events: few answers, many questions|date=2005-01-01|url=https://www.sciencedirect.com/science/article/pii/S0920544605800020|work=Developments in Palaeontology and Stratigraphy|volume=20|pages=5–36|editor-last=Over|editor-first=D. J.|series=Understanding Late Devonian And Permian-Triassic Biotic and Climatic Events|publisher=Elsevier|language=en|doi=10.1016/s0920-5446(05)80002-0|isbn=9780444521279|access-date=2021-03-19|editor2-last=Morrow|editor2-first=J. R.|editor3-last=Wignall|editor3-first=P. B.|url-access=subscription}}</ref> Canadian paleontologist [[Digby McLaren]] suggested in 1969 that the Devonian extinction events were caused by an asteroid impact. However, while there were Late Devonian collision events (see the [[Alamo bolide impact]]), little evidence supports the existence of a large enough Devonian crater.<ref>{{Cite journal|last1=Rendall|last2=Tapanila|date=2020|title=Impact resilience: Ecological recovery of a carbonate factory in the wake of the Late Devonian impact event|url=https://bioone.org/journals/Palaios/volume-35/issue-1/palo.2019.001/IMPACT-RESILIENCE--ECOLOGICAL-RECOVERY-OF-A-CARBONATE-FACTORY-IN/10.2110/palo.2019.001.short|journal=PALAIOS|volume=35|issue=1|pages=12–21|doi=10.2110/palo.2019.001|bibcode=2020Palai..35...12R|s2cid=210944155|url-access=subscription}}</ref>

==See also==
{{Portal|Devonian}}
* {{annotated link|Falls of the Ohio State Park}}. One of the largest exposed Devonian fossil beds in the world.
* {{annotated link|Geologic time scale}}
* {{annotated link|List of Early Devonian land plants}}
* {{annotated link|List of fossil sites}} ''(with link directory)''
* {{annotated link|Phacops rana|''Phacops rana''}}, a Devonian trilobite
;Categories:
* {{annotated link|Category:Devonian plants}}

==Notes==
{{notelist|1}}

==References==
{{reflist}}

==External links==
{{Sister project links|auto=1|s=Portal:Paleozoic#Devonian}}

* {{cite web |url=http://www.devoniantimes.org/index.html |archive-url=https://web.archive.org/web/20100211070749/http://www.devoniantimes.org/index.html |archive-date=2010-02-11 |title=Devonian |website=Devonian Times}}
* {{cite web |url=http://www.ucmp.berkeley.edu/devonian/devlife.html |publisher=UC Berkeley |title=Devonian life |df=dmy-all}} – site introduces the Devonian
* {{cite web |publisher=International Commission on Stratigraphy (ICS) |title=Geologic Time Scale |year=2004 |url=http://www.stratigraphy.org/ |access-date=September 19, 2005 |df=dmy-all}}
* {{cite web |url=http://www.geo-lieven.com/erdzeitalter/devon/devon.htm |title=Examples of Devonian Fossils}}
* {{cite web |url=https://ghkclass.com/ghkC.html?devonian |title=Devonian chronostratigraphy scale}}
* {{cite web |url=http://www.palaeos.com/Paleozoic/Devonian/Devonian.2.htm#Life |archive-url=https://web.archive.org/web/20071028173911/http://www.palaeos.com/Paleozoic/Devonian/Devonian.2.htm#Life |archive-date=2007-10-28 |title=Devonian |website=Palaeos |df=dmy-all}}
* {{cite web |url=http://www.ageoffishes.org.au/ |website=Age of Fishes |title=Museum}}

{{Devonian footer}}
{{Geological history|p|p|state=collapsed}}
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[[Category:Devonian| ]]
[[Category:Geological periods]]
[[Category:Geology of Devon|.]]