Editing Carboniferous

{{Short description|Fifth period of the Paleozoic Era}}
{{For|the album|Carboniferous (album){{!}}''Carboniferous'' (album)}}
{{Infobox geologic timespan
| name                         = Carboniferous
| color                        = Carboniferous
| top_bar                      =
| time_start                   = 358.9
| time_start_uncertainty       = 0.4
| time_end                     = 298.9
| time_end_uncertainty         = 0.15
| image_map                    = Mollweide Paleographic Map of Earth, 330 Ma (Serpukhovian Age).png
| caption_map                  = A map of Earth as it appeared 330 million years ago during the Carboniferous Period, Mississippian Subperiod
| image_outcrop                =
| caption_outcrop              =
| image_art                    =
| caption_art                  =
<!--Chronology-->
| timeline                     = Carboniferous
<!--Etymology-->
| name_formality               = Formal
| name_accept_date             =
| alternate_spellings          =
| synonym1                     =
| synonym1_coined              =
| synonym2                     =
| synonym2_coined              =
| synonym3                     =
| synonym3_coined              =
| nicknames                    = Age of Amphibians
| 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                  = [[William Daniel Conybeare]] and [[William Phillips (geologist)|William Phillips]], 1822
| timespan_formality           = Formal
| lower_boundary_def           = [[First appearance datum|FAD]] of the [[Conodont]] ''[[Siphonodella|Siphonodella sulcata]]'' (discovered to have biostratigraphic issues as of 2006){{sfn|Kaiser|2009}}
| lower_gssp_location          = [[La Serre]], [[Montagne Noire]], France
| lower_gssp_coords            = {{Coord|43.5555|N|3.3573|E|display=inline}}
| lower_gssp_accept_date       = 1990{{sfn|Paproth|Feist|Flajs|1991}}
| upper_boundary_def           = FAD of the [[Conodont]] ''[[Streptognathodus|Streptognathodus isolatus]]'' within the [[morphotype]] ''[[Streptognathodus|Streptognathodus wabaunsensis]]'' chronocline
| upper_gssp_location          = [[Aidaralash]], [[Ural Mountains]], [[Kazakhstan]]
| upper_gssp_coords            = {{Coord|50.2458|N|57.8914|E|display=inline}}
| upper_gssp_accept_date       = 1996{{sfn|Davydov|Glenister|Spinosa|Ritter|1998}}
<!--Atmospheric and Climatic Data-->
| sea_level                    = Falling from 120&nbsp;m to present-day level throughout the Mississippian, then rising steadily to about 80&nbsp;m at end of period{{sfn|Haq|Schutter|2008}}
}}The '''Carboniferous''' ({{IPAc-en|,|k|a:r|b|ə|ˈ|n|ɪ|f|ər|ə|s}} {{Respell|KAR|bə|NIF|ər|əs}}){{sfn|Wells|2008}} is a [[Geologic time scale|geologic period]] and [[System (stratigraphy)|system]] of the [[Paleozoic]] [[era (geology)|era]] that spans 60 million years, from the end of the [[Devonian]] Period {{Period end|Devonian}} Ma (million years ago) to the beginning of the [[Permian]] Period, {{Period start|Permian}} Ma. It is the fifth and penultimate period of the Paleozoic era and the fifth period of the [[Phanerozoic]] [[eon (geology)|eon]]. In [[North America]], the Carboniferous is often treated as two separate geological periods, the earlier [[Mississippian (geology)|Mississippian]] and the later [[Pennsylvanian (geology)|Pennsylvanian]].{{sfn|University of California, Berkeley|2012}}

The name ''Carboniferous'' means "[[coal]]-bearing", from the [[Latin]] {{Wikt-lang|la|carbō}} ("[[coal]]") and {{Wikt-lang|la|ferō}} ("bear, carry"), and refers to the many coal beds formed globally during that time.{{sfn|Cossey|Adams|Purnell|Whiteley|2004|page=3}} The first of the modern "system" names, it was coined by geologists [[William Conybeare (geologist)|William Conybeare]] and [[William Phillips (geologist)|William Phillips]] in 1822,{{sfn|Conybeare|Phillips|1822|loc=[https://books.google.com/books?id=ZcMQAAAAIAAJ&pg=PA323 p. 323: "Book III. Medial or Carboniferous Order."]}} based on a study of the British rock succession.

Carboniferous is the period during which both [[terrestrial animal]] and [[Embryophyte|land plant]] life was well established.{{sfn|Garwood|Edgecombe|2011}} [[Stegocephalia]] (four-limbed [[vertebrate]]s including true [[tetrapod]]s), whose forerunners ([[tetrapodomorph]]s) had evolved from [[lobe-finned fish]] during the preceding Devonian period, became [[pentadactylous]] during the Carboniferous.<ref>Irisarri, I., Baurain, D., Brinkmann, H. et al. Phylotranscriptomic consolidation of the jawed vertebrate timetree. Nat Ecol Evol 1, 1370–1378 (2017). https://doi.org/10.1038/s41559-017-0240-5</ref> The period is sometimes called the '''Age of Amphibians'''<ref>{{cite encyclopedia|url=https://www.britannica.com/science/Carboniferous-Period/Carboniferous-life|title=Carboniferous Period|encyclopedia=Encyclopædia Britannica|date=25 September 2024 }}</ref> because of the [[genetic divergence|diversification]] of early [[amphibian]]s such as the [[temnospondyl]]s, which became dominant land vertebrates,<ref>{{cite web|title=Animal Life in the Paleozoic |url=http://www.columbia.edu/~vjd1/pz_life.htm |url-status=live |archive-url=https://web.archive.org/web/20031217181240/http://www.columbia.edu:80/~vjd1/pz_life.htm |archive-date=2003-12-17 }}</ref> as well as the first appearance of [[amniote]]s including [[synapsid]]s (the [[clade]] to which modern [[mammal]]s belong) and [[sauropsid]]s (which include modern reptiles and birds) during the late Carboniferous. Land [[arthropod]]s such as [[arachnid]]s (e.g. [[trigonotarbid]]s and ''[[Pulmonoscorpius]]''), [[myriapod]]s (e.g. ''[[Arthropleura]]'') and especially insects (particularly [[Pterygota|flying insects]]) also underwent a major [[evolutionary radiation]] during the late Carboniferous. [[Coal forest|Vast swaths of forests and swamps]] covered the land, which eventually became the coal beds characteristic of the Carboniferous [[stratigraphy]] evident today.

The later half of the period experienced [[Glacial period|glaciations]], low sea level, and [[Mountain formation|mountain building]] as the continents collided to form [[Pangaea]]. A minor marine and terrestrial extinction event, the [[Carboniferous rainforest collapse]], occurred at the end of the period, caused by climate change.{{sfn|Sahney|Benton|Falcon-Lang|2010}} Atmospheric oxygen levels, originally thought to be consistently higher than today throughout the Carboniferous, have been shown to be more variable, increasing from low levels at the beginning of the Period to highs of 25–30%.<ref name=":2" />

== Etymology and history ==
The development of a Carboniferous [[Chronostratigraphy|chronostratigraphic]] timescale began in the late 18th century. The term "Carboniferous" was first used as an adjective by Irish geologist [[Richard Kirwan]] in 1799 and later used in a heading entitled "Coal-measures or Carboniferous Strata" by [[John Farey Sr.]] in 1811. Four units were originally ascribed to the Carboniferous, in ascending order, the [[Old Red Sandstone]], [[Carboniferous Limestone]], [[Millstone Grit]] and the [[Coal measures|Coal Measures]]. These four units were placed into a formalised Carboniferous unit by [[William Conybeare (geologist)|William Conybeare]] and [[William Phillips (geologist)|William Phillips]] in 1822 and then into the Carboniferous System by Phillips in 1835. The Old Red Sandstone was later considered [[Devonian]] in age.<ref name="Davydov-2012">{{Citation |last1=Davydov |first1=V.I. |title=The Carboniferous Period |date=2012 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780444594259000238 |work=The Geologic Time Scale |pages=603–651 |access-date=2021-06-17 |publisher=Elsevier |language=en |doi=10.1016/b978-0-444-59425-9.00023-8 |isbn=978-0-444-59425-9 |s2cid=132978981 |last2=Korn |first2=D. |last3=Schmitz |first3=M.D. |last4=Gradstein |first4=F.M. |last5=Hammer |first5=O.}}</ref>

The similarity in successions between the British Isles and Western Europe led to the development of a common European timescale with the Carboniferous System divided into the lower [[Dinantian]], dominated by [[Carbonate rock|carbonate]] deposition and the upper [[Silesian (series)|Silesian]] with mainly [[siliciclastic]] deposition.<ref name="Woodcock-2012">{{Cite book |title=Geological history of Britain and Ireland |date=2012 |publisher=Wiley-Blackwell |isbn=978-1-4051-9381-8 |editor-last=Woodcock |editor-first=Nigel H. |edition=2nd |location=Chichester |editor-last2=Strachan |editor-first2=R. A.}}</ref> The Dinantian was divided into the [[Tournaisian]] and [[Viséan]] stages. The Silesian was divided into the [[Namurian]], [[Westphalian (stage)|Westphalian]] and [[Stephanian (stage)|Stephanian]] stages. The Tournaisian is the same length as the [[International Commission on Stratigraphy]] (ICS) stage, but the Viséan is longer, extending into the lower [[Serpukhovian]].<ref name="Davydov-2012" />

North American geologists recognised a similar stratigraphy but divided it into two systems rather than one. These are the lower carbonate-rich sequence of the [[Mississippian (geology)|Mississippian]] System and the upper siliciclastic and coal-rich sequence of the [[Pennsylvanian (geology)|Pennsylvanian]]. The [[United States Geological Survey]] officially recognised these two systems in 1953.<ref name="Stanley-2015">{{Cite book |last1=Stanley |first1=Steven |title=Earth System History |last2=Luczaj |first2=John |publisher=W.H.Freeman and Company |year=2015 |isbn=978-1-319-15402-8 |edition=4th |location=New York}}</ref> In Russia, in the 1840s British and Russian geologists divided the Carboniferous into the Lower, Middle and Upper series based on Russian sequences. In the 1890s these became the Dinantian, [[Moscovian (Carboniferous)|Moscovian]] and Uralian stages. The Serpukivian was proposed as part of the Lower Carboniferous, and the Upper Carboniferous was divided into the Moscovian and [[Gzhelian]]. The [[Bashkirian]] was added in 1934.<ref name="Davydov-2012" />

In 1975, the ICS formally ratified the Carboniferous System, with the Mississippian and Pennsylvanian subsystems from the North American timescale, the Tournaisian and Visean stages from the Western European and the Serpukhovian, Bashkirian, Moscovian, [[Kasimovian]] and Gzhelian from the Russian.<ref name="Davydov-2012" /> With the formal ratification of the Carboniferous System, the Dinantian, Silesian, Namurian, Westphalian and Stephanian became redundant terms, although the latter three are still in common use in Western Europe.<ref name="Woodcock-2012" />

== Geology ==

=== Stratigraphy ===
Stages can be defined globally or regionally. For global stratigraphic correlation, the ICS ratify global stages based on a [[Global Boundary Stratotype Section and Point]] (GSSP) from a single [[Geological formation|formation]] (a [[stratotype]]) identifying the lower boundary of the stage. Only the boundaries of the Carboniferous System and three of the stage bases are defined by global stratotype sections and points because of the complexity of the geology.<ref name="Lucas-2022">{{Cite journal |last1=Lucas |first1=Spencer G. |last2=Schneider |first2=Joerg W. |last3=Nikolaeva |first3=Svetlana |last4=Wang |first4=Xiangdong |date=2022 |title=The Carboniferous timescale: an introduction |url=https://www.lyellcollection.org/doi/10.1144/SP512-2021-160 |journal=Geological Society, London, Special Publications |language=en |volume=512 |issue=1 |pages=1–17 |doi=10.1144/SP512-2021-160 |bibcode=2022GSLSP.512....1L |s2cid=245208581 |issn=0305-8719}}</ref><ref name="Davydov-2012" /> The ICS subdivisions from youngest to oldest are as follows:<ref name="Cohen-2013">Cohen, K.M., Finney, S.C., Gibbard, P.L. & Fan, J.-X. (2013; updated) [https://stratigraphy.org/ICSchart/ChronostratChart2020-03.pdf The ICS International Chronostratigraphic Chart]. Episodes 36: 199–204.</ref>
{|
|Series/epoch
|
|Stage/age
|Lower boundary
|-
| colspan="2" style="background-color: {{period color|Permian}};" |[[Permian]]
| style="background-color: {{period color|Asselian}};" |[[Asselian]]
|298.9 ±0.15 Ma
|-
| rowspan="4" style="background-color: {{period color|Pennsylvanian}};" |[[Pennsylvanian (geology)|Pennsylvanian]]
| rowspan="2" style="background-color: {{period color|Upper Pennsylvanian}};" |Upper
| style="background-color: {{period color|Gzhelian}};" |[[Gzhelian]]
|303.7 ±0.1 Ma
|-
| style="background-color: {{period color|Kasimovian}};" |[[Kasimovian]]
|307.0 ±0.1 Ma
|-
| style="background-color: {{period color|Middle Pennsylvanian}};" |Middle
| style="background-color: {{period color|Moscovian}};" |[[Moscovian (Carboniferous)|Moscovian]]
|315.2 ±0.2 Ma
|-
| style="background-color: {{period color|Lower Pennsylvanian}};" |Lower
| style="background-color: {{period color|Bashkirian}};" |[[Bashkirian]]
|323.2 ±0.4 Ma
|-
| rowspan="3" style="background-color: {{period color|Mississippian}};" |[[Mississippian (geology)|Mississippian]]
| style="background-color: {{period color|Upper Mississippian}};" |Upper
| style="background-color: {{period color|Serpukhovian}};" |[[Serpukhovian]]
|330.9 ±0.2 Ma
|-
| style="background-color: {{period color|Middle Mississippian}};" |Middle
| style="background-color: {{period color|Visean}};" |[[Visean]]
|346.7 ±0.4 Ma
|-
| style="background-color: {{period color|Lower Mississippian}};" |Lower
| style="background-color: {{period color|Tournaisian}};" |[[Tournaisian]]
|358.9 ±0.4 Ma
|}

==== Mississippian ====
The Mississippian was proposed by [[Alexander Winchell]] in 1870 named after the extensive exposure of lower Carboniferous [[limestone]] in the upper [[Mississippi River]] valley.<ref name="Stanley-2015" /> During the Mississippian, there was a marine connection between the [[Paleo-Tethys Ocean|Paleo-Tethys]] and [[Panthalassa]] through the [[Rheic Ocean]] resulting in the near worldwide distribution of marine faunas and so allowing widespread correlations using marine [[biostratigraphy]].<ref name="Lucas-2022" /><ref name="Davydov-2012" /> However, there are few Mississippian [[volcanic rock]]s, and so obtaining [[Radiometric dating|radiometric dates]] is difficult.<ref name="Lucas-2022" />

The Tournaisian Stage is named after the Belgian city of [[Tournai]]. It was introduced in scientific literature by Belgian geologist [[André Dumont (geologist)|André Dumont]] in 1832. The GSSP for the base of the Carboniferous System, Mississippian Subsystem and Tournaisian Stage is located at the [[La Serre]] section in [[Montagne Noire]], southern France. It is defined by the first appearance of the [[conodont]] ''[[Siphonodella|Siphonodella sulcata]]'' within the evolutionary lineage from ''[[Siphonodella|Siphonodella praesulcata]]'' to ''Siphonodella sulcata''. This was ratified by the ICS in 1990. However, in 2006 further study revealed the presence of ''Siphonodella sulcata'' below the boundary, and the presence of ''Siphonodella'' ''praesulcata'' and ''Siphonodella sulcata'' together above a local [[unconformity]]. This means the evolution of one species to the other, the definition of the boundary, is not seen at the La Serre site making precise correlation difficult.<ref name="Davydov-2012" /><ref name="Stratigraphy.org">{{Cite web |title=International Commission on Stratigraphy |url=https://stratigraphy.org/gssps/visean |access-date=2023-11-12 |website=stratigraphy.org}}</ref>[[File:Carboniferous regional subdivisions.png|thumb|upright=2|Chart of regional subdivisions of the Carboniferous Period]]The Viséan Stage was introduced by André Dumont in 1832 and is named after the city of [[Visé]], [[Liège Province]], Belgium. In 1967, the base of the Visean was officially defined as the first black limestone in the Leffe [[facies]] at the Bastion Section in the [[Dinant|Dinant Basin]]. These changes are now thought to be ecologically driven rather than caused by evolutionary change, and so this has not been used as the location for the GSSP. Instead, the GSSP for the base of the Visean is located in Bed 83 of the sequence of dark grey [[limestone]]s and [[shale]]s at the [[Peng Chong|Pengchong]] section, [[Guangxi]], southern China. It is defined by the first appearance of the [[Fusulinida|fusulinid]] ''Eoparastaffella simplex'' in the evolutionary lineage ''Eoparastaffella ovalis – Eoparastaffella simplex'' and was ratified in 2009.<ref name="Davydov-2012" />

The Serpukhovian Stage was proposed in 1890 by Russian stratigrapher [[Sergei Nikitin (geologist)|Sergei Nikitin]]. It is named after the city of [[Serpukhov]], near Moscow and currently lacks a defined GSSP. The Visean-Serpukhovian boundary coincides with a major period of glaciation. The resulting sea level fall and climatic changes led to the loss of connections between marine basins and [[endemism]] of marine fauna across the Russian margin. This means changes in [[Biome|biota]] are environmental rather than evolutionary making wider correlation difficult.<ref name="Davydov-2012" /> Work is underway in the [[Ural Mountains|Urals]] and Nashui, [[Guizhou]] Province, southwestern China for a suitable site for the GSSP with the proposed definition for the base of the Serpukhovian as the first appearance of conodont ''[[Lochriea|Lochriea ziegleri]].''<ref name="Stratigraphy.org" />

==== Pennsylvanian ====
The Pennsylvanian was proposed by [[J. J. Stevenson (geologist)|J.J.Stevenson]] in 1888, named after the widespread coal-rich strata found across the state of Pennsylvania.<ref name="Stanley-2015" /> The closure of the Rheic Ocean and formation of Pangea during the Pennsylvanian, together with widespread glaciation across [[Gondwana]] led to major climate and sea level changes, which restricted marine fauna to particular geographic areas thereby reducing widespread biostratigraphic correlations.<ref name="Lucas-2022" /><ref name="Davydov-2012" /> Extensive volcanic events associated with the assembling of Pangea means more radiometric dating is possible relative to the Mississippian.<ref name="Lucas-2022" />

The Bashkirian Stage was proposed by Russian stratigrapher [[Sofia Semikhatova]] in 1934. It was named after [[Bashkiria (1917–1919)|Bashkiria]], the then Russian name of the republic of [[Bashkortostan]] in the southern Ural Mountains of Russia. The GSSP for the base of the Pennsylvanian Subsystem and Bashkirian Stage is located at [[Arrow Canyon Range|Arrow Canyon]] in [[Nevada]], US and was ratified in 1996. It is defined by the first appearance of the conodont ''[[Declinognathodus|Declinognathodus noduliferus]]''. Arrow Canyon lay in a shallow, tropical seaway which stretched from Southern California to Alaska. The boundary is within a [[Cyclothems|cyclothem]] sequence of [[Sequence stratigraphy|transgressive]] limestones and fine [[sandstone]]s, and [[Sequence stratigraphy|regressive]] [[mudstone]]s and [[breccia]]ted limestones.<ref name="Davydov-2012" />

The Moscovian Stage is named after shallow marine limestones and colourful [[clay]]s found around Moscow, Russia. It was first introduced by Sergei Nikitin in 1890. The Moscovian currently lacks a defined GSSP. The fusulinid ''Aljutovella aljutovica'' can be used to define the base of the Moscovian across the northern and eastern margins of Pangea, however, it is restricted in geographic area, which means it cannot be used for global correlations.<ref name="Davydov-2012" /> The first appearance of the conodonts ''Declinognathodus donetzianus'' or ''Idiognathoides postsulcatus'' have been proposed as a boundary marking species and potential sites in the Urals and Nashui, Guizhou Province, southwestern China are being considered.<ref name="Stratigraphy.org" />

The Kasimovian is the first stage in the Upper Pennsylvanian. It is named after the Russian city of [[Kasimov]], and was originally included as part of Nikitin's 1890 definition of the Moscovian. It was first recognised as a distinct unit by A.P. Ivanov in 1926, who named it the "''Tiguliferina''" Horizon after a type of [[brachiopod]]. The boundary of the Kasimovian covers a period of globally low sea level, which has resulted in [[Unconformity|disconformities]] within many sequences of this age. This has created difficulties in finding suitable marine fauna that can used to correlate boundaries worldwide.<ref name="Davydov-2012" /> The Kasimovian currently lacks a defined GSSP; potential sites in the southern Urals, southwest USA and Nashui, Guizhou Province, southwestern China are being considered.<ref name="Stratigraphy.org" />

The Gzhelian is named after the Russian village of [[Gzhel (selo), Moscow Oblast]], near [[Ramenskoye, Moscow Oblast|Ramenskoye]], not far from Moscow. The name and type locality were defined by Sergei Nikitin in 1890. The Gzhelian currently lacks a defined GSSP. The first appearance of the fusulinid ''Rauserites rossicus'' and ''Rauserites'' ''stuckenbergi'' can be used in the [[Boreal Sea]] and Paleo-Tethyan regions but not eastern Pangea or Panthalassa margins.<ref name="Davydov-2012" /> Potential sites in the Urals and Nashui, Guizhou Province, southwestern China for the GSSP are being considered.<ref name="Stratigraphy.org" />

The GSSP for the base of the Permian is located in the Aidaralash River valley near [[Aqtöbe]], Kazakhstan and was ratified in 1996. The beginning of the stage is defined by the first appearance of the conodont ''[[Streptognathodus|Streptognathodus postfusus]].''<ref>Davydov, V.I., Glenister, B.F., Spinosa, C., Ritter, S.M., Chernykh, V.V., Wardlaw, B.R. & Snyder, W.S. 1998. [https://www.researchgate.net/publication/237222028_Proposal_of_Aidaralash_as_Global_Stratotype_Section_and_Point_GSSP_for_base_of_the_Permian_System Proposal of Aidaralash as Global Stratotype Section and Point (GSSP) for base of the Permian System]. Episodes, 21, 11–17.</ref>

=== Cyclothems ===
A cyclothem is a succession of non-marine and marine [[sedimentary rock]]s, deposited during a single sedimentary cycle, with an [[Erosion surface|erosional surface]] at its base. Whilst individual cyclothems are often only metres to a few tens of metres thick, cyclothem sequences can be many hundreds to thousands of metres thick and contain tens to hundreds of individual cyclothems.<ref name="Montañez-2022" /> Cyclothems were deposited along [[Continental shelf|continental shelves]] where the very gentle gradient of the shelves meant even small changes in sea level led to large advances or retreats of the sea.<ref name="Stanley-2015" /> Cyclothem lithologies vary from [[mudrock]] and carbonate-dominated to coarse siliciclastic sediment-dominated sequences depending on the paleo-topography, climate and supply of sediments to the shelf.<ref name="Fielding-2021">{{Cite journal |last=Fielding |first=Christopher R. |date=2021-06-01 |title=Late Palaeozoic cyclothems – A review of their stratigraphy and sedimentology |url=https://www.sciencedirect.com/science/article/pii/S0012825221001124 |journal=Earth-Science Reviews |volume=217 |pages=103612 |bibcode=2021ESRv..21703612F |doi=10.1016/j.earscirev.2021.103612 |issn=0012-8252 |s2cid=233618931}}</ref>
[[File:Red Wharf Limestone Formation, Red Wharf Bay, Anglesey, North Wales, UK.jpg|alt=A cliff with pale grey beds of limestone overlain by orange sandstone, above which are more pale grey mudstones and limestones. A large fracture in the limestone is filled by a bulbous extension of the sandstone down into the limestone.|thumb|Cliff section through the Serpukhovian Red Wharf Limestone Formation, [[Wales]]. A marine limestone at the base of the cliff is overlain by an orange-coloured fluvial sandstone. Subaerial exposure of the limestone during a period of falling sea level resulted in the formation of a karstic surface, which has then been infilled by the river sands. A thin, estuarine silty mudstone overlays the sandstone, which in turn is overlain by a second marine limestone.]]
The main period of cyclothem deposition occurred during the [[Late Paleozoic icehouse|Late Paleozoic Ice Age]] from the Late Mississippian to early Permian, when the waxing and waning of [[ice sheet]]s led to rapid changes in [[eustatic sea level]].<ref name="Fielding-2021" /> The growth of ice sheets led global sea levels to fall as water was locked away in glaciers. Falling sea levels exposed large tracts of the continental shelves across which river systems eroded channels and valleys and vegetation broke down the surface to form [[soil]]s. The non-marine sediments deposited on this erosional surface form the base of the cyclothem.<ref name="Fielding-2021" /> As sea levels began to rise, the rivers flowed through increasingly water-logged landscapes of swamps and lakes. [[Peatland|Peat mires]] developed in these wet and oxygen-poor conditions, leading to coal formation.<ref name="Woodcock-2012" /> With continuing sea level rise, coastlines migrated landward and [[River delta|deltas]], [[lagoon]]s and [[Estuary|esturaries]] developed; their sediments deposited over the peat mires. As fully marine conditions were established, limestones succeeded these marginal marine deposits. The limestones were in turn overlain by deep water black shales as maximum sea levels were reached.<ref name="Stanley-2015" />

Ideally, this sequence would be reversed as sea levels began to fall again; however, sea level falls tend to be protracted, whilst sea level rises are rapid, ice sheets grow slowly but melt quickly. Therefore, the majority of a cyclothem sequence occurred during falling sea levels, when rates of [[erosion]] were high, meaning they were often periods of non-deposition. Erosion during sea level falls could also result in the full or partial removal of previous cyclothem sequences. Individual cyclothems are generally less than 10 m thick because the speed at which sea level rose gave only limited time for sediments to accumulate.<ref name="Fielding-2021" />

During the Pennsylvanian, cyclothems were deposited in shallow, [[Inland sea|epicontinental]] seas across the tropical regions of [[Laurasia|Laurussia]] (present day western and central US, Europe, Russia and central Asia) and the [[North China craton|North]] and [[South China cratons]].<ref name="Stanley-2015" /> The rapid sea levels fluctuations they represent correlate with the glacial cycles of the Late Paleozoic Ice Age. The advance and retreat of ice sheets across Gondwana followed a 100 kyr [[Milankovitch cycles|Milankovitch cycle]], and so each cyclothem represents a cycle of sea level fall and rise over a 100 kyr period.<ref name="Fielding-2021" />

=== Coal formation ===
[[File:Hyden Formation over Pikeville Formation (Middle Pennsylvanian; Jackson North roadcut, Breathitt County, Kentucky, USA) 1.jpg|alt=Photo of a road cutting through a thick and repeating sequence of pale grey to black rock strata.|thumb|Hyden Formation over Pikeville Formation in the Pennsylvanian of Kentucky, US. The exposure has Pennsylvanian-aged cyclothemic sedimentary rocks of the Breathitt Group. The upper part of the roadcut is Hyden Formation, consisting of mixed siliciclastics and coal. The lower part is Pikeville Formation, also having mixed siliciclastics and coal.]]
Coal forms when organic matter builds up in waterlogged, [[Anoxic waters|anoxic]] swamps, known as peat mires, and is then buried, compressing the peat into coal. The majority of Earth's coal deposits were formed during the late Carboniferous and early Permian. The plants from which they formed contributed to changes in the Carboniferous Earth's atmosphere.<ref name="NelsenDiMichelePetersBoyce2016PNAS">{{cite journal |last1=Nelsen |first1=Matthew C. |last2=DiMichele |first2=William A. |last3=Peters |first3=Shanan E. |last4=Boyce |first4=C. Kevin |date=19 January 2016 |title=Delayed fungal evolution did not cause the Paleozoic peak in coal production |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=113 |issue=9 |pages=2442–2447 |bibcode=2016PNAS..113.2442N |doi=10.1073/pnas.1517943113 |pmc=4780611 |pmid=26787881 |doi-access=free}}</ref>

During the Pennsylvanian, vast amounts of organic debris accumulated in the peat mires that formed across the low-lying, humid equatorial wetlands of the [[foreland basin]]s of the [[Central Pangean Mountains]] in Laurussia, and around the margins of the North and South China cratons.<ref name="NelsenDiMichelePetersBoyce2016PNAS" /> During glacial periods, low sea levels exposed large areas of the continental shelves. Major river channels, up to several kilometres wide, stretched across these shelves feeding a network of smaller channels, lakes and peat mires.<ref name="Woodcock-2012" /> These wetlands were then buried by sediment as sea levels rose during [[interglacial]]s. Continued crustal [[subsidence]] of the foreland basins and continental margins allowed this accumulation and burial of peat deposits to continue over millions of years resulting in the formation of thick and widespread coal formations.<ref name="NelsenDiMichelePetersBoyce2016PNAS" /> During the warm interglacials, smaller coal swamps with plants adapted to the temperate conditions formed on the [[Siberia (continent)|Siberian craton]] and the western Australian region of Gondwana.<ref name="Stanley-2015" />

There is ongoing debate as to why this peak in the formation of Earth's coal deposits occurred during the Carboniferous. The first theory, known as the delayed fungal evolution hypothesis, is that a delay between the development of trees with the wood fibre [[lignin]] and the subsequent evolution of lignin-degrading fungi gave a period of time where vast amounts of lignin-based organic material could accumulate. Genetic analysis of [[Basidiomycota|basidiomycete]] fungi, which have [[enzyme]]s capable of breaking down lignin, supports this theory by suggesting this fungi evolved in the Permian.<ref>{{Cite journal |last1=Floudas |first1=Dimitrios |last2=Binder |first2=Manfred |last3=Riley |first3=Robert |last4=Barry |first4=Kerrie |last5=Blanchette |first5=Robert A. |last6=Henrissat |first6=Bernard |last7=Martínez |first7=Angel T. |last8=Otillar |first8=Robert |last9=Spatafora |first9=Joseph W. |last10=Yadav |first10=Jagjit S. |last11=Aerts |first11=Andrea |last12=Benoit |first12=Isabelle |last13=Boyd |first13=Alex |last14=Carlson |first14=Alexis |last15=Copeland |first15=Alex |date=2012-06-01 |title=The Paleozoic Origin of Enzymatic Lignin Decomposition Reconstructed from 31 Fungal Genomes |url=https://ui.adsabs.harvard.edu/abs/2012Sci...336.1715F |journal=Science |volume=336 |issue=6089 |pages=1715–1719 |doi=10.1126/science.1221748 |pmid=22745431 |bibcode=2012Sci...336.1715F |issn=0036-8075|hdl=10261/60626 |osti=1165864 |hdl-access=free }}</ref><ref>{{Cite web |last=Biello |first=David |title=White Rot Fungi Slowed Coal Formation |url=https://www.scientificamerican.com/article/mushroom-evolution-breaks-down-lignin-slows-coal-formation/ |access-date=2024-01-06 |website=Scientific American |language=en}}</ref> However, significant Mesozoic and Cenozoic coal deposits formed after lignin-digesting fungi had become well established, and fungal degradation of lignin may have already evolved by the end of the Devonian, even if the specific enzymes used by basidiomycetes had not.<ref name="NelsenDiMichelePetersBoyce2016PNAS" /> The second theory is that the geographical setting and climate of the Carboniferous were unique in Earth's history: the co-occurrence of the position of the continents across the humid equatorial zone, high biological productivity, and the low-lying, water-logged and slowly subsiding sedimentary basins that allowed the thick accumulation of peat were sufficient to account for the peak in coal formation.<ref name="NelsenDiMichelePetersBoyce2016PNAS" />

==Palaeogeography==
During the Carboniferous, there was an increased rate in [[Plate tectonics|tectonic plate]] movements as the [[supercontinent]] Pangea assembled. The continents themselves formed a near circle around the opening Paleo-Tethys Ocean, with the massive [[Panthalassa|Panthalassic Ocean]] beyond. Gondwana covered the [[South Pole|south polar]] region. To its northwest was Laurussia. These two continents slowly collided to form the core of Pangea. To the north of Laurussia lay [[Siberia]] and [[Amurian Plate|Amuria]]. To the east of Siberia, [[Kazakhstania]], North China and South China formed the northern margin of the Paleo-Tethys, with Annamia laying to the south.<ref name="Torsvik-2017">{{Cite book |last1=Torsvik |first1=Trond |title=Earth History and Palaeogeography |last2=Cocks |first2=L.Robin |publisher=Cambridge University Press |year=2017 |isbn=978-1-107-10532-4 |location=Cambridge}}</ref>
[[File:Early Carboniferous.png|thumb|Approximate positions of the continents in the early Carboniferous (c. 348 Ma). AM. Amuria; AN. Annamia; AT. Alexander terrane; ATA. Armorican terrane Assemblage; K. Kazakhstania; MO. Mongol-Okhotsk Ocean; NC. North China; OuO. Ouachita orogen; SC. South China; SP. South Patagonia; T. Tarim; UrO. Uralian orogen; VaO. Variscan orogen; YTQ. Yukon-Tanana and Quesnellia terranes. Plate boundaries: red – subduction; white – ridges; yellow – transform.<ref name="Domeier-2014" /><ref name=":3">{{Cite journal |last1=Cao |first1=Wenchao |last2=Zahirovic |first2=Sabin |last3=Flament |first3=Nicolas |last4=Williams |first4=Simon |last5=Golonka |first5=Jan |last6=Müller |first6=R. Dietmar |date=2017-12-04 |title=Improving global paleogeography since the late Paleozoic using paleobiology |url=https://bg.copernicus.org/articles/14/5425/2017/bg-14-5425-2017.html |journal=Biogeosciences |language=English |volume=14 |issue=23 |pages=5425–5439 |doi=10.5194/bg-14-5425-2017 |doi-access=free |bibcode=2017BGeo...14.5425C |issn=1726-4170}}</ref>|alt=Palaeogeographic map showing Gondwana in the southern hemisphere with ice sheets across its polar regions. Laurussia is across the equator. Siberia, Kazakhstania, North China and South China lay to the northeast separated from Gondwana and Laurussia by the Palaeotethys Ocean. Much of the northern hemisphere is covered by the Panthalassic Ocean.]]
[[File:Late Carboniferous.png|thumb|Approximate positions of the continents in the late Carboniferous (c. 302 Ma). AM. Amuria; AN. Annamia; AT. Alexander terrane; K. Kazakhstania; MO. Mongol-Okhotsk Ocean; NC. North China; PA. Paleoasian Ocean; SC. South China; SA. Slide Mountain-Angayucham Ocean; T. Tarim; YTQ. Yukon-Tanana and Quesnellia terranes. Plate boundaries: red – subduction; white – ridges; yellow – transform.<ref name="Domeier-2014" /><ref name=":3" />|alt=Palaeogeographic map showing Gondwana, Laurussia and Siberia now joined to form the supercontinent of Pangea. North China and South China lay to the northeast separated from Pangea by the Palaeotethys Ocean. Much of the northern hemisphere is covered by the Panthalassic Ocean.]]

=== Variscan-Alleghanian-Ouachita orogeny ===
The Central Pangean Mountains were formed during the [[Variscan orogeny|Variscan]]-[[Alleghanian orogeny|Alleghanian]]-[[Ouachita orogeny|Ouachita]] orogeny. Today their remains stretch over 10,000&nbsp;km from the [[Gulf of Mexico]] in the west to [[Turkey]] in the east.<ref name="Nance-2010">{{Cite journal |last1=Nance |first1=R. Damian |last2=Gutiérrez-Alonso |first2=Gabriel |last3=Keppie |first3=J. Duncan |last4=Linnemann |first4=Ulf |last5=Murphy |first5=J. Brendan |last6=Quesada |first6=Cecilio |last7=Strachan |first7=Rob A. |last8=Woodcock |first8=Nigel H. |date=March 2010 |title=Evolution of the Rheic Ocean |url=https://linkinghub.elsevier.com/retrieve/pii/S1342937X09001543 |journal=Gondwana Research |language=en |volume=17 |issue=2–3 |pages=194–222 |bibcode=2010GondR..17..194N |doi=10.1016/j.gr.2009.08.001}}</ref> The orogeny was caused by a series of continental collisions between Laurussia, Gondwana and the [[Armorican terrane|Armorican terrane assemblage]] (much of modern-day Central and Western Europe including [[Iberian Peninsula|Iberia]]) as the [[Rheic Ocean]] closed and Pangea formed. This mountain building process began in the Middle Devonian and continued into the early Permian.<ref name="Domeier-2014">{{Cite journal |last1=Domeier |first1=Mathew |last2=Torsvik |first2=Trond H. |date=2014-05-01 |title=Plate tectonics in the late Paleozoic |journal=Geoscience Frontiers |volume=5 |issue=3 |pages=303–350 |bibcode=2014GeoFr...5..303D |doi=10.1016/j.gsf.2014.01.002 |issn=1674-9871 |doi-access=free}}</ref>

The Armorican [[terrane]]s [[rift]]ed away from Gondwana during the Late [[Ordovician]]. As they drifted northwards the Rheic Ocean closed in front of them, and they began to collide with southeastern Laurussia in the Middle Devonian.<ref name="Domeier-2014" /> The resulting Variscan orogeny involved a complex series of oblique collisions with associated [[metamorphism]], [[Igneous rock|igneous]] activity, and large-scale [[Deformation (geology)|deformation]] between these terranes and Laurussia, which continued into the Carboniferous.<ref name="Domeier-2014" />

During the mid Carboniferous, the South American sector of Gondwana collided obliquely with Laurussia's southern margin resulting in the Ouachita orogeny.<ref name="Domeier-2014" /> The major [[Fault (geology)|strike-slip faulting]] that occurred between Laurussia and Gondwana extended eastwards into the [[Appalachian Mountains]] where early deformation in the Alleghanian orogeny was predominantly strike-slip. As the West African sector of Gondwana collided with Laurussia during the Late Pennsylvanian, deformation along the Alleghanian orogen became northwesterly-directed [[Compression (geology)|compression]].<ref name="Torsvik-2017" /><ref name="Nance-2010" />

=== Uralian orogeny ===
The [[Uralian orogeny]] is a north–south trending [[fold and thrust belt]] that forms the western edge of the [[Central Asian Orogenic Belt]].<ref name="Puchkov-2009">{{Cite journal |last=Puchkov |first=Victor N. |date=January 2009 |title=The evolution of the Uralian orogen |url=https://www.lyellcollection.org/doi/10.1144/SP327.9 |journal=Geological Society, London, Special Publications |language=en |volume=327 |issue=1 |pages=161–195 |doi=10.1144/SP327.9 |bibcode=2009GSLSP.327..161P |s2cid=129439058 |issn=0305-8719}}</ref> The Uralian orogeny began in the Late Devonian and continued, with some hiatuses, into the [[Jurassic]]. From the Late Devonian to early Carboniferous, the [[Magnitogorsk]] [[island arc]], which lay between Kazakhstania and Laurussia in the [[Ural Ocean]], collided with the [[passive margin]] of northeastern Laurussia ([[Baltica|Baltica craton]]). The [[Suture (geology)|suture zone]] between the former island arc complex and the continental margin formed the [[Main Uralian Fault]], a major structure that runs for more than 2,000&nbsp;km along the orogen. [[Accretion (geology)|Accretion]] of the island arc was complete by the Tournaisian, but subduction of the Ural Ocean between Kazakhstania and Laurussia continued until the Bashkirian when the ocean finally closed and continental collision began.<ref name="Puchkov-2009" /> Significant strike-slip movement along this zone indicates the collision was oblique. Deformation continued into the Permian and during the late Carboniferous and Permian the region was extensively intruded by [[granite]]s.<ref name="Domeier-2014" /><ref name="Puchkov-2009" />

=== Laurussia ===
The Laurussian continent was formed by the collision between [[Laurentia]], [[Baltica]] and [[Avalonia]] during the Devonian. At the beginning of the Carboniferous, some models show it at the equator, while others place it further south. In either case, the continent drifted northwards, reaching low latitudes in the northern hemisphere by the end of the Period.<ref name="Torsvik-2017" /><ref name=":3" /> The Central Pangean Mountain drew in moist air from the Paleo-Tethys Ocean resulting in heavy precipitation and a tropical wetland environment. Extensive coal deposits developed within the cyclothem sequences that dominated the Pennsylvanian [[sedimentary basin]]s associated with the growing orogenic belt.<ref name="Stanley-2015" /><ref name="PangaeaB">{{cite journal |last1=Kent |first1=D.V. |last2=Muttoni |first2=G. |date=1 September 2020 |title=Pangea B and the Late Paleozoic Ice Age |url=https://www.sciencedirect.com/science/article/abs/pii/S003101822030198X |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=553 |page=109753 |bibcode=2020PPP...55309753K |doi=10.1016/j.palaeo.2020.109753 |s2cid=218953074 |access-date=17 September 2022|hdl=2434/742688 |hdl-access=free }}</ref>

Subduction of the [[Panthalassa|Panthalassic]] oceanic plate along its western margin resulted in the [[Antler orogeny]] in the Late Devonian to Early Mississippian. Further north along the margin, [[Oceanic trench|slab roll-back]], beginning in the Early Mississippian, led to the rifting of the [[Yukon–Tanana terrane]] and the opening of the [[Slide Mountain Ocean]]. Along the northern margin of Laurussia, [[orogenic collapse]] of the Late Devonian to Early Mississippian [[Innuitian orogeny]] led to the development of the [[Sverdrup Basin Magmatic Province|Sverdrup Basin]].<ref name="Domeier-2014" />

=== Gondwana ===
Much of Gondwana lay in the southern polar region during the Carboniferous. As the plate moved, the South Pole drifted from southern Africa in the early Carboniferous to eastern Antarctica by the end of the period.<ref name="Torsvik-2017" /> [[Till|Glacial deposits]] are widespread across Gondwana and indicate multiple ice centres and long-distance movement of ice.<ref name="Montañez-2022">{{Cite journal |last=Montañez |first=Isabel Patricia |date=July 2022 |title=Current synthesis of the penultimate icehouse and its imprint on the Upper Devonian through Permian stratigraphic record |journal=Geological Society, London, Special Publications |language=en |volume=512 |issue=1 |pages=213–245 |doi=10.1144/SP512-2021-124 |bibcode=2022GSLSP.512..213M |issn=0305-8719|doi-access=free }}</ref> The northern to northeastern margin of Gondwana (northeast Africa, Arabia, India and northeastern West Australia) was a passive margin along the southern edge of the Paleo-Tethys with cyclothem deposition including, during more temperate intervals, coal swamps in Western Australia.<ref name="Torsvik-2017" /> The Mexican terranes along the northwestern Gondwana margin, were affected by the subduction of the Rheic Ocean.<ref name="Domeier-2014" /> However, they lay to west of the Ouachita orogeny and were not impacted by continental collision but became part of the active margin of the Pacific.<ref name="Nance-2010" /> The Moroccan margin was affected by periods of widespread dextral strike-slip deformation, magmatism and metamorphism associated with the Variscan orogeny.<ref name="Torsvik-2017" />

Towards the end of the Carboniferous, extension and rifting across the northern margin of Gondwana led to the breaking away of the [[Cimmerian terrane]] during the early Permian and the opening of the [[Tethys Ocean|Neo-Tethys Ocean]].<ref name="Domeier-2014" /> Along the southeastern and southern margin of Gondwana (eastern Australia and Antarctica), northward subduction of Panthalassa continued. Changes in the relative motion of the plates resulted in the early Carboniferous [[Kanimblan Orogeny]]. [[Continental arc]] magmatism continued into the late Carboniferous and extended round to connect with the developing [[Andean orogeny|proto-Andean]] subduction zone along the western South American margin of Gondwana.<ref name="Torsvik-2017" />

=== Siberia and Amuria ===
Shallow seas covered much of the Siberian craton in the early Carboniferous. These retreated as sea levels fell in the Pennsylvanian and as the continent drifted north into more temperate zones extensive coal deposits formed in the [[Kuznetsk Basin]].<ref name="PangaeaB" /> The northwest to eastern margins of Siberia were passive margins along the Mongol-Okhotsk Ocean on the far side of which lay Amuria. From the mid Carboniferous, subduction zones with associated magmatic arcs developed along both margins of the ocean.<ref name="Domeier-2014" />

The southwestern margin of Siberia was the site of a long lasting and complex accretionary orogen. The Devonian to early Carboniferous Siberian and South Chinese [[Altai Mountains|Altai]] [[Accretionary wedge|accretionary complexes]] developed above an east-dipping subduction zone, whilst further south, the Zharma-Saur arc formed along the northeastern margin of Kazakhstania.<ref>{{Cite journal |last1=Xu |first1=Yan |last2=Han |first2=Bao-Fu |last3=Liao |first3=Wen |last4=Li |first4=Ang |date=March 2022 |title=The Serpukhovian–Bashkirian Amalgamation of Laurussia and the Siberian Continent and Implications for Assembly of Pangea |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022TC007218 |journal=Tectonics |language=en |volume=41 |issue=3 |doi=10.1029/2022TC007218 |bibcode=2022Tecto..4107218X |s2cid=247459291 |issn=0278-7407}}</ref> By the late Carboniferous, all these complexes had accreted to the Siberian craton as shown by the intrusion of post-orogenic granites across the region. As Kazakhstania had already accreted to Laurussia, Siberia was effectively part of Pangea by 310 Ma, although major strike-slip movements continued between it and Laurussia into the Permian.<ref name="Domeier-2014" />

=== Central and East Asia ===
The Kazakhstanian microcontinent is composed of a series of Devonian and older accretionary complexes. It was strongly deformed during the Carboniferous as its western margin collided with Laurussia during the Uralian orogen and its northeastern margin collided with Siberia. Continuing strike-slip motion between Laurussia and Siberia led the formerly elongate microcontinent to bend into an [[orocline]].<ref name="Domeier-2014" />

During the Carboniferous, the Tarim craton lay along the northwestern edge of North China. Subduction along the Kazakhstanian margin of the Turkestan Ocean resulted in collision between northern Tarim and Kazakhstania during the mid Carboniferous as the ocean closed. The [[Tian Shan|South Tian Shan fold and thrust belt]], which extends over 2,000&nbsp;km from [[Uzbekistan]] to northwest China, is the remains of this accretionary complex and forms the suture between Kazakhstania and Tarim.<ref name="Domeier-2014" /><ref>{{Cite journal |last1=Alexeiev |first1=Dmitriy V. |last2=Cook |first2=Harry E. |last3=Djenchuraeva |first3=Alexandra V. |last4=Mikolaichuk |first4=Alexander V. |date=January 2017 |title=The stratigraphic, sedimentological and structural evolution of the southern margin of the Kazakhstan continent in the Tien Shan Range during the Devonian to Permian |url=https://www.lyellcollection.org/doi/10.1144/SP427.3 |journal=Geological Society, London, Special Publications |language=en |volume=427 |issue=1 |pages=231–269 |doi=10.1144/SP427.3 |bibcode=2017GSLSP.427..231A |s2cid=127707145 |issn=0305-8719}}</ref> A continental magmatic arc above a south-dipping subduction zone lay along the northern North China margin, consuming the Paleoasian Ocean.<ref name="Torsvik-2017" /> Northward subduction of the Paleo-Tethys beneath the southern margins of North China and Tarim continued during the Carboniferous, with the [[Qinling orogenic belt|South Qinling block]] accreted to North China during the mid to late Carboniferous.<ref name="Domeier-2014" /> No sediments are preserved from the early Carboniferous in North China. However, [[bauxite]] deposits immediately above the regional mid Carboniferous unconformity indicate warm tropical conditions and are overlain by cyclothems including extensive coals.<ref name="Torsvik-2017" />

South China and Annamia (Southeast Asia) rifted from Gondwana during the Devonian.<ref name="Domeier-2014" /> During the Carboniferous, they were separated from each other and North China by the Paleoasian Ocean with the Paleo-Tethys to the southwest and Panthalassa to the northeast. Cyclothem sediments with coal and [[evaporite]]s were deposited across the passive margins that surrounded both continents.<ref name="Torsvik-2017" />

==Climate==
[[File:Diorama of a Pennsylanian forest floor - Edaphosaurus (30660307277).jpg|alt=Picture of a large reptile with a sail along its back in a swampy forest setting.|thumb|A reconstruction of life on a forest floor during the Pennsylvanian Period. The animal is ''Edaphosaurus'', a synapsid. Plants are the seed ferns ''Neuropteris'' and ''Pectopteris'', the club mosses ''Lepidodendron'' and ''Sigillaria'', other plants include ''Cordaites'', ''Calamites'', climbing ferns, pond algae, and ''Sphenophyllum''.]]
The Carboniferous climate was dominated by the Late Paleozoic Ice Age (LPIA), the most extensive and longest icehouse period of the Phanerozoic, which lasted from the Late Devonian to the Permian (365 Ma-253 Ma).<ref name="Scotese-2021">{{Cite journal |last1=Scotese |first1=Christopher R. |last2=Song |first2=Haijun |last3=Mills |first3=Benjamin J. W. |last4=van der Meer |first4=Douwe G. |date=2021-04-01 |title=Phanerozoic paleotemperatures: The earth's changing climate during the last 540 million years |url=https://www.sciencedirect.com/science/article/pii/S0012825221000027 |journal=Earth-Science Reviews |volume=215 |pages=103503 |doi=10.1016/j.earscirev.2021.103503 |bibcode=2021ESRv..21503503S |issn=0012-8252}}</ref><ref name="Montañez-2022" /> Temperatures began to drop during the late Devonian with a short-lived glaciation in the late Famennian through Devonian–Carboniferous boundary,<ref name="Montañez-2022" /> before the Early Tournaisian Warm Interval.<ref name="Scotese-2021" /> Following this, a reduction in atmospheric CO<sub>2</sub> levels, caused by the increased burial of organic matter and widespread ocean anoxia led to climate cooling and glaciation across the south polar region.<ref name="Chen-2022" /> During the Visean Warm Interval glaciers nearly vanished retreating to the proto-Andes in Bolivia and western Argentina and the Pan-African mountain ranges in southeastern Brazil and southwest Africa.<ref name="Scotese-2021" />

The main phase of the LPIA (c. 335–290 Ma) began in the late Visean, as the climate cooled and atmospheric CO<sub>2</sub> levels dropped. Its onset was accompanied by a global fall in sea level and widespread multimillion-year unconformities.<ref name="Montañez-2022" /> This main phase consisted of a series of discrete several million-year-long glacial periods during which ice expanded out from up to 30 ice centres that stretched across mid- to high latitudes of Gondwana in eastern Australia, northwestern Argentina, southern Brazil, and central and Southern Africa.<ref name="Montañez-2022" />

Isotope records indicate this drop in CO<sub>2</sub> levels was triggered by tectonic factors with increased weathering of the growing Central Pangean Mountains and the influence of the mountains on precipitation and surface water flow.<ref name="Chen-2022" /> Closure of the oceanic gateway between the Rheic and Tethys oceans in the early Bashkirian also contributed to climate cooling by changing ocean circulation and heat flow patterns.<ref name="Qie-2019">{{Cite journal |last1=Qie |first1=Wenkun |last2=Algeo |first2=Thomas J. |last3=Luo |first3=Genming |last4=Herrmann |first4=Achim |date=2019-10-01 |title=Global events of the Late Paleozoic (Early Devonian to Middle Permian): A review |url=https://www.sciencedirect.com/science/article/pii/S003101821930625X |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |series=Global events of the Late Devonian to Early Permian |volume=531 |pages=109259 |doi=10.1016/j.palaeo.2019.109259 |bibcode=2019PPP...53109259Q |issn=0031-0182}}</ref>

Warmer periods with reduced ice volume within the Bashkirian, the late Moscovian and the latest Kasimovian to mid-Gzhelian are inferred from the disappearance of glacial sediments, the appearance of deglaciation deposits and rises in sea levels.<ref name="Montañez-2022" />

In the early Kasimovian there was short-lived (<1 million years) intense period of glaciation, with atmospheric CO<sub>2</sub> concentration levels dropping as low as 180 ppm.<ref name="Richey-2020">{{Cite journal |last1=Richey |first1=Jon D. |last2=Montañez |first2=Isabel P. |last3=Goddéris |first3=Yves |last4=Looy |first4=Cindy V. |last5=Griffis |first5=Neil P. |last6=DiMichele |first6=William A. |date=2020-09-22 |title=Influence of temporally varying weatherability on CO2-climate coupling and ecosystem change in the late Paleozoic |url=https://cp.copernicus.org/articles/16/1759/2020/ |journal=Climate of the Past |language=English |volume=16 |issue=5 |pages=1759–1775 |doi=10.5194/cp-16-1759-2020 |doi-access=free |issn=1814-9324}}</ref> This ended suddenly as a rapid increase in CO<sub>2</sub> concentrations to c. 600 ppm resulted in a warmer climate. This rapid rise in CO<sub>2</sub> may have been due to a peak in pyroclastic volcanism and/or a reduction in burial of terrestrial organic matter.<ref name="Richey-2020" />

The LPIA peaked across the Carboniferous-Permian boundary. Widespread glacial deposits are found across South America, western and central Africa, Antarctica, Australia, Tasmania, the Arabian Peninsula, India, and the Cimmerian blocks, indicating trans-continental ice sheets across southern Gondwana that reached to sea-level.<ref name="Montañez-2022" /> In response to the uplift and erosion of the more mafic basement rocks of the Central Pangea Mountains at this time, CO<sub>2</sub> levels dropped as low as 175 ppm and remained under 400 ppm for 10 Ma.<ref name="Richey-2020" />

=== Temperatures ===
Temperatures across the Carboniferous reflect the phases of the LPIA. At the extremes, during the Permo-Carboniferous Glacial Maximum (299–293 Ma) the global average temperature (GAT) was c. 13&nbsp;°C (55&nbsp;°F), the average temperature in the tropics c. 24&nbsp;°C (75&nbsp;°F) and in polar regions c. -23&nbsp;°C (-10&nbsp;°F), whilst during the Early Tournaisian Warm Interval (358–353 Ma) the GAT was c. 22&nbsp;°C (72&nbsp;°F), the tropics c. 30&nbsp;°C (86&nbsp;°F) and polar regions c. 1.5&nbsp;°C (35&nbsp;°F). Overall, for the Ice Age the GAT was c. 17&nbsp;°C (62&nbsp;°F), with tropical temperatures c. 26&nbsp;°C and polar temperatures c. -9.0&nbsp;°C (16&nbsp;°F).<ref name="Scotese-2021" />

=== Atmospheric oxygen levels ===
There are a variety of methods for reconstructing past atmospheric oxygen levels, including the [[charcoal]] record, [[halite]] gas inclusions, burial rates of organic carbon and [[pyrite]], carbon isotopes of organic material, isotope mass balance and forward modelling.<ref name="Mills-2023">{{Cite journal |last1=Mills |first1=Benjamin J.W. |last2=Krause |first2=Alexander J. |last3=Jarvis |first3=Ian |last4=Cramer |first4=Bradley D. |date=2023-05-31 |title=Evolution of Atmospheric O 2 Through the Phanerozoic, Revisited |url=https://www.annualreviews.org/doi/10.1146/annurev-earth-032320-095425 |journal=Annual Review of Earth and Planetary Sciences |language=en |volume=51 |issue=1 |pages=253–276 |doi=10.1146/annurev-earth-032320-095425 |issn=0084-6597}}</ref> Depending on the preservation of source material, some techniques represent moments in time (e.g. halite gas inclusions),<ref name=":0">{{Cite journal |last1=Brand |first1=Uwe |last2=Davis |first2=Alyssa M. |last3=Shaver |first3=Kristen K. |last4=Blamey |first4=Nigel J. F. |last5=Heizler |first5=Matt |last6=Lécuyer |first6=Christophe |date=2021-05-01 |title=Atmospheric oxygen of the Paleozoic |url=https://www.sciencedirect.com/science/article/pii/S0012825221000593 |journal=Earth-Science Reviews |volume=216 |pages=103560 |bibcode=2021ESRv..21603560B |doi=10.1016/j.earscirev.2021.103560 |issn=0012-8252}}</ref> whilst others have a wider time range (e.g. the charcoal record and pyrite).<ref name=":1">{{Cite journal |last=Scott |first=Andrew C. |date=2022-01-01 |title=Charcoalified vegetation from the Pennsylvanian of Yorkshire, England: Implications for the interpretation of Carboniferous wildfires |url=https://www.sciencedirect.com/science/article/pii/S0034666721001640 |journal=Review of Palaeobotany and Palynology |volume=296 |pages=104540 |bibcode=2022RPaPa.29604540S |doi=10.1016/j.revpalbo.2021.104540 |issn=0034-6667}}</ref><ref name=":2">{{Cite journal |last1=Cannell |first1=Alan |last2=Blamey |first2=Nigel |last3=Brand |first3=Uwe |last4=Escapa |first4=Ignacio |last5=Large |first5=Ross |date=2022-08-01 |title=A revised sedimentary pyrite proxy for atmospheric oxygen in the Paleozoic: Evaluation for the Silurian-Devonian-Carboniferous period and the relationship of the results to the observed biosphere record |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825222001465 |journal=Earth-Science Reviews |volume=231 |pages=104062 |doi=10.1016/j.earscirev.2022.104062 |bibcode=2022ESRv..23104062C |issn=0012-8252}}</ref> Results from these different methods for the Carboniferous vary.<ref name="Mills-2023" /> For example: the increasing occurrence of charcoal produced by wildfires from the Late Devonian into the Carboniferous indicates increasing oxygen levels, with calculations showing oxygen levels above 21% for most of the Carboniferous;<ref name=":1" /> halite gas inclusions from sediments dated 337–335 Ma give estimates for the Visean of c. 15.3%, although with large uncertainties;<ref name=":0" /><ref name="Mills-2023" /> and, pyrite records suggest levels of c. 15% early in the Carboniferous, to over 25% during the Pennsylvanian, before dropping back below 20% towards the end.<ref name=":2" /> However, whilst exact numbers vary, all models show an overall increase in atmospheric oxygen levels from a low of between 15 and 20% at the beginning of the Carboniferous to highs of 25–30% during the Period. This was not a steady rise, but included peaks and troughs reflecting the dynamic climate conditions of the time.<ref name="Mills-2023" /><ref name=":2" /> How the atmospheric oxygen concentrations influenced the large body size of arthropods and other fauna and flora during the Carboniferous is also a subject of ongoing debate.<ref>{{Cite journal |last1=Schachat |first1=Sandra R. |last2=Labandeira |first2=Conrad C. |last3=Saltzman |first3=Matthew R. |last4=Cramer |first4=Bradley D. |last5=Payne |first5=Jonathan L. |last6=Boyce |first6=C. Kevin |date=2018-01-31 |title=Phanerozoic p O 2 and the early evolution of terrestrial animals |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=285 |issue=1871 |pages=20172631 |doi=10.1098/rspb.2017.2631 |issn=0962-8452 |pmc=5805952 |pmid=29367401}}</ref>

=== Effects of climate on sedimentation ===
The changing climate was reflected in regional-scale changes in sedimentation patterns. In the relatively warm waters of the Early to Middle Mississippian, carbonate production occurred to depth across the gently dipping continental slopes of Laurussia and North and South China ([[Carbonate platform|carbonate ramp]] architecture)<ref name="Montañez-2022" /> and evaporites formed around the coastal regions of Laurussia, Kazakhstania, and northern Gondwana.<ref name="Stanley-2015" />

From the late Visean, the cooling climate restricted carbonate production to depths of less than c. 10 m forming [[Carbonate platform|carbonate shelves]] with flat-tops and steep sides. By the Moscovian, the waxing and waning of the ice sheets led to cyclothem deposition with mixed carbonate-siliciclastic sequences deposited on continental platforms and shelves.<ref name="Montañez-2022" /><ref name="Scotese-2021" />

Seasonal melting of glaciers resulted in near freezing waters around the margins of Gondwana. This is evidenced by the occurrence of glendonite (a pseudomorph of [[ikaite]]; a form of calcite deposited in glacial waters) in fine-grained, shallow marine sediments.<ref name="Scotese-2021" />

The glacial grinding and erosion of siliciclastic rocks across Gondwana and the Central Pangaean Mountains produced vast amounts of silt-sized sediment. Redistributed by the wind, this formed widespread deposits of loess across equatorial Pangea.<ref>{{Cite journal |last1=Soreghan |first1=Gerilyn S. |last2=Heavens |first2=Nicholas G. |last3=Pfeifer |first3=Lily S. |last4=Soreghan |first4=Michael J. |date=2023-01-09 |title=Dust and loess as archives and agents of climate and climate change in the late Paleozoic Earth system |url=http://dx.doi.org/10.1144/sp535-2022-208 |journal=Geological Society, London, Special Publications |volume=535 |issue=1 |pages=195–223 |doi=10.1144/sp535-2022-208 |bibcode=2023GSLSP.535..208S |issn=0305-8719}}</ref>

=== Effects of climate on biodiversity ===
The main phase of the LPIA was considered a crisis for marine biodiversity with the loss of many genera, followed by low biodiversity. However, recent studies of marine life suggest the rapid climate and environmental changes that accompanied the onset of the main glacial phase resulted in an adaptive radiation with a rapid increase in the number of species.<ref name="Montañez-2022" />

The oscillating climate conditions also led to repeated restructuring of Laurasian tropical forests between wetlands and seasonally dry ecosystems,<ref name="Qie-2019" /> and the appearance and diversification of tetrapods species.<ref name="Lucas-2023">{{Cite journal |last1=Lucas |first1=Spencer G. |last2=DiMichele |first2=William A. |last3=Opluštil |first3=Stanislav |last4=Wang |first4=Xiangdong |date=2023-06-14 |title=An introduction to ice ages, climate dynamics and biotic events: the Late Pennsylvanian world |url=https://www.lyellcollection.org/doi/10.1144/SP535-2022-334 |journal=Geological Society, London, Special Publications |language=en |volume=535 |issue=1 |pages=1–15 |doi=10.1144/SP535-2022-334 |bibcode=2023GSLSP.535..334L |issn=0305-8719}}</ref> There was a major restructuring of wetland forests during the Kasimovian glacial interval, with the loss of arborescent (tree-like) lycopisids and other wetland groups, and a general decline in biodiversity. These events are attributed to the drop in CO<sub>2</sub> levels below 400 ppm.<ref name="Montañez-2022" /><ref name="Qie-2019" /><ref name="Richey-2020" /> Although referred to as the Carboniferous rainforest collapse, this was a complex replacement of one type of rainforest by another, not a complete disappearance of rainforest vegetation.<ref name="Lucas-2023" />

Across the Carboniferous–Permian boundary interval, a rapid drop in CO<sub>2</sub> levels and increasingly arid conditions at low-latitudes led to a permanent shift to seasonally dry woodland vegetation.<ref name="Qie-2019" /><ref name="Richey-2020" /> Tetrapods acquired new terrestrial adaptations and there was a radiation of dryland-adapted [[amniote]]s.<ref name="Montañez-2022" />

== Geochemistry ==
As the continents assembled to form Pangea, the growth of the Central Pangean Mountains led to increased [[weathering]] and carbonate sedimentation on the ocean floor,<ref name="Turchyn-2019">{{Cite journal |last1=Turchyn |first1=Alexandra V. |last2=DePaolo |first2=Donald J. |date=2019-05-30 |title=Seawater Chemistry Through Phanerozoic Time |journal=Annual Review of Earth and Planetary Sciences |language=en |volume=47 |issue=1 |pages=197–224 |doi=10.1146/annurev-earth-082517-010305 |bibcode=2019AREPS..47..197T |issn=0084-6597|doi-access=free }}</ref> whilst the distribution of continents across the paleo-tropics meant vast areas of land were available for the spread of tropical rainforests.<ref name="Stanley-2015" /> Together these two factors significantly increased [[Carbon dioxide|CO<sub>2</sub>]] [[Drawdown (climate)|drawdown]] from the atmosphere, lowering global temperatures, [[Ocean|increasing ocean pH]] and triggering the Late Paleozoic Ice Age.<ref name="Turchyn-2019" /> The growth of the supercontinent also changed [[seafloor spreading]] rates and led to a decrease in the length and volume of [[mid-ocean ridge]] systems.<ref name="Stanley-2015" />

=== Magnesium/calcium isotope ratios in seawater ===
During the early Carboniferous, the Mg<sup>2+</sup>/Ca<sup>2+</sup> ratio in seawater began to rise and by the Middle Mississippian [[aragonite sea]]s had replaced [[calcite sea]]s.<ref name="Stanley-2015" /> The concentration of calcium in seawater is largely controlled by ocean pH, and as this increased the calcium concentration was reduced. At the same time, the increase in weathering, increased the amount of magnesium entering the marine environment. As magnesium is removed from seawater and calcium added along mid-ocean ridges where seawater reacts with the newly formed lithosphere, the reduction in length of mid-ocean ridge systems increased the Mg<sup>2+</sup>/Ca<sup>2+</sup> ratio further.<ref name="Stanley-2015" /> The Mg<sup>2+</sup>/Ca<sup>2+</sup> ratio of the seas also affects the ability of organisms to [[Biomineralization|biomineralize]]. The Carboniferous aragonite seas favoured those that secreted [[aragonite]] and the dominant reef builders of the time were aragonitic sponges and corals.<ref name="Stanley-2015" />

=== Strontium isotopic composition of seawater ===
The [[strontium]] isotopic composition (<sup>87</sup>Sr/<sup>86</sup>Sr) of seawater represents a mix of strontium derived from continental weathering which is rich in <sup>87</sup>Sr and from mantle sources e.g. mid-ocean ridges, which are relatively depleted in <sup>87</sup>Sr. <sup>87</sup>Sr/<sup>86</sup>Sr ratios above 0.7075 indicate continental weathering is the main source of <sup>87</sup>Sr, whilst ratios below indicate mantle-derived sources are the principal contributor.<ref name="Woodcock-2012" />

<sup>87</sup>Sr/<sup>86</sup>Sr values varied through the Carboniferous, although they remained above 0.775, indicating continental weathering dominated as the source of <sup>87</sup>Sr throughout. The <sup>87</sup>Sr/<sup>86</sup>Sr during the Tournaisian was c. 0.70840, it decreased through the Visean to 0.70771 before increasing during the Serpukhovian to the lowermost Gzhelian where it plateaued at 0.70827, before decreasing again to 0.70814 at the Carboniferous-Permian boundary.<ref name="Chen-2022">{{Cite journal |last1=Chen |first1=Jitao |last2=Chen |first2=Bo |last3=Montañez |first3=Isabel P. |date=2022 |title=Carboniferous isotope stratigraphy |url=https://www.lyellcollection.org/doi/10.1144/SP512-2020-72 |journal=Geological Society, London, Special Publications |language=en |volume=512 |issue=1 |pages=197–211 |doi=10.1144/SP512-2020-72 |bibcode=2022GSLSP.512..197C |s2cid=229459593 |issn=0305-8719}}</ref> These variations reflect the changing influence of weathering and sediment supply to the oceans of the growing Central Pangean Mountains. By the Serpukhovian [[Basement (geology)|basement]] rocks, such as [[granite]], had been uplifted and exposed to weathering. The decline towards the end of the Carboniferous is interpreted as a decrease in continental weathering due to the more arid conditions.<ref name="Chen-2018">{{Cite journal |last1=Chen |first1=Jitao |last2=Montañez |first2=Isabel P. |last3=Qi |first3=Yuping |last4=Shen |first4=Shuzhong |last5=Wang |first5=Xiangdong |date=2018-05-01 |title=Strontium and carbon isotopic evidence for decoupling of pCO2 from continental weathering at the apex of the late Paleozoic glaciation |journal=Geology |language=en |volume=46 |issue=5 |pages=395–398 |doi=10.1130/G40093.1 |bibcode=2018Geo....46..395C |issn=0091-7613|doi-access=free }}</ref>

=== Oxygen and carbon isotope ratios in seawater ===
Unlike Mg<sup>2+</sup>/Ca<sup>2+</sup> and <sup>87</sup>Sr/<sup>86</sup>Sr isotope ratios, which are consistent across the world's oceans at any one time, [[Δ18O|δ<sup>18</sup>O]] and [[Δ13C|δ<sup>13</sup>C]] preserved in the fossil record can be affected by regional factors.<ref name="Chen-2022" /> Carboniferous δ<sup>18</sup>O and δ<sup>13</sup>C records show regional differences between the South China open-water setting and the epicontinental seas of Laurussia. These differences are due to variations in seawater salinity and evaporation between epicontinental seas relative to the more open waters.<ref name="Chen-2022" /> However, large scale trends can still be determined. δ<sup>13</sup>C rose rapidly from c. 0 to 1‰ (parts per thousand) to c. 5 to 7‰ in the Early Mississippian and remained high for the duration of the Late Paleozoic Ice Age (c. 3–6‰) into the early Permian.<ref name="Chen-2022" /> Similarly from the Early Mississippian there was a long-term increase in δ<sup>18</sup>O values as the climate cooled.<ref name="Montañez-2022" />

Both δ<sup>13</sup>C and δ<sup>18</sup>O records show significant global isotope changes (known as excursions) during the Carboniferous.<ref name="Chen-2022" /> The mid-Tournaisian positive δ<sup>13</sup>C and δ<sup>18</sup>O excursions lasted between 6 and 10 million years and were also accompanied by c. 6‰ positive excursion in organic matter [[Δ15N|δ<sup>15</sup>N]] values,<ref name="Montañez-2022" /> a negative excursion in carbonate δ[[Uranium-238|<sup>238</sup>U]] and a positive excursion in carbonate-associated sulphate [[Δ34S|δ<sup>34</sup>S]].<ref name="Chen-2022" /> These changes in seawater geochemistry are interpreted as a decrease in atmospheric CO<sub>2</sub> due to increased [[Total organic carbon|organic matter]] burial and widespread ocean anoxia triggering climate cooling and onset of glaciation.<ref name="Chen-2022" />

The Mississippian-Pennsylvanian boundary positive δ<sup>18</sup>O excursion occurred at the same time as global sea level falls and widespread glacial deposits across southern Gondwana, indicating climate cooling and ice build-up. The rise in <sup>87</sup>Sr/<sup>86</sup>Sr just before the δ<sup>18</sup>O excursion suggests climate cooling in this case was caused by increased continental weathering of the growing Central Pangean Mountains and the influence of the orogeny on precipitation and surface water flow rather than increased burial of organic matter. δ<sup>13</sup>C values show more regional variation, and it is unclear whether there is a positive δ<sup>13</sup>C excursion or a readjustment from previous lower values.<ref name="Chen-2022" />

During the early Kasimovian there was a short (<1myr), intense glacial period, which came to a sudden end as atmospheric CO<sub>2</sub> concentrations rapidly rose.<ref name="Montañez-2022" /> There was a steady increase in arid conditions across tropical regions and a major reduction in the extent of tropical rainforests, as shown by the widespread loss of coal deposits from this time.<ref name="Chen-2018" /> The resulting reduction in productivity and burial of organic matter led to increasing atmospheric CO<sub>2</sub> levels, which were recorded by a negative δ<sup>13</sup>C excursion and an accompanying, but smaller decrease in δ<sup>18</sup>O values.<ref name="Montañez-2022" />

==Life==

===Plants===
[[File:Meyers b15 s0272b.jpg|thumb|upright|Etching depicting some of the most significant plants of the Carboniferous]]
Early Carboniferous land plants, some of which were [[permineralisation|preserved]] in [[coal ball]]s, were very similar to those of the preceding Late Devonian, but new groups also appeared at this time. The main early Carboniferous plants were the [[Equisetales]] (horse-tails), [[Sphenophyllales]] (scrambling plants), [[Lycopodiales]] (club mosses), [[Lepidodendrales]] (scale trees), [[Filicales]] (ferns), [[Medullosales]] (informally included in the "[[Pteridospermatophyta|seed ferns]]", an assemblage of a number of early [[gymnosperm]] groups) and the [[Cordaitales]]. These continued to dominate throughout the period, but during the late Carboniferous, several other groups, [[Cycadophyta]] (cycads), the [[Callistophytales]] (another group of "seed ferns"), and the [[Voltziales]], appeared.
[[File:Lycopsid joggins mcr1.JPG|thumb|left|Ancient ''in situ'' [[w:lycopsid|lycopsid]], probably ''[[w:Sigillaria|Sigillaria]]'', with attached [[w:stigmaria|stigmarian roots]], [[Joggins Formation]], Canada]]
[[File:Lycopsid mcr2.jpg|thumb|left|Base of a [[w:lycopsid|lycopsid]] showing connection with bifurcating [[w:Stigmaria|stigmarian]] roots]]
The Carboniferous lycophytes of the order Lepidodendrales, which are cousins (but not ancestors) of the tiny club-moss of today, were huge trees with trunks 30 meters high and up to 1.5 meters in diameter. These included ''[[Lepidodendron]]'' (with its cone called [[Lepidostrobus]]), ''[[Anabathra (plant)|Anabathra]]'', ''[[Lepidophloios]]'' and ''[[Sigillaria]]''.{{sfn|Howe|1911|p=311}} The roots of several of these forms are known as [[Stigmaria]]. Unlike present-day trees, their [[secondary growth]] took place in the [[Cortex (botany)|cortex]], which also provided stability, instead of the [[xylem]].{{sfn|Westfälische Wilhelms-Universität Münster|2012}} The [[Cladoxylopsida|Cladoxylopsids]] were large trees, that were ancestors of ferns, first arising in the Carboniferous.{{sfn|Hogan|2010}}

{{AmCyc Poster|Coal Plants}}

The fronds of some Carboniferous ferns are almost identical with those of living species. Probably many species were [[Epiphyte|epiphytic]]. Fossil ferns and "seed ferns" include ''[[Pecopteris]]'', ''[[Cyclopteris]]'', ''[[Neuropteris]]'', ''[[Alethopteris]]'', and ''[[Sphenopteris]]''; ''[[Megaphyton]]'' and ''[[Caulopteris]]'' were tree ferns.{{sfn|Howe|1911|p=311}}

The Equisetales included the common giant form ''[[Calamites]]'', with a trunk diameter of 30 to {{convert|60|cm|0|abbr=on}} and a height of up to {{convert|20|m|0|abbr=on}}. ''[[Sphenophyllum]]'' was a slender climbing plant with whorls of leaves, which was probably related both to the calamites and the lycopods.{{sfn|Howe|1911|p=311}}

''[[Cordaites]]'', a tall plant (6 to over 30 meters) with strap-like leaves, was related to the cycads and conifers; the [[catkin]]-like reproductive organs, which bore ovules/seeds, is called ''[[Cardiocarpus]]''. These plants were thought to live in swamps. True coniferous trees (''[[Walchia]]'', of the order Voltziales) appear later in the Carboniferous,{{sfn|Howe|1911|p=311}} and preferred higher drier ground.

===Marine invertebrates===
In the oceans the [[marine invertebrate]] groups are the [[Foraminifera]], [[Anthozoa|corals]], [[Bryozoa]], [[Ostracoda]], [[brachiopod]]s, [[Ammonoidea|ammonoids]], [[hederellid|hederelloids]], [[microconchids]] and [[echinoderm]]s (especially [[crinoid]]s).{{Citation needed|date=September 2022}} The diversity of brachiopods and fusilinid foraminiferans, surged beginning in the [[Visean]], continuing through the end of the Carboniferous, although cephalopod and nektonic conodont diversity declined. This evolutionary radiation was known as the Carboniferous-Earliest Permian Biodiversification Event.<ref>{{cite journal |last1=Shi |first1=Yukun |last2=Wang |first2=Xiangdong |last3=Fan |first3=Junxuan |last4=Huang |first4=Hao |last5=Xu |first5=Huiqing |last6=Zhao |first6=Yingying |last7=Shen |first7=Shuzhong |date=September 2021 |title=Carboniferous-earliest Permian marine biodiversification event (CPBE) during the Late Paleozoic Ice Age |url=https://www.sciencedirect.com/science/article/pii/S0012825221002002 |journal=Earth-Science Reviews |volume=220 |page=103699 |doi=10.1016/j.earscirev.2021.103699 |bibcode=2021ESRv..22003699S |access-date=24 August 2022}}</ref> For the first time foraminifera took a prominent part in the marine faunas. The large spindle-shaped genus [[Fusulinida|Fusulina]] and its relatives were abundant in what is now Russia, China, Japan, North America; other important genera include ''Valvulina'', ''Endothyra'', ''Archaediscus'', and ''Saccammina'' (the latter common in Britain and Belgium). Some Carboniferous genera are still [[Extant taxon|extant]]. The first true [[priapulid]]s appeared during this period.{{sfn|Howe|1911|p=311}}

The microscopic shells of [[radiolaria]]ns are found in [[chert]]s of this age in the [[Culm Measures|Culm]] of [[Devon]] and [[Cornwall]], and in Russia, Germany and elsewhere. [[Porifera|Sponges]] are known from [[spicule (sponge)|spicule]]s and anchor ropes,{{sfn|Howe|1911|p=311}} and include various forms such as the Calcispongea ''Cotyliscus'' and ''Girtycoelia'', the [[demosponge]] ''Chaetetes'', and the genus of unusual colonial [[Hexactinellid|glass sponges]] ''[[Titusvillia]]''. Both [[reef]]-building and solitary corals diversify and flourish; these include both [[Rugosa|rugose]] (for example, ''[[Caninia (genus)|Caninia]]'', ''Corwenia'', ''Neozaphrentis''), heterocorals, and [[Tabulata|tabulate]] (for example, ''Chladochonus'', ''Michelinia'') forms. [[Conularids]] were well represented by ''Conularia''

[[Bryozoa]] are abundant in some regions; the fenestellids including ''Fenestella'', ''Polypora'', and ''[[Archimedes (bryozoan)|Archimedes]]'', so named because it is in the shape of an [[Archimedean screw]]. [[Brachiopod]]s are also abundant;<ref>{{cite journal |last1=Pérez-Huerta |first1=Alberto |last2=Sheldon |first2=Nathan D. |date=30 January 2006 |title=Pennsylvanian sea level cycles, nutrient availability and brachiopod paleoecology |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018205004451 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=230 |issue=3–4 |pages=264–279 |doi=10.1016/j.palaeo.2005.07.020 |bibcode=2006PPP...230..264P |access-date=31 March 2023}}</ref> they include [[Productida|productids]], some of which reached very large for brachiopods size and had very thick shells (for example, the {{cvt|30|cm}}-wide ''[[Gigantoproductus]]''<ref name=Hall2004>{{cite book
| url         = https://books.google.com/books?id=65Bdfy-SOyMC&dq=largest+Gigantoproductus&pg=PA87
| title       = Environment, Development, and Evolution. Toward a Synthesis
| publisher   = MIT Press
| date        = 2004
| access-date  = 2022-08-23
| page        = 87
|first1= Brian Keith |last1=Hall|first2=Gerd B. |last2=Müller|first3=Roy Douglas |last3=Pearson
| isbn = 9780262083195
}}</ref><ref>{{cite book
| url         = https://books.google.com/books?id=bL60DwAAQBAJ&dq=largest+Gigantoproductus+giganteus&pg=PA47
| title       = Convergent Evolution on Earth. Lessons for the Search for Extraterrestrial Life
| publisher   = MIT Press
| date        = 2019
| access-date  = 2022-08-23
| page        = 47
| author      = George R. McGhee, Jr.
| isbn = 9780262354189
}}</ref>), while others like ''[[Chonetes]]'' were more conservative in form. [[Athyridida|Athyridids]], [[Spiriferida|spiriferids]], [[Rhynchonellida|rhynchonellids]], and [[Terebratulida|terebratulids]] are also very common. Inarticulate forms include ''[[Discina (brachiopod)|Discina]]'' and ''[[Crania (genus)|Crania]]''. Some species and genera had a very wide distribution with only minor variations.

[[Annelid]]s such as ''Serpulites'' are common fossils in some horizons. Among the mollusca, the [[bivalve]]s continue to increase in numbers and importance. Typical genera include ''[[Aviculopecten]]'', ''[[Posidonomya]]'', ''[[Nucula]]'', ''[[Carbonicola (bivalve)|Carbonicola]]'', ''Edmondia'', and ''Modiola''. [[Gastropod]]s are also numerous, including the genera ''Murchisonia'', ''[[Euomphalus]]'', ''Naticopsis''.{{sfn|Howe|1911|p=311}} [[Nautiloid]] [[cephalopod]]s are represented by tightly coiled [[Nautilida|nautilids]], with straight-shelled and curved-shelled forms becoming increasingly rare. [[Goniatite]] [[Ammonoidea|ammonoids]] such as [[Aenigmatoceras]] are common.

[[Trilobite]]s are rarer than in previous periods, on a steady trend towards extinction, represented only by the [[Proetida|proetid]] group. [[Ostracod]]a, a class of [[crustacean]]s, were abundant as representatives of the [[meiobenthos]]; genera included ''Amphissites'', ''Bairdia'', ''Beyrichiopsis'', ''Cavellina'', ''Coryellina'', ''Cribroconcha'', ''Hollinella'', ''Kirkbya'', ''Knoxiella'', and ''Libumella''. [[Crinoid]]s were highly numerous during the Carboniferous, though they suffered a gradual decline in diversity during the Middle Mississippian.<ref>{{cite journal |last1=Ausich |first1=William I. |last2=Kammer |first2=Thomas W. |last3=Baumiller |first3=Tomasz K. |date=8 February 2016 |title=Demise of the middle Paleozoic crinoid fauna: a single extinction event or rapid faunal turnover? |url=https://www.cambridge.org/core/journals/paleobiology/article/abs/demise-of-the-middle-paleozoic-crinoid-fauna-a-single-extinction-event-or-rapid-faunal-turnover/CCE6603D020FBCE7D793746990C5011A |journal=[[Paleobiology (journal)|Paleobiology]] |volume=20 |issue=3 |pages=345–361 |doi=10.1017/S0094837300012811 |s2cid=140542784 |access-date=21 April 2023}}</ref> Dense submarine thickets of long-stemmed crinoids appear to have flourished in shallow seas, and their remains were consolidated into thick beds of rock. Prominent genera include ''Cyathocrinus'', ''Woodocrinus'', and ''Actinocrinus''. Echinoids such as ''[[Archaeocidaris]]'' and ''Palaeechinus'' were also present. The [[blastoid]]s, which included the Pentreinitidae and Codasteridae and superficially resembled crinoids in the possession of long stalks attached to the seabed, attain their maximum development at this time.{{sfn|Howe|1911|p=311}}

<gallery mode="packed">
File:Aviculopecten subcardiformis01.JPG|''Aviculopecten subcardiformis''; a [[bivalve]] from the [[Logan Formation]] (lower Carboniferous) of [[Wooster, Ohio]] (external mold)
File:LoganFauna011312.jpg|Bivalves (''Aviculopecten'') and brachiopods (''Syringothyris'') in the Logan Formation (lower Carboniferous) in Wooster, Ohio
File:Syringothyris01.JPG|''Syringothyris'' sp.; a spiriferid [[brachiopod]] from the Logan Formation (lower Carboniferous) of Wooster, Ohio (internal mold)
File:Palaeophycus01.JPG|''Palaeophycus'' ichnosp.; a [[trace fossil]] from the Logan Formation (lower Carboniferous) of Wooster, Ohio
File:PlatyceratidMississippian.JPG|[[Crinoid]] calyx from the lower Carboniferous of Ohio with a conical [[Platyceratidae|platyceratid]] gastropod (''Palaeocapulus acutirostre'') attached
File:Conulariid03.jpg|Conulariid from the lower Carboniferous of Indiana
File:Syringoporid.jpg|Tabulate coral (a syringoporid); Boone Limestone (lower Carboniferous) near Hiwasse, Arkansas
File:Typhloesus interpretation 2022.jpg|''[[Typhloesus]]'' was a bizarre invertebrate that lived in Montana. It is possibly a mollusk related to gastropods.
File:Essexella asherae.JPG|''[[Essexella]]'' was a cnidarian that lived in Northern Illinois. It was long considered a [[scyphozoa]]n, but is now regarded as a [[Sea anemone]]
File:Concavicaris georgeorum.png|''Concavicaris'' was a long lasting genus of [[thylacocephala]]n arthropod that lived from the Devonian to the Carboniferous.
File:Triproetus bonbon cropped.jpg|''[[Triproetus]]'' was a genus of [[Proetida|proetid]] trilobite, which were the only order that survived the end-Devonian extinction 
File:Daidal.png|''[[Daidal]]'' was a basal species of Mantis shrimp ([[stomatopoda]])
File:Jeletzkya douglassae.jpg|''[[Jeletzkya]]'' was an early genus of [[Coleoidea|coleoid]] cephalopod from northern [[Illinois]] 
File:Syllipsimopodi bideni.webp|''[[Syllipsimopodi]]'' was the earliest known [[Vampyropoda|vampyropod]] cephalopod, originating from Carboniferous rocks of Montana.
</gallery>

===Freshwater and lagoonal invertebrates===
Freshwater Carboniferous invertebrates include various [[bivalve]] [[mollusc]]s that lived in brackish or fresh water, such as ''Anthraconaia'', ''[[Naiadites]]'', and ''[[Carbonicola (bivalve)|Carbonicola]]''; diverse [[crustacean]]s such as ''[[Candona]]'', ''[[Carbonita (crustacean)|Carbonita]]'', ''[[Darwinula]]'', ''[[Estheria (crustacean)|Estheria]]'', ''Acanthocaris'', ''Dithyrocaris'', and ''Anthrapalaemon''. The [[eurypterid]]s were also diverse, and are represented by such genera as ''[[Adelophthalmus]]'', ''[[Megarachne]]'' (originally misinterpreted as a giant spider, hence its name) and the specialised very large ''[[Hibbertopterus]]''. Many of these were amphibious. Frequently a temporary return of marine conditions resulted in marine or brackish water genera such as ''[[Lingula (genus)|Lingula]]'', ''Orbiculoidea'', and ''[[Productus]]'' being found in the thin beds known as marine bands.

<gallery mode="packed" heights="180">
File:20210116 Megarachne hypothetical reconstruction.png|''Megarachne'' was a large freshwater eurypterid from South America that was originally misidentified as a spider
File:Adelophthalmus irinae.png|''Adelophthalmus'' was the only genus of [[Eurypterina|eurypterine]] eurypterid that survived past the Devonian
File:Hibbertopterus scouleri.jpg|Due to its large and compact shell, ''Hibbertopterus'' was one of if not the heaviest eurypterid in the fossil record
</gallery>

=== Terrestrial invertebrates ===
Fossil remains of air-breathing [[insect]]s,{{sfn|Garwood|Sutton|2010}} [[Myriapoda|myriapod]]s, and [[arachnid]]s{{sfn| Garwood |Dunlop |Sutton |2009}} are known from the Carboniferous. Their diversity when they do appear, however, shows that these arthropods were both well-developed and numerous.<ref name=GrahamAguilarDudleyGans1995>{{cite journal |last1=Graham |first1=Jeffrey B. |last2=Aguilar |first2=Nancy M. |last3=Dudley |first3=Robert |last4=Gans |first4=Carl |date=11 May 1995 |title=Implications of the late Palaeozoic oxygen pulse for physiology and evolution |journal=Nature |volume=375 |issue=6527 |pages=117–120 |doi=10.1038/375117a0 |bibcode=1995Natur.375..117G |hdl=2027.42/62968 |hdl-access=free |s2cid=4308580 |url=https://www.nature.com/articles/375117a0?error=cookies_not_supported&code=23b4f690-2f27-4c0f-928c-5245d4b0d4f6#citeas |access-date=6 November 2022 }}</ref><ref name=CannellEtAl2022>{{cite journal |last1=Cannell |first1=Alan |last2=Blamey |first2=Nigel |last3=Brand |first3=Uwe |last4=Escapa |first4=Ignacio |last5=Large |first5=Ross |date=August 2022 |title=A revised sedimentary pyrite proxy for atmospheric oxygen in the Paleozoic: Evaluation for the Silurian-Devonian-Carboniferous period and the relationship of the results to the observed biosphere record |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825222001465 |journal=[[Earth-Science Reviews]] |volume=231 |page=104062 |doi=10.1016/j.earscirev.2022.104062 |bibcode=2022ESRv..23104062C |s2cid=249298393 |access-date=6 November 2022}}</ref>{{sfn|Verberk|Bilton|2011}} Some arthropods grew to large sizes with the up to {{convert|2.6|m|ft|sp=us|adj=mid|-long}} millipede-like ''[[Arthropleura]]'' being the largest-known land invertebrate of all time. In the mid-Mississippian the oldest known [[Pterygota|winged insects]] appears,<ref>{{cite journal | last1=Schachat | first1=Sandra R | last2=Goldstein | first2=Paul Z | last3=Desalle | first3=Rob | last4=Bobo | first4=Dean M | last5=Boyce | first5=C Kevin | last6=Payne | first6=Jonathan L | last7=Labandeira | first7=Conrad C | title=Illusion of flight? Absence, evidence and the age of winged insects | journal=Biological Journal of the Linnean Society | volume=138 | issue=2 | date=2023-02-02 | issn=0024-4066 | doi=10.1093/biolinnean/blac137 | doi-access=free | pages=143–168 | url=https://academic.oup.com/biolinnean/article-pdf/138/2/143/49055959/blac137.pdf}}</ref>
followed by the huge predatory [[Meganisoptera|Protodonata]] (griffinflies), which includes ''[[Meganeura]]'', a giant [[dragonfly]]-like insect and with a wingspan of ca. {{convert|75|cm|0|abbr=on}}—the largest flying insect ever to roam the planet. Further groups are the Syntonopterodea (relatives of present-day [[Ephemeroptera|mayflies]]), the abundant and often large sap-sucking [[Palaeodictyopteroidea]], the diverse herbivorous [[Protorthoptera]], and numerous [[Basal (phylogenetics)|basal]] [[Dictyoptera]] (ancestors of [[cockroach]]es).{{sfn|Garwood|Sutton|2010}}

Many insects have been obtained from the coalfields of [[Saarbrücken]] and [[Commentry]], and from the hollow trunks of fossil trees in Nova Scotia. Some British coalfields have yielded good specimens: ''Archaeoptilus'', from the Derbyshire coalfield, had a large wing with {{convert|4.3|cm|0|abbr=on}} preserved part, and some specimens (''[[Brodia]]'') still exhibit traces of brilliant wing colors. In the Nova Scotian tree trunks land snails (''[[Archaeozonites]]'', ''[[Dendropupa]]'') have been found.{{sfn|Howe|1911|p=312}}

<gallery mode="packed">
File:Meganeura.png|The late Carboniferous giant dragonfly-like insect ''[[Meganeura]]'' grew to wingspans over {{cvt|60|cm|ftin|0}}.
File:20210116 Pulmonoscorpius kirktonensis.png|The gigantic ''[[Pulmonoscorpius]]'' from the early Carboniferous reached a length of up to {{cvt|70|cm|ftin|0}}.
File:Arthropleura Reconstruction.jpg|''[[Arthropleura]]'' was a giant millipede that fed on the Carboniferous plants. At {{cvt|8|feet|cm}} long, it was the largest terrestrial arthropod that ever lived.
File:Homaloneura ligeia.jpg|''[[Homaloneura]]'', a [[palaeodictyoptera]]n insect which have two winglets on thorax in addition to four wings.
File:Helenodora inopinata.jpg|[[Helenodora|''Helenodora inopinata'']], a [[stem-group]] [[onychophora]]n known from [[Indiana]]
File:Blattoidae - Fossil.JPG|A [[roachoid]] insect found in Carboniferous rocks of France
File:20201202 Maiocercus celticus.png|''[[Maiocercus]]'' was a [[Trigonotarbida|trigonotarbid]] arachnid that lived in the United Kingdom around 310 million years ago.
</gallery>

===Fish===
Many fish inhabited the Carboniferous seas; predominantly [[Elasmobranch]]s (sharks and their relatives). These included some, like ''[[Psammodus]]'', with crushing pavement-like teeth adapted for grinding the shells of brachiopods, crustaceans, and other marine organisms. Other groups of elasmobranchs, like the [[ctenacanthiformes]] grew to large sizes, with some genera like ''[[Saivodus]]'' reaching around {{convert|6|–|9|m|ft|sp=us}}.<ref>{{Cite journal |last=Engelman |first=Russell K. |date=2023 |title=A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli (Placodermi: Arthrodira) |journal=Diversity |language=en |volume=15 |issue=3 |pages=318 |doi=10.3390/d15030318 |issn=1424-2818 |doi-access=free |bibcode=2023Diver..15..318E }}</ref> Other fish had piercing teeth, such as the [[Symmoriida]]; some, the [[petalodont]]s, had peculiar cycloid cutting teeth. Most of the other cartilaginous fish were marine, but others like the [[Xenacanthida]], and several genera like ''[[Bandringa]]'' invaded fresh waters of the coal swamps.<ref name="Sallan-2014">{{Cite journal |last1=Sallan |first1=Lauren Cole |last2=Coates |first2=Michael I. |date=January 2014 |title=The long-rostrumed elasmobranch Bandringa Zangerl, 1969, and taphonomy within a Carboniferous shark nursery |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.2013.782875 |journal=Journal of Vertebrate Paleontology |language=en |volume=34 |issue=1 |pages=22–33 |doi=10.1080/02724634.2013.782875 |bibcode=2014JVPal..34...22S |issn=0272-4634 |s2cid=86174861}}</ref> Among the [[Osteichthyes|bony fish]], the [[Palaeonisciformes]] found in coastal waters also appear to have migrated to rivers. [[Sarcopterygii|Sarcopterygia]]n fish were also prominent, and one group, the [[Rhizodont]]s, reached very large size.

Most species of Carboniferous marine fish have been described largely from teeth, fin spines and dermal ossicles,{{sfn|Howe|1911|p=311}} with smaller freshwater fish preserved whole. Freshwater fish were abundant, and include the genera ''[[Ctenodus]]'', ''Uronemus'', ''[[Acanthodes]]'', ''Cheirodus'', and ''[[Gyracanthus]]''. [[Chondrichthyes]] (especially [[Holocephali|holocephalans]] like the [[Stethacanthidae|Stethacanthids]]) underwent a major [[evolutionary radiation]] during the Carboniferous.{{sfn|Martin|2008}} It is believed that this evolutionary radiation occurred because the decline of the [[Placodermi|placoderms]] at the end of the Devonian caused many [[Niche (ecology)|environmental niches]] to become unoccupied and allowed new organisms to evolve and fill these niches.{{sfn|Martin|2008}} As a result of the evolutionary radiation Carboniferous holocephalans assumed a wide variety of bizarre shapes including ''[[Stethacanthus]]'' which possessed a flat brush-like dorsal fin with a patch of [[Dermal denticle|denticles]] on its top.{{sfn|Martin|2008}} ''[[Stethacanthus]]''{{'s}} unusual fin may have been used in mating rituals.{{sfn|Martin|2008}}

Other groups like the [[Eugeneodontida|eugeneodonts]] filled in the niches left by large predatory placoderms. These fish were unique as they only possessed one, at most two, rows of teeth in either their upper or lower jaws in the form of elaborate tooth whorls.<ref name="Lebedev20092">{{cite journal |last1=Lebedev |first1=O.A. |year=2009 |title=A new specimen of ''Helicoprion'' Karpinsky, 1899 from Kazakhstanian Cisurals and a new reconstruction of its tooth whorl position and function |url=https://www.researchgate.net/publication/249440368 |journal=Acta Zoologica |volume=90 |pages=171–182 |doi=10.1111/j.1463-6395.2008.00353.x |issn=0001-7272}}</ref> The first members of the [[helicoprionidae]], a family eugeneodonts that were characterized by the presence of one circular tooth whorl in the lower jaw, appeared during the early Carboniferous.<ref>{{cite journal |author1=Cicimurri, D. J. |author2=Fahrenbach, M. D. |year=2002 |title=Chondrichthyes from the upper part of the Minnelusa Formation (Middle Pennsylvanian: Desmoinesian), Meade County, South Dakota |url=http://www.sdaos.org/wp-content/uploads/pdfs/2002/81-92.pdf |journal=Proceedings of the South Dakota Academy of Science |volume=81 |pages=81–92}}</ref> Perhaps the most bizarre radiation of holocephalans at this time was that of the [[iniopterygiformes]], an order of holocephalans that greatly resembled modern day flying fish that could have also "flown" in the water with their massive, elongated pectoral fins. They were further characterized by their large eye sockets, club-like structures on their tails, and spines on the tips of their fins.

<gallery mode="packed">
File:Stethacanthus BW.jpg|''[[Akmonistion]]'' of the [[Holocephali]] order [[Symmoriida]] roamed the oceans of the early Carboniferous.
File:Falcatus.jpg|''[[Falcatus]]'' was a Carboniferous holocephalan, with a high degree of sexual dimorphism.
File:Dracopristis hoffmanorum.png|''[[Dracopristis]]'' was a [[Ctenacanthiformes|Ctenacanthiform]] [[Elasmobranchii|elasmobranch]] from the late Carboniferous of [[New Mexico]].
File:Ornithoprion hertwigi.png|''[[Ornithoprion]]'' was a small-sized [[Eugeneodontida|Eugeneodont]] holocephalan that had an elongated lower jaw.
File:Allenypterus montanus (Restoration) (cropped).jpg|''[[Allenypterus]]'' was a [[Coelacanth]] fish known from the [[Bear Gulch Limestone]] in [[Montana]].
File:†Phanerosteon phonax Carboniferous Bear Gulch.jpg|''[[Phanerosteon]]'' was a [[Osteichthyes|Bony fish]] belonging to the extinct order [[Palaeonisciformes]].
File:Edestus recon.png|''[[Edestus]]'' was a large [[Eugeneodontida|eugeneodontid]] fish that possessed two tooth whorls in its mouth
File:Rhizodus.jpg|''[[Rhizodus]]'' was a large freshwater [[Rhizodontida|Rhizodont]] [[Sarcopterygii|sarcopterygian]] from Europe and North America.
File:Squatinactis NT small.jpg|''[[Squatinactis]]'', a genus of elasmobranch fish from Montana that possessed enlarged pectoral fins similar to modern [[Angelshark|angel sharks]]
File:Bandringa SW.png|''[[Bandringa]]'' is a bizarre elasmobranch fish that lived in [[Illinois]], [[Ohio]] and [[Pennsylvania]] during the [[Moscovian (Carboniferous)|Moscovian]] stage. It superficially resembled a [[paddlefish]], with an elongated upper [[Rostrum (anatomy)|rostrum]].
File:Iniopteryx sp.png|''[[Iniopteryx]]'' was a holocephalan that lived in North America. This fish belonged to a group called the Iniopterygiformes, that possibly lived like [[flying fish]].
File:Strigilodus tollesonae-novataxa 2023-Hodnett Toomey Olson.jpg|Restoration of ''[[Strigilodus tollesonae|Strigilodus]]'', a [[Petalodontiformes|petalodont]] holocephalan from the upper Carboniferous of [[Kentucky]].
</gallery>

===Tetrapods===
Carboniferous [[amphibian]]s were diverse and common by the middle of the period, more so than they are today; some were as long as 6 meters, and those fully terrestrial as adults had scaly skin.{{sfn|Stanley|1999|pp=411–412}} They included basal tetrapod groups classified in early books under the [[Labyrinthodont]]ia. These had a long body, a head covered with bony plates, and generally weak or undeveloped limbs.{{sfn|Howe|1911|p=312}} The largest were over 2 meters long. They were accompanied by an assemblage of smaller amphibians included under the [[Lepospondyli]], often only about {{convert|15|cm|0|abbr=on}} long. Some Carboniferous amphibians were aquatic and lived in rivers (''[[Loxomma]]'', ''[[Eogyrinus]]'', ''[[Proterogyrinus]]''); others may have been semi-aquatic (''[[Ophiderpeton]]'', ''[[Amphibamus]]'', ''[[Hyloplesion]]'') or terrestrial (''[[Dendrerpeton]]'', ''[[Tuditanus]]'', ''[[Anthracosaurus]]'').

The Carboniferous rainforest collapse slowed the evolution of amphibians who could not survive as well in the cooler, drier conditions. Amniotes, however, prospered because of specific key adaptations.{{sfn|Sahney|Benton|Falcon-Lang|2010}} One of the greatest evolutionary innovations of the Carboniferous was the amniote egg, which allowed the laying of eggs in a dry environment, as well as keratinized scales and claws, allowing for the further exploitation of the land by certain [[tetrapod]]s. These included the earliest [[Sauropsida|sauropsid]] reptiles (''[[Hylonomus]]''), and the earliest known [[synapsid]] (''[[Archaeothyris]]''). Synapsids quickly became huge and diversified in the Permian, only for their dominance to stop during the Mesozoic. Sauropsids (reptiles, and also, later, birds) also diversified but remained small until the Mesozoic, during which they dominated the land, as well as the water and sky, only for their dominance to stop during the Cenozoic.

Reptiles underwent a major evolutionary radiation in response to the drier climate that preceded the rainforest collapse.{{sfn|Sahney|Benton|Falcon-Lang|2010}}{{sfn|Kazlev|1998}} By the end of the Carboniferous amniotes had already diversified into a number of groups, including several families of synapsid [[pelycosaur]]s, [[Protorothyrididae|protorothyridids]], [[captorhinidae|captorhinids]], [[sauria]]ns and [[Araeoscelidia|araeoscelid]]s.

<gallery mode="packed">
File:Pederpes2223DB.jpg|The [[amphibian]]-like ''[[Pederpes]]'', the most primitive tetrapod found in the [[Mississippian age|Mississippian]], and known from Scotland.
File:Hylonomus BW.jpg|''[[Hylonomus]]'', the earliest sauropsid [[reptile]], appeared in the [[Pennsylvanian (geology)|Pennsylvanian]], and is known from the [[Joggins Formation]] in Nova Scotia, and possibly [[New Brunswick]].
File:Petrolacosaurus BW.jpg|''[[Petrolacosaurus]]'', the earliest known [[diapsid]] reptile, lived during the late Carboniferous.
File:Archaeothyris BW.jpg|''[[Archaeothyris]]'' is the oldest known [[synapsid]], and is found in rocks from [[Nova Scotia]].
File:Coloraderpeton.jpg|''[[Coloraderpeton]]'' was a [[snake]]-like [[aïstopod]] [[Tetrapodomorpha|tetrapodomorph]] from the late Carboniferous of [[Colorado]].
File:Crassigyrinus BW.jpg|''[[Crassigyrinus]]'' was a carnivorous stem-tetrapod from the [[Viséan|early Carboniferous]] of Scotland.
File:Microbrachis pelikani.png|''[[Microbrachis]]'' was a [[Lepospondyli|lepospondyl]] amphibian known from the [[Czech Republic]].
File:Amphibamus BW.jpg|''[[Amphibamus]]'' was a [[Dissorophoidea|dissorophoid]] [[Temnospondyli|temnospondyl]] from the late Carboniferous of [[Illinois]].
</gallery>

===Fungi===
As plants and animals were growing in size and abundance in this time, land [[fungi]] diversified further. Marine fungi still occupied the oceans. All modern classes of fungi were present in the late Carboniferous.{{sfn|Blackwell|Vilgalys|James|Taylor|2008}}

==Extinction events==
===Romer's gap===
{{Main|Romer's gap}}
The first 15 million years of the Carboniferous had very limited terrestrial fossils. While it has long been debated whether the gap is a result of fossilisation or relates to an actual event, recent work indicates there was a drop in atmospheric oxygen levels, indicating some sort of [[ecological collapse]].{{sfn|Ward|Labandeira|Laurin|Berner|2006}} The gap saw the demise of the Devonian fish-like [[ichthyostegalia]]n [[labyrinthodont]]s and the rise of the more advanced [[temnospondyl]]ian and [[reptiliomorpha]]n [[amphibian]]s that so typify the Carboniferous terrestrial vertebrate fauna.

===Carboniferous rainforest collapse===
{{main|Carboniferous rainforest collapse}}
Before the end of the Carboniferous, an [[extinction event]] occurred. On land this event is referred to as the Carboniferous rainforest collapse.{{sfn|Sahney|Benton|Falcon-Lang|2010}} Vast tropical rainforests collapsed suddenly as the climate changed from hot and humid to cool and arid. This was likely caused by intense glaciation and a drop in sea levels.{{sfn|Heckel|2008}} The new climatic conditions were not favorable to the growth of rainforest and the animals within them. Rainforests shrank into isolated islands, surrounded by seasonally dry habitats. Towering [[lycopsid]] forests with a heterogeneous mixture of vegetation were replaced by much less diverse [[tree fern]] dominated flora.

Amphibians, the dominant vertebrates at the time, fared poorly through this event with large losses in biodiversity; reptiles continued to diversify through key adaptations that let them survive in the drier habitat, specifically the hard-shelled egg and scales, both of which retain water better than their amphibian counterparts.{{sfn|Sahney|Benton|Falcon-Lang|2010}}

==See also==
* [[List of Carboniferous tetrapods]]
* Important Carboniferous [[Lagerstätten]]
** [[Granton Shrimp Bed]]; 359 mya; [[Edinburgh]], Scotland
** [[East Kirkton Quarry]]; c.&nbsp;350 mya; [[Bathgate]], Scotland
** [[Bear Gulch Limestone]]; 324 mya; [[Montana]], US
** [[Mazon Creek]]; 309 mya; [[Illinois]], US
** [[Hamilton Quarry]]; 300 mya; [[Kansas]], US
* [[List of fossil sites]]

{{clear}}

==References==
{{Reflist}}

==Sources==
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* {{cite web|title=The Carboniferous Period |url=http://www.ucmp.berkeley.edu/carboniferous/carboniferous.php |url-status=live|archive-url=https://web.archive.org/web/20120210070913/http://www.ucmp.berkeley.edu/carboniferous/carboniferous.php |website=www.ucmp.berkeley.edu |archive-date=2012-02-10 |ref={{harvid|University of California, Berkeley|2012}}}}
* {{cite journal|last=Biello|first=David|title=White Rot Fungi Slowed Coal Formation|journal=Scientific American|date=28 June 2012|url=http://www.scientificamerican.com/article.cfm?id=mushroom-evolution-breaks-down-lignin-slows-coal-formation|access-date=8 March 2013|url-status=live|archive-url=https://web.archive.org/web/20120630235053/http://www.scientificamerican.com/article.cfm?id=mushroom-evolution-breaks-down-lignin-slows-coal-formation|archive-date=30 June 2012}}
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==External links==
{{Wikisource portal|Paleozoic#Carboniferous}}
{{Commons category|Carboniferous}}
* {{cite web
 | publisher = International Commission on Stratigraphy (ICS)
 | title = Geologic Time Scale 2004
 | url = http://www.stratigraphy.org/bak/geowhen/index.html
 | access-date = January 15, 2013
 | url-status = dead
 | archive-url = https://web.archive.org/web/20130106085716/http://www.stratigraphy.org/bak/geowhen/index.html
 | archive-date = January 6, 2013
 }}
* [http://www.geo-lieven.com/erdzeitalter/karbon/karbon.htm Examples of Carboniferous Fossils]
*[http://www.foraminifera.eu/querydb.php?&period=Carboniferous&aktion=suche 60+ images of Carboniferous Foraminifera]
*[https://ghkclass.com/ghkC.html?carboniferous Carboniferous (Chronostratography scale)]

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