Carboniferous

The development of a Carboniferous 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. These four units were placed into a formalised Carboniferous unit by William Conybeare and William Phillips in 1822 and then into the Carboniferous System by Phillips in 1835. The Old Red Sandstone was later considered Devonian in age. 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 deposition and the upper Silesian with mainly siliciclastic deposition. The Dinantian was divided into the Tournaisian and Viséan stages. The Silesian was divided into the Namurian, Westphalian and 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. 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 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. 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. 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. == 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 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. 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.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 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 limestones and shales at the Pengchong section, Guangxi, southern China. It is defined by the first appearance of the fusulinid Eoparastaffella simplex in the evolutionary lineage Eoparastaffella ovalis – Eoparastaffella simplex and was ratified in 2009. Cyclothems A cyclothem is a succession of non-marine and marine sedimentary rocks, deposited during a single sedimentary cycle, with an 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. . 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 Ice Age from the Late Mississippian to early Permian, when the waxing and waning of ice sheets led to rapid changes in eustatic sea level. 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 basins of the Central Pangean Mountains in Laurussia, and around the margins of the North and South China cratons. 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. 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. ==Palaeogeography==

During the Carboniferous, there was an increased rate in tectonic plate movements as the supercontinent Pangea assembled. The continents themselves formed a near circle around the opening Paleo-Tethys Ocean, with the massive Panthalassic Ocean beyond. Gondwana covered the 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 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. (much of modern-day Central and Western Europe including Iberia) as the Rheic Ocean closed and Pangea formed. This mountain building process began in the Middle Devonian and continued into the early Permian. The Armorican terranes rifted 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. 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 craton). The 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 km along the orogen. 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. Subduction of the Panthalassic oceanic plate along its western margin resulted in the Antler orogeny in the Late Devonian to Early Mississippian. Further north along the margin, 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. 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. 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. A continental magmatic arc above a south-dipping subduction zone lay along the northern North China margin, consuming the Paleoasian Ocean. Northward subduction of the Paleo-Tethys beneath the southern margins of North China and Tarim continued during the Carboniferous, with the South Qinling block accreted to North China during the mid to late Carboniferous. 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. South China and Annamia (Southeast Asia) rifted from Gondwana during the Devonian. 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 evaporites were deposited across the passive margins that surrounded both continents. ==Climate==

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). 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. This ended suddenly as a rapid increase in CO2 concentrations to c. 600 ppm resulted in a warmer climate. This rapid rise in CO2 may have been due to a peak in pyroclastic volcanism and/or a reduction in burial of terrestrial organic matter. Depending on the preservation of source material, some techniques represent moments in time (e.g. halite gas inclusions), whilst others have a wider time range (e.g. the charcoal record and pyrite). Results from these different methods for the Carboniferous vary. 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 ramp architecture) 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. 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 CO2 levels below 400 ppm. 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. Across the Carboniferous–Permian boundary interval, a rapid drop in CO2 levels and increasingly arid conditions at low-latitudes led to a permanent shift to seasonally dry woodland vegetation. Tetrapods acquired new terrestrial adaptations and there was a radiation of dryland-adapted amniotes. == 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, whilst the distribution of continents across the paleo-tropics meant vast areas of land were available for the spread of tropical rainforests. These variations reflect the changing influence of weathering and sediment supply to the oceans of the growing Central Pangean Mountains. By the Serpukhovian 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. Oxygen and carbon isotope ratios in seawater Unlike Mg2+/Ca2+ and 87Sr/86Sr isotope ratios, which are consistent across the world's oceans at any one time, δ18O and δ13C preserved in the fossil record can be affected by regional factors. Carboniferous δ18O and δ13C 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. However, large scale trends can still be determined. δ13C 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. Similarly from the Early Mississippian there was a long-term increase in δ18O values as the climate cooled. Both δ13C and δ18O records show significant global isotope changes (known as excursions) during the Carboniferous. The mid-Tournaisian positive δ13C and δ18O excursions lasted between 6 and 10 million years and were also accompanied by c. 6‰ positive excursion in organic matter δ15N values, a negative excursion in carbonate δ238U and a positive excursion in carbonate-associated sulphate δ34S. These changes in seawater geochemistry are interpreted as a decrease in atmospheric CO2 due to increased organic matter burial and widespread ocean anoxia triggering climate cooling and onset of glaciation. The Mississippian-Pennsylvanian boundary positive δ18O 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 87Sr/86Sr just before the δ18O 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. δ13C values show more regional variation, and it is unclear whether there is a positive δ13C excursion or a readjustment from previous lower values. During the early Kasimovian there was a short (2 concentrations rapidly rose. 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. The resulting reduction in productivity and burial of organic matter led to increasing atmospheric CO2 levels, which were recorded by a negative δ13C excursion and an accompanying, but smaller decrease in δ18O values. ==Life==

Plants Early Carboniferous land plants, some of which were preserved in coal balls, 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 "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. , probably Sigillaria, with attached stigmarian roots, Joggins Formation, Canada showing connection with bifurcating 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, Lepidophloios and Sigillaria. The roots of several of these forms are known as Stigmaria. Unlike present-day trees, their secondary growth took place in the cortex, which also provided stability, instead of the xylem. The Cladoxylopsids were large trees, that were ancestors of ferns, first arising in the Carboniferous. The fronds of some Carboniferous ferns are almost identical with those of living species. Probably many species were epiphytic. Fossil ferns and "seed ferns" include Pecopteris, Cyclopteris, Neuropteris, Alethopteris, and Sphenopteris; Megaphyton and Caulopteris were tree ferns. The Equisetales included the common giant form Calamites, with a trunk diameter of 30 to and a height of up to . Sphenophyllum was a slender climbing plant with whorls of leaves, which was probably related both to the calamites and the lycopods. 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, and preferred higher drier ground. Marine invertebrates In the oceans the marine invertebrate groups are the Foraminifera, corals, Bryozoa, Ostracoda, brachiopods, ammonoids, hederelloids, microconchids and echinoderms (especially crinoids). 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. For the first time foraminifera took a prominent part in the marine faunas. The large spindle-shaped genus 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. The first true priapulids appeared during this period. The microscopic shells of radiolarians are found in cherts of this age in the Culm of Devon and Cornwall, and in Russia, Germany and elsewhere. Sponges are known from spicules and anchor ropes, and include various forms such as the Calcispongea Cotyliscus and Girtycoelia, the demosponge Chaetetes, and the genus of unusual colonial glass sponges Titusvillia. Both reef-building and solitary corals diversify and flourish; these include both rugose (for example, Caninia, Corwenia, Neozaphrentis), heterocorals, and 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, so named because it is in the shape of an Archimedean screw. Brachiopods are also abundant; they include productids, some of which reached very large for brachiopods size and had very thick shells (for example, the -wide Gigantoproductus), while others like Chonetes were more conservative in form. Athyridids, spiriferids, rhynchonellids, and terebratulids are also very common. Inarticulate forms include Discina and Crania. Some species and genera had a very wide distribution with only minor variations. Annelids such as Serpulites are common fossils in some horizons. Among the mollusca, the bivalves continue to increase in numbers and importance. Typical genera include Aviculopecten, Posidonomya, Nucula, Carbonicola, Edmondia, and Modiola. Gastropods are also numerous, including the genera Murchisonia, Euomphalus, Naticopsis. Nautiloid cephalopods are represented by tightly coiled nautilids, with straight-shelled and curved-shelled forms becoming increasingly rare. Goniatite ammonoids such as Aenigmatoceras are common. Trilobites are rarer than in previous periods, on a steady trend towards extinction, represented only by the proetid group. Ostracoda, a class of crustaceans, were abundant as representatives of the meiobenthos; genera included Amphissites, Bairdia, Beyrichiopsis, Cavellina, Coryellina, Cribroconcha, Hollinella, Kirkbya, Knoxiella, and Libumella. Crinoids were highly numerous during the Carboniferous, though they suffered a gradual decline in diversity during the Middle Mississippian. 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 blastoids, 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. 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 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 scyphozoan, but is now regarded as a Sea anemone File:Concavicaris georgeorum.png|Concavicaris was a long lasting genus of thylacocephalan arthropod that lived from the Devonian to the Carboniferous. File:Triproetus bonbon cropped.jpg|Triproetus was a genus of 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 coleoid cephalopod from northern Illinois File:Syllipsimopodi bideni.webp|Syllipsimopodi was the earliest known vampyropod cephalopod, originating from Carboniferous rocks of Montana. Freshwater and lagoonal invertebrates Freshwater Carboniferous invertebrates include various bivalve molluscs that lived in brackish or fresh water, such as Anthraconaia, Naiadites, and Carbonicola; diverse crustaceans such as Candona, Carbonita, Darwinula, Estheria, Acanthocaris, Dithyrocaris, and Anthrapalaemon. The eurypterids 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, Orbiculoidea, and Productus being found in the thin beds known as marine bands. 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 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 Terrestrial invertebrates Fossil remains of air-breathing insects, myriapods, and arachnids are known from the Carboniferous. Their diversity when they do appear, however, shows that these arthropods were both well-developed and numerous. followed by the huge predatory Protodonata (griffinflies), which includes Meganeura, a giant dragonfly-like insect and with a wingspan of ca. —the largest flying insect ever to roam the planet. Further groups are the Syntonopterodea (relatives of present-day mayflies), the abundant and often large sap-sucking Palaeodictyopteroidea, the diverse herbivorous Protorthoptera, and numerous basal Dictyoptera (ancestors of cockroaches). 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 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. File:Meganeura.png|The late Carboniferous giant dragonfly-like insect Meganeura grew to wingspans over . File:20210116 Pulmonoscorpius kirktonensis.png|The gigantic Pulmonoscorpius from the early Carboniferous reached a length of up to . File:Arthropleura Reconstruction.jpg|Arthropleura was a giant millipede that fed on the Carboniferous plants. At long, it was the largest known terrestrial arthropod that ever lived. File:Homaloneura ligeia.jpg|Homaloneura, a palaeodictyopteran insect which have two winglets on thorax in addition to four wings. File:Helenodora inopinata.jpg|Helenodora inopinata, a stem-group onychophoran known from Illinois File:Blattoidae - Fossil.JPG|A roachoid insect found in Carboniferous rocks of France File:20201202 Maiocercus celticus.png|Maiocercus was a trigonotarbid arachnid that lived in the United Kingdom around 310 million years ago. Fish Many fish inhabited the Carboniferous seas; predominantly Elasmobranchs (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 . Other fish had piercing teeth, such as the Symmoriida; some, the petalodonts, 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. Among the bony fish, the Palaeonisciformes found in coastal waters also appear to have migrated to rivers. Sarcopterygian fish were also prominent, and one group, the Rhizodonts, reached very large size. Most species of Carboniferous marine fish have been described largely from teeth, fin spines and dermal ossicles, with smaller freshwater fish preserved whole. Freshwater fish were abundant, and include the genera Ctenodus, Uronemus, Acanthodes, Cheirodus, and Gyracanthus. Chondrichthyes (especially holocephalans like the Stethacanthids) underwent a major evolutionary radiation during the Carboniferous. It is believed that this evolutionary radiation occurred because the decline of the placoderms at the end of the Devonian caused many environmental niches to become unoccupied and allowed new organisms to evolve and fill these niches. 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 denticles on its top. Stethacanthus unusual fin may have been used in mating rituals. Other groups like the 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. 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. 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. File:Akmonistion_zangerli.png|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 Ctenacanthiform elasmobranch from the late Carboniferous of New Mexico. File:Ornithoprion.png|Ornithoprion was a small-sized 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 Bony fish belonging to the extinct order Palaeonisciformes. File:Edestus recon.png|Edestus was a large eugeneodontid fish that possessed two tooth whorls in its mouth File:Rhizodus.jpg|Rhizodus was a large freshwater Rhizodont 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 angel sharks File:Bandringa SW.png|Bandringa is a bizarre elasmobranch fish that lived in Illinois, Ohio and Pennsylvania during the Moscovian stage. It superficially resembled a paddlefish, with an elongated upper 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, a petalodont holocephalan from the upper Carboniferous of Kentucky. Tetrapods Carboniferous amphibians 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. They included basal tetrapod groups classified in early books under the Labyrinthodontia. These had a long body, a head covered with bony plates, and generally weak or undeveloped limbs. The largest were over 2 meters long. They were accompanied by an assemblage of smaller amphibians included under the Lepospondyli, often only about 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. 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 tetrapods. These included the earliest 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. By the end of the Carboniferous amniotes had already diversified into a number of groups, including several families of synapsid pelycosaurs, protorothyridids, captorhinids, saurians and araeoscelids. File:Pederpes2223DB.jpg|The amphibian-like Pederpes, the most primitive tetrapod found in the Mississippian, and known from Scotland. File:Hylonomus BW.jpg|Hylonomus, the earliest sauropsid reptile, appeared in the 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 tetrapodomorph from the late Carboniferous of Colorado. File:Crassigyrinus BW.jpg|Crassigyrinus was a carnivorous stem-tetrapod from the early Carboniferous of Scotland. File:Microbrachis pelikani.png|Microbrachis was a lepospondyl amphibian known from the Czech Republic. File:Amphibamus BW.jpg|Amphibamus was a dissorophoid temnospondyl from the late Carboniferous of Illinois. 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. ==Extinction events==

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. The gap saw the demise of the Devonian fish-like ichthyostegalian labyrinthodonts and the rise of the more advanced temnospondylian and reptiliomorphan amphibians that so typify the Carboniferous terrestrial vertebrate fauna. 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. 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. 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. ==See also==