Key Takeaway: The Carboniferous Period lasted about 359 to 299 million years ago. Across the tropics, huge wetlands built up peat that later became coal. Early amphibians diversified, the first known amniotes appeared, and giant arthropods such as Arthropleura and dragonfly-like griffinflies lived on land and in the air. Meanwhile, repeated glaciations in Gondwana drove major sea-level changes, and late in the period many equatorial wetland forests became fragmented and reorganized.
Fast Facts about the Carboniferous Period
Time Range: About 358.9 to 298.9 million years ago. The Carboniferous lasted nearly 60 million years and was the fifth period of the Paleozoic Era.
Era: Paleozoic Era, an interval when complex marine ecosystems flourished and increasingly diverse vertebrates and arthropods became established on land.
Period Before: Devonian Period. The Devonian saw the great diversification of fishes, the rise of the first forests, and the evolution of early tetrapods.
Period After: Permian Period. Pangaea continued to assemble, climates became more strongly seasonal across many continental interiors, and synapsids and reptiles diversified before the end-Permian mass extinction.
Major Divisions: The Mississippian, about 358.9 to 323.2 million years ago, and the Pennsylvanian, about 323.2 to 298.9 million years ago.
Name: The term Carboniferous means "coal-bearing." William Daniel Conybeare and William Phillips used the term in their 1822 work on the geology of England and Wales, where coal-bearing strata were a major part of the rock sequence.
Best Known For: Extensive coal-forming wetlands, giant arthropods, diverse early amphibians, the appearance of early amniotes, repeated glacial cycles, and major late Carboniferous changes in tropical forests.
Famous Life: Giant lycopsids such as Lepidodendron and Sigillaria, horsetail relatives such as Calamites, tree ferns, seed ferns, Cordaites, the giant myriapod Arthropleura, dragonfly-like griffinflies such as Meganeura, early amphibians, early amniotes such as Hylonomus, sharks, ray-finned fishes, crinoids, brachiopods, corals, bryozoans, and the last surviving trilobite lineage, the proetids.
Famous Fossil Sites: Joggins Fossil Cliffs in Nova Scotia; Mazon Creek in Illinois; Bear Gulch Limestone in Montana; East Kirkton in Scotland; Montceau-les-Mines in France; and many coal basins of the Appalachian region and Europe.
Where the Carboniferous Period Fits in Geologic Time
The Carboniferous Period was the fifth period of the Paleozoic Era. It followed the Devonian Period and came before the Permian. The current International Chronostratigraphic Chart places it from about 358.9 to 298.9 million years ago (International Commission on Stratigraphy, 2026).
On the international time scale, the Carboniferous is split into two major parts. The Mississippian spans about 358.9 to 323.2 million years ago and includes the Tournaisian, Visean, and Serpukhovian stages. The Pennsylvanian spans about 323.2 to 298.9 million years ago and includes the Bashkirian, Moscovian, Kasimovian, and Gzhelian stages.
In North America, the Mississippian and Pennsylvanian have traditionally been treated as separate geologic periods because their rocks often look very different. Mississippian sequences commonly contain marine limestones packed with crinoids and other invertebrates. Pennsylvanian rocks, by contrast, often contain repeating layers of sandstone, shale, limestone, ancient soils, and coal. On the international time scale, both are part of the Carboniferous Period.
The Carboniferous began in the aftermath of the end-Devonian Hangenberg crisis and ended at the Carboniferous-Permian boundary. Across those nearly 60 million years, continental collision, glaciation, sea-level change, tropical wetland expansion, and the evolution of increasingly terrestrial vertebrates repeatedly reshaped ecosystems.
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History of Discovery and Naming: Conybeare, Phillips, and the Carboniferous
The Carboniferous has one of the most practical names in the geologic time scale. The word comes from terms meaning coal-bearing, reflecting the thick coal measures that were economically and scientifically important in Britain and western Europe during the early nineteenth century.
William Daniel Conybeare and William Phillips used the Carboniferous designation in their influential 1822 book Outlines of the Geology of England and Wales (Conybeare & Phillips, 1822). Their work organized British strata using rock relationships, fossils, and regional mapping, and treated the coal measures and associated limestones as parts of a broad Carboniferous succession.
Coal mining helped make Carboniferous geology especially important. Mines, quarries, canals, railway cuttings, and industrial excavations exposed long sequences of coal, shale, sandstone, ironstone, and limestone. These exposures allowed geologists to trace individual beds, compare fossil assemblages, and recognize repeated changes between terrestrial, coastal, and marine environments.
As the geologic time scale became international, different regional systems developed. In North America, the lower, commonly limestone-rich part became known as the Mississippian and the younger, coal-rich part as the Pennsylvanian. Modern international stratigraphy retains both as subdivisions of the Carboniferous.
What Earth Was Like During the Carboniferous Period
The Carboniferous world was shaped by the continuing assembly of Pangaea. Euramerica, formed from earlier continental collisions, lay across the equatorial region. Gondwana occupied much of the Southern Hemisphere, while Siberia and other continental blocks remained separate or were being drawn into the growing supercontinent.
Mountain building accompanied these collisions. The ancestral Appalachian system in eastern North America and the Variscan or Hercynian mountain belts of Europe rose as continental masses converged. Erosion from these uplands supplied enormous volumes of sediment to adjacent basins, where rivers, deltas, coastal plains, shallow seas, and peat-forming wetlands shifted back and forth through time.
Climate was not uniformly hot and swampy. Equatorial lowlands supported extensive tropical wetlands during many intervals, but large ice sheets repeatedly expanded across southern Gondwana as part of the Late Paleozoic Ice Age. Growth and melting of these ice sheets changed global sea level, helping produce repeated cycles of terrestrial and marine sedimentation.
These sea-level changes are especially easy to see in Pennsylvanian rocks. Geologists call many of the repeating rock packages cyclothems. A cyclothem may include river sandstone, floodplain shale, ancient soils, coal, marine shale, and limestone. In other words, the same area could change from a forested coastal plain to a shallow sea and back again many times.
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Life and Major Evolutionary and Environmental Events
Carboniferous ecosystems were remarkably varied. Tropical wetlands supported tall spore-producing plants and dense ground vegetation, drier uplands contained different seed-plant communities, rivers and lakes held fishes and tetrapods, and shallow seas supported rich invertebrate faunas. The period also saw important changes in reproduction and terrestrial life, including the rise of amniotes, whose reproductive biology reduced dependence on standing water.
Carboniferous Coal Forests
The classic Carboniferous coal forests were most extensive across the humid equatorial lowlands of Euramerica during much of the Pennsylvanian. These landscapes were not one continuous swamp. They formed a shifting mosaic of peat-forming wetlands, river channels, floodplains, ponds, lakes, and somewhat better-drained forest patches. Western Pennsylvania lay close to the equator, placing the future Appalachian Basin within this broad tropical belt.
What Grew in the Coal Forests?
The plants in these forests looked very different from the flowering trees that dominate most forests today. Among the tallest were arborescent lycopsids, or tree-sized relatives of modern clubmosses. Genera such as Lepidodendron and Sigillaria are easy to recognize as fossils because their trunks are covered with repeated leaf-scar patterns. Their underground rooting systems are commonly preserved as Stigmaria.
Other important plants included Calamites, tree-sized relatives of modern horsetails with segmented stems; large tree ferns; seed ferns such as medullosans; Cordaites with long strap-like leaves; and smaller climbing or ground-cover plants. Different groups preferred different moisture levels and soils, so the Carboniferous lowlands were really a patchwork of plant communities rather than one uniform forest.
How the Coal Forests Became Coal
In the wettest lowlands, waterlogged soils slowed the complete decay of dead vegetation. Plant material accumulated as thick peat deposits in subsiding basins. With burial, compaction, heat, and geologic time, many of these peat layers were transformed into coal. Not every Carboniferous forest became a coal seam; the great coal beds record particular environments where peat could accumulate and be preserved faster than it was destroyed.
The Carboniferous was also part of the Late Paleozoic Ice Age. Repeated growth and melting of Gondwanan ice sheets drove large sea-level changes. In equatorial basins, shorelines repeatedly shifted across low-lying coastal plains, producing stacked cycles of terrestrial sediments, peat and coal, marine shale, and limestone. These repeating rock packages are often called cyclothems.
The Ambridge section near Pittsburgh preserves a local example of this environmental switching. Plant-bearing Mahoning strata record the terrestrial coal-forest setting, while the overlying Brush Creek Marine Zone records a return of marine conditions. The nearby alternation of plant beds and marine fossils makes the site a useful real-world example of how Carboniferous sea-level cycles were written into the rocks.
Plant fossils from coal-bearing rocks can preserve fronds, leaves, bark, stems, cones, roots, and compressed plant debris. Because isolated organs were often given separate fossil names, a single Carboniferous plant may be represented by several different form genera in the fossil record. This is one reason Carboniferous plant identification often begins with the specific part of the plant that is preserved.
Giant Arthropods and Insects
Carboniferous land ecosystems contained insects, arachnids, scorpions, millipedes, centipedes, and other arthropods. Some became exceptionally large. The most spectacular was Arthropleura, a heavily segmented myriapod that grew to more than two meters in length (6.6 feet) and is the largest known terrestrial arthropod.
New fossils have changed how scientists picture Arthropleura. A 2024 study of juvenile heads found a mix of millipede-like and centipede-like features, helping researchers place the animal more confidently within the myriapod family tree (Lhéritier et al., 2024). Its diet is still uncertain, so reconstructions should avoid showing it as definitely predatory or definitely plant-eating.
Large flying insects also appeared. The famous Meganeura and related forms are often called giant dragonflies, but they belonged to an extinct group called Meganisoptera, commonly known as griffinflies. They were close relatives of dragonflies rather than true members of the modern dragonfly group.
Atmospheric oxygen reached unusually high levels during parts of the late Paleozoic and probably made giant body sizes easier for some insects. But oxygen was not the whole story. Fossil evidence indicates that ecology and interactions with other animals also helped shape insect size through time (Clapham & Karr, 2012).
Amphibians and Early Tetrapods
The Carboniferous was a major chapter in tetrapod evolution. Early in the period, fossils of land vertebrates are unusually scarce during an interval known as Romer's Gap. Earlier research linked this sparse record in part to low atmospheric oxygen (Ward et al., 2006). Later discoveries in Scotland filled in part of the gap and showed that early Carboniferous tetrapods and arthropods were more diverse than the older fossil record had implied (Smithson et al., 2012).
Many Carboniferous tetrapods were still strongly tied to water for reproduction and early development. These amphibians and other early tetrapods included a wide variety of body forms, from small salamander-like species to large aquatic predators with broad skulls. Temnospondyls and several other early tetrapod lineages diversified in rivers, lakes, swamps, floodplains, and coastal wetlands.
Calling all of these animals "amphibians" can be misleading. Many Carboniferous tetrapods were not part of the modern amphibian lineage at all, but belonged to other branches of the early tetrapod family tree. Their fossils capture a time when vertebrates were evolving many different combinations of aquatic and land-based adaptations.
Early Amphibians and the Origin of Amniotes
One of the biggest evolutionary changes of the Carboniferous was the rise of amniotes, the group that includes reptiles, birds, and mammals. Their embryos developed with protective membranes, reducing the need to reproduce directly in open water. That gave early amniotes more freedom to live in drier habitats and farther from ponds and streams.
Hylonomus lyelli from Joggins, Nova Scotia, has long been one of the earliest well-known amniote body fossils. Small skeletons were preserved within hollow tree trunks in Pennsylvanian rocks, providing a remarkable window into early terrestrial vertebrate communities.
A 2025 discovery may push the amniote story much farther back. Researchers described clawed trackways from earliest Carboniferous rocks in Australia, about 355 million years old, and interpreted them as tracks made by a crown-group amniote (Long et al., 2025). If that interpretation is correct, amniotes must have originated close to, or possibly before, the Devonian-Carboniferous boundary. Because footprints are indirect evidence and the conclusion depends on identifying the trackmaker correctly, it is best to keep this evidence separate from the younger body-fossil record.
Carboniferous Marine Ecosystems
One of the strangest predators in Carboniferous seas was Edestus, an extinct cartilaginous fish more closely related to chimaeras than to modern sharks. Its upper and lower jaws carried curved whorls of sharp, serrated teeth. A 2019 analysis of the teeth and tooth whorls found that Edestus likely used a forward-to-backward slicing bite, cutting into prey in a way unlike any living shark (Tapanila & Pruitt, 2019).
Although coal forests dominate popular images of the Carboniferous, much of the period's fossil record is marine. Shallow tropical seas covered broad continental shelves, especially during the Mississippian. Crinoids were extraordinarily abundant in many settings, and their broken skeletal pieces accumulated into thick limestones.
Brachiopods, bryozoans, rugose and tabulate corals, gastropods, bivalves, cephalopods, echinoids, and other invertebrates were common. Ammonoids diversified, while nautiloid cephalopods remained important. Sharks and other cartilaginous fishes included a remarkable variety of tooth and fin-spine forms, and ray-finned fishes continued to diversify.
Trilobites survived the end-Devonian crisis, but only the proetid lineage remained. Carboniferous proetids were generally small compared with many earlier trilobites and persisted into the Permian before trilobites finally disappeared at the end of the Paleozoic.
During the Pennsylvanian, shallow seas repeatedly advanced across low-lying coastal plains and coal basins. Geologists call these flooding events marine transgressions. They left marine shales and limestones above or between terrestrial coal-bearing layers. At sites such as Ambridge in western Pennsylvania, plant-bearing strata can occur close to marine beds containing mollusks, corals, and fish remains.
Glaciation, Cyclothems, and the Carboniferous Rainforest Collapse
The Carboniferous was part of the Late Paleozoic Ice Age. Ice sheets repeatedly expanded and contracted over Gondwana, particularly in the Southern Hemisphere. These glacial cycles caused large changes in global sea level and strongly influenced the sedimentary record of equatorial basins.
Around 305 million years ago, the extensive humid tropical forests of Euramerica underwent a major ecological reorganization often called the Carboniferous rainforest collapse. This was not a single moment when every rainforest vanished. Instead, formerly widespread wetland forests became fragmented, some lycopsid-dominated swamp communities declined sharply, and more seasonally dry floras expanded.
The change also affected vertebrates. A 2010 study found that tetrapod communities became more geographically distinct as the once-broad rainforest habitat broke into smaller regions (Sahney et al., 2010). This fragmentation could have encouraged diversification by isolating populations and creating new ecological conditions.
Carboniferous environments therefore changed continuously. The classic image of an endless humid coal swamp is accurate for some places and times, especially parts of the Pennsylvanian tropics, but it does not represent the entire period or the whole planet.
Famous Fossil Sites from the Carboniferous Period
Joggins Fossil Cliffs in Nova Scotia preserve Pennsylvanian coastal-plain deposits with upright fossil lycopsid trees, plant remains, trackways, invertebrates, and early tetrapods. Hollow tree stumps have yielded small vertebrate skeletons, including Hylonomus, making Joggins one of the classic sites for understanding early terrestrial ecosystems.
Mazon Creek in Illinois is famous for siderite concretions that preserve an exceptionally diverse Pennsylvanian biota. Fossils include plants, insects, arachnids, worms, crustaceans, fishes, amphibians, and soft-bodied animals from both terrestrial and marine-influenced environments. The unusual Tullimonstrum, or Tully monster, comes from this deposit.
The Bear Gulch Limestone of Montana preserves a Mississippian marine ecosystem with exceptionally preserved fishes, including sharks, holocephalans, ray-finned fishes, and other vertebrates. Some specimens preserve fine anatomical details rarely seen in ordinary limestone.
East Kirkton in Scotland preserves a Visean terrestrial and freshwater ecosystem with early tetrapods, arthropods, plants, and volcanic-hydrothermal deposits. The site is especially important for understanding vertebrate life during the early Carboniferous interval traditionally associated with Romer's Gap.
Montceau-les-Mines in France preserves a Late Carboniferous freshwater and terrestrial biota in ironstone nodules. Arthropods are especially important here, including juvenile Arthropleura specimens whose head anatomy has recently helped clarify where this giant myriapod fits in the arthropod family tree (Lhéritier et al., 2024).
Across eastern North America and western Europe, enormous coal basins preserve repeated snapshots of Pennsylvanian forests, floodplains, deltas, and shallow marine incursions. Plant impressions, coalified trunks, trackways, freshwater fossils, and marine shell beds together document rapidly shifting environments along the equatorial belt.
Carboniferous Fossil Hunting Sites
Carboniferous rocks are widespread across the Appalachian region and many other parts of North America. Fossils can occur in shale, sandstone, limestone, coal-associated beds, and ironstone concretions. Access, ownership, road conditions, construction, and collecting regulations can change, so always verify current conditions and obtain permission where required.
Ambridge, Pennsylvania: Pennsylvanian Coal Forest and Marine Fossils
The Ambridge Pennsylvania Carboniferous Fossil Guide covers Upper Pennsylvanian rocks near Pittsburgh, approximately 299 to 300 million years old. The exposed section is part of the Conemaugh Group and includes the Glenshaw Formation, with the Mahoning Shale and Brush Creek Marine Zone.
The plant-bearing Mahoning Shale preserves remains of a Pennsylvanian coal-forest ecosystem. Black carbon plant imprints on shale are common here.
Above the plant-bearing interval, the Brush Creek Marine Zone records a marine transgression, when shallow seas spread across the area. Black shale and limestone can contain marine invertebrates. The close association of terrestrial plant beds and marine fossils makes Ambridge a useful place for seeing how Carboniferous environments shifted as sea level changed.
Safety: The Ambridge exposures are near with busy roads and steep rock cuts. Never collect near the road or near the cliff faces. Only collect the rocks that have fallen far from the cliffs behind the road barriers. Always verify current access before visiting.
Recommended Carboniferous Books and Fossils
A Guide to Pennsylvanian (Carboniferous) Age Plant Fossils of Southwest Virginia
Thomas F. McLoughlin: 2019
Although focused on Virginia, this guide is useful for many Carboniferous plant fossils found across Pennsylvania, Maryland, and West Virginia. With 280 illustrations, many in color, it is a well-organized identification guide for common coal forest plants.
Earth before the Dinosaurs
Sebastien Steyer: 2012
This book explores the strange and fascinating world before dinosaur dominance, tracing the rise of tetrapods, early amphibians, and amniotes through fossils, evolutionary detective work, and vivid reconstructions of ancient life.
Carboniferous Giants and Mass Extinction: The Late Paleozoic Ice Age World
George McGhee Jr.: 2018
A very detailed, visually written look at the Carboniferous world, from giant arthropods and vast coal forests to ancient climate change and mass extinction. Best for readers with some geology background, not a casual overview.
References / Works Cited
International Commission on Stratigraphy. (2026). International Chronostratigraphic Chart, v2026/06.
International Chronostratigraphic Chart
Conybeare, W. D., & Phillips, W. (1822). Outlines of the Geology of England and Wales, with an Introductory Compendium of the General Principles of that Science. William Phillips, London.
Darwin Online transcription
Ward, P. D., Labandeira, C., Laurin, M., & Berner, R. A. (2006). Confirmation of Romer's Gap as a low oxygen interval constraining the timing of initial arthropod and vertebrate terrestrialization. Proceedings of the National Academy of Sciences, 103(45), 16818-16822.
https://doi.org/10.1073/pnas.0607824103
Smithson, T. R., Wood, S. P., Marshall, J. E. A., & Clack, J. A. (2012). Earliest Carboniferous tetrapod and arthropod faunas from Scotland populate Romer's Gap. Proceedings of the National Academy of Sciences, 109(12), 4532-4537.
https://doi.org/10.1073/pnas.1117332109
Sahney, S., Benton, M. J., & Falcon-Lang, H. J. (2010). Rainforest collapse triggered Carboniferous tetrapod diversification in Euramerica. Geology, 38(12), 1079-1082.
https://doi.org/10.1130/G31182.1
Clapham, M. E., & Karr, J. A. (2012). Environmental and biotic controls on the evolutionary history of insect body size. Proceedings of the National Academy of Sciences, 109(27), 10927-10930.
https://doi.org/10.1073/pnas.1204026109
Lheritier, M., et al. (2024). Head anatomy and phylogenomics show the Carboniferous giant Arthropleura belonged to a millipede-centipede group. Science Advances, 10(41), eadp6362.
https://doi.org/10.1126/sciadv.adp6362
Tapanila, L., & Pruitt, J. (2019). Redefining species concepts for the Pennsylvanian scissor tooth shark, Edestus. PLOS ONE, 14(9), e0220958.
https://doi.org/10.1371/journal.pone.0220958
Long, J. A., et al. (2025). Earliest amniote tracks recalibrate the timeline of tetrapod evolution. Nature, 641, 1193-1200.
https://doi.org/10.1038/s41586-025-08884-5
FAQs: Carboniferous Period Frequently Asked Questions
Quick answers to common questions about Carboniferous time, coal forests, giant arthropods, amphibians, early amniotes, marine fossils, climate, and fossil collecting.
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When was the Carboniferous Period?
The Carboniferous Period lasted from about 358.9 to 298.9 million years ago. It followed the Devonian and preceded the Permian, and it was the fifth period of the Paleozoic Era.
See: Geologic Time -
Why is it called the Carboniferous Period?
The name Carboniferous means coal-bearing. William Daniel Conybeare and William Phillips used the term in their 1822 work on the geology of England and Wales because thick coal-bearing rock sequences were an important part of the interval.
See: Discovery and Naming
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What are the Mississippian and Pennsylvanian?
The Carboniferous is internationally divided into two major subdivisions: the Mississippian, from about 358.9 to 323.2 million years ago, and the Pennsylvanian, from about 323.2 to 298.9 million years ago. In North American usage, these names have also traditionally been treated as separate periods.
See: Geologic Time -
What plants formed the Carboniferous coal forests?
Coal-forming wetlands included giant lycopsids such as Lepidodendron and Sigillaria, horsetail relatives such as Calamites, tree ferns, seed ferns, and Cordaites. Their remains accumulated as peat in waterlogged tropical wetlands and were later transformed into coal.
See: Carboniferous Coal Forests -
Why were some Carboniferous arthropods so large?
High atmospheric oxygen during parts of the Carboniferous probably made very large body sizes easier for some insects and other air-breathing arthropods, but oxygen was not the only factor. Ecology, climate, competition, and evolutionary history also affected body size.
See: Giant Arthropods -
Did giant dragonflies live during the Carboniferous?
Large dragonfly-like insects lived during the Carboniferous, including griffinflies such as Meganeura. They belonged to the extinct group Meganisoptera and were close relatives of dragonflies rather than true members of the modern dragonfly group. Some reached wingspans approaching 70 centimeters.
See: Giant Arthropods -
What animals lived during the Carboniferous Period?
Carboniferous ecosystems included abundant marine invertebrates and fishes, many early amphibians, early amniotes, insects, arachnids, and giant myriapods such as Arthropleura. The exact communities differed greatly between marine seas, tropical wetlands, rivers, and drier uplands.
See: Life and Major Events -
When did the first amniotes appear?
Amniotes were established by the Carboniferous. Hylonomus from Joggins is one of the earliest well-known amniote body fossils. A 2025 study also described clawed trackways about 355 million years old that were interpreted as crown-group amniote tracks, which could place their origin close to the Devonian-Carboniferous boundary.
See: First Amniotes -
What was the Carboniferous rainforest collapse?
Near 305 million years ago, extensive equatorial wetland forests became fragmented and reorganized as climates became more variable. Lycopsid-dominated coal swamps contracted in many areas, more seasonally dry vegetation expanded, and tetrapod faunas became increasingly regionalized. It was a major ecological transition rather than the disappearance of all tropical forests.
See: Climate and Rainforest Change -
Where can you collect Carboniferous fossils in Pennsylvania?
The Fossilguy Ambridge guide covers Upper Pennsylvanian rocks near Pittsburgh, Pennsylvania. The site includes the Mahoning Shale, which preserves coal-forest plants, and the Brush Creek Marine Zone, which contains marine fossils. Access and safety conditions can change, so collectors should verify current rules and permissions.
See: Carboniferous Fossil Hunting Sites
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