The Carboniferous Period is a geologic period of the Paleozoic Era.
It began 358.9 million years ago and lasted until the beginning of the Permian Period 289.9 million years ago.
The Carboniferous is most popular for its abundance of fossilized plant remains that formed extensive coal deposits in various locations all over the world.
The name Carboniferous is a reference to these carbon-rich coal deposits.
During this period, the continents were located near the equator, resulting in a warm tropical climate that favored the growth of lush forests dominated by giant ferns, club mosses, horsetails, and early conifers.
These forests covered vast areas of the Earth’s continents.
These dense forests would later profoundly impact the carbon cycle as the plants absorbed vast amounts of atmospheric carbon dioxide, tipping the atmospheric balance towards a cooling trend.
Both Marine and terrestrial life flourished during the Carboniferous Period.
The period witnessed the emergence of several notable marine animal species, including the early sharks and bony fish.
The Carboniferous Period also marked a crucial milestone in the evolution of vertebrates as amphibians became the dominant land-dwelling animals.
The evolution of the amphibians was the first significant transition of animal life from aquatic to terrestrial and laid the groundwork for the appearance of the early reptiles.
Terrestrial invertebrates and insects were also present throughout the period and underwent significant evolutionary development, taking advantage of the abundant plant life and forest habitats.
This article details all the major events and development that took place during the Carboniferous between 359 to 299 million years ago.
Timeline of the Carboniferous Period
The Carboniferous Period is the fifth subdivision of the Paleozoic Era.
It follows the Devonian Period and precedes the Permian Period, which is the last period of the Paleozoic Era.
The Carboniferous Period lasted approximately 60 million years, from 358.9 million years ago to 298.9 million years ago.
Although it is considered a single period everywhere else in the world, North American Scientists divide the Carboniferous Period into two smaller subdivisions, namely: the Mississippian (between 358.9 and 323.2 million years ago) and the Pennsylvanian (between 323.2 and 298.9 million years ago).
Each of these periods is further divided into smaller sub-periods.
The Mississippian Period is subdivided into the Tournaisian, Visean, and Serpukhovian subperiods, while Pennsylvanian is divided into Bashkirian, Moscovian, Kasimovian, and Gzhelian.
Mississippian Period (Lower Carboniferous) — 358.9 to 323.2 Million Years Ago
The Mississippian subdivision of the Carboniferous Period began 358.9 million years ago and ended 323.2 million years ago.
The period is named after the extensive sequence of rocks from that period, mainly found along the Mississippi River region of North America.
The Early Carboniferous climate was warm and humid, supporting the growth of diverse ecosystems both on land and in the oceans.
The Mississippian is characterized by the development of carbonate platforms and reefs formed in shallow marine environments.
These reefs were built by various marine organisms, including rugose and tabulate corals, brachiopods, crinoids, and bryozoans.
These reef ecosystems also supported several other marine invertebrate groups.
On land, the Mississippian is characterized by coal deposits formed in low-lying areas by the lush vegetation of giant ferns, club mosses, and early conifers that were abundant during that period of geologic history.
The plants of the Early Carboniferous Period were similar to those of the Late Devonian.
However, many new groups also emerged during this period.
Amphibians, particularly labyrinthodonts, were the dominant land vertebrates during the Early Carboniferous.
These early semi-aquatic animal groups evolved from the lobe-finned fishes of the Devonian Period.
The Mississippian saw significant tectonic activity as the landmass of Laurussia (which mainly occupied the Northern Hemisphere) drifted towards Gondwana in the Southern Hemisphere.
The collision of the continents this way influenced the geography and distribution of land and sea, shaping the habitats available for different organisms.
Despite the ongoing diversification, the Mississippian ended with a major extinction event.
This event probably resulted from climate change, sea-level fluctuations, and volcanic activity.
This extinction event led to the reorganization of marine ecosystems because it mainly affected reef-building organisms.
Pennsylvanian (Upper Carboniferous) — 323.2 to 298.9 Million Years Ago
The last 25 million years of the Carboniferous Period is known as the Pennsylvanian Subdivision.
It is named after the State of Pennsylvania, where extensive coal-rich deposits from this period have been found.
During the Pennsylvanian, the terrestrial environments of the planet underwent significant changes.
Plate movements finally brought the continents of Laurussia into contact with Gondwana.
This led to extensive mountain building and closed the prehistoric Tethys Sea.
The forests of the Pennsylvanian were slightly different from those of the Early Carboniferous Period.
Progymnosperms and early seed plants became more abundant, especially in tropical latitudes.
Ferns also overtook club mosses as the dominant land plant.
The Pennsylvanian forest still supported a diverse range of organisms, including amphibians and the nearly emerging reptiliomorphs, the ancestors of the reptiles.
Another major animal group that became more important in Pennsylvania was the insects.
They evolved into primitive winged forms such as dragonflies and mayflies.
These insects were able to take advantage of the abundant plant life to become an important component of the terrestrial ecosystems.
In the marine ecosystems of the Pennsylvanian, carbonate platforms and reefs started to decline as reef-building organisms became less abundant due to dropping sea levels.
Marine organisms like the brachiopods, crinoids, and ammonoids continued to thrive, but the reefs were not as prominent as in the Mississippian.
Towards the end of the Pennsylvanian, the Earth experienced significant climatic changes.
A global cooling trend led to widespread glaciations, especially in the continents closer to the southern polar regions.
These climatic fluctuations, along with other factors, contributed to a major extinction event at the end of the Carboniferous Period.
This event affected both marine and terrestrial life.
Climate and Geography of the Carboniferous Period
At the beginning of the Carboniferous Period, the Earth had a warm, humid, and tropical climate.
The climate was stable and uniform throughout the planet, with no distinct seasonal variations during the year.
Due to this humid climate, Carboniferous plants were very similar to those found in tropical or mildly temperate areas today.
The uniformity in Earth’s climate can be attributed to the geography of the planet at the time.
All the continents were drifting towards each other, forming a single landmass known as Pangea, which was surrounded by a large ocean that covered the entire surface of the globe.
There were fluctuations in sea levels throughout the Carboniferous Period.
Towards the end of the Carboniferous Period, the climate grew colder.
This was more severe in the landmasses closer to the southern polar regions.
These glaciations likely resulted from changing climatic conditions caused by the new continental configurations and the presence of forests that trapped greenhouse gasses, keeping the planet from warming up.
This new, cool, arid climate could not support the extensive forest habitats, leading to the Carboniferous Rainforest Collapse at the end of the Cretaceous.
Key Events and Developments of the Carboniferous Period
Formation of Pangaea
During the Carboniferous Period, the Earth’s continents were in the process of coming together to form a supercontinent known as Pangaea.
This convergence resulted in the amalgamation of the landmass into a single landmass.
This collision and subsequent formation of Pangaea had significant implications for Earth’s geography and climate.
Formation of Carboniferous Forests
The Carboniferous Period is renowned for the development of extensive forests dominated by giant ferns, club mosses, horsetails, and early conifers.
These lush forests covered large areas of land and played a crucial role in the formation of coal deposits that are still seen today.
The abundant plant materials accumulated in swampy environments were eventually transformed into coal seams found in various regions of the world, especially North America.
Rise of Amphibians
The rise of amphibians started during the Devonian Period and continued throughout the Carboniferous with the significant diversification and dominance of this group of tetrapods.
Primitive amphibians evolved from lobe-finned fishes and were well-adapted to both aquatic and terrestrial environments.
The Carboniferous amphibians, known as labyrinthodonts, were the dominant land vertebrates, and they played a vital role in the emerging terrestrial ecosystems.
Diversification of Insects
The Carboniferous Period was characterized by the remarkable diversification of insects.
Many groups of primitive winged insects, such as dragonflies and mayflies, as well as crawlies like giant centipedes, appeared during this time.
Mammoth cockroaches and scorpions that grew to impressive sizes were also present during this phase.
The evolution and diversification of insects during the Carboniferous laid the foundation for the subsequent dominance and ecological importance of insects on Earth.
Perhaps the biggest evolutionary adaptation of the Cambrian Period was the evolution of amphibians that laid amniote eggs.
This type of egg had shells that protected the embryo within a fluid-retaining membrane which still allowed the circulation of air.
This adaptation made it possible for early amphibians to live farther away from marine ecosystems; this eventually led to the evolution of the earliest reptiles.
Major Groups of Organisms in the Carboniferous Period
The Carboniferous Period hosted a rich array of plant and animal life.
There were lush forests in terrestrial habitats.
Amphibians ruled the land, while insects diversified and became more abundant as the period progressed.
Marine ecosystems were populated by a diverse range of invertebrates, and reptiles began to emerge towards the end of the period.
The Devonian Period was known as the “Age of the Fishes” due to the massive evolution and diversity of this group during the period.
The dominance of this group continued during the Carboniferous as many new fish groups emerged.
They include the cartilaginous fish (sharks and rays) and several new groups of ray-finned fish and lobe-finned fish.
The marine ecosystems of the Carboniferous still teemed with a variety of invertebrates.
Brachiopods, crinoids, corals, ammonoids, and trilobites were among the prominent groups thriving in the oceans during this period.
Reef-building organisms were quite abundant in the early part of the period but started to experience a decline in the second half of the period.
Lizard-like amphibians such as the labyrinthodonts were the dominant land vertebrates during the Carboniferous Period.
These four-limbed tetrapods were adapted to both aquatic and terrestrial environments and occupied various ecological niches in the Carboniferous swamps.
Towards the end of the Carboniferous, primitive reptiles, known as reptiliomorphs, emerged.
These small reptiles were similar to their amphibian ancestors but displayed adaptations that allowed them to inhabit drier terrestrial environments more effectively.
Members of the Protodonata group were ancient insects commonly referred to as “griffin-flies.”
They were similar in appearance to dragonflies but were significantly bigger and had distinct characteristics, including long and slender bodies.
Some species had wingspans of over 70 centimeters (27.5 inches).
Giant, tree-sized club mosses were quite common during the Carboniferous.
They were the earliest vascular plants that formed extensive forests and contributed to the formation of coal deposits during the Carboniferous.
Some of the sphenophytes of the Carboniferous include Calamites and Equisetum (horsetails).
They were abundant in the Carboniferous swamps, reaching very impressive heights.
Notable Species from the Carboniferous Period
They were significantly larger than the flying insects of today.
With wingspans of up to 75 centimeters (29.5 inches), the Meganeura is considered one of the largest flying insects ever found.
Arthropleura was a type of giant millipede that lived during the second half of the Carboniferous Period.
They grew to lengths of up to 2.5 meters (8.2 feet), making them one of the largest land-dwelling arthropods to have ever existed.
Diplocaulus was a large amphibian known for its distinctive boomerang-shaped head and salamander-like body.
It is one of the best-known amphibians from the Late Carboniferous Period.
Calamites were tall, tree-like plants that were quite common in Carboniferous forests.
They belong to a group of plants commonly referred to as horsetails (sphenophytes).
Calamites had jointed stems and grew to lengths of up to 30 meters (98 feet).
Lepidodendron was a genus of tree-sized club mosses known for its tall trunks covered in scaly bark.
They were prominent in the Carboniferous swamps and are commonly found in the coal deposits from that period.
Also known as sea scorpions, eurypterids were marine arthropods that thrived in Carboniferous marine ecosystems.
They grew to very large sizes and were among the largest arthropods at some point.
Although the eurypterids were affected by the Late Devonian extinction event, they were still very abundant during the Carboniferous.
Xenacanthus was a genus of primitive freshwater sharks that first appeared during the Devonian and lived through the Carboniferous.
They had a distinctive fin spine with backward-pointing denticles. Some species reached lengths of several meters but were still smaller than present-day sharks.
Fossils and Their Significance in Understanding the Carboniferous Period
Many plants and animal groups evolved for the first time during the Carboniferous Period.
This includes the first true bony fishes, the first sharks, the first amphibians, and even the earliest reptiles.
Thus, fossils from this time of geologic period are considered very important, not just to our understanding of the period, but also for the rest of Earth’s history.
Fossilized remains of plants that lived in the Carboniferous are also very important because they help us reconstruct the ancient forests that once dominated the landscapes of Carboniferous Earth.
Some of these prehistoric plants, such as ferns, horsetails, club mosses, and the earliest flowering plants, have formed coal deposits found in various locations all over the world.
They provide evidence of the evolution of early land plants and their ecological importance.
Fossils of amphibians, particularly labyrinthodonts, are also very abundant in Devonian and Carboniferous deposits.
These fossils help us trace the transition from fish to amphibians and to the reptiliomorphs that evolved from them.
They help us understand the adaptations of these ancient groups to the changing environments of the Carboniferous ecosystems where they lived.
The Carboniferous-Earliest Permian Biodiversification Event and its Impact on Evolution
This marine biodiversification event occurred for a duration of 41 million years during the Late Paleozoic Era.
It began in the middle of the Carboniferous Period and continued until the end of the Permian Period.
It represents a dynamic period in Earth’s history characterized by an expansion and diversification of various marine groups.
The number of species in the marine ecosystems within this period increased by up to 246%.
This includes the rise of new coral groups like the scleractinians (modern corals), which became major reef builders of that period.
Brachiopods, ammonoids, bivalves, and echinoderms (such as crinoids) also experienced significant diversification during this period.
The proliferation of new coral groups led to the development of extensive coral reefs in shallow marine environments.
These reefs became favorable habitats for numerous organisms, further contributing to the overall increase in biodiversity.
It is worth noting that despite the overall increase in biodiversity, the Carboniferous-Permian marine biodiversity crisis was also interrupted by several extinction events and turnover events.
Some groups, such as blastoids and rugose corals, experienced significant declines and eventual extinctions during this period.
These extinctions were likely driven by environmental changes and ecological interactions.
Extinction Events and Their Effects on the Carboniferous Period
The Carboniferous Period began with an extinction event that took out several marine animal groups at the end of the Devonian.
The evolutionary progress that occurred during the period was also interrupted by two major extinction events in the middle and at the end of the period.
They’re highlighted below:
Late Visean Extinction
This extinction event took place during the middle of the Carboniferous Period (end of the Mississippian Subperiod), around 330 million years ago.
It primarily affected marine communities and was probably caused by environmental changes like sea-level fluctuations and changes in ocean chemistry.
Early Serpukhovian Extinction
The Early Serpukhovian extinction event occurred towards the end of the Carboniferous Period about 318 million years ago during the Late Carboniferous.
It affected both marine and terrestrial ecosystems but had a bigger effect on the marine ecosystems.
The exact causes of this extinction event are still under investigation, but they are likely linked to environmental changes and the general cooling trend that occurred during this period.
These environmental changes may have also caused the collapse of the Carboniferous rainforest ecosystems during the Late Carboniferous and Early Permian.