All About the Carboniferous Period: Great Forests and Giant Swamps

Photo: selvanegra via Getty Images

Following the Devonian and leading up to the Permian, the Carboniferous Period is the fifth stage of the Paleozoic Era. The birth of the Carboniferous Period occurred about 358.9 mega annum (Ma), and its end at 298.9 Ma. It is the longest period in the Paleozoic Era and the longest continuous period in the Phanerozoic Eon, with around 60 million years. 

The Carboniferous System is made up of rocks that were either produced or accumulated at that time. The term "Carboniferous" is derived from the coal-bearing strata characteristic of the top part of the worldwide series.

For purposes of chronostratigraphy, the Carboniferous Period is split into two main sections, the Mississippian (358.9 to 323.2 Ma) and the Pennsylvanian (323.2 to 298.9 Ma). Their rocks are acknowledged as subsystems by worldwide consensus. Europeans split the Carboniferous Era into the Dinantian and Silesian subsystems. However, this division occurs below the globally recognized Mississippian-Pennsylvania divide.

Why Is The Carboniferous Period Like?

The trees thrived in the enormous lowland swamp forests and provided the bark used to make carboniferous coal. There were tall trees with strap-shaped foliage, gigantic club moss, tree ferns, and enormous horsetails for cover. Humans have used coal from these ancient plant remnants for thousands of years. We're still using it since we burned through the fossil fuel left behind by animal matter.

The region's topography strongly influenced the Carboniferous era's worldwide climate. During the previous Devonian epoch, Pangaea was formed when the northern landmass Euramerica combined with the southern supercontinent Gondwana, creating the huge super-supercontinent Pangaea, which inhabited most of the southern hemisphere during the subsequent Carboniferous epoch.

The continental collisions raised some of the lands into mountains. More erosion and the formation of floodplains and river deltas followed this process of mountain formation.

Some marine creatures, like some corals and crinoids, were extinct due to the increasing freshwater environment. New species, such as freshwater clams, gastropods, sharks, and bony fish, emerged in response to the decreased salinity of these waters.

The warmer, shallower seas of the Carboniferous Period resulted from frequent flooding of the continents by the gigantic oceans that dominated the planet at the time. Armored fish, which had been common in the Devonian Period, went extinct then and were succeeded by more contemporary fishes.

The formation of Pangaea significantly altered air and water circulation patterns, leading to the widespread glaciation of southern Pangaea and a general cooling trend over the globe. The coal swamps that blanketed the temperate areas of Pangaea were mostly unaffected by this.

As these trees grew, massive volumes of carbon dioxide were taken from the air, resulting in an oxygen surplus. When oxygen levels in the atmosphere were at their highest, they were roughly 35%, but they are just 21% now. This allowed for the development of terrestrial megafaunas such as amphibians and large insects.

What Life Existed In The Carboniferous Period?

Life on Land

The following are some of the terrestrial life in the Carboniferous Period that we know of.

Romer's Gap is a 15-million-year interval (from 360 to 345 million years ago) in which almost no vertebrate fossils have been discovered, limiting our knowledge of life throughout the Carboniferous period.

However, by the conclusion of this time gap, the first tetrapods (four-footed creatures) had evolved from lobe-finned fishes, discarded their interior gills, and were well on their path toward becoming true amphibians.

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Significant amphibian genera like Amphibamus and Phlegethontia appeared in the late Carboniferous; like present amphibians, they needed water to hatch their eggs and maintain skin moisture, limiting their ability to go far from water.

One of the first amphibians from the Carboniferous Period was the Amphibamus, whose name means "equal legs," It may have been the progenitor of current frogs and salamanders, and it was about the size of a newt.

Conversely, the Phlegethontia were amphibians but had given up their legs and evolved snakelike physiques. Rows of tiny, spiky teeth lined its mouth, much like the teeth of some modern, nonvenomous snakes. There were about 200 vertebrae in its spine; the majority of them were located in its tail.

As mentioned previously, the amount of oxygen in Earth's atmosphere reached a record high during the late Carboniferous period, reaching an extraordinary 35%.

Insects and other terrestrial invertebrates that breathe through their exoskeletons rather than using lungs or gills benefited greatly from this abundance.

Most notably. Meganeura, a gigantic dragonfly, and Arthropleura, a gigantic millipede, flourished throughout the Carboniferous.

The airborne Meganeura is perhaps the biggest insect to ever traverse the skies. It resembled dragonflies but is classified into a close cousin called griffinflies. This monstrous insect had a 2.5-foot wingspan, almost 12 times larger than the wings of modern dragonflies.

Arthropleura, on the other hand, is a land-stuck herbivore that strongly resembles and is related to modern millipedes and centipedes. These arthropods grew up to 8.5 feet long and are considered the largest land invertebrates ever, possibly with few to no predators.

When comparing reptiles with amphibians, the reproductive process is the most telling difference. Reptile eggs, which have a hard shell, may survive without being deposited in water or on damp ground.

Reptiles had already made significant progress into the heart of Pangaea by the end of the Carboniferous. These forerunners eventually led to archosaurs, pelycosaurs, and therapsids in the Permian era. Almost a hundred million years later, the first dinosaurs will evolve from archosaurs.

The cold and dry conditions of the late Carboniferous period pushed the development of reptiles further. About 315 million years ago, Hylonomus, one of the oldest reptiles discovered to date, emerged, followed by the enormous (nearly 10 feet long) Ophiacodon just a few million years later.

It is unarguable that the Hylonomus is the first reptile ever to live. Including the tail, it could reach a length of 20 centimeters (8 inches), and its appearance is likely to have been similar to that of today's lizards.

Even though the Ophiacodon was probably a terrestrial creature, some paleontologists have speculated that it may have spent part of its time in the water. It grew between 1.6 and 3 meters (5.2 and 9.8 ft) in length and between 26 and 230 kilograms (57 and 507 lbs), making it the largest tetrapod of its time.

Life On Water

Photo: CoreyFord via Getty Images

Carboniferous aquatic life is not well-known since the distinguishing placoderms (armored fish) died out around the conclusion of the Devonian period. However, several taxa of lobe-finned fish were strongly linked to the very first tetrapods and amphibians to colonize dry ground. 

Although the considerably larger Edestus is better recognized due to its teeth, the related of Stethacanthus, Falcatus, is the most well-known Carboniferous shark. Carboniferous waters were teeming with minute invertebrates like corals, crinoids, and arthropods, much as they had been in previous epochs.

Plant Life

Even though plants didn't fare well in the drier, colder weather of the late Carboniferous period, these resilient organisms still dominated every biosphere on dry ground.

First flowering plants with seeds appeared in the Carboniferous, along with some really strange families like the Lepidodendron club moss, which can grow to heights of 100 feet, and the Sigillaria, which grows to a more modest 30 feet.

Almost all of the coal we use nowadays originated from plants that grew during the Carboniferous period in a huge strip of carbon-rich "coal swamps" that circled the equator and were subsequently compacted by pressure and thermal stress over millennia.

Cheers!

~GB