The Carboniferous Period, the building of coal beds and the invention of the egg

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Article 24: The Carboniferous Period answers the question “Which came first, the chicken or the egg?” definitely. This period is famous for its vast swamp forests, the primary source of the carbon for the coal beds we are burning

The Carboniferous Period of the Earth’s history spans 60 million years, from 360 to 300 million years ago.

The Carboniferous Period answers the question “Which came first, the chicken or the egg?” definitely. Long before birds evolve, tetrapods begin to lay eggs on land for the first time during this period, allowing them to break away from an amphibious lifestyle.

The beginning of the Carboniferous generally has a more uniform, tropical and humid climate than exists today. Average global temperatures in the Early Carboniferous Period are high, approximately 20 °C (68 °F).

Seasons if any are indistinct. Shallow, warm, marine waters often flood the continents.

Trilobites are fading as fish becomes more diverse.

The ancestors of conifers appear and dragonflies rule the skies.

Dragonfly to the size of a seagull

These insects, as well as millipedes, scorpions and spiders become important in the ecosystem.

Tetrapods are becoming more specialized and two new groups of animals evolve. The first are marine reptiles, including lizards and snakes. The second are the archosaurs, which will give rise to crocodiles, dinosaurs and birds.

Life reconstruction of the large Archosaur Prestosuchus, based on the skeleton cast on display at the American Museum of Natural History, Artwork by Nobu Tamura

This era is sometimes referred to as the Age of the Cockroaches, because roaches’ ancient ancestor, Archimylacris eggintoni, is found all across the globe during the Carboniferous.

Archimylacris eggintoni fossil in siderite

The Carboniferous Period is famous for its vast swamp forests. Such swamps produce the coal from which the term ‘Carboniferous’ or ‘carbon- bearing’ is derived. In the swamp forests flourish seedless plants such as lycopsids; they are the primary source of carbon for the coal beds (which can be up to 11 to 12 meters thick) that are characteristic of this period.

In addition to having the ideal conditions for the formation of coal, several major biological, geological and climatic events occur during this time.

Carboniferous forest
Carboniferous forest by Mary Parrish. Credit: Smithsonian Institution

Biologically, we see one of the greatest evolutionary innovations of the Carboniferous: the egg, which allows for the further exploitation of the land by certain tetrapods. It gives the ancestors of birds, mammals and reptiles the ability to lay their eggs on land without fear of desiccation.

The amniotic egg represents a critical divergence within the vertebrates, the ability to reproduce on dry land—free of the need to return to water for reproduction as required of the amphibians. From this point the amniotes spread around the globe, eventually to become the dominant land vertebrates.

Amniotic egg
Amniotic egg, from Greek ἀµνίον, “membrane surrounding the fetus”

Geologically, the Late Carboniferous collision of Laurasia (present-day Europe, Asia, and North America) into Gondwana (present-day Africa, South America, Antarctica, Australia, and India) produces the Appalachian Mountain belt of Eastern North America and the Hercynian Mountains in the United Kingdom. A further collision of Siberia and Eastern Europe creates the Ural Mountains of Russia.

As the continents move closer to form Pangea, there is a net decrease in coastline, which in turn affects the diversity of marine life in the shallow continental waters.

By the Late Carboniferous, the continents that make up modern North America and Europe have collided with the southern continents of Gondwana to form the western half of Pangea. Ice covers much of the southern hemisphere and vast coal swamps form along the equator.

Late Carboniferous

Climatic, we see two large ice sheets at the Southern Pole, locking up large amounts of water as ice. With so much water taken out of the water cycle, sea levels drop, leading to an increase in terrestrial habitat.

Thanks to the University of California, Berkeley, Museum of Paleontology, to Planet Earth online, to Christopher R. Scotese, and to the McGraw-Hill Companies

ShantiShanti is a regular contributor to Osho News
All essays of this series can be found in: At Home in the Universe
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