January 18, 2022

The Carboniferous period is one of the divisions of the geological age. It refers to the latter half of the Paleozoic, after the Devonian and before the Permian, which is approximately 359.2 million years ago to 299 million years ago. This period is separated by the millions of years of ice age, from the mass extinction at the end of the Devonian to the millions of years just before the Permian. The name comes from the fact that a lot of coal is produced from the strata of this era. Producing coal from this stratum is a proof that a very large forest was formed at that time. In North America, some researchers call the first half of the Carboniferous the Mississippian and the second half the Pennsylvanian. These are roughly divided into before and after 323 million years ago.


On land, fern plants developed and insects and amphibians flourished. During this period, amniotes adapted to land life emerged from amphibians, and eventually two large groups diverged. Sauropsida (a strain that leads to reptiles including birds) and synapsids (a strain that leads to mammals). Hylonomus is known as a reptile at that time. Insects with wings such as Paleodictioptera and Protophasma, the ancestor of cockroaches, have appeared for the first time. These are the first creatures to enter the sky in history. Since the Devonian period, arthropods have become huge, and giant erypterids (megarachne) with a total length of 45 cm, giant dragonflies (meganisoptera) with a wing length of 70 cm, and giant millipedes (arthropleura) with a total length of 2 m have been discovered. These arthropods are said to have become a valuable source of protein for amphibians and amniotes that have advanced to land. On the contrary, the trilobites declined and became only Proetus (or Proetas). At the end of the year, millions of years of ice ages arrived and many creatures died. Giant pterophyta prospered, and among them, Lepidodendron (Lepidodendron) was large, with a diameter of 2 m and a height of 38 m, and such giant pterophyta formed a large forest in the wetland. These giant trees, even standard ones, were 20 to 30 meters high. In the state of Illinois in the United States, there is a stratum that produces a large amount of carboniferous invertebrate fossils, and the fauna found here is especially called the Maison Creek fauna. The Maison Creek fauna is rich in brachiopods and sea lilies, and there are also strange forms of animals such as Trimonstram and GregariUM (Tullimonstrum). Synapsids (mammalian reptiles) such as Edaphosaurus prosper in the latter period.


It is said that many areas have a humid tropical climate all year round, with little seasonal change throughout the year. On the other hand, cooling was progressing in Antarctica, such as the formation of glaciers. In the Carboniferous, fungi capable of decomposing wood lignin have not evolved sufficiently, and a large amount of carbon has been fixed as coal due to the prosperity of forests, and it is said that the oxygen concentration in the atmosphere in the early Permian reached 35%. (21% in modern times). It is believed that this made it possible to increase the size of animals and plants. In addition, the prosperity of plants absorbed a large amount of carbon dioxide, and most of it was converted to coal without being reduced to the atmosphere, resulting in a drastic decrease in the concentration of carbon dioxide in the atmosphere. This is attributed to cooling, glacier development, and even the ice age. Synapsids (mammalian reptiles) flourished most in the Permian (299-251 million years ago), following the Carboniferous, and impaired breathing under high oxygen.

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