After another mass extinction event closing the Devonian period, it is time to move to the next-to-lat period of the Paleozoic era. The Carboniferous period is marked with two new major ecosystems: rainforests and fresh-waters.
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The Freshwater Life
After eons of living in the seas, some organisms moved and adapted to fresh-waters. Many invertebrates, including the ancestors of shrimps, and some colorful mollusks, found freshwater slightly easier to live in. After them came vertebrate predators, like eurypterids. They were genetically closer to modern amphibians than fish. However, conditions in fresh-waters were not always stable, frequently marine waters returned to rivers or lakes. As a result, brackish- slightly salty waters we can find today in lagoons-appeared. Some organisms, including Lingula living on Earth probably since Cambrian, adapted to those ‘marine beds.
The Rainforests
Another major change of the Carboniferous took place on land. Land organisms started forming more complex ecological relations than ever before. As a result of the evergoing pray-predator war, species developed rapidly creating many chains, collaborating, and eliminating each other. Therefore, more and more species became dependant on one another, creating ecosystems full of life. Those ecosystems were first-ever rainforests on Earth. The biggest plants included giant ferns and massive cousins of modern mosses. Animals also developed, amphibians became very diverse and common during the Carboniferous period. The largest of them was almost 2 meters long. The biggest change in animals was the new adaptation to life without water around. Amniotes- animals in which embryos form several extensive membranes- can survive and lay eggs without water. The first species of this group were reptiles. Despite them also birds and mammals are amniotes, so humans probably evolved from reptile ancestors.
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Changes on Earth
As in rainforests, during most of the period, there were no seasons. The temperature was about 20 degrees Celcius, creating hospitable conditions for life. Sometime in the end, they suddenly dropped to 12 degrees. This climate change probably caused an extinction event. Part of Gondwana was covered with ice because of dropping temperature. In the early stage, sea levels rose, however, they dropped in the middle. The Pangea came together, which caused a huge mountain formation. Two major oceans existed during the period, three minor ones were eventually closed by continental movement.
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The End of the Carboniferous Period
Both the beginning and the end of the period come with extinction. Firstly, Romer’s gap lasted through the first 15 million years. The lack of animal fossils from that time suggests an ecological collapse. It was a minor situation, so life found its way back and blossomed for the rest of the period. Well, almost. The end of the period comes with the Carboniferous Rainforest Collapse (CRC). Due to the sudden temperature drop and sudden lack of water, organisms used to warm conditions went extinct. Some others could not survive without them, many were also extinct. Rainforests had to shrink in to little ecosystems surrounded by dry places. Amphibians also did very poorly, many could not adapt to new conditions. However, some developed hard-shelled eggs that did not lose water.
Carboniferous Period Evidence
The lack of evidence can also be a piece of evidence. As for Romer’s gap, ’empty’ 15 million years suggest extinction at that time. Later on, we can find many fossilized plants, both on land and in the water. The number of land plant fossils, as well as their diversity, suggests that rainforest developed. Modern coal beds are also the remains of those first tropical forests. Other important pieces include preserved eggshells and other pieces of evidence suggesting the appearance of amniotes. There is, for example, an ancestor of lizards- cotylosaurs. Many animal fossils appear also in oceans and freshwaters. There are also quite many fossils of sharks, which had a great time developing due to many new niches. For sure, evidence from that period is very diverse and shows how life developed in all kinds of places.
Fossil of cotylosaurus
Image Courtesy: Wikipedia
Read the previous in the series: The Devonian Period (The Era of the Fish)
Author’s Message
I hope that the article helped you learn about first rainforests and other Carboniferous phenomenons. If you enjoyed it, please share it with your family and friends. In the next article, we will talk about the lat period of the Paleozoic era. We will also conclude the first era of Phanerozoic before moving on to the next one. If you have any questions, please contact me. You can find my email address in the ‘Our Team’ section of the page.
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