The Carboniferous rainforest collapse had a significant influence on vertebrate evolution

Artist's concept of Carboniferous rainforest (Image courtesy Mark Ryan. All rights reserved)
Artist’s concept of Carboniferous rainforest (Image courtesy Mark Ryan. All rights reserved)

An article published in the journal “Proceedings of the Royal Society B” describes a research on the changes that occurred during the Carboniferous rainforest collapse. According to a team of scientists led by the British University of Birmingham, a climate change that occurred about 307 million years ago caused a drought that led to the extinction of some groups of tetrapods, the first vertebrates that lived on the mainland, favoring at the same time other groups.

During the Carboniferous and Permian periods, between 358 and 272 million years ago, Europe and North America made a single land mass at the equator. The hot-humid climate allowed the lush growth of a rainforest that covered that vast area and there early tetrapods also found a favorable environment to develop and diversify into many different species.

According to various estimates there was a continuity in that diversification in the course of Carboniferous and Permian. The fragmentation of the habitats that followed the rainforest collapse increased the endemism, which is the presence of certain animal and plant species exclusively in a certain territory. According to this new research’s authors, those estimates suffered from insufficient samples and there’s a need to reassess the consequences of that collapse occurred about 307 million years ago.

The researchers used the tools of biogeography, which in very simple words studies the distribution in space and time of living organisms. A new set of information was created thanks to the Paleobiology Database, an online resource specific for fossil organisms. The application of advanced statistical methods allowed to estimate the changes in tetrapods’ biogeography and diversity.

The results obtained from the analysis of the data gathered indicate that there was a decrease in tetrapod diversity after the rainforest collapse and the beginning of drier weather conditions. That’s because amphibian tetrapods needed wet environments so they were struck by rainforest reduction.

However, the analysis also showed that the tetrapod species that survived that collapse started expanding into new habitats, migrating to places far from the equator. Among these species there were the early amniotes, in which an embryonic development takes place so that they’re born not as larvae but rather having the same physical characteristics as the adults.

Amniotic tetrapods include reptiles, dinosaurs, birds and mammals. The Carboniferous rainforest collapse is not considered among the great mass extinctions, yet this new research suggests that it had a crucial influence on the evolution of mainland vertebrates. The species that survived managed to adapt to very different environments, even migrating to far away places, a success that can be seen even today, 300 million years later.

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