Global warming and climate change triggered a rapid evolution of reptiles nearly 60 million years ago.
Research has shown that climate-induced mass extinctions in the geological past can have dramatic effects on organismal evolution.
In the Permian-Triassic climatic crises (265 million years ago and 230 million years ago), climatic shifts caused by global warming led to a series of climatic shifts.
Two of the largest extinctions in life’s history occurred at the end of the Permian period. The first was 261 million years ago, and the second was 252 million years ago, with the latter resulting in the extinction of 86% of all animal species on earth.
It is important to note that the end-Permian extinctions are significant in their magnitude and mark the beginning of a new era in animal evolution while reptiles dominated on land.
On land, synapsids, the ancestors of mammals, dominated the vertebrate fauna during the Permian.
In the Triassic Period, following the Permian extinctions (252-200 million years ago), reptiles evolved rapidly, resulting in a huge variety of reptiles. The expansion of ecosystems contributed to the creation of modern ecosystems and many extinct ones as well.
According to most paleontologists, these rapid evolutions and diversifications were caused by the extinction of competitors, which allowed reptiles to take over the habitats and food resources that several synapsid groups dominated before they disappeared.
In a study published in Sciences Advances, the Harvard University Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology argue that reptiles began rapidly evolving and reproducing much earlier than the end of the Permian, following a series of climate changes that steadily increased global temperatures for nearly 60 million years.
According to the study, a growing temperature was intimately related to these periods of rapid reptile evolution. It was estimated that nearly all reptile groups had evolved much faster than they had ever before, said lead author postdoctoral fellow Tiago R Simões.
A lack of data has restricted previous studies on these changes in marine animals, focusing mainly on the responses of terrestrial vertebrates.
The study authors examined early amniotes in the early stages of their evolution, which are precursors to all modern mammals, reptiles, birds, and their closest extinct relatives. Reptiles and mammals split from each other at this time and evolved independently.
“Reptiles represent an ideal and rare terrestrial system to study this question as they have a relatively good fossil record and survived a series of climatic crises, including the ones leading up to the largest extinction in the history of complex life, the Permian-Triassic mass extinction,” said Simões.
Mammalian ancestors were more prevalent than reptiles during the Permian period. The number of species and morphological variety of reptiles underwent a major shift during the Triassic. As a result, most living reptile groups (crocodiles, lizards, turtles) were formed, as well as several groups that are now extinct.
Scientists collected more than 1,000 fossils belonging to 125 species of reptiles, synapsids, and their closest relatives from the Permian-Triassic extinction, some 140 million years ago.
They were able to determine when these species first evolved and how fast they evolved using state-of-the-art analytical techniques such as Bayesian evolutionary analysis.
To provide a broad overview of the animals’ major adaptations to climatic changes, researchers combined the new dataset with global temperature data covering several million years.
“Our results reveal that periods of fast climatic shifts and global warming are associated with exceptionally high rates of anatomical change in most groups of reptiles as they adapted to new environmental conditions,” said Professor Stephanie E. Pierce.
The diversification of reptile body plans did not occur as a result of the Permian-Triassic extinction event as previously believed but began tens of millions of years before that time. This process began at least 270 million years ago, the researcher concluded.
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