Evolution and Diversity of Reptiles Driven by 60 Million Years of Climate Change

Just over 250 million years ago, at the conclusion of the Permian and the beginning of the Triassic, reptiles enjoyed a huge coming-out party.

Their rates of evolution and diversity started to soar, resulting in an absurdly wide range of skills, body types, and features. This contributed to their being recognized as one of the most prosperous and diverse animal groupings the world has ever seen, including both their extinct lineages and those that still live today. For a long time, scientists believed that this bloom was the result of reptile competitors being wiped out by two of the most devastating mass extinctions in earth history. Around 261 and 252 million years ago, these things happened.

A recent study conducted by Harvard that rebuilt how the bodies of prehistoric reptiles developed and matched it to the results of millions of years of climate change has altered this theory.

The research of Harvard paleontologist Stephanie Pierce demonstrates that early reptiles began to diversify and undergo morphological development years before these huge extinction events. Furthermore, they were directly influenced by the rising global temperatures brought on by climate change, which was what initially sparked the mass extinction events.

Tiago R. Simes, the study's lead author and a postdoc, said, "We are suggesting that we have two major factors at play — not just this open ecological opportunity that has always been thought by several scientists, but also something that nobody had previously come up with, which is that climate change actually directly triggered the adaptive response of reptiles to help build this vast array of new body plans and the explosion of groups that we see in the Triassic."

According to Simes, "essentially, [increasing global temperatures] launched all these diverse morphological experiments, some of which worked really well and have endured for millions of years, and others of which have pretty well perished a few million years later."

The study, which was just published in the journal Science Advances, details the extensive anatomical changes that occurred in many reptile groups, including the ancestors of dinosaurs and crocodiles, as a direct result of significant climate shifts that occurred between 260 and 230 million years ago.                                 

The study offers a detailed examination of how a broad group of creatures evolve as a result of climate change, which is particularly important at this time given the ongoing increase in global temperatures. In fact, the amount of carbon dioxide released into the atmosphere today is around nine times greater than it was during the Permian-Triassic mass extinction, which occurred 252 million years ago and is considered to be the largest climate change-related mass extinction in history.

According to Stephanie E. Pierce, "significant changes in the global temperature can have substantial and varied effects on biodiversity." She is the curator of vertebrate paleontology at the Museum of Comparative Zoology as well as the Thomas D. Cabot Associate Professor of Organismic and Evolutionary Biology. Here, we demonstrate how the Permian-Triassic era's rising temperatures caused the extinction of a number of organisms, including a large number of mammal progenitors, but also encouraged the rapid evolution of others, particularly the reptiles that would later come to dominate the Triassic period.

Simes traveled to more than 20 nations and more than 50 different institutions to take scans and photographs of more than 1,000 reptile fossils for the project, which required roughly eight years of data collecting.

With all the data, the researchers produced a sizable dataset that was examined using cutting-edge statistical techniques to generate a picture known as an evolutionary time tree. Time trees show the relationships between early reptiles, the beginning of their lineages, and the rate of evolution. They then merged it with prehistoric global temperature records.

It is clear that these alterations weren't brought about by the Permian-Triassic extinction as previously believed because reptile body plans started to diversify roughly 30 million years before the disaster. Although they were kicked into high speed by the extinction catastrophes.

The data also demonstrated that most reptile lineages underwent fast bodily modifications after increases in global temperatures, which started at around 270 million years ago and persisted until at least 240 million years ago. For instance, some of the larger cold-blooded animals have evolved to grow smaller in order to cool off more quickly, while others have developed to dwell in water in order to achieve the same goal. A tiny chameleon-like creature with a bird-like skull and beak, a large, long-necked sea reptile that was previously believed to be the Loch Ness monster, and a gliding reptile that looked like a gecko with wings were all part of the later group of extinct reptiles. It also includes the ancestors of living reptiles like turtles and crocodiles today.

The ancestors of the first lizards and tuataras were smaller reptiles, who followed a distinct evolutionary trajectory than their larger reptile cousins. The increasing temperatures caused their evolutionary rates to slow and stabilize. The researchers hypothesize that this is because smaller-bodied reptiles were already more acclimated to the increasing heat because they were able to dissipate heat from their bodies more readily than larger reptiles as temperatures rose rapidly all over Earth.

According to the researchers, they intend to build on this work by examining how environmental catastrophes have affected the evolution of species with a wealth of contemporary variety, such as the main lizard and snake subgroups.

See Researchers Find That Global Warming Created the Age of Reptiles for more information on this study.

By HARVARD UNIVERSITY