During the end of the Permian period and beginning of the Triassic, reptiles had one heck of a come out party.
Their rate of evolution and diversity exploded, leading to a variety of abilities, body plans, and traits, and helping to establish both their extinct lineages and those that still exist today as one of the most successful and diverse animal groups in the world. Their competitors were wiped out by two of the biggest mass extinction events in the history of the planet.
The Harvard-led study reconstructed how the bodies of ancient reptiles changed and compared it against millions of years of climate change in order to rewrite the explanation.
Climate change was the cause of the rise in global temperatures that led to the mass extinctions of early reptiles.
"We are suggesting that we have two major factors at play, not just this open ecological opportunity that has been thought by several scientists, but also something that nobody had previously come up with, which is that climate change directly triggered the adaptive response of reptiles to help build this vast array of animals
Simes said that "rising global temperatures triggered all these different morphological experiments, some that worked well and survived for millions of years up to this day, and some that vanished a few million years later."
In the paper, which was published Friday in Science Advances, the researchers lay out the vast changes that took place in many reptile groups, including the forerunners of crocodiles and dinosaurs.
As temperatures continue to rise, the study shows how a large group of organisms evolve. The rate of carbon dioxide released into the atmosphere is nine times what it was when the mass extinction began.
Changes in global temperature can have dramatic and varying impacts on the environment. The extinction of many animals, including many of the ancestors of mammals, was caused by rising temperatures during the Permian-Triassic, but also sparked the evolution of other animals.
The study involved close to eight years of data collection and took a heavy dose of camerawork,CT scanning, and loads of passport stamps as Simes traveled to more than 20 countries and more than 50 different museums to take scans and snapshots of more than 1000 reptilian fossils
The researchers used state-of-the-art statistical methods to create a diagram called an evolutionary time tree. Time trees show how early reptiles were related to each other and how quickly they evolved. The data from millions of years ago was combined with it.
Diversification of reptile body plans began about 30 million years before the extinction of theTriassic. The extinction events helped put them in a good position.
Rises in global temperatures, which began at about 270 million years ago and lasted until at least 480 million years ago, were followed by rapid body changes in most reptile lineages. Some of the larger cold-blooded animals evolved to be smaller so they could cool down more easily, while others evolved to live in water. One of the strangest forms of reptile that would become extinct was a giant, long-necked marine reptile that was thought to be the Loch Ness monster. The ancestors of turtles and crocodiles are included.
The first lizards and tuataras were smaller than the larger reptiles. The rising temperatures slowed down the evolutionary rate. The researchers believe it was because the small-bodied reptiles were already better adapted to the rising heat since they could more easily release heat from their bodies.
The impact of environmental catastrophes on the evolution of organisms with abundant modern diversity is being investigated by the researchers.
More information: Tiago R. Simões, Successive climate crises in the deep past drove the early evolution and radiation of reptiles, Science Advances (2022). DOI: 10.1126/sciadv.abq1898. www.science.org/doi/10.1126/sciadv.abq1898 Journal information: Science Advances
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