Global warming has given us hundreds of millions of years of reptile dominance

If your loyalty is to mammals versus rampaging reptiles, you have one more reason to worry about global warming. The reason reptiles, including dinosaurs, took precedence over mammals and our ancestors has been attributed by new research to a long period of warming, not a pair of mass extinctions as previously thought. .

The beginning of the Triassic era saw a rapid pace of reptile evolution. Creatures such as archosaurs came to dominate the lands, only to be repelled by their reptile companions the dinosaurs. These events followed the largest mass extinction event in Earth’s history, the Permian-Triassic Extinction Event (PTE), also known as the Great Dying, when an estimated 86% of animals disappeared. .

Mass extinctions create great opportunities for survivors, and paleontologists have attributed the reptile takeover to the space created by the PTE, plus a smaller calamity nine million years ago. Of course, the first crocodiles, lizards and turtles all appeared in the Triassic, as well as the major groups of reptiles that are now extinct. However, an article in Scientists progress presents evidence that the roots of reptile ascension lie earlier, in late Permian temperature fluctuations.

Mammals have only been the dominant class on Earth since the asteroid cleared the way for us 66 million years ago. However, our ancestors, the synapsids, had their own turn during the Permian era. It makes intuitive sense that the Age of Reptiles began with an extinction event and ends with an event. The causes of PTE are much debated, but there is no doubt that synapsids have been a major casualty.

However, the paper notes that although the greatest rate of reptile diversification occurred after the extinctions, there was already an increase in new reptile species before that. Also, the timing of their appearance was not random.

“We found that these periods of rapid evolution in reptiles were intimately linked to rising temperatures. Some groups changed very quickly and others less rapidly, but almost all reptiles evolved much faster than they expected. ‘had never done before,’ said the lead author. Dr Tiago R Simoes from Harvard University in a statement.

The peak of new reptile species came in the early Triassic, but the recovery had started earlier and coincided with temperature fluctuations and accelerated between the two major extinctions: Image credit: Tiago Simoes

Co-author Professor Stephanie Pierce noted that it was not just the number of new species that coincided with warming episodes, but the diversity of body shapes and ecological niches filled. “This process began long before the Permian-Triassic extinction event, at least 270 million years ago, indicating that the diversification of reptile body plans was not triggered by the PT extinction event as is believed. previously thought, but actually began tens of millions of years before that.” Pierce said.

Unable to regulate their own body temperature, reptiles are much better adapted to hot than cold climates, although at least some dinosaurs managed to warm their blood enough to occupy the poles. However, the authors think it’s not as simple as more heat equals more reptiles.

“Small-sized reptiles can better exchange heat with their environment”, Simões said. “Early lizards and tuataras were much smaller than other reptile groups, not so different from their modern relatives, and so they were better adapted to cope with drastic temperature changes. The much larger ancestors of crocodiles, turtles and dinosaurs could not lose heat so easily and had to quickly change bodies to adapt to new environmental conditions.

Consequently, the relatively rapid fluctuations of the Permian favored small reptiles; the larger ones benefited from the constant heat of the early Triassic. During the warmest parts of the Permian, the tropics became so hot that reptiles could not grow very large there without moving into the oceans.

The authors believe that this early diversification of reptiles has been overlooked because land records are sparse. Marine fossils are more abundant, making them the focus of mass extinction studies. The article used the largest database of appearances and extinctions of early reptiles, synapsids and predecessors ever created to solve this problem.

Comments are closed.