Animals grew back faster and smarter after mass extinction

The diversification of saurichthyiform fishes (“lizardfishes”) in the Middle Triassic of southern China (Eastern Paleo-Tethys), reflecting the establishment of a complex multilevel marine ecosystem (or marine fish communities) with intensive predator-prey interactions along food web chains. 1 credit

Paleontologists in the UK and China have shown that the natural world rebounded vigorously from the late Permian extinction event.

In a review published today in the journal Frontiers in Earth Sciences, scientists reveal that predators have become meaner and prey have quickly adapted to find new ways to survive. On land, the ancestors of mammals and birds became warm-blooded and could move faster.

At the end of the Permian period, 252 million years ago, there was a devastating mass extinction, when almost all life died out, and this was followed by one of the most extraordinary in the history of life. The Triassic period, 252 to 201 million years ago, marks a dramatic rebirth of life on land and in the oceans, and was a time of massive increases in energy levels.

“Everything was accelerating,” said Professor Michael Benton of the University of Bristol School of Earth Sciences, the lead author of the new study.

“Today, there is a huge difference between birds and mammals on the one hand, and reptiles on the other. Reptiles are cold-blooded, which means that they themselves do not generate much of body heat and, although they can bite fairly quickly, they have no stamina and they cannot live in the cold,” Prof Benton said.

“It’s the same in the oceans,” said Dr Feixiang Wu from the Institute of Vertebrate Palaeontology in Beijing. “After the mass extinction at the end of the Permian, fish, lobsters, gastropods and starfish showed new and unpleasant hunting styles. They were faster, sharper and stronger than their ancestors.”

Dr Wu has studied amazing new fossil fish assemblages from the Triassic of China, and these include many types of predators that show how new ways of hunting emerged earlier than previously thought. He found modern style sharks and the long fish Saurichthys, which was very common in the world and was an ambush hunter. This meter-long fish lurked in the murky shallow seas and shot forward to grab all kinds of prey in its toothy jaws.

“Other Triassic fishes from China were adapted to shell crushing,” Dr Wu said. “Several large groups of fish, and even some reptiles, became shell crushers, with large cobblestones of teeth. We even found the world’s oldest flying fish, and it was probably to escape new predators.”

On earth, too, there were revolutionary changes. Late Permian reptiles generally moved slowly and used a kind of sprawling posture, like modern lizards, where the limbs stick out to the side. When they walked they probably generally moved slowly and quickly, they could run or breathe, but not both at the same time. This limited their stamina.

“Biologists have long debated the origins of endothermy, or warm blood, in birds and mammals,” Prof Benton said. “We can trace their ancestry back to the Carboniferous, over 300 million years ago, and some researchers have recently suggested that they were already endothermic at the time. Others say they only became endothermic than in the Jurassic, say 170 million years ago. But all sorts of evidence from studying their bone cells, and even their bone chemistry, suggests that both groups became blood hot following the great mass extinction at the end of the Permian, at the beginning of the Triassic.

The origins of endothermy in Early to Middle Triassic birds and mammals are suggested by two other changes: their ancestors primarily straightened in posture at this time. By standing high on their limbs like modern dogs, horses, and birds, they could take longer strides. This probably goes hand in hand with some level of endothermy to allow them to move quickly and for longer periods of time.

Second, it now appears that the ancestors of Early and Middle Triassic birds and mammals had some form of insulation, hair in the mammalian line, feathers in the bird line. If true, and new fossil discoveries seem to confirm it, all the evidence points to major changes in these reptiles as the world rebuilds after the late Permian mass extinction.

“Overall, animals on land and in the oceans were accelerating, consuming more energy and moving faster,” Professor Benton said. “Biologists call this kind of process ‘arms races’, a reference to the Cold War. As one side speeds up and gets hotter, the other must too. This affects competition between herbivores or the competition between predators. It also refers to predator-prey relationships – if the predator gets faster, the prey also does it to escape.”

“It was the same underwater too,” Dr. Wu said. Some had thicker shells, or developed spines, or became faster themselves in order to help them escape.”

“These are not new ideas,” Benton said. “What’s new is that we’re now finding that they were apparently all happening around the same time, through the Triassic. This emphasizes some sort of positive aspect of mass extinctions. Mass extinctions were of course terrible news for all the victims, but the massive ecosystem cleanup in this case gave the biosphere a huge number of opportunities to rebuild, and it did so at an index of higher octane than before the crisis.”

The World’s Largest Mass Extinction Triggered the Hot-Blooded Shift

More information:
Michael J. Benton et al, Triassic Revolution, Frontiers in Earth Sciences (2022). DOI: 10.3389/fear.2022.899541

Provided by University of Bristol

Quote: Triassic Revolution: Animals grew back faster and smarter after mass extinction (June 20, 2022) Retrieved June 20, 2022 from grew-faster.html

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