The Permian extinction, which occurred about 252 million years ago, left the Earth with a shattered biosphere and greatly reduced life. Yet the aftermath set the stage for a rapid resurgence in the Triassic period, an explosive rebound in both land and sea life that researchers from the United Kingdom and China have just documented.
In a study published recently in Frontiers in Earth Sciences, scientists show that predators grew more aggressive while prey adapted quickly to new survival strategies. On land, the ancestors of mammals and birds began to warm their blood and move more swiftly, reshaping entire ecosystems.
At the end of the Permian, a mass extinction wiped out nearly all life on Earth’s surface. The Triassic, spanning from 252 to 201 million years ago, followed as a period of remarkable life reassembly, both on land and in the oceans.
“Everything accelerated,” explains Professor Michael Benton of the University of Bristol’s School of Earth Sciences, lead author of the new study. “Today there is a clear split between birds and mammals on one side and reptiles on the other. Reptiles are cold-blooded, producing body heat less efficiently, and while they can generate heat, they face limitations that affect their endurance in cold conditions.”
“The same pattern unfolded in the oceans,” notes Feixiang Wu, from the Institute of Vertebrate Paleontology in Beijing. “After the end-Permian extinction, fish, lobsters, gastropods, and starfish adopted sharper hunting methods. They became faster, more agile, and stronger than their ancestors.”
Widespread changes in the fauna
Wu has examined remarkable fossil fish assemblages from China’s Triassic sediments, revealing many predators that employed earlier, more effective hunting strategies. Sharks and elongated fish resembled modern forms, with Saurichthys dominating many waters and ambushing prey with a long, toothy snout.
“Other Triassic Chinese fishes adapted to crack shells,” Wu adds. “Some large groups of fish and even certain reptiles became shell breakers with dense rows of teeth. We even find the world’s oldest flying fish, likely a response to new predators.”
Across the mainland, late Permian reptiles tended to be slow and relied on a sprawling stance with limbs splayed to the sides. Their walking pace could be slow, and their endurance was limited, a constraint that shifted as evolution pressed forward.
“Biologists have debated the origins of endothermy in birds and mammals,” Benton notes. “Evidence suggests that both groups trace their warm-blooded heritage to deep time, with bones and cellular chemistry pointing to earlier beginnings than once assumed. The ancestors likely evolved endothermy after the Permian mass extinction, during the early Triassic.”
The emergence of endothermy in birds and mammals during the early or middle Triassic is tied to other major shifts: upright limb posture and longer strides, enabling faster movement. This change appears to align with evolving heat management, allowing these groups to act quickly for longer periods.
“Analyses of this period reveal that the ancestors of birds and mammals developed isolation features, such as distinct feather-like structures, which supported rapid, energy-driven activity,” Benton says. “If confirmed by new fossil discoveries, these traits mark a pivotal transition as life rebuilt after the Permian catastrophe.”
Arms race
“Across land and sea, organisms were using more energy and moving faster,” Benton observes. “Biologists describe this as an arms race: as one side increases speed and warmth, the other side must respond. This dynamic shapes competition among plant eaters and among predators, and it drives predator-prey interactions as predators get faster and prey seek better escape routes.”
Wu adds, “The same pattern played out underwater. As predators gained speed, agility, and hunting smarts, prey developed defenses—thicker shells, spines, and swifter evasive tactics.”
“These ideas aren’t new,” Benton notes, “but we’re seeing them unfold simultaneously across the Triassic. This was a period of synchronized, rapid change.”
“Of course the mass extinctions were devastating for many life forms, but the clearing of ecosystems also opened multiple avenues for rebuilding the biosphere with greater momentum than before the crisis,” he concludes.
Reference: DOI: 10.3389/feart.2022.899541
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