Primitive amphibians called temnospondyls survived the aftermath of the end-Permian mass extinction, which occurred about 252 million years ago, by feeding on freshwater prey that evaded terrestrial predators, according to a new study from the University of Bristol.
Life reconstruction of the temnospondyl species Mastodonsaurus. Image credit: Mark P. Witton, https://www.markwitton.co.uk.
The end-Permian mass extinction was the most severe biotic crisis in the past 540 million years, eliminating more than 90% of marine and 75% of terrestrial species.
“One of the great mysteries has been the survival and flourishing of a major group of amphibians called the temnospondyls,” said Dr. Aamir Mehmood, a researcher at the University of Bristol.
“These were predatory animals that fed on fishes and other prey, but were primarily linked to the water, just like modern amphibians such as frogs and salamanders.”
“We know that climates then were hot, and especially so after the extinction event. How could these water-loving animals have been so successful?”
The Early Triassic epoch was a time of repeated volcanic activity leading to long phases of global warming, aridification, reductions in atmospheric oxygen, acid rain and widespread wildfires, creating conditions so hostile that the tropics became devoid of animal life.
This ‘tropical dead zone’ drastically impacted the distributions of both marine and terrestrial organisms.
“We collected data on 100 temnospondyls that lived throughout the Triassic and wanted to look at how their ecologies changed,” said Dr. Suresh Singh, also from the University of Bristol.
“We measured their body sizes and features of the skulls and teeth that tell us about function.”
“Much to our surprise, we found that they did not change much through the crisis,” said University of Bristol’s Dr. Armin Elsler.
“The temnospondyls showed the same range of body sizes as in the Permian, some of them small and feeding on insects, and others larger.”
“These larger forms included long-snouted animals that trapped fishes and broad-snouted generalist feeders.”
“What was unusual though was how their diversity of body sizes and functional variety expanded about 5 million years after the crisis and then dropped back.”
Due to the intense global warming of the first five million years of the Triassic, there is evidence that life on land and in the sea moved away from the tropics to avoid the heat.
“Our work shows that the temnospondyls, unexpectedly, were able to cross the tropical dead zone,” said University of Bristol’s Professor Mike Benton.
“Fossils are known from South Africa and Australia in the south, as well as North America, Europe and Siberia in the north.”
“The temnospondyls must have been able to criss-cross the tropical zone during cooler episodes.”
“Their burst of success in the Early Triassic was not followed up,” Dr. Aamir said.
“They coped with the hot conditions probably by having a low requirement for food, by being able to eat most prey animals, and by hiding in sparse water bodies.”
“But when the ancestors of dinosaurs and of mammals began to diversify in the Middle Triassic, the temnospondyls began their long decline.”
A paper on the findings will be published in the journal Royal Society Open Science.
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Aamir Mehmood et al. 2025. The ecology and geography of temnospondyl recovery after the Permian – Triassic mass extinction. Royal Society Open Science, in press; doi: 10.1098/rsos.241200
