Of all the animals facing a major mass extinction event 252 million years ago, it is perhaps appropriate that frog-like creatures were able to bounce back.
The amphibious nature of proto-frogs called temnospondyls provided a food-seeking edge, according to a study in the journal Royal Society Open Science.
Surviving a Mass-Extinction Event
Conditions during the Early Triassic were harsh. Repeated volcanic activity triggered long periods of global warming, aridification, reductions in atmospheric oxygen, acid rain, and widespread wildfires. The tropics became devoid of animal life, and as much as 90 percent of animal species went extinct.
So how did the remaining 10 percent survive? While those conditions rendered much of the land a not-very-happy hunting ground, the temnospondyls’ generalist approach served them well. They found plenty of food in fresh water habitats, while their land-based competition starved.
“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,” Aamir Mehmood, a Bristol University biologist and co-author of the study, said in a press release.
Read More: The Late Permian Mass Extinction Explained
Evolutionary Adaptations
To study how the temnospondyls adapted and survived over the next five million years, researchers examined about 100 of their fossils from throughout that period. They measured the fossils’ body size, skull shape, and teeth type, looking for adaptive advantages.
“Much to our surprise, we found that they did not change much through the crisis,” Armin Elsler, a University of Bristol biologist and an author of the study, said in the release. “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.”
Crossing Dead Zones
Despite the intense heart, the temnospondyls were able to expand throughout the Earth, with fossils appearing in South Africa and Australia in the south, as well as North America, Europe, and Russia in the north. The authors theorize that they could cross what they call the tropical “dead zones” during brief cooling periods.
While the lack of evolution kept the temnospondyls alive during the cataclysmic climate during the Triassic’s first five million years, their inability to adapt ultimately did them in.
“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,” Mehmood added in the press release. “But when the ancestors of dinosaurs and of mammals began to diversify in the Middle Triassic, the temnospondyls began their long decline.”
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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
