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Fossils of an unusual saber-toothed predator that lived during Earth’s worst mass extinction event reveal just how precarious things were for animals during the Great Dying.
A chain of supervolcanoes erupted in Eurasia 250 million years ago at the end of the Permian period, expelling greenhouse gases and causing catastrophic climate change. The planet’s temperature rose and oxygen in the oceans and atmosphere decreased – and about 90% of life on Earth disappeared, paving the way for the dinosaurs to emerge and rule the planet until their extinction 66 million years ago.
But the Permian mass extinction event didn’t happen overnight. Instead, it spread over a million years ago, leading researchers to dub the event the “great dying.”
The fossil record acts like a time capsule, and the bones reveal the diverse animals that fought for survival as their environments changed around them. One of those creatures was the saber-toothed Inostrancevia, a mammalian ancestor the size of a leopard, with the skin of a rhinoceros or elephant, somewhat resembling a reptile.
Scientists first discovered fossils of two specimens in 2010 and 2011 in the Karoo Basin of South Africa. After years of preparing the fossils—cleaning them up, piecing them together like a puzzle and pinning them together using snapshots and drills—the researchers were finally able to study the creature in detail.
The large fossils, including skulls, ribs, vertebrae, and leg bones, surprised the team because they looked like they belonged to Inostrancevia, one of the earliest toothed predators on the planet, whose fossils had only been found in Russia. The researcher’s findings were published Monday in the journal Current Biology.
All large predators became extinct in the late Permian in southern Africa before the mass extinction at the end of the Permian. “We learned that this vacancy in the niche was occupied, for a brief period, by Inostrancevia,” study co-author Pia Viglietti, a research scientist at the Field Museum in Chicago, said in a statement. “The fossils themselves were completely unexpected.”
For the past 100 years, scientists have thought that the inturansifia lived only in the northern hemisphere, and a different group of predatory mammal ancestors lived in the southern hemisphere. Inostrancevia lived through a period of massive upheaval, managing to migrate 7,000 miles across the supercontinent Pangea and becoming a predator in a different environment before eventually becoming extinct.
“When things started to go wrong, in the early stages of what would become the worst mass extinction in Earth’s history, the southern group died out. The northern species, Inosrancevia , apparently moved to fill that gap.” As they say, nature abhors a vacuum — if there’s an open space in an ecosystem and the resources to support it, life will find a way. Unfortunately for Inostrancevia, things soon got so bad that they (and most other organisms) went extinct too.”
Studying the Karoo Basin helps scientists piece together what happened during the Permian mass extinction.
“The Karoo Basin holds the best record of life on Earth before and after the mass extinction,” Kammerer said. “Nowhere else has there been so many fossils from the relevant time period (tens of thousands of skulls and skeletons collected) or such an extensive continuous exposure of rocks across the extinction frontier.”
While the basin represents only what was happening in a part of the world at the time, the fossils reveal how the setting of Inostrancevia foreshadowed what was to come as essential roles within ecosystems shifted due to the disappearance of species. It was more complicated than when an asteroid wiped out the dinosaurs, giving rise to mammals.
Kammerer said the fossil record shows that about 251.9 million years ago, the dividing line between the Permian and Triassic periods, four different animal groups took their turns as major predators, became extinct and then replaced them. That’s a high turnover rate in two million years compared to the way animal groups function today.
“Currently, for example, the top predators in most terrestrial environments are carnivorous mammals (such as cats, dogs and bears), and this was the case about 25 million years ago,” he said. “What we see about the Permian extinction is the occupation of the roles of apex predators—the position at the top of the food chain—that changes very rapidly, over the course of two million years or less. This speaks to a biosphere that is fundamentally unstable.”
Kammerer said top predators are some of the most vulnerable groups when it comes to the threat of extinction because they are slower to reproduce and grow and require large areas to roam and hunt, such as wolves in Europe and tigers in Asia.
Fossils from Russia and South Africa tell part of the story of Inostrancevia, but researchers want to know what happened during that vast migration between the two regions. Other promising fossil sites in North Africa could fill in those knowledge gaps and reveal more information about how the animals lived.
“Protomammals are a curious group of organisms, not quite reptiles, but not yet mammals, and it can be hard to imagine how they actually functioned, which is why good fossils and detailed study of them is so important,” Kammerer said.
The researchers said that studying what happened during Earth’s greatest loss of biodiversity in millions of years could serve as a mirror to what is happening globally now because of the climate crisis.
“It’s always good to get a better understanding of how mass extinction events affected ecosystems, especially since the Permian is basically parallel to what we’re going through now,” Viglietti said.
“We don’t really have any recent analogues of what to expect with the mass extinction happening today, and the Permo-Triassic mass extinction event is one of the best examples of what we can have with the climate crisis and extinction,” she said. .
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