Rapid ruler change in the death era

Rapid ruler change in the death era

Artist’s rendering of an Inostrancevia that has killed a dicynodont. © Matt Celeskey

Apex predators appear strong and powerful—but they’re actually delicate: They’ve always carried an increased risk of extinction, a paleontological study reflects. Newly discovered fossils of an astonishingly well-travelled large predator show that in the era surrounding the Permian-Triassic mass extinction, the position of the top predator in today’s South Africa changed rapidly and frequently.

The demise of the world of dinosaurs at the end of the Cretaceous is the best-known mass extinction in the history of the earth – but a worse one had happened much earlier: around 250 million years ago, nine out of ten species disappeared on average. This mass extinction marks the end of the Permian era and the beginning of the Triassic epoch. The trigger for the process is considered to be massive changes in environmental conditions due to strong volcanism on earth. Some fossil evidence already reflects how creatures struggled to survive in this turbulent era.

Now the researchers led by Christian Kammerer from the North Carolina Museum of Natural Sciences in Raleigh are reporting on an interesting animal from this difficult time. Kammerer found his remains at a site in South Africa’s Karoo Basin, which is already known for its Permian-age fossils. After some guesswork, the unusual skeletal parts turned out to be the remains of Inostrancevia. It is a representative of the gorgonopsia group, which was about the size of a tiger and had impressive saber teeth in its mouth. The astonishing aspect of the find, however, is that so far fossils of Inostrancevia were only known from Russia and it was assumed that the predator only occurred there.

Well-travelled saber-toothed raider

The new site is therefore particularly astonishing, because even in the Permian era, today’s Russia and South Africa were extremely far apart. As the Russian finds are older, the new discovery now suggests that Inostrancevia once traveled over 11,000 kilometers to migrate into the distant ecosystem. “The fossil finds were a real surprise,” says co-author Pia Viglietti of the Field Museum in Chicago. Because it seems unclear how these animals managed to traverse these enormous distances in the complex world of what was then the supercontinent Pangea.

However, the researchers see the main aspect of their study in further results that resulted from the find: “When we compared the ages of the other top predators that were already known from the region, namely the Rubidgeinae gorgonopsias, with the Inostrancevia fossils , we noticed something very interesting,” says Viglietti. It is therefore becoming apparent that the large native predators had apparently died out as a result of the fluctuating environmental conditions at the end of the Permian, leaving an ecological gap. Apparently, there were still prey animals in the region: fossil finds show that the herbivores were able to defy the environmental changes comparatively well. The researchers say that the Inostrancevia then apparently advanced into the gap left by the Rubidgeinae predators.

Fluctuation in the top position

But their reign was short-lived, as the scanty finds suggest. Apparently, Inostrancevia was soon replaced by other top predators: the researchers report that fossils of large predators from the group of Therocephalia can be found in younger strata in the region where it was found. However, even they were probably not able to cope with the environmental changes of the era for long. At the end of the turbulent period, the Proterosuchidae took over the role of the top predators in the region. “We have shown that the change in animal groups that acted as apex predators occurred four times in less than two million years during the Permian-Triassic mass extinction event, which is unprecedented in the history of life on land. This underscores how intense this crisis was,” says Kammerer.

The fact that the top predators were hit particularly hard back then fits in with developments that are also becoming apparent today, the scientists emphasize in conclusion: “Top predators usually have a high risk of extinction and are among the first species to be killed due to human activities such as hunting or the destruction of habitats,” says Kammerer. “The results seem to reflect that earlier apex predators were similarly vulnerable and were among the species that were first in line for mass extinctions,” he said. His colleague Viglietti says: “It’s always good to get a better understanding of how mass extinction events can affect ecosystems. The Permian can be interpreted as a parallel to what we are experiencing today,” says the scientist.

Source: Field Museum, Article: Current Biology, doi: 10.1016/j.cub.2023.04.007

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