They had good reason. The fossils date from the late Permian period, an era of mass extinction so extreme that it is known as the “Great Dying.” During the extinction, 9 out of 10 species is thought to have died.

The event, triggered by climate change and fueled by volcanic eruptions, would have made it difficult for large predators such as Inostrancevia to find food. As a result, researchers write, the species probably migrated to a place where there was “an open niche for a top predator.”

But the gigantic creatures’ reign was probably short-lived. Inostrancevia soon went extinct, too, in an example of the era’s rapid transitions across ecosystems.

The swiftness of Inostrancevia’s rise and fall underscores the extreme flux of animals during the event, the researchers say in a news release. And they warn that Earth’s largest mass extinction has parallels today as the planet undergoes another mass extinction.

“It’s always good to get a better understanding of how mass extinction events affect ecosystems, especially because the Permian is basically a parallel on what we’re going through now,” said Pia Viglietti, a research scientist at the Field Museum in Chicago and one of the study’s co-authors, in a news release. “We don’t really have any modern analogs of what to expect with the mass extinction happening today, and the Permo-Triassic mass extinction event represents one of the best examples of what we could experience with our climate crisis and extinctions. I guess the only difference is, we know what to do and how to stop it from happening.”