Seventh Mass Extinction? Severe and Deadly Event 260 Million Years Ago Discovered by Scientists

Scientists believe that the Earth is currently going through its sixth mass extinction event. However, there may have been another such incident in our planet's past that researchers had overlooked until now, according to a study published in the journal Historical Biology.

In light of these findings, the authors of the study—Michael Rampino from New York University and Shu-Zhong Shen from Nanjing University in China—suggest that the current loss in biodiversity should perhaps be called the "seventh" mass extinction.

The scientists say that the event in question—known as the end-Guadalupian biodiversity crisis—took place around 260 million years ago and its severity has previously been underestimated.

"The end-Guadalupian crisis was considered by many to be only a minor extinction event," Rampino told Newsweek. "The latest data, however, suggest that around 60 percent of marine species became extinct, and possibly an equal number of non-marine species. So the end-Guadalupian crisis was apparently a major mass extinction."

"The end-Guadalupian event was somewhat selective," he continued. "Coral reef environments were very hard hit. Ocean bottom communities, and swimming organisms such as the coiled ammonoids, were hard hit. On land, many reptile species disappeared. So the event was severe, both in the number of species going extinct and in the major ecological damage."

This event affected life on land and at sea, occurring around the same time as a huge volcanic eruption that produced the Emeishan Traps—a vast rocky formation that lies in what is now southwestern China.This eruption was likely one of the main drivers of this mass extinction event, according to the researchers.

"Massive eruptions such as this one release large amounts of greenhouse gases, specifically carbon dioxide and methane, that cause severe global warming, with warm, oxygen-poor oceans that are not conducive to marine life," Rampino said in a statement.

"In terms of both losses in the number of species and overall ecological damage, the end-Guadalupian event now ranks as a major mass extinction, similar to the other five," the authors wrote in the study.

Previously, scientists generally agreed that there were five mass extinction events in the geological record. Each of these wiped out huge numbers of species and marked the ends of their respective geological eras.

In order, these extinctions are known as the Ordovician (443 million years ago), the Late Devonian (372 million years ago), the Permian (252 million years ago), the Triassic (201 million years ago) and the Cretaceous (66 million years ago).

"In the last few years it has become apparent that the five previously recognized major mass extinctions were correlated with large flood-basalt eruptions, which released massive amounts of carbon dioxide and methane, producing lethal greenhouse climate warming, ocean acidification, and warm oceans depleted in dissolved oxygen, not conducive to marine life," Rampino said. "In the Guadalupian event, we have another mass extinction correlated with the age of another flood lava eruption."

"The implications are that major mass extinctions are more common than previously thought, and the Guadalupian event represents another mass extinction that is correlated with a major flood basalt eruption—the Emeishan Basalts in China."

The end-Cretaceous extinction—probably the most well-known of them all, is thought to have wiped out around three-quarters of plant and animal species on Earth—including all non-avian dinosaurs. The expert consensus is that it was caused by the impact of a huge asteroid or comet, which devastated the global environment.

The modern, ongoing loss of biodiversity has previously been described as the Earth's six mass extinction crisis. Species are disappearing at a worryingly fast rate. A landmark U.N. report recently warned that one million species around the world are at risk of disappearing due to human pressures and climate change.

"It is crucial that we know the number of severe mass extinctions and their timing in order to investigate their causes," Rampino, said in a statement. "Notably, all six major mass extinctions are correlated with devastating environmental upheavals—specifically, massive flood-basalt eruptions, each covering more than a million square kilometers with thick lava flows."

This article was updated to include additional comments from Michael Rampino.

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