Researchers have finally figured out what happened to a group of marine animals that went extinct on the ancient supercontinent Gondwana, and the finger points squarely to climate change.

The Malvinochosan biota (an ancient group of aquatic animals) appeared to have disappeared from Gondwana within 5 million years due to the gradual decline in sea level, according to a new study published Oct. 13 in the journal Earth-Science. Comments found. And the climate change that wiped out this group of animals has disturbing parallels with changes occurring today.

Cameron Penn-Clark, the study’s lead author and an evolutionary scientist at the University of the Witwatersrand in Johannesburg, said in a statement that the reason for their disappearance “has remained a mystery for almost two centuries until now.” “This is a 390 million year old murder mystery.”

At the time of extinction, the region near the South Pole was home to Gondwana, which included modern-day Africa, South America, Australia, Antarctica, the Indian subcontinent, and the Arabian Peninsula. Gondwana was formed by the break-up of the supercontinent Pangea about 600 million years ago and began to break up about 180 million years ago.

Gondwana was home to a wide variety of plants and animals. But some of its least understood inhabitants were the Malvinokhosan biota. This group, which lived in the waters covering what is now southern Africa, included mainly trilobites and bivalve brachiopods, but also some molluscs and echinoderms. But they all mysteriously disappeared between 390 and 385 million years ago.

To understand this unknown case, the team reanalyzed hundreds of fossils from the Malvinoxhosan biota, paying particular attention to the location, depth and geological characteristics of the rocks in which each fossil was found. This allowed them to break it down into layers, putting together a timeline of what happened to the area, like “separating the layers of a cake,” according to the description.

The team found seven to eight basic fossil layers of the Malvinokhosan biota. With each new layer added to the “pie” the number and diversity of fossils decreased.

After comparing the fossil layers with local sea level data, the researchers realized that each layer corresponded to a slight drop in sea level, making it a “sure weapon” for these extinction events, Penn-Clark said. This decline did not dry out the oceans where these animals lived, but it probably triggered climate changes to which the creatures could not adapt.

Researchers believe that the Malvinokhosan biota evolved to survive in colder waters. But falling sea levels have disrupted ocean currents known as “circumpolar thermal barriers” around the South Pole, allowing warmer water from the equator to mix with cooler southern waters. As a result, the Malvinochosan biota “was replaced by more generalist marine species that were well adapted to warmer waters,” Penn-Clark said.

The disappearance of the Malvinokhosan biota likely “led to the complete collapse” of the ecosystem around the South Pole. Biodiversity has still not fully recovered to these historic levels, the researchers write. The team also believes that this historic extinction mirrors what is happening in modern polar ecosystems as a result of human-caused climate change.

“This research is important as we look at the biodiversity crisis we face today,” said Penn-Clark. “This demonstrates the sensitivity of polar environments and ecosystems to changes in sea level and temperature,” he added. “Any changes that occur are unfortunately permanent.” Source