Science News

‘Ecosystem engineers’ responsible for first mass extinction

Some 540 million years ago, the first animals disappeared. It’s an event known as the end-Ediacaran extinction. New research suggests another group of early animals, known as Metazoans, were responsible.

Ediacarans were the first successful group of multicellular organisms. Though largely immobile, the marine creatures thrived across much of the planet. They took on a variety of shapes and sizes — some simple blobs, other segmented and complex. Many took on disk and tube shapes, others featured a quilted appearance.

After thriving for more than 60 million years, they quickly died out.

Until now, researchers hadn’t had recovered much evidence of an overlap between the reigns of Ediacarans and Metazoans. A wealth of new fossils in Namibia, however, prove that for a brief period prior to the Cambrian explosion, the two animal groups shared the planet.

As the end-Ediacaran extinction made clear, cohabitation wasn’t in the cards.

The new research suggests that before the Metazoans went on to spawn a variety of new animal types — vertebrates, mollusks, arthropods, annelids, sponges and jellyfish — during the Cambrian explosion, they made life untenable for the Ediacarans.

“These new species were ‘ecological engineers’ who changed the environment in ways that made it more and more difficult for the Ediacarans to survive,” Simon Darroch, assistant professor of Earth and environmental sciences at Vanderbilt University, said in a news release.

“We’ve discovered some new fossil sites that preserve both Ediacara biota and animal fossils, both animal burrows — ‘trace fossils’ — and the remains of animals themselves, sharing the same communities, which lets us speculate about how these two very different groups of organisms interacted,” Darroch explained.

Though there’s evidence that Metazoans preyed upon Ediacarans, reserachers say it was their transformation of the ecosystem that spelled the end for the earliest animals.

Researchers say the findings — detailed in the journal Palaeogeography, Palaeoclimatology, Palaeoecology — can serve as cautionary tale for modern times.

“There is a powerful analogy between the Earth’s first mass extinction and what is happening today,” Darroch said. “The end-Ediacaran extinction shows that the evolution of new behaviors can fundamentally change the entire planet, and today we humans are the most powerful ‘ecosystems engineers’ ever known.”