Quirks & Quarks

'Weird wonders' in China: Half-billion year-old fossils from the dawn of animal life unearthed

A newly discovered fossil site in China is a treasure trove for paleontologists studying the Cambrian explosion, when life on Earth suddenly and massively expanded in diversity about 550 million years ago.

More than 2,000 pristine fossils have been found and half are animals completely new to science

Reconstruction of the Qingjiang fossil site during the Cambrian period approximately 518 million years ago. (Dongjing Fu)
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Originally published on March 23, 2019.

A newly discovered fossil site in China is a treasure trove for paleontologists studying the Cambrian explosion, when life on Earth suddenly and massively expanded in diversity about 550 million years ago.

More than 2,000 specimens were found at the 518 million-year-old site. More than half the species they represent are animals that scientists had never seen before.

"The Qingjiang biota is really one of the most exciting fossil discoveries in the last few decades," Allison Daley, a Canadian paleontologist at the University of Lausanne in Switzerland, told Quirks & Quarks host Bob McDonald.

She reviewed the research paper that announced the discovery, and says the site is hugely important because of the abundance and diversity of fossils that preserve exquisite details of these early animals.

An extremely well-preserved site

The fossils were found in a river bed near the junction of the Danshui River with Qingjiang River in Hubei, China.

Water flowing through the river bed cut down on the bedrock and exposed layers of rock that scientists were able to excavate.

Digging up a Qingjiang fossil on a bank of the Danshui River, near its junction with the Qingjiang River, Hubei Province, China. (Ao Sun )

"When the water level is really low, the scientists can get in and crack open the rocks to reveal the fossils," said Daley. "But it's a tricky place to work."

The thousands of fossils collected so far are in pristine condition, unaltered over the last half-billion years.

One of the most exciting aspects of the find were the soft tissues and soft-bodied organisms that were preserved. These kinds of tissues typically do not make it into the fossil record. Researchers found not just bones and shells, but skin, organs, and even impressions of the animals' brains. 

Undescribed leanchoiliid from the Qingjiang biota (Ao Sun )

"You can see the eyes, internal organs, the gut and sometimes even their last meal," said Daley. "The fossils are absolutely stunning in terms of abundance and the amount of detail."

The organisms likely lived and died in a shallow marine environment before they were transported into the deeper ocean environment where there were fewer animals and microbes to decompose them.

"The cold, dark, hypoxic environment means there was no chance for the soft tissues to decay," explained Daley. "They were rapidly buried in sand and sealed from outside factors."

Species completely new to science

During the period known as the Cambrian explosion, life on Earth evolved from small and simple, mostly single-celled organisms, to big and complicated animals.

Many of the fossils found during that period showed a wide diversity of strange looking animals — sometimes called the "weird wonders" of the Cambrian.

It may be the most important evolutionary transition in the history of life on Earth, and scientists are still trying to work out what caused it.

Undescribed jellyfish from the Qingjiang biota (Ao Sun)

A wide range of animals was found at Qingjiang site including the simplest sponges, jellyfish, sea anemones, worms, primitive fish and different kinds of arthropods.

More than half of the animal species were also completely new to science. Researchers were baffled by their strange forms and have struggled to classify them.

One of the more outrageous organisms had a body shaped like a bag with an internal gut and tentacles protruding from its mouth. Scientists are currently studying these new specimens to try and place them in the tree of life.

Significance of the finding

Daley believes this new site is hugely important in furthering our knowledge about the Cambrian period.

"Future work will help us better understand how these animals interacted with each other, how they diverged, what the Cambrian environment was like, and maybe even the causes of the Cambrian explosion," he said.

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