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Sea worm that lived more than half a billion years ago unearthed in China

"Detailed fossils of this type of worm are extremely rare."

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Reconstruction of the sea worm from 515 million years ago. (Durham University via SWNS)

By Mark Waghorn via SWNS

A strange sea worm that lived more than half a billion years ago has been unearthed in China.

The bizarre creepy-crawly was just half-an-inch long, but scientists said it had a complex structure - similar to its descendants today.

Bundles of spiky bristles emerged from its fleshy body, researchers discovered.

It was identified from 15 exceptionally preserved fossils dug up from rocks that lay below a shallow lagoon during the Cambrian explosion.

This was when major groups of animals that now make up life on Earth first appeared.

Remarkably, remains included evidence of the creatures' guts and kidneys, scientists said.

Named Iotuba chengjiangensis, it belongs to the family of segmented worms called annelids - and dates back 515 million years.

The discovery shows they diversified into different lineages some 200 million years earlier than previously thought - and were part of the 'evolutionary leap' in evolution.

Iotuba was found at a site in Kunming, eastern Yunnan Province. (Durham University via SWNS)

Dr. Martin Smith, of Durham University and a co-author of the study, said: "We know the main animal lines we see today emerged during the Cambrian explosion.

"But we always thought annelid worms were late to the party, and their major subgroups didn't begin to diversify until nearly 200 million years later.

"But the amazingly preserved fossils we have studied and the structure of these amazing little creatures challenge this picture and show that annelid worms – including Iotuba chengjiangensis – seemed to follow the pattern of events initiated by the Cambrian explosion.

"Detailed fossils of this type of worm are extremely rare, so it was great to be able to study the fossilized record of this tiny animal in such detail.

"It turns out they weren’t late to the party at all, they were just hiding in a side room."

Iotuba was a cage worm able to move its head in and out of a casing made of bristly spines.

This makes the worm a close relative of families of annelid sea worms such as Flabelligeridae and Acrocirridae.

Dr. Smith added: "These families are like the top rungs on an evolutionary ladder.

"For these groups to have appeared so early in the day, there must have been a dramatic unseen origin of modern annelid diversity in the heat of the Cambrian explosion.

"It turns out that many of the annelids we know and love today may have begun to evolve much sooner than we think."

Iotuba was found at a site in Kunming, eastern Yunnan Province.

Oxygen-poor conditions limit the presence of bacteria that normally degrade soft tissues in fossils, scientists said.

The prehistoric sea worm was half an inch long and bundles of spiky bristles emerged from its fleshy body. (Durham University via SWNS)

Dr. Zhifei Zhang, of Northwest University, Xi'an and the lead author of the study, said: "Annelids are one of the largest and most successful phyla of animals that are flourishing in both terrestrial and marine ecosystems with the most diversified living lineage, Polychaeta, living in sea.

"The most well-known are, for example, earthworms, leeches and clam worms. There are also at least 20,000 species and 80 families of polychaete in the modern sea.

"However, their earliest geological records of fossils in Cambrian deposits are quite rare.

"Is this because the delicate worms didn’t exist, or simply didn't preserve? Our research gives the first insightful answer - biodiversification of the segmented worms occurs much earlier than thought before."

Life would vanish pretty quickly without worms as they distribute nutrients and decompose matter, researchers said.

They also provide a crucial protein-rich source of food for other important species like birds, hedgehogs and frogs, experts said.

Iotuba is described in Proceedings of the Royal Society B.

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