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Ancient fossils shed new light on evolution of sea worm

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A complete specimen of the Cambrian cage worm Iotuba from the Chengjiang fossil deposit. Credit: Zhang Zhifei

Ancient fossils have shed new light on a species of sea worm that links it to the era of the evolutionary explosion that gave rise to modern animal life.

Researchers from Durham University in the UK and Xi’an University in China examined 15 remarkably well-preserved fossils of the early Cambrian annelid Iotuba chengjiangensis, 515 million years ago.

In fossilized remains, EarthwormThe intestine and kidney were found to have unexpectedly complex structures similar to those of other annelids.

The researchers believe this was due to the diversification of annelids (segmented nematodes) into different lineages about 200 million years earlier than previously thought, in an evolutionary leap known as the Cambrian explosion. It says it means it was a part.

The Cambrian Explosion caused a burst of life between 540 and 530 million years ago. fossil record– and saw the appearance of many of the major groups that make up animal life on earth.

Findings are published in the journal Proceedings of the Royal Society B.

Ancient fossils shed new light on sea worm evolution

Iotuba Artist Reconstruction – Complete Organism. Credit: Zhang Zhifei

Study co-author Martin R. Smith, Ph.D., Department of Earth Sciences, University of Durham, said: parties, and their major subgroups did not begin to diversify until nearly 200 million years later.

“However, the remarkably preserved fossils we have studied and the structures of these amazing little creatures challenge this picture, suggesting that annelids, including Iotuba chenjangensis, were initiated by a Cambrian explosion. It shows that it seems to follow the pattern of events.

Ancient fossils shed new light on sea worm evolution

A reconstruction of Iotuba. The anterior part of the body is turned inside out, and the head (including gill fibers and mouth) is surrounded by a cage of spines (chaetae). Credit: Zhang Zhifei.

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

“They weren’t late to the party, they were hiding in the side room.”

The researchers say Iotuba chengjiangensis was a caged worm that could move its head in and out of a cage made of bristly barbs. This makes the worm a close relative of the family of annelid sea worms, such as flavergeridae and acrocylindae.

Ancient fossils shed new light on sea worm evolution

Frontal reconstruction of Iotuba. Shows cage of spines (chaetae) surrounding inverted head, with gill filaments and mouth. Credit: Zhang Zhifei

“These families are like the top rungs on the evolutionary ladder,” Smith said. must have had a dramatic, invisible origin.

“It turns out that many of the annelids we know and love today may have begun evolving much earlier than we think.”

Dr. Zhifei Zhang (Northwest University, Xi’an, China), lead author of the study, said: marine ecosystem Polycaeta, the most diverse lineage of creatures living in the sea.

Ancient fossils shed new light on sea worm evolution

A specimen of the Cambrian cageworm Iotuba from the Chengjiang fossil deposit.Credit: Martin R. Smith

“The best known are, for example, earthworms, leeches and clam worms. There are also at least 20,000 species and 80 families of polychaetes in the modern sea. The famous Konservat-Lagerstätten is extremely rare. .

“Was this because the delicate worms weren’t present, or were they simply not preserved? Our study gives the first insightful answer: the segmented worm’s Biodiversity is happening much faster than previously thought.”

For more information:
Cambrian cirrus Iotuba shows early annelid radiation. Proceedings of the Royal Society B: Biological Sciences (2023). DOI: 10.1098/rspb.2022.2014. Royalsocietypublishing.org/doi….1098/rspb.2022.2014

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Durham University

Quote: Ancient Fossils Shed New Light on Sea Worm Evolution (31 January 2023) from https://phys.org/news/2023-01-ancient-fossils-evolution-sea-worm.html to 2023 Obtained on 31st January

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