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Fossil shows starfish relative ‘lost its skeleton’ half a billion years ago

Researchers have identified the specimen, which they named Yorkicystis haefneri, as new to science.

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Fossil shows starfish-relative ‘lost its skeleton’ half a billion years ago (Hugo Salais/Metazoa Studio)

Fossil shows starfish-relative ‘lost its skeleton’ half a billion years ago (Hugo Salais/Metazoa Studio)

Fossil shows starfish-relative ‘lost its skeleton’ half a billion years ago (Hugo Salais/Metazoa Studio)

The fossil of a 510-million-year-old relative of modern starfish and sea urchins has revealed new insights into the early evolution of a hard skeleton, scientists have said.

Researchers from Spain, the UK and USA – including experts from the Natural History Museum (NHM), identified the specimen, which they named Yorkicystis haefneri, as new to science.

The finding contributes to scientists’ understanding of an important period of Earth’s history – when animals emerged.

Unlike its modern relatives such as starfish and sea urchins, Yorkicystis did not have a skeleton developed across most of its body, and only the arms were mineralised, the researchers found.

It is really exciting to be able to explore the development of an animal that lived over half a billion years agoDr Jeffrey Thompson

They suggest the arm coverings would have helped to protect the creature’s delicate feeding structures.

It is not clear why the animal reduced its skeleton, but one reason might have been to save energy, the experts indicate.

They suggest the absence of a skeleton may represent a case of a characteristic being lost during the course of evolution.

The specimen was named in honour of amateur palaeontologist Chris Haefner, who discovered it in a churchyard in York, Pennsylvania.

Mr Haefner shared his discovery on Facebook where it was spotted by the study’s lead author Dr Samuel Zamora.

When Dr Zamora contacted Mr Haefner explaining the significance of his discovery, he agreed to donate the specimen to the Natural History Museum.

Mr Haefner, president of the Lancaster County Fossil and Mineral Club, said: “I spent just over four years digging pocket holes in the grass to locate fossils in the churchyard.

“Lenses with fossils are everywhere there. When I found Yorkicystis, I didn’t know its relevance, but I knew it was worth keeping.

“The City View Church site is 90% undiscovered and who knows what is still hidden there.”

Dr Jeffrey Thompson, a co-author and Leverhulme Trust Early Career Research Fellow at the NHM, said: “This is a major discovery with important implications for understanding the history of echinoderms, the animal group that includes starfish, sea urchins, brittle stars and their relatives.

“Yorkicystis represents the oldest example of an echinoderm that has secondarily reduced the skeleton.

“We were surprised to see this had happened so close to the origins of the group over half a billion years ago.”

The animal is a member of an extinct group called the edrioasteroids, which are characterised by a disc-shaped body with five arms and a central mouth.

All other edrioasteroids have a hard skeleton across their entire body made of calcium carbonate, and so Yorkicystis is unique as it is partly soft-bodied.

Dr Thompson added: “By studying the genes involved in the formation of the skeleton in modern echinoderms, we can make predictions about skeletal development in Yorkicystis.

“For example, we think that many of the genes that build the skeleton in modern echinoderms probably weren’t expressed in the soft-bodied portions of the animal.

“It is really exciting to be able to explore the development of an animal that lived over half a billion years ago.”

The creature comes from a period called the Cambrian, which ranged from about 539 to 485 million years ago.

Dr Zamora, researcher at the Spanish Research Council (IGME-CSIC), said: “The Cambrian explosion was one of the most significant events in the history of life.

“A key innovation at this time was the evolution of a hard mineralised skeleton, which helped protect early animals from possible predators.

“The reasons why Yorkicystis reduced its skeleton at this time are unclear, but it might have helped conserve energy for other metabolic processes.”

Co-author Dr Imran Rahman, principal researcher at the NHM, added: “This discovery contributes to our understanding of a crucial episode in Earth’s history – the emergence of animals.

“By studying fossils from the Cambrian period, we can obtain key insights into the origins of the major groups that are alive today.”

The findings are published in Proceedings of the Royal Society B.

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