New star-like fossils reveal evolution in action

Researchers from Cambridge University have discovered a fossil of the earliest star-like animal, which will help us understand where the armed creature came from.

The prototype star, which has features similar to sea lilies and modern day stars, is a much-needed connection for scientists trying to compile a history of early evolution.

The specially preserved fossil, called Cantabrigiaster fezouataensis, was found in the Morroco Anti-Atlas mountain range. Its elegant design – with feathery arms resembling lace work – has been frozen in time for about 480 million years.

The new genre is unusual in that it lacks many of the key features of its contemporary relatives, with around 60% of today’s star body plan.

The crown’s features are instead a hybrid between the characteristics of a star and a sea lily or crinoid – it is not a plant but a filtering life with a wavy weapon that attaches itself to the seabed through a cylindrical ‘gas’.

The discovery, reported in Biology Letters, capturing the early evolutionary stages of the animal at a time in Earth’s history when life suddenly expanded, a time known as the Ordovician Biodiversification Event.

The discovery also means that scientists can now use the new discovery as a template to work out how it evolved from this more basic form to the complexity of their contemporaries.

“It is very exciting to find this connection that their ancestors need. If you go back in time and put your head under the sea in the Ordovician you would not recognize any of the marine organisms – with the exception of the stars, they are one of the first animals of the day. today, “said lead author Dr Aaron Hunter, a visiting postdoctoral researcher in the Department of Earth Sciences.

Modern stars and brutal stars are part of a family of sharp-edged animals called echinoderms that, although they do not have a backbone, are one of the closest animals to spines. Crinoids, and other creatures like the sea urchins and sea cucumbers are all echinoderms.

The origins of stars have fascinated scientists for decades. But the new species is so well preserved that its body can be precisely mapped and its evolution understood. “The level of detail in the crown is amazing – its structure is so complex that it took us a while to unravel the importance,” Hunter said.

It was Hunter’s work on both living and fossil echinoderms that helped him see his transgenic traits. “I was looking at a modern crinoid in one of the collections at the Museum of Western Australia and realized that the arms looked very familiar, they reminded me of this strange fossil I found. years earlier in Morocco but found it difficult to work with him, “he said.

Fezouata in Morocco is something of a sacred tomb for palaeontologists – the new fossil is one of many well-preserved bodily animals found from the site.

Hunter and co-author Dr. Javier Ortega-Hernández, formerly based at the Cambridge Department of Zoology and now based at Harvard University, named the genus Cantabrigiaster in honor of the long history of echinoderm research at the -institiudan aca.

Hunter and Ortega-Hernández explored their new species along with a catalog of hundreds of star-like animals. They indexed their body structures and features, building a roadmap of the echinoderm skeleton that they could use to assess how Cantabrigiaster related to other family members.

Modern echinoderms come in many shapes and sizes, so it can be difficult to work out how they are related to each other. The new analysis, which uses an external axial theory – a model of biology usually only based on living species – meant that Hunter and Ortega-Hernández could identify signals and differences between identify the body plan of modern echinoderms and then discover how each member of the family was connected to their Cambrian ancestors.

They found that only the main part or back of the body, the food groove – which distributes food next to each star’s arm – was present in Cantabrigiaster. Everything outside of this, the external body parts, was added later.

The authors plan to expand their work detecting early echinoderms. “One thing we hope to answer in the future is why stars developed their five arms,” Hunter said. “It seems like it’s a permanent shape for them to accept – but we still don’t know why. We need to continue to find the crown that will give us that special connection, but by going back to the early ancestors like Cantabrigiaster we are getting closer to that answer. ”

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