'Inside-out, headless wonder' fossil discovered

A professor has published details of a rare "inside-out, legless, headless wonder" fossil from 444 million years ago, which belonged to a previously undiscovered species.

Prof Sarah Gabbott has been studying the arthropod fossil for 25 years after she found it in a small quarry in South Africa.

Her findings, published on Thursday, reveal the discovery is very rare, as most fossils are of an animal's external features, whereas the internal organs are preserved in this case.

Prof Gabbott uncovered the fossil, which she has named Sue after her mother, at the start of her career. She had hoped to find another example in the years which followed, but had no joy.

The University of Leicester academic said she had decided to finally make her findings public after her mum said if she intended to name the fossil after her, she ought to "get on and do it before she becomes a fossil herself".

Sue was found in the Soom Shale, a band of silt and clay at a location 250 miles north of Cape Town, which was laid on the seafloor more than 440 million years ago after a devastating glaciation had wiped out about 85% of Earth's species.

It is believed the marine basin where the arthropod swam was somehow protected from the worst of the freezing conditions.

The sediments where Sue came to rest were also toxic, with no oxygen and hydrogen sulphide dissolved in the water, which the researchers suspect might have led to her unusual inside-out preservation.

It is, however, difficult to compare her to other fossils from the same era due to the unique way Sue was preserved.

Prof Gabbott, who is based at the university's school of geography, geology and the environment, added: "Sue is an inside-out, legless, headless wonder.

"Remarkably her insides are a mineralised time-capsule: muscles, sinews, tendons and even guts all preserved in unimaginable detail.

"And yet her durable carapace, legs and head are missing – lost to decay over 440 million years ago.

"We are now sure she was a primitive marine arthropod but her precise evolutionary relationships remain frustratingly elusive."

The small quarry where the fossil was found has now virtually disappeared, which means another example is unlikely to be discovered.

Prof Gabbott said: "This has been an ultramarathon of a research effort. In a large part because this fossil is just so beautifully preserved, there's so much anatomy there that needs interpreting. Layer upon layer of exquisite detail and complexity.

"I'd always hoped to find new specimens but it seems after 25 years of searching, this fossil is vanishingly rare – so I can hang on no longer.

"Recently my mum said to me, 'Sarah, if you are going to name this fossil after me, you'd better get on and do it before I am in the ground and fossilised myself'.

"I tell my mum in jest that I named the fossil Sue after her because she is a well-preserved specimen.

"But, in truth, I named her Sue because my mum always said I should follow a career that makes me happy – whatever that may be.

"For me, that is digging rocks, finding fossils and then trying to figure out how they lived and what they tell us about ancient life and evolution on Earth."

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