'Mysterious' object found on Jurassic Coast turns out to be oldest fossil of its kind

The oldest discovered fossil of its kind has been found on the Jurassic Coast.

A 150-million-year-old "stomach stone" was uncovered in Kimmeridge, Dorset. It is 59 million years older than any others found before.

Dr Steve Etches, a palaeontologist, was the one to find the fist-shaped fossil. He passed it to fossil experts who dismissed it as something formed by geological processes.

But Nigel Larkin, another palaeontologist and visiting research fellow at the University of Reading, thought there was more to it.

He was sure that the fossil had come from an animal, rather than geology.

He said: “I was fascinated by this very curious mystery object and was determined to discover what it was.

“Unless stomach stones are actually found preserved within a skeleton it is almost impossible to tell what sort of animal it might have formed inside.

“The size of this stomach stone, and considering it was found in clay from the Upper Jurassic era, indicates it most likely formed inside a large marine reptile such as an ichthyosaur, plesiosaur, pliosaur or crocodilian.

"The stomach stone did not come from a dinosaur - as dinosaurs lived on land - but this is still a very exciting and rare discovery.”

Nigel Larkin compared the stone to material in the collections of the Royal College of Surgeons, England, and the UCL Pathology collections.

He soon identified it as a "calculus" – a stomach stone, bladder stone, kidney stone or similar, due to its very specific internal structure.

These mineral "stones" can form naturally in any animal, not just humans, under certain dietary or environmental conditions.

Ancient examples have been discovered in Egyptian mummies but only a handful have been found in the fossil record.

It is suspected that more must exist, but they have not been recognised for what they are.

Dr Ivan Sansom, senior lecturer in Palaeobiology at the University of Birmingham, carried out microscopic analyses of the stone to determine what minerals it was made of.

He found the specimen has all the characteristics of a calculus formed in a gastro-intestinal tract, known as a "stomach stone".

This very rare find adds to the range of unusual fossils discovered in the Kimmeridgian cliffs by Dr Steve Etches.

Believed to be 150-million-years-old, the find extends the range of known calculi (stomach stones, bladder stones etc) in the fossil record by almost 59 million years.

It also confirms their occurrence in marine palaeo-environments rather than just terrestrial deposits. It is the only specimen known to have been found in the UK.

Steve’s extensive collection of Jurassic fossils is world-famous and is now housed in its own museum, open to the public, on the coast where the fossils have been found.

The collection contains the skeletons of prehistoric fish, ichthyosaurs, pliosaurs, plesiosaurs and pterosaurs.