Prehistoric reptile pregnant with octuplets

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Credit: (c) Nobumichi Tamura

Palaeontologists have discovered part of the skeleton of a 180 million-year-old pregnant ichthyosaur with the remains of between six and eight tiny embryos between its ribs.

The new specimen was studied by palaeontologists Mike Boyd and Dean Lomax from The University of Manchester. It was collected around 2010 from near Whitby, North Yorkshire and is from the Early Jurassic. The fossil was in the collection of fossil collector, Martin Rigby, who thought the specimen might be a block of embryos. Dean confirmed the suspicion and the specimen was acquired by the Yorkshire Museum, York.

Ichthyosaurs were aquatic reptiles that dominated the Jurassic seas. They gave birth to live young, rather than laying eggs, and did not need to return to land, even to breed. They were carnivores, feeding upon other reptiles, fish, and marine invertebrates such as the squid-like belemnites.

Ichthyosaur fossils are quite common in the UK and often found in British Jurassic rocks. However, only five ichthyosaur specimens from Britain have ever been found with embryos and none with this many. All five were collected from Jurassic exposures in the south-west of

England and are between 200-190 million years old. This is the first to be found in Yorkshire. The new specimen is a star attraction in the new major exhibition, Yorkshire's Jurassic World, which recently opened on March 24.

The Jurassic rocks of Yorkshire have produced hundreds of ichthyosaur and other marine reptile skeletons, but have not, until now, yielded any reptilian embryos. The new specimen, as well as being the first embryo-bearing ichthyosaur recorded from Yorkshire, is also geologically the youngest of the British embryo-bearing specimens, being from the Toarcian Stage of the Jurassic, around 180 million-year-old.

The specimen is a small boulder that has been cut in half and polished, which exposes several large ribs (of the adult) and several strings of vertebrae and various indeterminate tiny bones. Boyd and Lomax say there are at least six embryos present, but probably eight.

Mike said: "We also considered the possibility that the tiny remains could be stomach contents, although it seemed highly unlikely that an ichthyosaur would swallow six to eight aborted embryos or newborn ichthyosaurs at one time. And this does not seem to have been the case, because the embryos display no erosion from stomach acids. Moreover, the embryos are not associated with any stomach contents commonly seem in Early Jurassic ichthyosaurs, such as the remains of squid-like belemnites".

Eight different species of ichthyosaur have been documented with embryos. By far, the most commonly found ichthyosaur with embryos is Stenopterygius. Over a hundred specimens of Stenopterygius from Holzmaden and surrounding areas in Germany have been found with embryos, ranging from one to eleven in number.

"The German sites are approximately the same age as the new specimen from Whitby and it is possible that the new specimen is also Stenopterygius, but no identifiable features are preserved in the adult or embryos. Nonetheless, this is an important find." added Dean.

Sarah King, curator of natural science at the Yorkshire Museum, said: "This is an incredible find and the research by Dean and Mike has helped us confirm it is the first example of fossilised ichthyosaur embryos to be found in Yorkshire. Its display in Yorkshire's Jurassic World incorporates the latest digital technology to reveal the embryos and to explain the significance of the discovery. It also allows us to show a softer and more nurturing side to the Sea Dragons which were the top marine predator of their time."

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Please reference the article as: Boyd, M. J. and Lomax, D. R. 2018. The youngest occurrence of ichthyosaur embryos in the UK: A new specimen from the Early Jurassic (Toarcian) of Yorkshire. Proceedings of the Yorkshire Geological Society, https://doi.org/10.1144/pygs2017-008

Notes to editors

For media interviews with Dean Lomax, please email [email protected] or ring 0161 275 8257

The new study has been published today in the scientific journal, Proceedings of the Yorkshire Geological Society.

Yorkshire's Jurassic World explores the tropical seas, deep oceans and dinosaur country of the region we now call Yorkshire. The new permanent galleries were officially opened by Sir David Attenborough on March 23. For more information please visit: http://www.yorkshiremuseum.org.uk

Dean is an internationally recognised multi-award-winning palaeontologist, science communicator and author. He has travelled the globe and worked on many fascinating projects from excavating dinosaurs in the American West, to describing new species of extinct marine reptiles and winning a gold medal for excellence in science. A visiting scientist at The University of Manchester, Dean is passionate about communicating palaeontology with the public and regularly appears on television, including as series advisor and recurring on-screen expert presenter for ITV's Dinosaur Britain. He has written two books, numerous scientific papers, and many popular articles. Dean is also the patron of the UK Association of Fossil Hunters (UKAFH). More here: http://www.deanrlomax.co.uk.

Please reference the article as: Boyd, M. J. and Lomax, D. R. 2018. The youngest occurrence of ichthyosaur embryos in the UK: A new specimen from the Early Jurassic (Toarcian) of Yorkshire. Proceedings of the Yorkshire Geological Society, https://doi.org/10.1144/pygs2017-008

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Related Journal Article

http://dx.doi.org/10.1144/pygs2017-008

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