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Fossilized ‘Sea Monster’ Found Pregnant With Eight Babies

The fossil provides the earliest evidence of ichthyosaur embryos from the UK

Illustration of pregnant ichthyosaur with octuplets. (Nobumichi Tamura)
smithsonian.com

Fossils of ichthyosaur—extinct carnivorous marine reptiles—are not uncommon. The first was discovered in 1846, reports Gizmodo’s George Dvorsky. And scientists even found a near-complete skeleton of one in India last year.

But to scientists' delight, the latest ichthyosaur fossil had a surprise inside: it was preserved while carrying up to eight babies.

The fossilized remains belonged to an ichthyosaur that lived between 200 and 190 million years ago, during the Jurassic Period. It was found in 2010 in Yorkshire, England, lodged within a small broken boulder, and made its way into the private collection of Martin Rigby.

According a press release, Rigby had an inkling the fossil might contain the tiny bones of embryos. So he contacted Mike Boyd and Dean Lomax, paleontologists at the University of Manchester, to ask if they were interested in investigating. The duo confirmed the embryos' presence, making it the first known case of fossilized ichhyosaur embryos in Yorkshire, and the earliest evidence of ichthyosaur embryos in the UK, Dvorsky writes.

"This is an incredible find, and the research by Dean and Mike has helped us confirm it is the first example of fossilized ichthyosaur embryos to be found in Yorkshire," Sarah King, curator of natural science at the Yorkshire Museum, says in the press release. After researchers confirmed the suspicion, the Yorkshire Museum​ acquired the specimen.

According to the researchers’ findings, outlined in a study published in the Proceedings of the Yorkshire Geological Society, each of the embryos measured about four-inches long. Researchers identified six embryos, but suggest there are likely two more.

During their examination, Boyd and Lomax considered the option that the tiny bones that lingered inside the creature were the animal’s stomach contents. But, as Boyd says in the press release: “It seemed highly unlikely that an ichthyosaur would swallow six to eight aborted embryos or newborn ichthyosaurs at one time."

He adds that if the creature had consumed the embryos, they would expect to observe some erosion of the bones from stomach acids. And the embryos were not floating among other expected bits of ichthyosaurs' favorite foods, he notes, such as squid-like belemnites.

Researchers couldn’t identify the size or species of the ichthyosaur because the remains were poorly preserved. But, as Dvorsky reports, ichthyosaurs were commonly 13 feet long as adults and gave birth to as many as 11 young.

According to the press release, eight different species of ichthyosaur have been found with embryos, the most common being the Stenopterygius. Even the first ichthyosaur fossil found contained an embryo, Dvorsky notes.

The new specimen is currently on display at the Yorkshire Museum in a new major exhibition called Yorkshire's Jurassic World.

About Julissa Treviño

Julissa Treviño is a writer and journalist based in Texas. She has written for Columbia Journalism Review, BBC Future, The Dallas Morning News, Racked, CityLab and Pacific Standard.

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