The mysterious Nevada fossil site could be an old maternity ward

Scientists have uncovered new evidence of a strange fossil site in Nevada, a graveyard for dozens of giant marine reptiles. Instead of the suspected mass extinction, it may have been an old maternity ward where the creatures were born.

The site is famous for its fossils of giant ichthyosaurs – reptiles that ruled the ancient seas and could reach the size of a school bus. The creatures—the name means fish lizard—were underwater predators with large paddle-shaped fins and long, toothy jaws.

Ever since the ichthyosaur bones were unearthed in Nevada in the 1950s, many paleontologists have investigated how all of these creatures might have died together. Now researchers have proposed a different theory in a study published Monday in the journal Current Biology.

“Several lines of evidence here all point to one argument: that this was a site where giant ichthyosaurs gave birth,” said co-author Nicholas Pyenson, curator of fossil marine mammals at the Smithsonian National Museum of Natural History.

Once a tropical sea, the site — part of Nevada’s Berlin-Ichthyosaur State Park — now lies in an arid, dusty landscape near an abandoned mining town, said lead author Randy Irmis, a paleontologist at the University of Utah.

To get a better look at the massive skeletons, which feature vertebrae the size of plates and bones from their flippers as thick as boulders, the researchers used 3D scanning to create a detailed digital model, Irmis said.

They identified fossils of at least 37 ichthyosaurs scattered around the area, dating back around 230 million years. The bones were preserved in different layers of rock, suggesting the creatures may have died hundreds of thousands of years apart rather than all at once, Pyenson said.

A major breakthrough came when researchers discovered some tiny bones beneath the massive adult fossils and determined they belonged to embryos and newborns, Pyenson said. The researchers concluded that the creatures, like modern-day sea giants, traveled in groups for protection at birth. The fossils are believed to be from the mothers and offspring who died there over the years.

“It’s really common in the modern world to find a place to give birth that’s separate from a place where you could feed — among whales, among sharks,” Pyenson said.

Other clues helped rule out some previous explanations.

Testing of the chemicals in the dirt revealed no signs of volcanic eruptions or major changes in the local environment. And geology showed that the reptiles were preserved on the seabed quite a distance from shore — meaning they likely didn’t die in a mass stranding event, Irmis said.

The new study offers a plausible explanation for a site that has puzzled paleontologists for decades, said Dean Lomax, an ichthyosaur specialist at England’s University of Manchester who was not involved with the research.

The case may not be fully closed yet, but the study “really helps to learn a little bit more about this intriguing site,” Lomax said.

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