Mysterious Nevada fossil site may be an ancient maternity ward

Scientists have discovered new evidence about an intriguing fossil site in Nevada, a graveyard for dozens of giant marine reptiles. Rather than a massive death site as suspected, it may have been an ancient maternity ward where creatures came to give birth.

The site is famous for its fossils of giant ichthyosaurs – reptiles that dominated the ancient seas and could be as large as a school bus. The creatures—the name meaning fish lizard—were underwater predators with large paddle-shaped flippers and long jaws full of teeth.

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

“There are several lines of evidence all pointing to one argument here: that this was a place where giant ichthyosaurs gave birth,” said co-author Nicholas Benson, Curator of Fossil Marine Mammals at the Smithsonian National Museum of Natural History.

The site was once a tropical sea—part of Berlin Ichthyosaurus State Park in Nevada—in a dry, dusty area near an abandoned mining town, said lead author Randy Ermes, a University of Utah paleontologist.

To get a better look at the massive skeletons, which boast vertebrae the size of dinner plates and flipper bones as thick as rocks, the researchers used 3D scanning to create a detailed digital model, Ermes said.

They identified fossils of at least 37 ichthyosaurs scattered across the region, dating back some 230 million years. The bones are preserved in different rock layers, Benson said, suggesting that the creatures may have died out hundreds of thousands of years apart rather than all at once.

The big break, Benson said, occurred when researchers discovered some small bones among the adult colossal fossils, and realized they belonged to fetuses and newborns. The researchers concluded that the creatures traveled to the site in groups for protection as they were born, much like the giants of the seas today. It is believed that the fossils are from mothers and sons who died there over the years.

“Finding a birthing place away from a place where you can feed him is really common in the modern world – among whale sharks,” Benson said.

Other evidence helped rule out some of the earlier explanations.

Testing of the chemicals in the dirt revealed no signs of volcanic eruptions or massive shifts in the local environment. And the geology showed that the reptiles were preserved on the ocean floor very far from shore—meaning they probably didn’t die out in a mass coastal event, Irmis said.

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

The case may not be fully closed yet, but the study “really helps unlock more information about this fascinating site,” Lomax said.

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The Associated Press Health and Science section receives support from the Howard Hughes Medical Institute’s Science and Education Media group. AP is solely responsible for all content.

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