NEW YORK (AP) —
Scientists have uncovered new clues at a curious fossil site in Nevada, a graveyard for dozens of giant marine reptiles. Instead of the site of a mass death as suspected, it could have been an old maternity ward where the creatures came to give birth.
The site is famous for its fossils of giant ichthyosaurs – reptiles that ruled the ancient seas and could grow to the size of a school bus. The creatures – the name means lizardfish – were underwater predators with large, paddle-like fins and long, toothy jaws.
Since the ichthyosaur bones of Nevada were excavated in the 1950s, many paleontologists have studied how all these creatures could have died together. Now, researchers have offered a different theory in a study published Monday in the journal Current Biology.
“Multiple pieces of evidence all point to one argument here: that this was a place where giant ichthyosaurs came to give 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 sits in a dry, dusty landscape near an abandoned mining town, said lead author Randy Irmis, a paleontologist at the University of Utah.
To better see the massive skeletons, which feature plate-sized vertebrae and fin bones 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 across the region, dating back around 230 million years. The bones were preserved in different rock layers, suggesting the creatures could have died hundreds of thousands of years apart rather than all at once, Pyenson said.
A major break came when researchers spotted tiny bones among the massive adult fossils and realized they belonged to embryos and newborns, Pyenson said. The researchers concluded that the creatures traveled to the site in groups for protection when they gave birth, like today’s sea giants. The fossils are thought to come from the mothers and offspring who died there over the years.
“Finding a place to give birth separate from a place where you could feed is very common in the modern world — among whales, among sharks,” Pyenson said.
Other clues have made it possible to rule out certain previous explanations.
The soil chemical test revealed no signs of volcanic eruption or significant changes in the local environment. And geology showed the reptiles were preserved on the ocean floor quite far from shore, meaning they probably didn’t die in a mass stranding, Irmis said.
The new study offers a plausible explanation for a site that has baffled paleontologists for decades, said Dean Lomax, an ichthyosaur specialist at the University of Manchester in England who was not involved in the research.
The case may not be completely closed yet, but the study “really helps to learn a little more about this fascinating site,” Lomax said.
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