Scientists find new clues to the mystery of Nevada’s fossil-rich cemetery
Since the ichthyosaur bones in Nevada were excavated in the 1950s, many paleontologists have investigated how all these creatures could have died together. Now researchers have proposed a different theory in a study published recently in the journal Current Biology.
“Several lines of evidence all kind of point towards 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 — sits in a dry, dusty landscape near an abandoned mining town, said lead author Randall Irmis, a paleontologist at the University of Utah.
To get a better look at the massive skeletons, which boast vertebrae the size of dinner plates and bones from their flippers as thick as boulders, researchers used 3D scanning to create a detailed digital model, Irmis said.
They identified fossils from at least 37 ichthyosaurs scattered around the area, dating back about 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 the 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 as they gave birth, like today’s marine giants. The fossils are believed to be from the mothers and offspring that died there over the years.
“Finding a place to give birth separated from a place where you might feed is really common in the modern world — among whales, among sharks,” Pyenson said.
Other clues helped rule out some previous explanations.
Testing the chemicals in the dirt didn’t turn up any signs of volcanic eruptions or huge shifts to the local environment. And the geology showed that the reptiles were preserved on the ocean floor pretty far from the shore — meaning they probably didn’t die in a mass beaching event, Irmis said.
The new study offers a reasonable explanation for a site that has puzzled paleontologists for decades, said Dean Lomax, an ichthyosaur specialist at Britain’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 unlock a little bit more about this fascinating site,” Lomax said.