The Mystery of Nevada’s Ancient Reptilian Boneyard

Berlin, Nevada, is a treasure chest for paleontologists. Just down the road from now-abandoned gold and silver mines, a rockbound collection of bones hints at an even richer past. The Berlin-Ichthyosaur State Park is teeming with dozens of fossils of ancient marine reptiles. That bone bed is so abundant and weird that researchers have been scratching their heads over it for decades.

“There are sites with way more dense occurrences of ichthyosaur skeletons, including places in Chile and Germany,” says Nick Pyenson, curator of fossil marine mammals at the Smithsonian National Museum of Natural History. “But this place, Berlin-Ichthyosaur in eastern Nevada, has really escaped explanation for a long time.” In one particular quarry, at least seven individuals from the genus Shonisaurus—a bloated, bus-sized dolphin with four limb-like flippers—lay essentially stacked atop one another.

Previous hypotheses largely focused on physical or environmental reasons for the cluster of fossils. One suggested that the animals had gotten stranded in shallow water and died as a group some…