While working on a highway-widening project in the middle of South America's Atacama Desert, Chilean workers unearthed an eerie scene that had no business being more than a kilometer away from the ocean: a mass fossil graveyard containing more than 75 ancient whales, reports MSNBC.

 

Finding whale bones in the middle of the desert is strange enough, but scientists were quick to notice a deeper mystery. The fossils ended up right next to one another — some mere meters apart — as if to suggest that the whales all died at once, possibly during some cataclysmic tragedy. What could have happened?

 

"That's the top question," said Mario Suarez, director of the Paleontological Museum in the nearby town of Caldera.

 

According to Nicholas Pyenson, curator of fossil marine mammals at the Smithsonian's National Museum of Natural History, the whales probably died between 2 million and 7 million years ago, during a time when the area would have been a "lagoon-like environment," much different than the desert landscape it is today. The real mystery, then, has less to do with how the whales got there, and more to do with why they died.

 

Could they have beached themselves after becoming disoriented in the shallows? Perhaps the lagoon had become separated from the sea by a landslide, earthquake or storm, trapping the whales within? Maybe there was something else about this lagoon that made it a whale trap. Right now, scientists aren't sure.

 

"There are many ways that whales could die, and we're still testing all those different hypotheses," said Pyenson. But, he added: "I think they died more or less at the same time."

 

Of the 75 whales that have been discovered so far, 20 of them represent perfectly intact skeletons, making the site one of the best preserved fossil beds from that time period along the west coast of South America. Most of the fossils are baleen whales that measure about 25 feet long, and one startling fossilized scene depicts two adult whales with a juvenile between them, a possible family group.

 

Researchers have also discovered fossils of other unusual creatures at the site, including a now-extinct dolphin that had two walrus-like tusks, an extinct aquatic sloth and an ancient seabird with a 17-foot wingspan. All in all, the site represents a remarkable snapshot of the ecosystem millions of years ago.

 

Although officials have asked that fossils that rest along the path of the widened Pan American Highway be moved out of the way, the Chilean government has declared the site a protected area.

 

"We have a unique opportunity to develop a great scientific project and make a great contribution to science," said Suarez.