SANTIAGO, Chile -- More than 2 million years ago, scores of whales congregating off the Pacific Coast of South America mysteriously met their end.
Maybe they became disoriented and beached themselves. Maybe they were trapped in a lagoon by a landslide or a storm. Maybe they died there over a period of a few millennia. But somehow, they ended up right next to one another, many just yards apart, entombed as the shallow sea floor was driven upward by geological forces and transformed into the driest place on the planet.
Today, they have emerged again atop a desert hill more than a half-mile from the surf, where researchers have begun to unearth one of the world's best-preserved graveyards of prehistoric whales.
Chilean scientists together with researchers from the Smithsonian Institution are studying how these whales, many of the them the size of buses, wound up in the same corner of the Atacama Desert.
"That's the top question," said Mario Suarez, director of the Paleontological Museum in the nearby town of Caldera, about 440 miles north of Santiago, the Chilean capital.
Experts say other groups of prehistoric whales have been found together in Peru and Egypt, but the Chilean fossils stand out for their staggering number and beautifully preserved bones. More than 75 whales have been discovered so far -- including more than 20 perfectly intact skeletons.
"I think they died more or less at the same time," said Nicholas Pyenson, curator of fossil marine mammals at the Smithsonian's National Museum of Natural History. Pyenson and Suarez are jointly leading the research.
As for why such a great number perished in the same place, Pyenson said: "There are many ways that whales could die, and we're still testing all those different hypotheses."
The scientists have yet to publish their findings about the fossil bed and the extensive remains, which began to emerge in June last year during a highway project that is now on hold.
So far, the fossils have been found in a roadside strip the length of two football fields -- about 260 yards long and 20 yards wide.
Pyenson said the spot was once a "lagoon-like environment" and that the whales probably died between 2 million and 7 million years ago.
Most of the fossils are baleen whales that measured about 25 feet long, Pyenson said.
The researchers also discovered a sperm whale skeleton and remains of a now-extinct dolphin that had two walrus-like tusks and previously only had turned up in Peru, he said.
"We're very excited about that," Pyenson said in a telephone interview. "It is a very bizarre animal."
Other unusual creatures found elsewhere in the fossil-rich Atacama Desert include an extinct aquatic sloth and a seabird with a 17-foot wingspan, bigger than a condor's.
Erich Fitzgerald, a vertebrate paleontologist at Museum Victoria in Melbourne, Australia, said in an email that the latest find is very significant.
"The fossils are exceptionally well preserved and quite complete -- a rare combination in paleontology and one that will likely shed light on many facets of the ... ecology and evolution of these extinct species," Fitzgerald said.
He said it's possible "these fossilized remains may have accumulated over a relatively long period of time."
Hans Thewissen, an expert on early whales, agreed. Another scenario, he said, is that the whales might have gathered in a lagoon and then an earthquake or storm could have closed off the outlet to the ocean.