In 2010, a road construction crew in the Atacama region of Chile was working on a project to widen the Pan-American Highway when it reached Cerro Ballena or "Whale Hill" — an outcropping where whale bones could be seen sticking out of the rock face. When they started digging away at the hill, they uncovered one of the most remarkable fossil discoveries of recent times: a "graveyard" containing the remains of at least 40 whales.
Now a team of scientists believes it's solved the mystery of how all those bones ended up piled in the same location. It has to do with what the whales ate.
The team, made up of paleontologists from the Smithsonian and a few Chilean institutions, were given two weeks to recover the fossils before construction resumed. As they report in the journal Proceedings of the Royal Society B, they found the remains of 10 different kinds of marine vertebrates, including 40 baleen whales, as well as unusual extinct species like a walrus-like whale and aquatic sloths.
"To me, it's amazing that in 240m of road-cut, we managed to sample all the superstars of the fossil marine-mammal world in South America in the Late Miocene," Nicholas Pyenson, a paleontologist at the Smithsonian, told BBC News.
Unlike many such fossil sites, the skeletons at Cerro Ballena were nearly all complete, and many of them were facing upside-down and in the same direction, in four separate layers.
The culprit, according to the researchers: a series of four separate toxic algae blooms that occurred at four different occasions within a 10,000- to 16,000-year period.
"The key for us was its repetitive nature at Cerro Ballena: no other plausible explanation in the modern world would be recurring, except for toxic algae, which can recur if the conditions are right,” Pyenson said in a release.
Here's the story the scientists pieced together. First, toxins produced by algae blooms poisoned the whales, probably through intermediate species that they ate, causing near-immediate death at sea. Then the carcasses floated toward the coast, and were washed into a tidal flat. The carcasses were then stranded away from the ocean and marine scavengers, and eventually buried by sand.
Sol Square, another paleontologist on the team, told The Guardian that the massive find was "a discovery of global importance.... There has never been a find of this size or this diversity anywhere in the world."
Check out the gallery above for some views of the find and head over to the Smithsonian's Cerro Ballena website for extensive photographs, 3D models and videos of the fossils.
Meanwhile, in other whale news, about 7,000 km away from Cerro Ballena: on Saturday, 19-year-old Chelsea Crawford from Bridgewater, N.S. was on a whale-watching excursion off the coast of Mexico when she had an extremely unexpected encounter. With a whale's tail. On her face:
Crawford told her full story to CBC News.