Chilean and US researchers found a 5-million-year old mass graveyard of whales beside the Pan-American Highway located at Chile.

The graveyard was found in the Atacama Desert in Chile, which was already well-known to be a place where whale fossils are found. Sometimes, bones belonging to whale skeletons are seen to be sticking out of the dunes and rock faces and the people started calling this area as Cerro Ballena, meaning whale hill.

However, the researchers found more whale skeletons when a cut was made due to recent road-widening project that was being carried out in the periphery of the area. The scientists were given two weeks to gather as much data as they could before the road construction resumed.

During these two weeks, the researchers were able to produce 3D models of the remains in the original position by which they were found and they also gathered the bones for further analysis in the laboratory. There were over 40 rorquals discovered in the area. Rorquals are huge cetacean creatures whose modern descendants include the minke, blue, and fin whales.

"We found extinct creatures such as walrus whales - dolphins that evolved a walrus-like face. And then there were these bizarre aquatic sloths," Nicholas Pyenson, a palaeontologist from the Smithsonian's National Museum of Natural History, told BBC News.

According to the Smithsonian Science, the whales found in this mass graveyard were believed to be killed by algae poisoning. The toxins ingested by the animals were from algal blooms. As to how they reach their current position, researchers theorized that the dying and the dead animals were slowly washed away into an estuary and eventually reached the sands where they were buried for millions of years.

However, the theory about the algae poisoning is not yet confirmed as the researchers failed to get distinct algal samples from the sediments. What they discovered were some grains which contained iron oxide, a clue which says that there could be algal presence in the area.

This study was published in the Feb. 25 issue of Proceedings of the Royal Society B.