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Before being blasted off the face of the earth 66 million years ago by a city-sized asteroid that evidence suggests hit the Gulf of Mexico with the impact of 10 billion WWII-era atomic bombs, a more insidious fate may've befallen dinosaurs: They may've been poisoned. A study published this week in the journal Nature Communications suggests potential mercury poisoning of the Cretaceous monsters, based on analysis of marine mollusk fossils.

While human-generated sources of mercury include coal-fired power plants and gold mines, the largest natural sources of mercury entering the atmosphere are volcanoes, which were the University of Michigan researchers' focus. Massive volcanic eruptions in India -- known as the Deccan Traps eruptions, which lasted for nearly a million years -- contributed to both rapid ocean warming and elevated toxic mercury levels around the world during the time of the dinosaurs. When the researchers compared mercury levels from the fossils to those gathered in a present-day Shenandoah Valley site of industrial mercury pollution, the levels were roughly equivalent.

"For the first time, we can provide insights into the distinct climatic and environmental impacts of Deccan Traps volcanism by analyzing a single material," the study's lead author, Kyle Meyer, said in a release. "It was incredibly surprising to see that the exact same samples where marine temperatures showed an abrupt warming signal also exhibited the highest mercury concentrations, and that these concentrations were of similar magnitude to a site of significant modern industrial mercury contamination."

The scientists said that Mercury anomalies have been documented in sediments before, but never in shells. So the new technique could help further the study of mass extinctions and climate shake-ups in the geological record.

Read more: Scientists discover more evidence that dinosaurs were killed by a gigantic asteroid