A fossil discovery suggests that mammals may have preyed on dinosaurs several times their size, according to a new study published Tuesday. The fossil, first stumbled upon by a farmer in 2012, was uncovered at a site known as "China's Pompeii" in the country's northeast. There, millions of years ago, a volcanic eruption took place, burying plants and animals. Scientific Reports, the journal that published the study, said the fossil showed two creatures — a mammal and a dinosaur — from around 125 millions years ago, during the Cretaceous period. Even though the mammal is much smaller, researchers think it was attacking the dinosaur when they both got caught in the volcanic flow, study author Jordan Mallon, said. The mammal is perched on the dinosaur, its paws gripping the reptile's jaw and a hind limb while its teeth are stuck into the ribcage. A paleobiologist at the Canadian Museum of Nature, Mallon said he had "never seen a fossil like this before." The new find suggests that mammals may have actually preyed on dinosaurs several times their size and didn't just scavenge ones that were already dead, Mallon explained. Fossil shows two creatures, with the mammal attacking the bigger-sized dinosaur Researchers think the mammal was attacking the dinosaur when they both got caught in the volcanic flow. The mammal in the fossil duo is the meat-eating Repenomamus robustus, which is about the size of a house cat, Mallon said.