Seventy-five million years ago, mammals couldn’t compare to the big boy reptiles ruling the earth. Still, that didn’t stop one spunky, prehistoric squirrel-like creature. He wasn’t hungry for meat, but he needed his minerals. He eyed a dino bone, the equivalent of modern-day vitamin shop, and wrapped his teeth around it, his very own corn-on-the-cob-osaurus.

Yesterday, researchers published a paper in Palentology on these exploits. They claim to have found the oldest known mammal bite marks.

The researchers found the bones bites in two Canadian, Late Cretaceous-period dinosaur bone collections–and also on additional bones during fieldwork in Alberta. They suspect the marks were made by multituberculates, extinct rodent-like creatures, and they first found them on the femur bone of Champsosaurus, a swamp-dweller that looked a bit like an crocodile.

The researchers say that the form of the bite marks indicate that they were made by opposing pairs of teeth, a tell-tale sign of mammal chompers (think rats). And the fact that they came from paired upper and lower incisors points to multituberculates. Though these early mammals didn’t have the bite power that modern day rodents developed, their marks look similar.

Nicholas Longrich, lead author on the paper, says in a Yale press release:

“The marks stood out for me because I remember seeing the gnaw marks on the antlers of a deer my father brought home when I was young,” he said. “So when I saw it in the fossils, it was something I paid attention to.”

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Image: Nicholas Longrich/Yale University