The bite marks are about 75 million years old from near the end of the age of dinosaurs. They are the oldest mammalian tooth marks found yet. Though small mammals existed in the dinosaur era, it was the fall of dinosaurs that spurred the rise of large mammals, theory holds.
Scientists discovered the marks during fieldwork in Canada, as well as during analyses of university and museum bone collections there.
“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,” said researcher Nicholas Longrich, a vertebrate paleontologist at Yale University in New Haven, Conn. “So when I saw it in the fossils, it was something I paid attention to.”