Bite marks on dinosaur bones aren't often found—but they recently turned up in multitudes at the Mygatt-Moore Quarry in Colorado, and researchers say the find could indicate certain carnivorous dinos were cannibals. According to a study published in PLOS One Wednesday, scientists found that, of the 2,368 bones collected at the quarry over an entire season, 684 of them (or nearly 30%) had bite marks from meat-eating theropods; usually that figure hovers around 5%. "To find 30% was really nuts," study lead author Stephanie Drumheller-Horton tells New Scientist. Bites on bones of body parts that didn't have the best meat suggest that carnivores "late to the party"—ie, scavengers, not predators—took what they could get when they stumbled on carcasses in desperate times, like during fires or drought, per Smithsonian.
The scientists believe environmental conditions may have enabled this scavenging to happen: There's evidence lots of water evaporated during the dry season in this region during Jurassic times, meaning dinosaur carcasses would've been exposed "for a pretty long time" on the ground before the rains came again and buried the bones under sediment, Drumheller-Horton says. She adds, "We've been joking that the site probably smelled terrible." Evidence suggests that Allosaurus may have been the carnivores doing the eating, though it's possible other known (or unknown) large dinosaurs could also have been involved. And while a large number of the bones found with bite marks belonged to the herbivore Apatosaurus, ones belonging to Allosaurus were found with bite marks, too—meaning it appears the dinosaur ate its own. (Read more discoveries stories.)