Everybody knows Triceratops. Like most horned dinosaurs, or ceratopsians, Triceratops had a rhino-like body, a beak, and a collared head. Yet scientists have never been sure of the purpose of the ceratopsian collar, or frill. Was it meant to be scary to predators? Or sexy to another ceratopsian? Did it protect the animal’s neck from attacking predators? Or serve as a kind of heat radiator, helping ceratopsians cool off? Now the discovery of an even older ceratopsian—smaller than Triceratops’ skull—has given them a clue: The frill may have helped ceratopsians eat.

Liaoceratops yanzigouensis was discovered in northeastern China by paleontologist Xu Xing, a National Geographic Society grantee. Xu’s beagle-size dino, which lived some 130 million years ago, had markings on its rudimentary frill bone—not evident in the more elaborate headgear of Triceratops—that show that powerful jaw muscles were once attached there. According to paleontologist Peter Makovicky of the Field Museum in Chicago, these muscles must have helped Liaoceratops slice off and eat the fibrous plants that made up its vegetarian diet. “This discovery gives us a window on the evolution of all the horned dinosaurs,” he says.