Kevin Terris, a student at The Webb Schools, a private high-school campus outside of Los Angeles, stumbled on the fossil -- which professional paleontologists had missed -- on a field trip to Utah sponsored by the Raymond M. Alf Museum of Paleontology in Claremont, Calif.
The fossil is nearly the entire skeleton of a baby dinosaur measuring only six feet long when it died, a museum release reported Tuesday.
It's the most complete specimen yet known for Parasaurolophus, a duck-billed (hadrosaurid) dinosaur that lived in western North America around 75 million years ago, notable for a long and hollow bony tube on the top of its skull though to be used like a trumpet to emit sound for communication, as well as a billboard for visual display.
The baby Parasaurolophus had a low bump on top of its head, which only later morphed into the curved tube of adults, the researchers said.
"Our baby Parasaurolophus is barely one-quarter of adult size, but it had already started growing its crest," museum curator Andrew Farke said.
As for high school student Terris, he says he's pleased to be able to have added to the world's knowledge of such dinosaurs.
"At first I was interested in seeing what the initial piece of bone sticking out of the rock was," he said. "When we exposed the skull, I was ecstatic!"