A chance find by a high school student in US has led to the youngest, smallest and most complete fossil skeleton yet known from the iconic duck-billed Parasaurolophus dinosaur.
Parasaurolophus lived throughout the western part of North America around 75 million years ago.
The herbivore is notable for a long and hollow bony tube on the top of its skull, which scientists speculate was used like a trumpet to blast sound for communication, as well as a billboard for visual display.
The discovery, announced by the Raymond M Alf Museum of Paleontology in California, shows that the prehistoric beast sprouted its strange headgear before it celebrated its first birthday.
The fossil skeleton was discovered in 2009 by high school student Kevin Terris, from The Webb Schools, within Grand Staircase-Escalante National Monument in southern Utah.
"At first I was interested in seeing what the initial piece of bone sticking out of the rock was. When we exposed the skull, I was ecstatic!" Terris said.
Excavation and subsequent cleaning of the fossil, nicknamed "Joe", revealed nearly the entire skeleton of a baby dinosaur measuring only six feet long when it died.
Detailed study of the skeleton of "Joe" identified it as the most complete specimen yet known for Parasaurolophus.
Although partial skulls and skeletons of full-grown Parasaurolophus have been known for over 90 years, scientists previously knew little about how Parasaurolophus grew up.
The new fossil shows that baby Parasaurolophus had a low bump on top of its head, which only later morphed into the curved tube of adults.
"Our baby Parasaurolophus is barely one-quarter of adult size, but it had already started growing its crest," said lead project scientist Andrew Farke, who is Augustyn Family Curator at the Raymond M Alf Museum of Paleontology.
"This is surprising, because related dinosaurs didn't sprout their ornamentation until they were at least half-grown. Parasaurolophus had to get an early start in order to form its unique headgear," Farke said.
A sample of bone from the leg helped estimate the animal's age at death.
"Dinosaurs have yearly growth rings in their bone tissue, like trees. But we didn't see even one ring. That means it grew to a quarter of adult size in less than a year," commented co-author Sarah Werning of Stony Brook University.
The study describing the new fossil was published in the journal PeerJ.
