It's #FossilFriday at #MORPaleo! Today we share a pic of MOR 548, the composite skull of a juvenile Hypacrosaurus. Hypacrosaurus was a crested hadrosaur (duck-billed dinosaur) that lived during the Late Cretaceous. Like other duckbills, it was a large, herbivorous dinosaur that lived in groups (herds). Nests, eggs, juvenile and adult specimens of Hypacrosaurus have provided a wealth of information about how they changed as they grew. As a juvenile, Hypacrosaurus lacked its distinct hollow skull crest. As it matured, the crest would develop and was likely used as a display mechanism and possibly as a resonating chamber to communicate with other Hypacrosaurs. Additionally, histological evidence suggests that Hypacrosaurus grew quite fast, reaching adult size (skeletal maturity) between 10-12 years of age. This specimen is a composite made of several cranial elements from similarly sized juveniles that were found at the same location in the Two Medicine Formation of Montana.