LAMBEOSAURUS

genus of duck-billed dinosaurs (hadrosaurs) found as fossils in Late Cretaceous rocks (66.4 to 97.5 million years old) of North America. Lambeosaurus was first discovered in the Oldman Formation, Alberta, Canada; more recently, larger specimens, up to 16.5 m (54 feet) in length, have been found in Baja California, Mexico. Lambeosaurus is notable for the hatchet-shaped hollow bony crest on top of its skull. This crest contained complex chamber extensions of the breathing passage between the nostrils and the trachea. The function of these chambers is not known, but it has been suggested that they served as resonating chambers (for honking) or as expanded olfactory membranes to increase the sense of smell. Other researchers believe that the crest served in species recognition. As in all duck-billed dinosaurs, the dentition was expanded and adapted for chewing large quantities of harsh plant tissues.