The skull of the plant-eating dinosaur Parasaurolophus displays a bizarre shape. Beginning at the nares, a bony ridge of up to 1.8 meters in length extends backwards like a horn. The nasal ducts traverse this entire ridge to its tip, where they reverse direction and ultimately terminate in the throat area. It is likely that these cavities served as resonating bodies during vocalization. This may have allowed the dinosaur to generate low sound, as if using a trombone, and to communicate across wide distances.