Parasaurolophus (Para-soar-ol-of-fuss) was, perhaps, the most spectacular of the duck-billed dinosaurs. It bore a long, recurved crest on top of its head, often longer than the skull itself! As in all crested duckbills, the crest contained an elaborate and winding nasal passage. The nasal passage ran from the nostrils to the back of the crest and then looped forward to enter the skull.
The function of this unusual feature is unclear. Scientists have speculated that it might have served as a resonating chamber to produce low-frequency sounds. Such sounds might have been used in courtship behavior, as a threat, or to communicate over long distances. Indeed, elephants and whales today use such sounds for communication. It is also possible that the enlarged nasal cavity enhanced the dinosaur's sense of smell, since similarly enlarged nasal passages in modern-day reptiles contain sensory tissue. It is likely that Parasaurolophus also used the crest as a visual display to help recognize species and sex.
Parasaurolophus, like other duck-billed dinosaurs, may have had a frill that ran down the back from the neck area to the tail. Some scientists have suggested that this frill may have spanned between the crest and neck, forming a sail-like membrane.
Parasaurolophus was a relatively rare duck-bill. It lived during the Late Cretaceous Period in North America. It was about 30 feet long.