A “near-crested lizard”
Reconstruction of the environment where Parasaurolophus walkeri lived during the Cretaceous period.
Credit: Marco Antonio Pineda/CC BY-SA 4.0
The most intriguing hypothesis is that the crest served as a resonating chamber, first proposed in 1931 by Swedish paleontologist Carl Wiman, who noted that the structure of the crest was similar to that of a swan and thus could have been used for vocalization . Lin came across a 1981 paper by David Weishampel that expanded on this idea and predicted that the dinosaur's calls would have fallen in the frequency range of 55 to 720 Hertz. Weishampel's model treated the top as an open pipe/closed pipe system. Lin did some more research and a 2013 article convinced him that Weishampel's model needed an update.
Lin created a physical setup to empirically test his own mathematical model of what might be happening acoustically inside Parasaurolophus' weapon, also called the 'Linophone', although it is not a perfect anatomical replica of the dinosaur's weapon. The setup consisted of two connected open pipes, designed to mimic the vibrations of vocal cords. Lin performed frequency sweeps using a loudspeaker to generate the sounds and recorded the resonance data with microphones in three different locations. An oscilloscope brought that data back to his computer.
He found that the crest did indeed appear to be useful for resonance, similar to the crest in modern birds. “If I were to guess what this dinosaur sounded like, it would be a brass instrument, like a huge trumpet or saxophone,” Lin said, based on the simple pipe-like structure of his model. However, the presence of soft, tissue-like vocal cords could have made the sound closer to that of a clarinet.
Lin is still refining his mathematical model, and he thinks he should be able to extend it to studying other creatures with similar vocal structures. “Once we have a working model, we will move on to using fossil scans” to further improve it, Lin said, although he noted that one challenge is that soft tissue such as vocal cords is often poorly preserved. His ultimate goal is to make the sound of the Parasaurolophus – and maybe even design his own accessible plug-in to add dinosaur sounds to his musical compositions.
