It's Valentine's Day, and that means that millions of people will be riffling through their record and CD collections to find the right music to set the proper mood with their special someone. Seventy five million years ago, though, there was no Barry White, and so some deep-voiced dinosaurs made beautiful music together in their own way.
For decades, the crest of the hadrosaur Parasaurolophus puzzled scientists. Such a prominent ornament must have had a function, but what? There were almost as many opinions as there were scientists. Depending on who you asked, the crest was used as a weapon, a foliage deflector, a cranial air tank, or even as a snorkel.
But James Hopson had a different idea. In 1975, he hypothesized that the crests of hadrosaurs like Parasaurolophus were visual display structures that doubled as resonating chambers for vocal communication. (A notion that had also been suggested by Carl Wiman decades before.) The crests were signs of dinosaur sociality. The question was how to test these ideas, but in a landmark 1981 Paleobiology paper David Weishampel looked to the internal anatomy of hadrosaur skulls to see if they could have been using their skulls in the way Hopson had proposed.
Studied from an acoustical perspective, Weishampel found that the crest of Parasaurolophus truly was capable of acting as a resonating chamber for sound. In fact, the internal anatomy of the Parasaurolophus crest was very similar to a woodwind instrument called the crumhorn, and Weishampel proposed that adult Parasaurolophus communicated over long distances through low-frequency sounds. Though not included in this paper itself, Weishampel even created a model of a Parasaurolophus crest using PVC pipe, which sounded something like a tuba when played. Likewise, a recent study of the crested hadrosaurs Lambeosaurus, Corythosaurus and Hypacrosaurus by David Evans and colleagues found that their nasal passages may have had similar sound-producing capabilities and that their ears were also suited to detecting low-frequency sounds. One can only imagine what an entire hadrosaur symphony—encompassing all the different crest shapes—might have sounded like.
YouTube video of Weishampel playing his hadrosaur horn:
Parasaurolophus did not sound throughout its lifetime, though. By comparing crest shape to the structure of the inner ear, Weishampel suggested that young individuals produced higher-frequency sounds—which traveled shorter distances—whereas adults could produce low-frequency honks that could be heard over much wider areas. (On the basis of potentially different crest shapes for males and females, he also suggested that the different sexes made slightly different sounds, but this difference has not been supported by additional evidence.) During mating season, one could imagine dozens of Parasaurolophus calling to each other, much like living alligators and crocodiles do today. The Late Cretaceous certainly would have been a very noisy place.
For more on dinosaur romance, see my recent Smithsonian article Everything You Wanted to Know About Dinosaur Sex.
Evans, D., Ridgely, R., & Witmer, L. (2009). Endocranial Anatomy of Lambeosaurine Hadrosaurids (Dinosauria: Ornithischia): A Sensorineural Perspective on Cranial Crest Function The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 292 (9), 1315-1337 DOI: 10.1002/ar.20984
Hopson, J.A. (1975). The Evolution of Cranial Display Structures in Hadrosaurian Dinosaurs Paleobiology, 1 (1), 21-43
Vergne, A., Pritz, M., & Mathevon, N. (2009). Acoustic communication in crocodilians: from behaviour to brain Biological Reviews, 84 (3), 391-411 DOI: 10.1111/j.1469-185X.2009.00079.x
Weishampel, D.B. (1981). Analyses of Potential Vocalization in Lambeosaurine Dinosaurs (Reptilia: Ornithischia) Paleobiology, 7 (2), 252-261
Weishampel, D.B. (1997). Dinosaurian Cacophony Bioscience, 47 (3), 150-159