Parasaurolophus

Parasaurolophus, which means “near crested lizard,” was a bird-hipped dinosaur that lived during the Cretaceous period and belongs to a group of dinosaurs called hadrosaurs. It’s most prominent feature is the long crest that extends from the skull of the Parasaurolophus. The function of its crest has been subject to many theories and explanations that will be discussed later on.

File:Human-parasaurolophus size comparison.svg

By Marmelad [CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons

Hadrosaurs

Hadrosaurs were plant-eating dinosaurs that have been found in every continent except Antarctica and Australia and lived at the same time as Tyrannosaurus Rex. Generally, hadrosaurs had duck-like mouths, which they used for cropping, grabbing, and cutting vegetation. The front of their mouths didn’t have any teeth, but farther back near their cheeks, they had hundreds of teeth. They were aligned similar to a cheese grater so that their teeth could withstand the wear and tear of grinding tough plant food. The duck-like mouth, the webbed feet, and how close the fossils were found to the shorelines all indicated to some scientists that they were aquatic. However, scientists later confirmed that these characteristics do not necessarily mean they were aquatic organisms. Hadrosaurs were gregarious creatures that lived together and took care of the young until they were old enough to survive on their own. However, the notion that the young were taken care off has been called into question recently. Hadrosaurs are divided into two main groups: hadrosaurins and lambeosaurines. Hadrosaurins had flat heads, while lambeosaurines had crests. As you could guess, Parasaurolophus was a lambeosaurine.

Function of the Crest

When the Parasaurolophus was thought to have lived in aquatic environments, scientists believed that the crest could have been used as a snorkel to breathe, while swimming underwater. However, CT scans later showed that there was no opening at the top of the crest. These CT scans showed that there were actually nasal passages in the crest, similar to a trombone. Later on, research found that these nasal passages were even more complex than the simple looped tubes found at first. Hence, the Parasaurolophus was thought to have produced low frequency sounds with the crest to communicate with one another. Computer and physical models confirm that this was possible so it has been widely accepted that the crest could have been used for this purpose. In 1962, a paleontologist proposed that the crest led to heightened olfactory capabilities. This paleontologist believed that the olfactory nerves were within the crest passages and the crest served as an enlarged olfactory region. However, the olfactory bulb and the position of the olfactory nerve sulci seem to show that the majority of olfactory epithelium was outside the crest. Hence, olfaction as a function of the crest has been rejected. Another hypothesis stated that the crest regulated the temperature of the brain. Neurological data doesn’t contradict this and a comparison with birds suggest that it could be possible that the crest had some physiological functions. The enlargement of the vestibule, a small cavity, in birds is associated with higher metabolic rates, water retention, and thermoregulation. There is still a lot of research to be done to see whether the crest was related to any physiological functions. ┬áIn addition, the crest is thought to have played a large role in visual display for the mating process.

File:Parasaurolophuspic steveoc.jpg

I, Steveoc 86 [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY 2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons

Works Cited
Evans, D. C. “Nasal Cavity Homologies and Cranial Crest Function in Lambeosaurine Dinosaurs.” Paleobiology 32.1 (2006): 109-25. Web.
Taylor, D. “Ancient Sounds, Modern Technology.” IEEE Parallel Distrib. Technol., Syst. Appl. IEEE Parallel & Distributed Technology: Systems & Applications 4.2 (1996): 12-14. Web.