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Parasaurolophus

Parasaurolophus is a late Cretaceous duck-billed dinosaur that is among the most recognizable of the Mesozoic era because of its long distinctive backward curved crest. Like other hadrosaurs of this period, Parasaurolophus was an absolutely massive herbivore - among the largest terrestrial animals - with a size averaging 30 feet long and a weight hovering around 4 tons. Parasaurolophus was named in reference to his contemporary compatriot Saurolophus, another hadrosaur to which it was more or less related. These two dinosaurs probably descended from Prosaurolophus, a hadrosaur that lived millions of years earlier and whose ridge was much less developed. But in general, hadrosaurs of the Upper Cretaceous period evolved from ornithopod herbivores of the Upper Jurassic and Lower Cretaceous periods, such as the famous Iguanodon.

Like the vast majority of duck-billed dinosaurs, Parasaurolophus used its narrow, solid beak to cut rough vegetation from trees and shrubs; it then crushed each bite of food with hundreds of small teeth wrapped in his jaw. As the front teeth wore out, new ones from behind came forward to replace them; a process that was repeated itself indefinitely throughout the life of this animal.

Incomplete fossils

As is often the case in the world of paleontology, Parasaurolophus holotype specimen, Parasaurolophus walkeri, is an incomplete fossil discovered in 1922 by Levi Sternberg in the province of Alberta, Canada, in a place that now corresponds to Dinosaur Provincial Park. As of this day, this fossil remains the most complete specimen of Parasaurolophus. Other species of this dinosaur have also been dug up in different places such as P. tubicen found in New Mexico, which was slightly larger than walkeri and had a longer ridge. There is also P. cyrtocristatus which was found in the southwestern United States and was the smallest of Parasaurolophus, with a weight of about one ton.

Long backward curved crest

Parasaurolophus hadrosaur fossil
Skeleton fossil of Parasaurolophus cyrtocristatus

As mentioned above, the distinguishing feature of Parasaurolophus which makes it so easily recognizable is its long backward curved crest that grew on top of its cranium and whose hollow, empty surface connected with the nasals and back of the throat. This ridge could play many functions and there is several theory to explain its usefulness.

Communication tool

Recently, a team of paleontologists computer-modeled the Parasaurolophus crest from several fossil specimens and virtually circulated air through it. The simulation produced a deep and resonant sound indicating that the ridge of this dinosaur allowed him to at least communicate with other members of the herd, as example to report danger or sexual availability.

Several hypotheses on the utility of the ridge

When the first remains of Parasaurolophus were discovered, there was much speculation about the role of its strange cranial decoration. Some paleontologists believed that this dinosaur spent most of its time underwater and used its empty crest as a snorkel to breathe. Others have suggested that the ridge was used as a weapon in intra-species fighting or that it was even studded with specialized nerve endings that could easily shred nearby vegetation. These two hypotheses, however, have not stood the test of time very long since they have no scientific basis.

Thermal regulator

Evolution rarely produces an anatomical structure for a single reason and it is highly likely that, in addition to allowing him to communicate with its fellows, the ridge of Parasaurolophus also played the role of thermal regulator. The broad surface of this bone could allow this cold-blooded hadrosaur (at least that's what we presume) to absorb the ambient heat during the day and slowly dissipate it during the night, allowing it to maintain a near-constant homeothermic body temperature. Unlike feathered dinosaurs, Parasaurolophus is unlikely to have had a warm-blooded metabolism.

Sexual selection characteristic and recognition tool

On the other hand, the crest of this hadrosaur fulfilled a third function: like the antlers of modern deer, it had a slightly different shape on each individual in order to allow the members of a herd to recognize each other from a far. In addition, it is plausible that males had larger ridges than females and that they were a sexual selection feature during mating season - males with larger ridges were more attractive.

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