With its long, distinctive, backward-curving crest, Parasaurolophus was one of the most recognizable dinosaurs of the Mesozoic Era. Here are 10 facts you may (or may not) have known about this gentle plant-eater. (See also a gallery of Parasaurolophus pictures.)
1. Parasaurolophus was a duck-billed dinosaur.
Even though its snout was far from its most prominent feature, Parasaurolophus is classified as a hadrosaur, or duck-billed dinosaur. Hadrosaurs evolved from (and technically are counted among) the plant-eating ornithopods of the late Jurassic and early Cretaceous periods, the most famous example of which was Iguanodon--and no, they have nothing to do with modern ducks.
2. There are three known species of Parasaurolophus.
As is often the case in paleontology, the "type fossil" of Parasaurolophus, Parasaurolophus walkeri, consists of a single, incomplete skeleton discovered in Canada. Parasaurolophus tubicen, from New Mexico, was slightly bigger than walkeri, with a longer head crest, and Parasaurolophus cyrtocristatus (of the southwestern U.S.) was the smallest of the group, only weighing about a ton.
3. Parasaurolophus was a close relative of Charonosaurus...
One of the odd things about the late Cretaceous period is that the dinosaurs of North America closely mirrored those of Eurasia, a reflection of how the earth's continents were arranged tens of millions of years ago. For all intents and purposes, the Asian Charonosaurus was identical to Parasaurolophus, albeit slightly larger, measuring about 40 feet from head to tail and weighing upwards of six tons.
4. ...but not necessarily of Saurolophus or Prosaurolophus.
Confusingly, Parasaurolophus ("almost Saurolophus") was named in reference to its fellow hadrosaur Saurolophus, to which it wasn't particularly closely related. Further complicating matters, both of these dinosaurs may (or may not) have descended from the much less ornately decorated Prosaurolophus, which lived a few million years earlier; paleontologists are still sorting this out!
5. Parasaurolophus used its head crest for mating calls...
The most distinctive feature of Parasaurolophus was its long, narrow, backward-curving head crest. Recently, a team of paleontologists computer-modeled this crest from various fossil specimens and fed it with a virtual blast of air. Lo and behold, the crest produced a deep, resonating sound--evidence that Parasaurolophus communicated this way with other members of the herd.
6. ...and to regulate its body temperature...
Evolution rarely produces an anatomical structure for strictly one function. It's very likely that the head crest of Parasaurolophus served double duty as a temperature-regulation device: that is, its large surface area allowed this presumably cold-blooded dinosaur to soak up heat during the day, and dissipate it slowly at night, allowing it to enjoy a "homeothermic" metabolism.
7. ...and to differentiate itself from other members of the herd...
The head crest of Parasaurolophus probably had yet a third function: like the antlers of a modern-day deer, its slightly different shape on different individuals allowed members of the herd to recognize one another. It's also likely, but not yet proven, that male Parasaurolophus possessed bigger crests than females, an example of a sexually selected characteristic that came in handy during mating season.
8. ...but not as a weapon or as a snorkel!
When Parasaurolophus was first discovered, in 1920, speculation about its crest ran rampant. Some paleontologists thought this dinosaur spent most of its time underwater, using its crest like a snorkel, while others proposed that the crest functioned as a weapon during intra-species combat or even had specialized nerve endings that could "sniff out" nearby vegetation. Short answer: No!
9. Parasaurolophus could run on two or four legs.
As a rule, hadrosaurs were the largest land animals capable of running on two legs, albeit only for short stretches of time. The five- or six-ton Parasaurolophus probably spent most of its day browsing for vegetation on all four legs, but could break into a reasonable trot when it was being pursued by predators (babies and juveniles, at most risk of being eaten, were particularly nimble).
10. The teeth of Parasaurolophus grew throughout its lifetime.
Like most hadrosaurs, Parasaurolophus used its tough, narrow beak to clip off vegetation, then ground up each mouthful with the hundreds of small teeth packed into its teeth and jaws. As the teeth near the front of its mouth eroded away, new ones from the back gradually made their way forward, a process that presumably continued unabated throughout this dinosaur's lifetime.