Description and Classification

Parasaurolophus was a large herbivorous dinosaur, typically reaching lengths of about 9 to 10 meters (30 to 33 feet) and weighing an estimated 2.5 to 5 metric tons (2.7 to 5.5 short tons). It could walk on two legs (bipedal) to run or reach higher vegetation, and also on all four legs (quadrupedal), likely for slower walking or grazing. Skin impressions found with some fossils show that its skin was covered in small, bumpy scales, known as tubercles, with no larger armor.

Parasaurolophus belongs to the order Ornithischia (bird-hipped dinosaurs) and the family Hadrosauridae. Within Hadrosauridae, it is classified under the subfamily Lambeosaurinae, which includes other hadrosaurs with hollow, elaborate cranial crests, such as Corythosaurus and Lambeosaurus. The crest of Parasaurolophus was formed by elongated nasal and premaxillary bones that extended backward from the snout. Internally, the crest contained a series of hollow tubes that connected to the dinosaur’s nostrils and airway. Three species are generally recognized: P. walkeri from Alberta, P. tubicen from New Mexico, and P. cyrtocristatus from New Mexico and Utah, each differing mainly in the size and shape of their crests.

Distinguishing Features

Several features make Parasaurolophus distinct, especially its unique headgear:

• Large Cranial Crest: The most iconic feature is its long, hollow, curved crest projecting backward from the skull. The internal passages within the crest varied between species. For example, P. walkeri had a long, gently curving crest, P. tubicen had a very long and straighter crest with more complex internal tubes, and P. cyrtocristatus had a much shorter, more strongly curved crest.
• Duck-like Beak: Like other hadrosaurs, Parasaurolophus had a broad, toothless beak at the front of its mouth, well-suited for cropping leaves and twigs.
• Dental Batteries: Further back in its jaws, it possessed hundreds of closely packed teeth arranged in “dental batteries.” These teeth were constantly replaced as they wore down, providing an efficient grinding surface for tough plant material.
• Facultative Quadrupedalism: Its strong hind limbs were longer than its forelimbs, but the forelimbs were robust enough to support its weight, indicating it could switch between two-legged and four-legged movement.

Paleoenvironment and Diet

Parasaurolophus lived in warm, humid coastal plain environments, often near rivers, swamps, and inland seas that covered parts of North America during the Late Cretaceous. These environments supported lush vegetation, providing ample food for large herbivores. Its diet consisted of various plants, likely including conifers, ferns, cycads, and flowering plants. It would have used its beak to snip vegetation and its powerful dental batteries to grind it down before swallowing.

Parasaurolophus shared its habitat with a diverse range of other dinosaurs. Predators in these ecosystems included large theropods like Albertosaurus and Daspletosaurus. Other herbivores living alongside Parasaurolophus included other hadrosaurs such as Edmontosaurus, horned dinosaurs like Chasmosaurus and Pentaceratops, and armored dinosaurs like Ankylosaurus. While direct evidence of herding in Parasaurolophus is limited, many other hadrosaurs are known to have lived in groups, so it is plausible that Parasaurolophus did as well.

Significance and Ongoing Research

Parasaurolophus is significant for several reasons, particularly due to its unique crest. The function of this crest has been a subject of much scientific debate and research. The most widely accepted theory is that the hollow chambers within the crest acted as a resonating device, allowing Parasaurolophus to produce distinctive, low-frequency sounds for communication over long distances. This could have been used for warning others of danger, attracting mates, or maintaining social cohesion within a group. The crest may have also served as a visual display feature for species recognition or attracting mates, with different crest shapes possibly distinguishing between species or sexes.

Ongoing research continues to explore the biology and behavior of Parasaurolophus. Scientists use CT scans to study the internal structure of the crest in more detail, helping to reconstruct how it might have produced sound. Studies of its bone structure, growth patterns, and the environments it inhabited help paint a fuller picture of this remarkable dinosaur. As one of the most recognizable and popular dinosaurs, Parasaurolophus continues to captivate public interest and serves as an excellent example of the diverse adaptations found in the dinosaur world.