Parasaurolophus was a large, herbivorous, or plant-eating, dinosaur that inhabited North America during the late Cretaceous period, about 65 to 98 million years ago. Parasaurolophus is classified as a member of the family Hadrosauridae, which contains the crested, duckbilled dinosaurs and belongs to the order Ornithischia (the bird-hipped dinosaurs). 

Apart from its bill, which was shorter than that of other hadrosaurs, the most distinctive feature of Parasaurolophus was its hornlike crest, which reached up to 6 feet (1.8 meters) in length and curved back from the head. This attribute inspired the name Parasaurolophus, which means “beside Saurolophus,” referring to another crested dinosaur. Inside the crest, which may have been shorter in females, paired nasal passages extended from the nostrils to the tip and then curved back down to the snout. Although paleontologists are not certain of the crest’s function, many believe that it served as a resonating chamber, producing a distinctive bellow that allowed conspecifics—that is, members of the same species—to communicate. While Parasaurolophus moved through heavy brush, the crest may have tucked into an unusual notch in the spine at the point where the crest abutted the back. In this position, the crest would have cleared a path by sweeping vegetation up or sideways, away from the body, in a manner similar to that of the cassowary, a modern bird. 

Parasaurolophus grew to an adult length of about 33 feet (10 meters), height of 15 feet (4.6 meters), and weight of 3 to 4 tons. Like all hadrosaurs, Parasaurolophus had long hind limbs and shorter forelimbs. Although it probably moved on all fours while foraging, presumably it was capable of sprinting away from predators on its rear legs. Parasaurolophus had a tail with an unusually broad base, which has caused paleontologists to speculate that it may have been used as a signaling device, either in courtship displays or possibly as another identifier among conspecifics.

The first fossil evidence of Parasaurolophus was found in the Canadian province of Alberta and described in 1922. Remains have also been recovered in New Mexico and Utah in the United States.

-information above is from Brittanica Kids