Parasaurolophus

Parasaurolophus, meaning "near crested lizard," is one of the most recognisable lambeosaurine hadrosaurids. It is famous for the long, tubular crest that curves backward from its skull. Paleontologists universally recognise three species: P. walkeri, the type species found with a long, curved crest; P. tubicen, a longer-crested variety from New Mexico; and P. cyrtocristatus, which had a smaller, more strongly recurved crest. A potential fourth species from China, P. jiayinensis, is typically assigned to the genus Charonosaurus.

This large herbivore reached up to 9.5 m in length and possessed the standard hadrosaurid anatomy: a duck-billed skull, complex dental batteries, fleshy cheeks, and the ability to move on either two or four legs. Its most distinctive trait was its hollow crest, formed by elongated nasal bones and connected to its nasal passages. CT scans of P. tubicen (Sullivan & Williamson 1999; Diegert & Williamson 1998) have revealed a complex internal structure of folded tubes. This arrangement functioned much like a built-in trombone or other wind instrument.

Fossilized skin impressions show that Parasaurolophus was covered in small polygonal scales, potentially with longer scutes running along its spine. The crests grew as the animal aged. Juveniles had very short crests that lengthened as they reached maturity, making them a useful marker for identifying different growth stages.

Researchers have established several likely functions for the dinosaur's crest. Acoustic resonance is well-supported by studies such as Weishampel (1981). Biomechanical models show the hollow tubes could produce low-frequency calls, around a 30 Hz fundamental, which would carry across long distances. The distinct shapes of the crests among species also suggest they served for species recognition. Additionally, the crests probably functioned as display structures, possibly enhanced by vibrant colour patterns for sexual selection. While earlier theories suggested thermoregulation, this view has lost support in recent years.

Parasaurolophus inhabited coastal floodplains, living in herds alongside other hadrosaurids, ankylosaurs, ceratopsians, and large predators like tyrannosaurids.

• P. walkeri holotype (ROM 768) — Royal Ontario Museum.
• P. tubicen holotype (PMU R1250) — most-CT-scanned crest specimen.
• P. cyrtocristatus holotype (FMNH P 27393) — Field Museum.
• Multiple growth-series specimens from various Laramidian formations.

Crest acoustic function — well-supported; precise frequency range debated. Species count and validity — three species widely accepted. Internal crest morphology — well-mapped for P. tubicen, less so for other species.

Parasaurolophus is one of the most-recognisable hadrosaurs in popular culture. Walking with Dinosaurs (1999) features it calling with the resonator-tube crest. Jurassic Park (1993) shows a herd in the iconic "they do move in herds" scene. Disney's Dinosaur (2000) features a Parasaurolophus as a supporting character.

• ornithopoda
• edmontosaurus
• lambeosaurus
• hadrosaurus

• Sullivan, R. M., & Williamson, T. E. (1999). A new skull of Parasaurolophus from the Kirtland Formation of New Mexico and a revision of the genus. New Mexico Museum of Natural History and Science Bulletin, 15.
• Weishampel, D. B. (1981). Acoustic analyses of potential vocalization in lambeosaurine dinosaurs. Paleobiology, 7, 252–261.
• Diegert, C. F., & Williamson, T. E. (1998). A digital acoustic model of the lambeosaurine hadrosaur Parasaurolophus tubicen. Journal of Vertebrate Paleontology, 18, 38A.
• Evans, D. C., et al. (2009). A juvenile Parasaurolophus (Ornithischia: Hadrosauridae) braincase from the Kaiparowits Formation. Journal of Vertebrate Paleontology, 29, 1080–1087.