New tubular crested dinosaur skull reveals evolution of bizarre crest

The first new skull discovered in nearly a century from a rare species of the iconic tubular-crested dinosaur Parasaurolophus was announced in the newspaper today PeerJ. The exquisite preservation of the skull, especially the odd tube-shaped nasal passage, finally revealed the structure of the ridge after decades of disagreement.

Despite its extreme morphology, the details of the specimen show that the ridge is shaped much like the ridges of other related duck-billed dinosaurs. Joe Sertich, curator of dinosaurs at the Denver Museum of Nature & Science and leader of the team that discovered the specimen said, “This specimen is a wonderful example of amazing creatures evolving from a single ancestor.”

“Imagine your nose growing out of your face, three feet behind your head, then turning around to fix itself above your eyes. The parasaurolophus was breathing through eight feet of pipe before the oxygen reached its head,” said Terry Gates, a paleontologist at North Carolina State University.

“Over the past 100 years, ideas for the exaggerated tube ridge have ranged from snorkels to super sniffers,” said David Evans, Temerty Chair in Vertebrate Paleontology and Vice President of Natural History at the Royal Museum. from Ontario. “But after decades of study, we now believe that these ridges primarily functioned as sound resonators and visual displays used to communicate within their own species.”

Among the most recognizable dinosaurs, the duck-billed Parasaurolophus sported an elongated tube-like crest on its head containing an internal network of airways. Three species of Parasaurolophus are currently recognized, ranging from Alberta to New Mexico in rocks between 77 and 73.5 million years old. The new skull belongs to Parasaurolophus cyrtocristatus, previously known from a single specimen collected in the same area of ​​New Mexico in 1923 by the legendary fossil hunter Charles H. Sternberg. Both specimens exhibit a shorter and more curved ridge than the other species, a feature that may be related to their immaturity at death.

The partial skull was discovered in 2017 by Erin Spear, Ph.D., an ecology researcher for the Smithsonian, while exploring the badlands of northwestern New Mexico as part of a team from the Denver Museum of Nature. & Science. Located deep in the Bisti / De-Na-Zin Desert in New Mexico, only a tiny portion of the skull was visible on a steep sandstone slope. Museum volunteers led by Sertich were surprised to find the ridge intact as they carefully chiseled the specimen into the sandstone. Abundant bone fragments at the site indicated that much of the skeleton may have been preserved on an ancient sand bar, but the partial skull, part of the lower jaw, and a handful of ribs survived. to erosion.

Today, the badlands of northwestern New Mexico are dry and sparsely vegetated, a dramatic contrast to the lush lowland floodplains preserved in their rocks. 75 million years ago, when Parasaurolophus lived in the region, North America was divided into two landmasses by a wide seaway. Laramidia, the ribbon of land to the west, stretched from today’s Alaska to central Mexico, hosting several episodes of mountain building in the early stages of today’s Rocky Mountain building. These mountain building events have helped preserve various dinosaur ecosystems along their eastern flanks, some of the best preserved and most continuous on the planet. Parasaurolophus shared lush, subtropical floodplains with other crested duck-billed dinosaurs, a wide array of horned dinosaurs, and the early tyrannosaurs alongside many emerging and modern groups of alligators, turtles, and plants.

“The preservation of this new skull is spectacular, finally revealing in detail the bones that make up the crest of this incredible dinosaur known to almost every dinosaur-obsessed child,” Sertich said. “This only reinforces the importance of protecting our public lands for scientific discovery.”

“My jaw dropped when I first saw the fossil,” Gates said. He continued, “I have been waiting for almost 20 years to see a specimen of this quality.”

“This specimen is truly remarkable in its preservation,” said Evans, who also worked on this iconic dinosaur for almost two decades. “He answered long-standing questions about how the ridge is constructed and the validity of this particular species. For me, this fossil is very exciting.”

For decades, the Parasaurolophus family tree has placed the two long species of straight crested Parasaurolophus (P. walkeri from Alberta and P. tubicen from younger rocks in New Mexico) as the most closely related, although they are separated by more than 1000 miles (1600 km) and 2.5 million years. Analysis of additional features of the skull excluding the crest, along with information from other Parasaurolophus finds from southern Utah, suggests for the first time that all species from southern New Mexico and of Utah might be more closely related than they are to their northern cousin. . This matches patterns seen in other groups of dinosaurs of the same age, including the horned dinosaurs.

The article describing the new skull of Parasaurolophus appears in the January 25, 2021, issue of the newspaper PeerJ.

Provided by Denver Museum of Nature & Science