Piece of the Puzzle

Grad student identifies a new species of dinosaur.
August 2010

"According to my parents, I've been interested in dinosaurs since I was a very young child," notes graduate student Andrew McDonald, "farther back than I can remember." By high school, he had decided to make a career out of studying them. Now, still two years short of his Ph.D., he's made a major contribution to the field of paleontology by becoming the first to describe a new dinosaur species.

Eking out a rough life in the late Cretaceous epoch about 96 million years ago, Jeyawati rugoculus inhabited a swampy landscape near an inland sea that covered the central regions of what is now North America. Jeyawati had a highly developed set of teeth, evolved to consume vegetation, hence its first name, which translates to "grinding mouth" in the Zuni language. The herbivore was probably about 13 to 16 feet in length.

Jeyawati's partial remains were discovered in 1996 in western New Mexico by Douglas Wolfe, principal investigator of the Zuni Basin Paleontological Project. At first, the fact that the specimen represented an entirely new species wasn't fully recognized because the Zuni Basin work was overshadowed by more glamorous discoveries elsewhere in North America, including a Tyrannosaurus Rex in 1990.

But in 2006, McDonald, then a sophomore in geology at the University of Nebraska casting about for a senior-thesis topic, became intrigued by this odd beast that Wolfe had dug up a decade before. "Every year since 2003, I've joined Doug in the field for a couple of weeks in the summer," he says. "I asked Doug if I could work on this fossil, and he agreed." McDonald carried on his work when he came to Penn as a graduate student in 2008 to study with Peter Dodson, a professor in anatomy and paleontology with appointments in the School of Arts and Sciences as well as the School of Veterinary Medicine.

"Eking out a rough life in the late Cretaceous epoch about 96 million years ago, Jeyawati rugoculus inhabited a swampy landscape near an inland sea that covered the central regions of what is now North America." -Andrew McDonald

It was something of a risk because, as McDonald recalls, "it wasn't exactly clear whether the fossil was preserved enough to determine if it was a new species or not." As he continued to study the fossil, comparing it with other specimens preserved in museums and described in the scientific literature, he says, "it became clear that there were a few features in this material that were unique and that indicated that this fossil represented a new species."

One of those characteristics gave the animal the second part of its name: rugoculus, which is Latin for "wrinkle eye." That refers to the rough, wrinkly texture of the bones around the eye socket. "In other dinosaurs with this texture, it's thought that these ridges and pits supported enlarged scales for some purpose," says McDonald. So far, Jeyawati is the only dinosaur of its type known to display such a trait. Known as basal hadrosaurids, they include the earliest known horned dinosaur in North America and are the forerunners of one of the most successful and widespread dinosaur types, the "duck-billed" dinosaurs or hadrosaurs.

Although it's difficult to draw too many conclusions from only a single specimen, it's possible to make some educated speculations about Jeyawati's day-to-day life, which, says McDonald, probably consisted of "a lot of eating punctuated by sheer terror every now and then." Natural enemies would have included large predators such as T. Rex, although Jeyawati may have been able to outrun larger animals. If Jeyawati was a herding animal, McDonald speculates, it would also have found safety in numbers.

McDonald and Wolfe, along with colleague James Kirkland, the state paleontologist of Utah, published their findings in the May 2010 issue of the Journal of Vertebrate Paleontology.

Although further answers about Jeyawati await discovery of other fossil specimens, McDonald is continuing to study this family of dinosaurs for his dissertation, exploring the evolutionary relationships of these animals to other species throughout the world. The identification of Jeyawati is an important early step. "Jeyawati is really a very interesting piece of the puzzle," he remarks.