Jeyawati rugoculus A new Genus of Basal Hadrosaur from New Mexico

A team of American palaeontologists have announced the discovery of a new primitive duck-billed dinosaur from western New Mexico (United States).  This new ornithopod is just one of a number of discoveries made in the state of New Mexico that is permitting scientists a glimpse into life in a Cretaceous ecosystem, that until fifteen years ago was unknown to science.

Lead author and 2008 University of Nebraska-Lincoln graduate Andrew McDonald, has named this new species of dinosaur based on an incomplete skeleton found on land administered by the U.S. Bureau of Land Management.

Duck-billed Dinosaur

The new species, dubbed Jeyawati rugoculus, comes from rocks that preserve a swampy forest ecosystem that thrived near the shore of a vast inland sea 91 million years ago (Cenomanian faunal stage of the Cretaceous).  Jeyawati is a member of a remarkable assemblage of dinosaurs and other animals that was totally unknown 15 years ago.  Although the geology of the United States is extremely well known and has been intensively studied, these new finds will help palaeontologists piece together the varied faunas that existed on the coastal margins of the Western Interior Seaway.

Dinosaurs that co-existed with Jeyawati include Zuniceratops, one of the earliest known North American horned dinosaurs, and Nothronychus, a therizinosaur, strange herbivorous theropod dinosaurs belonging to a lineage that, until the discovery of Nothronychus, were known only from Asia.  Jeyawati adds another fascinating character to the story of North America’s dinosaurs.

An Illustration of Zuniceratops

Zuniceratops scale drawing.

Picture credit: Everything Dinosaur

Zuniceratops (Zuniceratops christopheri), is the earliest known ceratopsian to have sported a pair of brow horns in North America.  Known from several specimens, its presence in New Mexico suggests that ceratopsians with brow horns evolved in North America and not in their ancestral home of Asia.

An Illustration of Nothronychus

Picture credit: Everything Dinosaur

Nothronychus (Nothronychus mckinleyi) is the first member of the therizinosaurids to be found outside Asia.  It is also one of the most complete fossils of these bizarre theropod dinosaurs.

To view a model of Nothronychus and other dinosaur models: CollectA Age of Dinosaurs Prehistoric Life Models.

The discovery of dinosaur fossils such as Zuniceratops, Nothronychus and Jeyawati is helping scientists to understand more about the unique fauna of the New Mexico swampland habitat.

The first part of the name Jeyawati rugoculus is pronounced “HEY-a-WHAT-ee,” essentially meaning “grinding mouth,” and is derived from two words in the language of the Zuni people, who have long inhabited western New Mexico.  The meaning of the name Jeyawati is a reference to the sophisticated chewing mechanism evolved by the herbivorous lineage of hadrosaurs to which Jeyawati belongs.  The second part of the name, rugoculus, comes from the Latin words ruga and oculus and means “wrinkle eye,” describing a unique feature of the new species.

One of the bones that forms the eye socket exhibits a peculiar rough or wrinkly texture on its outer side; in other dinosaurs, such a texture on skull bones has been suggested to have supported enlarged scales on the top of the skull.  Thus, Jeyawati rugoculus might have sported one or more large scales above and behind its eye, giving it a strangely striking appearance.

Jeyawati rugoculus

The enlarged scales around the eye, may have developed in mature adults and could have been used to communicate visually with other members of the herd.  It is not known whether Jeyawati rugoculus sported these eye markings all the time once it had reached breeding age, or whether the eye markings developed purely for the breeding season each year, in the same way that stags develop their antlers for rutting.

This herbivorous dinosaur evidently endured a hard life.  Among the many bits of ribs found with the skull bones, several large pieces have a swollen, rough surface, indicating that the animal suffered broken ribs through some misfortune and that those injuries had healed by the time the animal died.

The partial skull and other fragments including vertebrae of Jeyawati were discovered in 1996 by paleontologist Douglas Wolfe, principal investigator of the Zuni Basin Palaeontological Project, his wife Hazel, and their son Christopher.  Subsequent excavation and collection was carried out with the permission of the Bureau of Land Management over the following 13 years with the aid of James Kirkland (State Palaeontologist with the Utah Geological Survey ), volunteers from the Southwest Palaeontological Society, and many other volunteers from around the country.

Fragile Fossils

The fragile fossils were carefully freed from the remaining rock by preparators Harold and Phyllis Bolan and are being stored at the Arizona Museum of Natural History in Mesa.

In 2006, Andrew McDonald, then an undergraduate geology student at the University of Nebraska-Lincoln under the supervision of Professor David Loope, began a project to describe the fossil in the university’s Undergraduate Creative Activities and Research Experiences (UCARE) programme.  McDonald and Wolfe first met when McDonald was a student at Sacred Heart-Griffin High School in Springfield, Illinois and when it came time for him to look for a UCARE research project, he received permission from Wolfe to work on the specimen.

McDonald’s analysis revealed that the bones were sufficiently distinct from those of other dinosaurs to warrant the naming of a new species.  It also became clear that Jeyawati is a close relative of the duck-billed hadrosaurs, which were immensely abundant across the Northern Hemisphere for much of the Cretaceous.  However, Jeyawati retains some primitive features of the teeth and jaws that preclude it from being a fully-fledged hadrosaur, so it has been ascribed to basal Hadrosauridae.  McDonald, a PhD student, the lead author on the paper featuring this new dinosaur, published in the scientific journal “Journal of Vertebrate Palaeontology”, has been a student since 2008 at the University of Pennsylvania, where he works with palaeontologist Peter Dodson.

He has a more extensive project under way to determine the evolutionary relationships of Jeyawati and many of its relatives.

The above article has been sourced from media/newswire press release.