A new analysis indicates that the newfound, 76-million-year-old ankylosaur species, dubbed Akainacephalus johnsoni, likely had Asian ancestors that migrated to North America when sea levels between the continents were low, researchers said in a new study, published online today (July 19) in the journal PeerJ.
The extensive skeletal remains, including a complete skull, were excavated in Grand Staircase-Escalante National Monument.
It includes a complete skull, much of the vertebral column, including a complete tail club, several fore and hind limbs elements, and bony body armour that includes two neck rings and spiked armour plates. It's considered the most complete Late Cretaceous ankylosaur ever found in Utah - or in the entire southwestern United States for that matter. The species name of the dinosaur honors museum volunteer Randy Johnson, who prepared the skull.
"Someone once told me that Akainacephalus, and ankylosaurs in general, were quite ugly and had a face only a mother could love".
Wiersma described the Akainacephalus as a four-legged, medium-sized dinosaur that was roughly 5 metres long and 1.5 metres tall.
Excitingly, casts of the Akainacephalus johnsoni fossil are now on public display at the Natural History Museum of Utah in Salt Lake City If you're in the area, check it out and leave us a review of the exhibit below.
It was found in the monument's Kaiparowits Formation, where rocks and mud were deposited by rivers and streams.
The uniquely pointy and more pronounced shape of the armour covering the Akainacephalus has led researchers to believe that while the species was discovered in North America, its closest relatives come from Asia.
Ankylosaurids were herbivores known for their intimidating bony tail clubs and body armor, and their fossils have been found in North America before.
The paleontologists found a great number of A. johnsoni's remains - so many that after the researchers covered the finds in plaster jackets and brought them to the lab, it took almost four years for preparators to remove the fossils from the surrounding rock and debris.
"Most of the armour on Ankylosaurids from North America are relatively flat but [the Akainacephalus] actually has very spiky and bulbus armour all across its head so that makes it very unique", Mr Wiersma said.
Akainacephalus, as well as a cousin called Nodocephalosaurus that lived in New Mexico a couple million years later, possessed spiky head armor similar to Asian members of this dinosaur group.
Dr Randall Irmis, co-author of the study, said: "A reasonable hypothesis would be that ankylosaurids from Utah are related to those found elsewhere in western North America, so we were really surprised to discover that Akainacephalus was so closely related to species from Asia".
When sea levels reached some of the highest in the history of our planet, the Western Interior Seaway effectively split the North American continent in two. This part of Laramidia was incredibly diverse in plant and animal life between 75 million and 80 million years ago.