Akainacephalus Artist Illustration
Life reconstruction (closeup) of the new armored dinosaur Akainacephalus johnsoni. Andrey Atuchin and the Denver Museum of Nature & Science

With the help of 76-million-year-old fossils unearthed from the Grand Staircase-Escalante National Monument (GSENM) in southern Utah, scientists have described a whole new genus and species of the heavily armored ankylosaurid dinosaurs.

The new species, which is now being called Akainacephalus johnsoni, was found 10 years ago. It is the most complete skeleton of an ankylosaurid dinosaur ever to be discovered in the southwestern United States with a complete skull and tail club, nearly complete vertical column, several limb elements, and a bony body armor with two neck rings.

Back then, the team behind the discovery thought the dinosaur, expected to be 13-16 feet long, was pretty similar to other members of the family described in North American fossil record, but the analysis of the remains revealed a completely different story.

During the Late Cretaceous or some 100 to 66 million years ago, the continent of North America was split into two western and eastern parts due to an interior seaway in between.

Ankylosaurids first originated in Asia some 125 to 100 million years, but they didn’t appear on the western North-American fossil record until the 77 million years ago. This led the group to think that the armored dinosaur found would have had a smooth bony armor on the skull, just like others in the region.

However, a detailed study of the fossils revealed that the dinosaur found in Utah had a bony armor with pronounced spikes covered its head and snout. This particular feature, as the researchers described, was more closely related to those ankylosaurids that lived much earlier in Asia.

"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," Randall Irmis, a co-author of the study, said in a statement.

On the basis of the surprising find, the researchers involved in the study posited that some of the armored dinosaurs from Asia, including A. johnsoni, might have migrated to western North America, aka Laramidia, during the Late Cretaceous through a land bridge, which likely appeared for brief periods due to decreasing sea-levels.

"It is always exciting to name a new fossil taxon, but it is equally exciting if that taxon also provides additional insights into the bigger picture of its life, such as its diet or aspects of its behavior, and the environment it lived in," Jelle Wiersma, the lead author of the study, stated.

The researchers think that at least two immigration events took place during that period, which probably allowed two different groups of ankylosaurids to thrive in the same region, far away from those living in the eastern part of the continent.

The study titled “A new southern Laramidian ankylosaurid, Akainacephalus johnsoni gen. et sp. nov., from the upper Campanian Kaiparowits Formation of southern Utah, USA,” was published in the journal PeerJ.