Researchers have uncovered a remarkable set of fossils in southern Utah, belonging to an entirely new species and genus (group of species) of armored dinosaur, according to a study published in the open-access journal PeerJ.
Akainacephalus johnsoni, as the dinosaur has been named, lived around 76 million years ago during the late Cretaceous Period (100.5 million to 66 million years ago) in the southern region of Laramidia—an island continent located to the west of an ocean that once split North America in two.
The bones were found 10 years ago in the Kaiparowits Formation—a formation of sedimentary rock in the Grand Staircase-Escalante National Monument, Kane County—during an expedition led by the Natural History Museum of Utah, although the remains have only recently been prepared and analyzed.
A. johnsoni belongs to a family of dinosaurs known as Ankylosauridae—four-legged herbivorous dinosaurs with imposing bony tail clubs and that originated in what is now Asia between 125 million and 100 million years ago. They later appeared in the fossil record of western North America around 77 million years ago.
The newly discovered fossils represent the most complete skeleton of an ankylosaurid dinosaur ever found in the southwestern United States and could reveal new details about the diversity and evolution of this group. The set of bones includes a complete skull, much of the vertebral column, a complete tail club, several fore and hind limb parts and body armor.
The bones suggest the animal measured between 13 feet and16 feet long and stood 3-and-a-half feet tall at the hips. It was covered in body armor from head to tail.
Intriguingly, the skeleton contains several unique features, including spikes and cones on the bony plate covering the head and snout. These traits are similar to those found on the New Mexican ankylosaurid Nodocephelausaurus kirtlandensis;however, they are distinct from all other known late Cretaceous North American dinosaurs from this family.
In fact, the two species appear to be much more closely related to Asian ankylosaurids, which have more pronounced spikes covering their skulls.
"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 from the Natural History Museum of Utah, said in a statement.
This close relationship with species from Asia could be explained by a series of migrations during the late Cretaceous Period, which took place when sea levels dropped, exposing the Beringian land bridge. This allowed animals to move between Asia and western North America, or Laramidia.
The fact that North America was split in two meant that these migrants evolved differently to Ankylosaurids in the eastern portion of the continent, hence their distinctive characteristics.
"It is extremely fascinating and important for the science of paleontology that we can read so much information from the fossil record, allowing us to better understand extinct organisms and the ecosystems they were a part of," Jelle Wiersma, lead author of the study from James Cook University Australia, said.
The first of the new dinosaur's name—which denotes the genus—derives from the Greek words akaina meaning "thorn" or "spike" and cephalus meaning "head." The second part—marking the species—refers to Randy Johnson, a volunteer at the Natural History Museum of Utah, where the bones are being exhibited, who helped to prepare the skull.
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