The ankylosaurs of North America, with their heavy armor and massive tail clubs, are a familiar sight for dino enthusiasts and paleontologists. These four-legged herbivores roamed the Earth during the Late Cretaceous, some 68 million to 66 million years ago, and are considered among the last non-avian dinosaurs.
But a completely new species of ankylosaur discovered in Utah has thrown researchers for a loop because it doesn’t look anything like its North American relatives.
Unlike the commonly known ankylosaurs of the north — with skulls clad in a smooth, bony armor — the newfound species hailing from southwestern United States had a spiky head covered in pointy thorns.
Its peculiar appearance perplexed the science world for quite some time, Live Science reports, but now its secret has finally been revealed.
An Ankylosaur Like No Other
Discovered in 2008 in the Grand Staircase-Escalante National Monument (GSENM) of Kane County in southern Utah, the new ankylosaur species is being described in a study published today in the journal PeerJ.
At the same time, the eccentric armored dinosaur has been unveiled as a new exhibit at the Natural History Museum of Utah in Salt Lake City and will be housed by the institution’s Past Worlds Gallery starting today.
Unearthed from the GSENM’s Kaiparowits Formation — together with the remains of a duck-bill dinosaur, a new species of turtle, and a relative of alligators, notes CNN — the dinosaur’s bones took almost four years of preparations before they could be studied and made ready for the big unveiling.
A large part of this work has been performed by museum volunteer Randy Johnson, a retired chemist who helped prepare the dinosaur’s skull.
In honor of this effort, the newly discovered ankylosaur species has been dubbed Akainacephalus johnsoni — with the species name, johnsoni, recognizing Johnson’s contribution to the work and the genus name, Akainacephalus, literally meaning “spiky head” in Greek.
"Newly discovered armored dinosaur lived on a lost continent" — @CNNAshley reports on @NHMU's new ankylosaurid #dinosaur announcement in Salt Lake City this morning: https://t.co/znah68zVE8 pic.twitter.com/fwxp6CIz2g— NHMU (@NHMU) July 19, 2018
This unusual dinosaur is unique in more ways than one. First off, this is the most complete ankylosaur fossil from the Late Cretaceous ever uncovered both in Utah and the southwestern United States.
The A. johnsoni remains are comprised of the intact skull; much of the vertebral column, including a complete tail club; several elements from its fore and hind limb; and pieces of bony body armor that includes two neck rings and spiked armor plates, shows Phys.org, citing the University of Utah.
“It’s pretty rare to find so much of the skeleton in one place,” study co-author Randall Irmis remarks in a presentation video detailing the new find, given at the end of this article.
An ‘Intriguing’ Family History
But the truly remarkable thing about the newly discovered dinosaur in Utah is its “intriguing” blood ties, according to Phys.org.
In the video below, study lead author Jelle Wiersma, from James Cook University in Queensland, Australia, explains what makes A. johnsoni so unique among other ankylosaurs.
This 76-million-year-old ankylosaur stood 3.5 feet tall (a little over one meter) and measured around 16 feet in length (4.8 meters). Considered a medium-size ankylosaur, A. johnsoni was closely related to another ankylosaur found in the U.S. Southwest, namely the Nodocephalosaurus kirtlandensis of New Mexico.
Paleontologists were expecting to find that the two dinosaurs were, in turn, related to their North American cousins, such as the flat-armored Ankylosaurus and Euoplocephalus.
But the researchers were headed for a big surprise and ended up uncovering that A. johnsoni and N. kirtlandensis actually had more things in common with the Asian ankylosaurs that appeared 125 million years ago.
“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,” said Irmis, who is a curator of paleontology at the museum that now houses the dinosaur specimen and an associate professor at the University of Utah.
These findings suggest that ankylosaurs first arose in Asia between 125 million and 110 million years ago, during the Cretaceous Period, and later immigrated to North America in the Late Cretaceous by way of the Beringian land bridge.
The lowered sea levels recorded at the time facilitated the dinosaurs’ crossing from Asia to North America some 77 million years ago, when ankylosaurs first appeared in the region’s fossil record, explains Wiersma.
Since the northern and southern ankylosaurs of the Americas look so different from one each other, Wiersma believes the Late Cretaceous witnessed at least two migrations of ankylosaurids.
A previous migration event likely took place between 95-70 million years ago, when rising sea levels divided North America into two separate continents: Laramidia, to the west, and Appalachia — to the east.
Ankylosaurids likely made the crossing from Asia to western North America many times over, resulting in two distinct groups of ankylosaurs: one group that evolved a flatter skull armor, like the Ankylosaurus and Euoplocephalus in the north, and one group sporting a very spiky skull armor, such as Akainacephalus (which occupied the southern part of Laramidia) and Nodocephalosaurus in the south.
“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,” said Wiersma.