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Armoured dinosaur with spiky head unveiled at Utah museum

23 July 2018

Although parts of the roughly 16-foot-long (4.8 meters), spiky-headed dinosaur are missing, the scientists did manage to uncover a complete skull, pieces of bony armor, vertebrae and limb bones, as well as an nearly perfectly preserved tail and tail club.

The species of ankylosaur was a squat plant-eater that roamed southern Utah on four legs about 76 million years ago, during the late Cretaceous Period.

The extensive skeletal remains, including a complete skull, were excavated in Grand Staircase-Escalante National Monument.

Casts of the Akainacephalus johnsoni fossil are now on public display at the Natural History of Museum of Utah in Salt Lake City.

The arrangement of the dinosaur's bony armor - which features small cones and pyramids - was the key giveaway that it is more closely related to Asian species (such as Saichania and Tarchia) than to other North American species of its time (including Ankylosaurus and Euoplocephalus). The genus name comes from the Greek words akaina, which means "thorn" or "spike", and cephalus, meaning 'head.' The other part of the name honors Randy Johnson, a dedicated museum volunteer who skillfully reconstructed its skull. It also helped the team identify the close ties between this new species and the New Mexican ankylosaurid Nodocephalosaurus kirtlandensis. Although many ankylosaurids dinosaur fossils have been found over the years in the southwestern United States, the recent fossil offers the most complete skeleton of an ankylosaurid in the region.

It took four years to prepare the whole skeleton after the skeleton was first discovered. The characteristic bony armor covered it from head to tail, including bony plates for protection.

SWNSThe dinosaur was dug up from the desert at the Grand Staircase Escalante National Monument in Utah
SWNSThe dinosaur was dug up from the desert at the Grand Staircase Escalante National Monument in Utah

"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.

A working hypothesis is that two separate groups of ankylosaurid dinosaurs existed in North America during this time, and that a second migration wave from Asia, likely via a land bridge, made it possible.

Dubbed the Akainacephalus johnsoni, the herbivorous dinosaur, which has never before been described in scientific literature, was discovered by paleontologists in southern Utah. This one had pronounced spiky, bony armor covering the skull and snout, closely related to Asian ankylosaurids that lived 125 million years ago. Eventually, the sea shrank and the two parts combined to form what is now known as North America.

Artist's impression of the newly-discovered species. This is because the lowering of sea levels exposed the Beringian land bridge, which these dinosaurs must have crossed.

"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", said Ph.D student Jelle Wiersma.

The museum's palaeontology curator, Randall Irmis, who also advised Mr Wiersma and was the co-author of the study, said the reconstructed skeleton would excite many visitors.

Armoured dinosaur with spiky head unveiled at Utah museum