A fossil of a new species of armoured dinosaur has been discovered in Utah, changing how scientists believe the animals evolved.
It took almost four years to prepare and analyse the medium-sized dinosaur’s skeleton, which is 13-16ft long (4-5m) and about 42 inches (1.5m) tall at the hip, and one of the most complete ever discovered in this region of the US.
Armoured dinosaurs, or ankylosauridae, existed exclusively in the northern hemisphere before they became extinct 66 million years ago.
Fossils have been found in North America, East Asia and Europe, and the three regions have different forms of armour to differentiate them.
But the new species, Akainacephalus johnsoni, breaks the rules for North American ankylosaurids.
Instead of the distinctive smooth armour on the skull shown on other North American fossils, the new species has pointed bones protruding in ridges up to its snout – similar to Asian ankylosaurid fossils.
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.”
“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 behaviour, and the environment it lived in,” said lead author Jelle Wiersma.
The species’ name was given in honour of Randy Johnson, a dedicated museum volunteer who spent hundreds of hours preparing the fossil’s skull by separating it from surrounding rock and debris.
He said it was a “once in a lifetime honour” to have the dinosaur named after him.
“I’m a retired chemist, but I’ve always been interested in most of the science disciplines,” Mr Johnson said.
“I never thought that I would have the opportunity to actually work on fossils that could be important for palaeontologists.
“Now that I’m a museum volunteer, I’m getting the opportunity to work on a large variety of fossils and consult with top palaeontologists – it’s like a dream second career.”
Ankylosaurids are a family of four-legged herbivores with powerful tail clubs and armoured plating covering their bodies.
The species is believes to have originated in Asia up to 125 million years ago, but did not appear in the North American fossil record until 77 million years ago.
The species was announced in the scientific journal PeerJ and unveiled on exhibit at the Natural History Museum of Utah in Salt Lake City.