In the late Cretaceous period, a remarkable bloom of horned dinosaurs occurred along the coastal floodplains of western North America. Two different families – each with every conceivable combination of spikes, horns and fringes – spread across the landscape, using their headgear to signal friends and challenge rivals.
Seventy-eight million years later, members of that ancient plethora continue to emerge, leading to a modern boom in discoveries. The latest – described Thursday by a team of researchers in the journal PeerJ — is Lokiceratops rangiformis, a five-ton herbivore with spectacular, curved brow horns and enormous, leafy spines on its meter-long collar.
The researchers claim this is a new species, and others like it suggest the area from Mexico to Alaska was full of local dinosaur biodiversity. However, other experts argue that there is not enough evidence to draw such conclusions based on one set of remains.
The skull of the dinosaur in question was discovered in 2019 by a commercial paleontologist on private property in northern Montana. It was acquired by the Museum of Evolution in Maribo, Denmark.
“They saved it by buying it, so now it’s available forever for scientists to look at,” said Joseph Sertich, a paleontologist at the Smithsonian Tropical Research Institute and author of the study. “We couldn’t write an article about a fossil sitting in a rich person’s living room being treated as art.”
The team of researchers initially thought they were working with the remains of a Medusaceratops. But as they clicked the pieces of the shattered skull together, they began to notice differences.
The animal missed a rhino. The forehead horns were hollow. Then there were the curved paddle-like horns on the back of the collar – the largest ever found on a horned dinosaur – and a distinct, asymmetrical point in the center.
“That’s when we started to get really excited,” says Mark Loewen, a paleontologist at the Natural History Museum of Utah and author of the study. “Because it became clear that we had something new.”
Because the skull was destined for a museum in Denmark, the team named the animal after the Norse god Loki. “It really looks like the helmet Loki wears,” said Dr. Loewen.
The discovery sheds light on the evolution of horned dinosaurs in North America, said Dr. Sertich. During the Late Cretaceous, the continent was divided in two by an inland sea. Two groups of horned dinosaurs spread across the western subcontinent of Laramidia. Chasmosaurines – the family that eventually gave rise to Triceratops – tend to appear in the southern half of the subcontinent, while Centrosaurines – the family to which Lokiceratops belongs – are generally found further north.
Lokiceratops is the fourth Centrosaurine found in the Montana ecosystem.
Remains of these species have not been found in other parts of North America, which fits a broader pattern of horned dinosaur diversity in the West, the researchers say.
“We don’t find any animals that lived in Canada in Utah, or animals that lived in Utah in New Mexico,” said Dr. Loewen.
The team suggests that the dynamic may have been driven by sexual selection, with different populations of female horned dinosaurs developing specific aesthetic tastes that caused explosions in the evolution of local species. In modern ecosystems, that process has led closely related birds of paradise to evolve different types of displays while sharing ecological niches.
By the end of the period, the Centrosaurines had largely disappeared, and animals like Triceratops and T.rex ranged from Mexico to Canada, indicating a much more homogeneous continent, said Dr. Sertich.
“It has implications for the modern world – as we warm and change the climate, the distribution of animals is changing,” he added. “Studying past climates and ecosystems and how they responded will influence our understanding of what may happen in the future.”
Not everyone shares this statement or believes that animals like Lokiceratops represent different species. Denver Fowler, a paleontologist at the Dickinson Museum in North Dakota who was not involved in the study, said many ceratopsian species are based on limited remains, leading to the possibility of overinterpretation.
The hollow brow horns found in Lokiceratops, for example, are also present in the oldest adult Triceratops, he said, while the asymmetrical horn peak on the frill could be a genetic quirk.
“Many of the features here could just be signs of a very adult Medusaceratops, and that would be the more conservative explanation,” said Dr. Fowler.
Dr. Fowler and some of his colleagues favor a different proposal: fewer species with more individual variation that have gradually shifted from Mexico to Alaska. As more fossil remains come to light, it will become clearer which differences are significant, he added.
“It’s a spectacular specimen and it absolutely needs to be described,” said Dr. Fowler. “It really helps us shape the wildlife.”
As more remains appear, Dr. Sertich, teams will be able to test whether Lokiceratops is its own species.
“I can think of eight undescribed species soon,” said Dr. Loewen. “I don’t think we have 1 percent of the true Ceratopsid diversity that lived in North America.”