During the Late Cretaceous period, there was a remarkable flowering of horned dinosaurs along the coastal floodplains of western North America. Two different families—each with every imaginable combination of spikes, horns, and curls—spread across the landscape, using their headdresses to signal friends and challenge rivals.
Seventy-eight million years later, members of this ancient abundance continue to emerge, leading to the modern boom in discovery. The latest — described Thursday by a team of researchers in the journal PeerJ — is Lokiceratops rangiformis, a five-ton herbivore with spectacular, curved horns on its forehead and huge blade-like spikes on its meter-long collar.
Scientists say this is a new species and, along with others like it, suggests that the area from Mexico to Alaska was full of local dinosaur biodiversity. However, other experts say there is not enough evidence to draw such conclusions based on a single 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 Marib, Denmark.
“They saved it by buying it, so now it’s available in perpetuity for scientists to look at,” said Joseph Sertich, a paleontologist at the Smithsonian Tropical Research Institute and an author of the study. “We couldn’t write an article about a fossil that sits in a rich person’s living room and is treated like art.”
The team of researchers initially believed they were working with the remains of Medusaceratops. But as they clicked the pieces of the broken skull together, they began to notice differences.
The animal was missing its nose horn. The corners of the eyebrows 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 prominent, asymmetrical spike in the middle.
“That’s when we got really excited,” said Mark Loewen, a paleontologist at the Natural History Museum of Utah and an author of the study. “Because it was clear 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 does look 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 split in half by an inland sea. Two groups of horned dinosaurs roamed the western subcontinent of Laramidia. Chasmosaurines – the family that eventually gave rise to Triceratops – tend to be found in the southern half of the subcontinent, while centrosaurines – the family that Lokiceratops belongs to – are generally more northerly.
Lokiceratops is the fourth centrosaurine found in its Montana ecosystem.
The 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 animals that lived in Canada, Utah, or animals that lived in Utah, New Mexico,” said Dr. Loewen.
The team suggests that the dynamics may have been driven by sexual selection, with different populations of horned dinosaurs developing specific aesthetic tastes that led to explosions in the evolution of local species. In modern ecosystems, this process has led closely related parakeets to evolve different expressions while sharing ecological niches.
At the very end of the period, centrosaurines largely disappeared, and animals like Triceratops and T.rex ranged from Mexico to Canada, suggesting a much more homogeneous continent, Dr. Sertich.
“It has implications for the modern world – as we warm and change the climate, the distribution of animals changes,” he added. “Studying past climates and ecosystems and how they responded will influence our understanding of what potentially happens going forward.”
Not everyone shares this explanation or believes that animals like Lokiceratops represent distinct species. Denver Fowler, a paleontologist at the Dickinson Museum in North Dakota who was not involved in the research, said many ceratopsian species were based on limited remains, leading to the potential for over-interpretation.
The hollow eyebrow horns found in Lokiceratops, for example, are also present in the oldest adult Triceratops, he said, while the asymmetric horn tip on the collar could be of idiosyncratic genetics.
“Many of the features here could just be signs of a very mature Medusaceratops, and that would be a more conservative explanation,” said Dr. Fowler.
Dr. Fowler and some of his colleagues favor a different proposal: fewer species with more individual variation that gradually moved from Mexico to Alaska. As more fossil remains emerge, it will become clearer which differences are significant, he added.
“It’s a magnificent specimen and absolutely must be described,” said Dr. Fowler. “It really helps us flesh out the fauna.
As more remains emerge, said Dr. Sertich, the teams will be able to test whether Lokiceratops is its own species.
“I can imagine eight undescribed species emerging soon,” said Dr. Loewen. “I don’t think we have 1 percent of the true diversity of Ceratopsids that lived in North America.”