In the Late Cretaceous, a remarkable bloom of horned dinosaurs occurred along the coastal plains 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 mates and challenge rivals.
Seventy-eight million years later, members of that ancient plethora continue to emerge, leading to a modern explosion of 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 frill.
The researchers claim this is a new species, and with other similar species they 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 an author of the study. “We couldn’t write a paper about a fossil sitting in a rich person’s living room being treated like art.”
The team of researchers initially thought they were working with the remains of a Medusaceratops. But as they pieced together the pieces of the shattered skull, 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 getting really excited,” said Mark Loewen, a paleontologist at the Natural History Museum of Utah and one of the study’s authors. “Because it became clear that we had something new.”
Because the skull was destined for a museum in Denmark, the team named it after the Norse god Loki. “It really looks like the helmet that Loki wears,” Dr. Loewen said.
The discovery sheds light on the evolution of horned dinosaurs in North America, Dr. Sertich said. During the late Cretaceous, the continent was split in two by an inland sea. Two groups of horned dinosaurs spread across the western subcontinent of Laramidia. Chasmosaurines—the family from which Triceratops ultimately evolved—are typically found in the southern half of the subcontinent, while Centrosaurines—the family to which Lokiceratops belongs—are generally found farther 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 animals that lived in Canada in Utah, or animals that lived in Utah in New Mexico,” said Dr. Loewen.
The team suggests that the dynamics may have been driven by sexual selection, with different populations of female horned dinosaurs developing specific aesthetic tastes that caused explosions in the local evolution of species. In modern ecosystems, that process has led to closely related birds of paradise developing different 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 the climate changes, animal distributions change too,” 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 tip 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 gradually moved 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 clarify the fauna.”
As more remains emerge, teams can test whether Lokiceratops is a separate species, Dr. Sertich said.
“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.”
