During the late Cretaceous period, a remarkable flowering of horned dinosaurs occurred in the coastal floodplains of western North America. Two different families – each sporting a fanciful combination of spikes, horns and frills – are diversified across the landscape, using their headdresses to identify mates and challenge rivals.
Seventy-eight million years later, members of that ancient horde are still changing, leading to the modern boom in discovery. The new one — described Thursday by a team of researchers In the journal PeerJ — Logiceratops rungiformis, a five-tonne herbivore with spectacular, curved brow horns and large, bladed spikes on its meter-long frill.
Researchers argue that this is a new species, and say that the region from Mexico to Alaska, along with others like it, was rich in pockets of local dinosaur biodiversity. However, other experts argue that there is insufficient evidence to draw such conclusions based on a single set of remains.
The dinosaur skull in question was discovered in 2019 by a commercial paleontologist on private land in northern Montana. It was acquired by the Museum of Evolution in Maribo, Denmark.
“They saved it by buying it, so now it’s permanently available for scientists to look at,” said Joseph Serdich, a paleontologist at the Smithsonian Tropical Research Institute and an author of the study. “We couldn’t sit in a rich man’s living room and write a paper on fossils that are considered art.”
The team of researchers initially believed they were working with the remains of a medusaceratops. But when they clicked the broken skull pieces together, they began to notice differences.
The animal does not have a nose horn. The brow ridges were hollow. At the back of the frill were curved fin-like horns – the largest ever seen on a horned dinosaur – and a distinctive, asymmetrical spike in the middle.
“That’s when we started to get excited,” said study author Mark Loewen, a paleontologist at the Utah Museum of Natural History. “Because it’s clear we have something new.”
As the skull was bound for a museum in Denmark, the team named the animal after the Norse god Loki. “It actually looks like the helmet Loki is wearing,” Dr Loewen said.
Dr Serdich said the discovery sheds light on the evolution of North America’s horned dinosaurs. In the late Cretaceous, the continent was split in two by an inland sea. Two groups of horned dinosaurs lived in the western subcontinent of Laramidia. Chasmosaurines – the family from which Triceratops eventually evolved – appear in the southern part of the subcontinent, while centrosaurines – the family Loiceratops belongs to – are generally more northerly.
Logiceratops is the fourth centrosaurine to be discovered from its Montana ecosystem.
Remains of these species are not found in other parts of North America, matching the broader pattern of horned dinosaur diversity in the West, the researchers say.
“We haven’t found animals that lived in Utah in Canada, or animals that lived in Utah in New Mexico,” Dr. Lowen said.
The team suggests that different populations of female horned dinosaurs may have been driven by dynamic sexual selection, as different populations of female horned dinosaurs developed specific aesthetic tastes, causing bursts in local species evolution. In modern ecosystems, that process has led to the creation of different scenarios when closely related birds of paradise share ecological importance.
By the end of the period, the centrosaurines had largely disappeared, and Triceratops and D. Rex-like animals ranged from Mexico to Canada, suggesting a more homogeneous continent, Dr Serdich said.
“This 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 have adapted is going to affect our understanding of the possibilities going forward.”
Not everyone shares this interpretation or believes that animals like Logiceratops 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 are based on limited remains, leading to the potential for over-interpretation.
For example, hollow brow horns found in Logiceratops are also present in primitive mature triceratops, while the asymmetrical horn spike may be a genetic quirk, he said.
“Many of the features here could be signs of a very mature Medusaceratops, and that would be a very conservative interpretation,” Dr Fowler said.
Dr. Fowler and some of his colleagues support another proposal: that fewer species with individual variation gradually migrated from Mexico to Alaska. As more fossil remains come to light, it will become clear which differences are significant, he said.
“This is a fascinating specimen that absolutely needs to be described,” Dr. Fowler said. “It really helps drive out the fauna.”
As more remains emerge, Dr. Serdich said, teams will be able to test whether Logiceratops was its own species.
“I can think of eight undescribed species coming soon,” Dr Lowen said. “I don’t think we have 1 percent of the true ceratopsid diversity that lived in North America.”
