Paleontologists have identified a new genus and species of centrosaurine dinosaur from the fossilized remains found in the Judith River Formation in the Kennedy Coulee region, Montana, the United States. Named Lokiceratops rangiformis, the new species appeared at least 12 million years earlier than its famous cousin Triceratops and was the largest horned dinosaur of its time.
Reconstruction of Lokiceratops rangiformis surprised by a crocodilian in the 78-million-year-old swamps of northern Montana. Image credit: Andrey Atuchin / Museum of Evolution in Maribo, Denmark.
Lokiceratops rangiformis lived in what is now Montana during the Cretaceous period, some 78 million years ago.
This species was around 6.7 m (22 feet) long and weighed 5 tons, making it the largest dinosaur from the group of horned dinosaurs called Centrosaurinae ever found in North America.
“Within the dinosaur ecosystems of the ancient island continent Laramidia, the Ceratopsidae were geographically widespread and morphologically diverse, possessing highly variable cranial ornaments including horns and morphologically diverse parietosquamosal frills,” said University of Utah’s Professor Mark Loewen and his colleagues.
“Two distinct clades within Ceratopsidae diverged by at least 83 million years ago.”
“These are the long-nosed, long-frilled Chasmosaurinae and the round-nosed, relatively short-frilled Centrosaurinae.”
“Centrosaurinae represent an ecologically important and diverse radiation of ceratopsids, reaching peak diversity in the Campanian, between 83 and 70 million years ago.”
“Historically known from abundant remains in Alberta, Canada and Montana, the United States, discoveries over the past two decades have rapidly expanded our understanding of the group, particularly its geographic and morphologic breadth, with additional insights into centrosaurine ontogeny.”
“Though locally abundant in some localities in southern Alberta and northern Montana, centrosaurines were previously rare or poorly known from other regions of Laramidia.”
Fossil skull bones of Lokiceratops rangiformis. Image credit: Museum of Evolution in Maribo, Denmark.
The paleontologists discovered an associated skeleton of a mature individual of Lokiceratops rangiformis in 2019 in the Loki Quarry, which is part of the Judith River Formation.
“The Loki Quarry producing the new specimen lies on private land in the badlands of Kennedy Coulee, north of the town of Rudyard in Hill County, northern Montana, the United States, they said.
Lokiceratops rangiformis had the largest frill horns ever seen on a horned dinosaur and lacks the nose horn that is characteristic among its kin.
“This new dinosaur pushes the envelope on bizarre ceratopsian headgear, sporting the largest frill horns ever seen in a ceratopsian,” said Colorado State University paleontologist Joseph Sertich.
“These skull ornaments are one of the keys to unlocking horned dinosaur diversity and demonstrate that evolutionary selection for showy displays contributed to the dizzying richness of Cretaceous ecosystems.”
“We think that the horns on these dinosaurs were analogous to what birds are doing with displays. They’re using them either for mate selection or species recognition.”
Lokiceratops rangiformis co-existed with three other centrosaurine dinosaurs (Wendiceratops pinhornensis, Albertaceratops nesmoi, and Medusaceratops lokii) and one chasmosaurine (Judiceratops tigris).
“It’s unheard-of diversity to find five living together, similar to what you would see on the plains of East Africa today with different horned ungulates,” Dr. Sertich said.
“Unlike the broad range of large wild mammals that roam the U.S. West today, such as elk, these ancient animals were geographically limited.”
“The discovery of Lokiceratops rangiformis provides evidence that these species evolved rapidly within a small area, a process sometimes seen in birds. “
“By the time Triceratops came onto the scene 12 million years later, regional differences had been homogenized into just two species of horned dinosaurs from Canada to Mexico — possibly in response to a more homogenous climate.”
“The study shows that dinosaur diversity has been underestimated and presents the most complete family tree of horned dinosaurs to date.”
“Lokiceratops rangiformis helps us understand that we only are scratching the surface when it comes to the diversity and relationships within the family tree of horned dinosaurs,” Professor Loewen said.
The study was published online in the journal PeerJ.
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M.A. Loewen et al. 2024. Lokiceratops rangiformis gen. et sp. nov. (Ceratopsidae: Centrosaurinae) from the Campanian Judith River Formation of Montana reveals rapid regional radiations and extreme endemism within centrosaurine dinosaurs. PeerJ 12: e17224; doi: 10.7717/peerj.17224
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