science

New horned dinosaur found in US was ancestor to triceratops, paleontologists say


Paleontologists in the US have discovered a new species of horned dinosaur which was an ancestor to the triceratops and lived in New Mexico 82 million years ago.

The species comes from a group of herbivorous rhinoceros-like dinosaurs known as the ceratopsid species, which generally lived in herds and are characterised by horns and frills and beaked faces.

The newly described species – Menefeeceratops sealeyi – adds important information to scientists’ understanding of the evolution of ceratopsid dinosaurs, as it is now the oldest member of the group.

The fossilised remains of the dinosaur were found in rocks known as the Menefee Formation in northwestern New Mexico in 1996 by Paul Sealey, a research associate of the New Mexico Museum of Natural History and Science. New research has revealed the fossils as a previously unknown species.

“There has been a striking increase in our knowledge of ceratopsid diversity during the past two decades,” said Peter Dodson from the University of Pennsylvania, who specialises in the study of horned dinosaurs.

“Much of that has resulted from discoveries farther north, from Utah to Alberta.

“It is particularly exciting that this find so far south is significantly older than any previous ceratopsid discovery.”

He added: “It underscores the importance of the Menefee dinosaur fauna for the understanding of the evolution of late cretaceous dinosaur faunas throughout western North America.”

Menefeeceratops is related to but predates the triceratops, another ceratopsid dinosaur. However menefeeceratops was a relatively small member of the group, growing to around 13 to 15 feet (3 – 4.5 metres) long, compared to triceratops, which could grow to up to 30 feet (9 metres) long and up to 10 feet (3 metres) tall.

Although bones of the entire dinosaur were not recovered, a significant amount of the skeleton was preserved, including parts of the skull and lower jaws, forearm, hindlimbs, pelvis, vertebrae, and ribs.

The research team said the bones not only show the animal is unique among known dinosaur species but also they provide additional clues to this individual dinosaur’s life history. For example, the fossils show evidence of a potential pathology, resulting from a minor injury or disease, on at least one of the vertebrae near the base of its spinal column.

One of the key features which distinguish menefeeceratops from other horned dinosaurs is the bone which makes up the sides of the dinosaur’s frill, known as the squamosal. While less ornate than those of some other ceratopsids, Menefeeceratops’ squamosal has a distinct pattern of concave and convex parts.

By analysing the features the fossils revealed with other known ceratopsid dinosaurs, the team was able to trace the dinosaur’s evolutionary relationships.

They said menefeeceratops was at the base of the evolutionary tree of the centrosaurines subfamily, suggesting not only that the species is one of the oldest known centrosaurine ceratopsids, but also one of the most basal evolutionarily.

“Menefeeceratops was part of an ancient ecosystem with numerous other dinosaurs, including the recently recognised nodosaurid ankylosaur invictarx and the tyrannosaurid dynamoterror, as well as hadrosaurids and dromaeosaurids,” the researchers said.

“Menefeeceratops was part of a thriving cretaceous ecosystem in the southwestern United States with dinosaurs that predated a lot of the more well-known members closer to the end of the Cretaceous,” said Steven Jasinski of the University of Pennsylvania, who was a co-author of the study.

While relatively less work has been done collecting dinosaurs in the Menefee Formation to date, the researchers hope that more field work and collecting in these areas, together with new analyses, will turn up more fossils of Menefeeceratops and ensure a better understanding of the ancient ecosystem of which it was part.

The research is published in the journal PalZ.



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