Oldest Horned Dinosaur in North America Discovered in Montana

Aquilops horned dinosaur

The oldest known species of horned dinosaur in North America has been identified from a fossil skull no larger than your fist.

Although it’s a distant relative of the great horned beasts that browsed the Ancient West, like Triceratops, it bears little resemblance to them.

Instead, it was no larger than a common bird, with a spiky frill framing its small face, and the sharpest cheekbones you’ve ever seen.

But of greater interest to paleontologists, the newly identified species — named Aquilops americanus, or “American eagle face” — bears striking similarities to dinosaurs found half a world away, in China and Mongolia.

Discovered in Montana mudstone that dates back some 108 million years, Aquilops is the continent’s first horned-faced dinosaur from the Early Cretaceous period, which lasted from about 145 million to 100 million years ago. [Read about another recent discovery made nearby: “New Species of Horned Dinosaur With Flashy, Butterfly-Shaped Frill Discovered in Montana“]

aquilops dinosaur skull
Skull of the newly identified dinosaur Aquilops. (Photo by Scott Nichols, copyright Raymond M. Alf Museum of Paleontology)

“We’ve known from fragmentary teeth and bones that some kind of horned dinosaur lived in North America during the Early Cretaceous,” said Dr. Andrew Farke, paleontologist with the Raymond M. Alf Museum of Paleontology, in an interview.

“But, because the finds were so incomplete, nobody had any real clear idea of what these animals looked like or if they were ancestral to later horned dinosaurs that lived in North America.”

The discovery of Aquilops provides crucial data about the evolutionary ties between the very earliest horned dinosaurs, or ceratopsians, which arose in Asia more than 150 million years ago, and the large, lumbering American types like Triceratops, which thrived until the extinction of non-avian dinosaurs 66 million years ago.

Aquilops lived 40 million years before Triceratops, and nearly 20 million years before Zuniceratops,” Farke said.

“In terms of evolutionary relationships, Aquilops is best termed as a ‘distant cousin’ of Triceratops,” he added.

“It wasn’t a direct ancestor of these animals, but was a side-branch on the ceratopsian family tree.”

For sure, there would have been no mistaking 10-ton Triceratops for this diminutive dinosaur, which likely measured just over a half-meter (2 feet) in length and weighed around 1.5 kilograms (3.5 pounds).

“This is roughly the same size as a raven,” Farke noted.

But despite its modest size, Aquilops was nonetheless a distinctive member of the ceratopsian family, with a strongly hooked beak-like mouth and long, sharp, bony protrusions over each cheek.

These and other features suggest a close evolutionary link to the earlier horned dinosaurs of Asia, Farke said.

“The skull of Aquilops — which is all we have — looks very similar to that of Asian ceratopsians such as Archaeoceratops and Liaoceratops,” he said.

“Unlike later horned dinosaurs such as Triceratops, Aquilops and its relatives lacked big horns over their eyes or nose, and they also had a much shorter neck frill.

Aquilops horned dinosaur picture
In one of the more adorable life reconstructions that we’ve seen, an artist’s rendering shows a human holding Aquilops, for scale. (Copyright Brian Engh, courtesy of Raymond M. Alf Museum of Paleontology)

“The more specific features that tie Aquilops to its Asian cousins include details of the teeth and the shape of the connections between individual bones of the skull.

“These are pretty subtle details, but very powerful for figuring out evolutionary relationships.”

Since Aquilops seems to be more closely related to its Asian predecessors than to the large American ceratopids that came after it, its presence in Montana 108 million years ago suggests that horned dinosaurs populated North America over many separate migrations, likely millions of years apart, Farke said.

Aquilops is so important because it tells so much about the kinds of ceratopsians that lived in North America around 108 million years ago,” he said.

“It shows that the first horned dinosaurs in North America weren’t closely related at all to later ones, such as Triceratops or Leptoceratops.

“This suggests that there were multiple waves of immigration from Asia into North America — one that brought Aquilops, and perhaps two or three more that brought later horned dinosaurs. ” [Learn about more ancient migrations: “America’s Saber-Toothed Cats Weren’t ‘Native,’ Study Finds“]

Farke and his colleagues report their findings in the online, open-access journal, PLoS One.


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  1. vicki stone

    oh, look at that cute little dino, just a baby, awwwwww. just a widdle ting, awwww

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