‘Audacious’ New Species of Horned Dinosaur Discovered in Montana

She lived much of her life in pain, and with an appearance that might’ve seemed cockeyed to some.

But to paleontologists, she left behind something beautiful — a fossil that enshrines a new species of ceratopsian dinosaur that experts are describing as “boldly audacious.”

Discovered a decade ago eroding out of a hillside in Montana, the fossil includes most of the animal’s skull, hips, and legs, providing a detailed view not only of a new genus of dinosaur but also of one ancient animal’s intimate life history.

“This is a spectacular new addition to the family of horned dinosaurs that roamed western North America between 85 and 66 million years ago,” said Dr. Jordan Mallon, paleontologist with the Canadian Museum of Nature, in a press statement.

The dinosaur appeared in a stratum of earth dating back 76 million years, Mallon noted, when the windswept prairie of central Montana was a balmy floodplain.

A cast of the reconstructed skull of Spiclypeus shipporum, showing the sideways oriented horns, and the “spikes” on the margin of the frill. (Image by Martin Lipman (c) Canadian Museum of Nature)

The team that excavated the fossil — which included the land-owner who found it — affectionately named the specimen Judith, after Montana’s famously fossil-rich region known as the Judith River Formation, where she was found. [See a huge new dinosaur discovered nearby: “New Dinosaur Discovered in Montana Reveals How Duckbills Got Their Crests“]

But analysis of the fossil earned it another name as well: Spiclypeus — from the Latin words for “spiked shield.”

Judging by her appearance, Judith turned out to represent an important phase in the evolutionary development of the continent’s northern horned dinosaurs.

First, the horns over her eyes stick out laterally from the sides of her skull, an unusual look even for a ceratopsid.

What’s more, the frill that framed her face was studded with spikes, some of which curve forward, while others sprout straight out.

“In this sense, Spiclypeus is transitional between more primitive forms, in which all the spikes at the back of the frill radiate outward, and those such as Kosmoceratops in which they all curl forward,” Mallon said.

He and his team pointed out that Spiclypeus is at least the ninth genus of dinosaur to be discovered in Montana’s Judith River Formation — some of which have been found farther north, like in Alberta, but none of which appear in the fossil record to the south.

This seems to add to the growing body of evidence that northern and southern populations of dinosaurs were, for some reason, isolated from each other, left to live and evolve separately and in parallel. [Learn about the discovery of another horn-faced dinosaur, announced on the same day as Spiclypeus: “New ‘Sword-Horned’ Dinosaur Unearthed in Utah“]

But the fossil has yielded insights about the individual animal herself, as well as about dinosaur life in general at the end of the Cretaceous.

The study of Judith’s remains revealed that her left humerus, or front arm or leg bone, showed signs of arthritis and osteomyelitis, or infection of the bone tissue.

The condition appeared to have been severe enough, Mallon added, that the pain it caused likely cost Judith the use of her left front leg.

“If you look near the elbow, you can see great openings that developed to drain an infection,” Mallon said.

Artist’s illustration of Spiclypeus shipporum walking along a floodplain 76 million years ago in what is now the Judith River Formation of Montana. Studies show that the specimen’s humerus, or upper arm bone, shows signs of arthritis and bone infection. This specific dinosaur’s left forelimb was therefore probably useless for walking. (Image (c) Mike Skrepnick)

“We don’t know how the bone became infected, but we can be sure that it caused the animal great pain for years and probably made its left forelimb useless for walking.”

Despite her affliction, the layers of bone growth in the fossil indicate that she lived at least to the age of 10 before she died. [See evidence of an even grislier death: “Allosaurus Died From Stegosaur Spike to the Crotch, Wyoming Fossil Shows“]

In the end, the story of Spiclypeus adds one more chapter to the continually unfolding narrative of natural history in the Judith River Formation, Mallon said.

“It provides new evidence of dinosaur diversity during the Late Cretaceous period from an area that is likely to yield even more discoveries,” he said.

Mallon and his colleagues report their findings in the online journal PLOS One.

ResearchBlogging.orgMallon, J., Ott, C., Larson, P., Iuliano, E., & Evans, D. (2016). Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia) from the Judith River Formation (Upper Cretaceous: Campanian) of Montana, USA PLOS ONE, 11 (5) DOI: 10.1371/journal.pone.0154218

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