Ceratopsia is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier,

A Curious Ceratopsian
The ceratopsians, or horned dinosaurs, were one of the most diverse and successful of the dinosaur groups. Dozen of species roamed across North America during the Late Cretaceous Period, and new species are still being discovered. When a new skeleton was discovered in 2007, there wasn’t much fanfare – until paleontologists realized they had been tricked! This new skeleton represented a previously unknown species of horned dinosaur. And thus began the story of Medusaceratops lokii.

“Loki’s Horned Face Medusa” was discovered in a bonebed in Montana, only a few miles from the border of Alberta, Canada. The bones were initially thought to be from Albertaceratops, another horned dinosaur from the same time and place. The “discovery” of Medusaceratops did not occur until the bones had been excavated, prepared, and mounted as a full skeleton.

Ceratopsians are easily recognized by features of the skull. On the tip of a ceratopsian upper jaw is the rostral bone, an edentulous (toothless) ossification, unique to ceratopsians. Othniel Charles Marsh recognized and named this bone, which acts as a mirror image of the predentary bone on the lower jaw. This ossification evolved to morphologically aid the mastication of plant matter. Along with the predentary bone, which forms the tip of the lower jaw in all ornithischians, the rostral forms a superficially parrot-like beak. Also, the jugal bones below the eye are very tall and flare out sideways, making the skull appear somewhat triangular when viewed from above. This triangular appearance is accentuated in later ceratopsians by the rearwards extension of the parietal and squamosal bones of the skull roof, to form the neck frill.

Medusa’s Headress
It was the shape and robustness of the unusual frill that gave Michael Ryan, Ph.D. (the scientist who described Albertaceratops) the idea that this new skeleton was a new species; the specimens of Albertaceratops were smaller and not as heavily built as this new skeleton. This led to the reevaluation of the skeleton that would soon be renamed as Medusaceratops.

Confusing headgear
The distinctive, curved appendages on the frill of Medusaceratops. These strange features inspired the genus name for this new species – they inspired images of the Greek monster Medusa, who has a head covered in snakes. Many dinosaurs are named for unique skeletal features. The species name – lokii – refers to the Marvel Comics’s character Loki, God of Mischief, since this specimen was deceptively similar to Albertaceratops.

Horn and Bone
The horn core of Medusaceratops. The horns of the ceratopsians were solid bone, covered with a layer of keratin, the same material that makes up human hair and fingernails. The horn core is two feet long, but the horn itself was probably over three feet in length. Medusaceratops had one horn over each eye, resembling its more famous cousin – and possible descendant – Triceratops.

Quite the bite
The mandible – lower jaw – of Medusaceratops. All ceratopsians had very powerful jaws, unusually strong for herbivorous animals. They used the jaws and bladed teeth to eat a wide variety of tough vegetation. Since they had had the ability to eat such a variety of plant life, the ceratopsians flourished in the Cretaceous; several different species of horned dinosaur lived alongside Medusaceratops.

This scientific drawing provides a interpretation of what Medusaceratops might have looked like in the flesh. The elaborate headgear of the ceratopsians has been the subject of scientific debate. At first, they were believed to be defensive weapons, used to ward off the likes of Tyrannosaurus and its relatives. Now, paleontologists believe they served a less violent purpose – to compete for mates, and to tell each other apart in a crowd. After all, there were dozens of ceratopsian species in the Late Cretaceous.

Odd horns
Many ceratopsians had very odd ornamentation. Einiosaurus, another ceratopsian from Montana, had a forward – facing curved horn. This would not have been much of a weapon if attacked. This strange headgear strengthens the argument the horns and frills of ceratopsians – like Einiosaurus and Medusaceratops – were more for display than defense.

Family Tree
Triceratops and Medusaceratops are both chasmosaurines, a subgroup within the ceratopsians. Medusaceratops is the oldest known chasmosaurine in the fossil record, meaning Triceratops may be its direct descendant. Future discoveries and analysis of Medusaceratops may prove this family connection.

The skeleton of Medusaceratops. “Mary” is about 70% complete – a high percentage for a 75 million year old skeleton. Many dinosaur species are known from only a few fragments of bone.

The reconstructed frill and horns. In order to mount a complete skeleton, missing bones are sculpted and assembled with the real bones. All the bones of the skull are sculptures or casts of real bone.

All ceratopsians had powerful jaws with strong teeth – but teeth only in the back of the jaws. The powerful beak at the front was used to cut vegetation, so the teeth could process it further.

The frill was not only for display. Powerful neck muscles attached to the back of the skull to help move the massive head. Along the edges, muscles helped the powerful jaws process vegetation.

The post cranial bones of ceratopsians (bones from the body) are so similar, it is very difficult to tell different species apart. This is my most ceratopsians are described by their unique skulls.

Medusaceratops was not a speed demon; the legs and hips are designed for strength, helping to propel the animal forward. What it lack in speed, it made up for with strength.

Most dinosaurs had long tails for balance, but ceratopsian tails are comparatively short. This is because ceratopsians were so solidly supported by their four powerful legs.

The size of Medusaceratops is intriguing. It is quite a bit larger than the other ceratopsians in its environment – and larger herbivores mean larger, as of yet unknown carnivores . . .

Ongoing Investigation
Despite the initial trickery, Medusaceratops has finally come to light, after 75 million years buried in the badlands of Montana. But, just like any great scientific discovery, answering one big question leads to several new questions. Why was it so large? Was it the ancestor of Triceratops? Scientific research on this specimen will continue to seek for those answers. Medusaceratops has already provided many insights into the anatomy and life of the ceratopsians, and the world in which they lived. There are still many secrets preserved in this skeleton.