Story highlights Triceratops didn't always look like the way we picture them

It took a million years for its horn to evolve

The researchers spent 15 years to come up with the finding

Researchers at the Montana State University have breaking news -- one million years in the making.

Triceratops, the three horned dinosaur, didn't always look like the famous silhouette we know and love. Its signature profile, according to newly published research, took over a million years to develop.

It took researchers 15 years to come up with this finding.

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The researchers returned year after year to one area in Montana known as The Hell Creek Formation.

There, they found enough triceratops specimens to see the development of its facial anatomy.

John Scannella headed up the project and is the lead author of the paper in the Proceedings of the National Academy of Sciences

The group compared over 50 skulls. It found that "over one to two million years at the end of the Cretaceous Period, Triceratops went from having a small nasal horn and long beak to having a long nasal horn and shorter beak."

Although not ferocious in reputation like the Tyrannosaurus Rex, Triceratops was a beast of epic proportions. Thirty feet long, weighing up to 16,000 pounds, the creatures also featured a distinctive bony frill at the back of the head, covering the neck.

Previously, the group working at Hell Creek found that as an individual creature aged, the shape of its horns and skull changed.

"The new study finds evidence that not only did Triceratops change shape over the lifetime of an individual, but that the genus transformed over the course of the end of the age of dinosaurs," Scannella said.

Triceratops roamed the Earth near the end of the Cretaceous Period, a half a million years before the dinosaurs went extinct.

The first skeleton, found in 1887, was initially mistaken for a buffalo.

A scientist at Yale gave the creature its name two years later, translating from Greek as "three horned face."