Triceratops Horn Evolution: a Million Year Process

The triceratops didn't always have the magnificent rack of horns that they are so well known for. The beaked dinosaur once sported a longer beak and shorter horns, but over the course of evolution it developed a more impressive and deadly display, according to a recent study.

The study, published in the journal Proceedings of the National Academy of Science (PNAS), details the results of a 15 year excavation of triceratops fossils in the Hell Creek Formation located in the badlands of Eastern Montana.

According to study, scientists have long struggled to determine what the relationship was between triceratops horridus - characterized by a long beak and stubby nasal horn - and triceratops prorsus - characterized by a short, thick beak with a long nasal horn.

Previous research had theorized that these might be one and the same dinosaur, with only slight differences in facial structure between males and females. Other researchers believed that they were in fact two separate branches of Triceratops that evolved from the same ancestor to adapt to different environments.

However, researchers from Montana State University and the Museum of the Rockies - which now has the largest collection of triceratops fossils in the world - claim that both these theories are incorrect.

Instead, they claim, horridus evolved into prorsus over the course of an estimated 1.5 million years.

"This study provides a detailed look at shifts in the morphology of a single dinosaur genus over time," study author John Scannella said in a statement.

According to Scannella, the Hell Creek Formation offered paleontologists a rare opportunity to observe various fossils from the same species, evenly divided by rock strata representing hundreds of thousands of years.

"Some dinosaurs are known from a large number of specimens, but they're often found all in one place - on a single stratigraphic horizon," he explained. "A beautiful Triceratops without detailed stratigraphic data cannot answer as many questions as a fragmentary specimen with stratigraphic data."

"The study emphasized how important it is to know exactly where dinosaur fossils are collected from... you can learn much more about variation, growth and evolution," Scannella added.

The study was published in PNAS on July 1.