A study of Triceratops fossils at Hell Creek Formation in Montana has shown new insight into the evolution of the dinosaur species.
Researchers from Montana State University examined 50 skulls of two known Triceratops species, and based on morphological differences and placement in the strata, decided that one species transformed into the other, according to a press release issued by the university.
Paleontologists have identified two Triceratops species: Triceratops horridus and Triceratops prorsus, based on the size and and shape of the horns and skull.
The two species could have been descendants of a previous dino however, evolving as their ancestor's evolutionary tree split into two branches, according to the study.
Their study appears in the Proceedings of the National Academy of Sciences. It took researchers 15 years to come up with this finding.
John Scannella was in charge of the project and is the lead author of the paper. Co-authors were MSU graduate student Denver Fowler, paleontologist Mark Goodwin from the University of California Museum of Paleontology, Berkeley, and Regents Professor of Paleontology Jack Horner of MSU, according to the release.
Scannella and his colleagues determined 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."
The average Triceratops were 30 feet long, weighted up to 16,000 pounds, and featured a distinctive bony frill at the back of their heads, covering their neck.
Triceratops traveled the Earth towards the end of the Cretaceous Period, over a half a million years before the dinosaurs went extinct.
"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.
The point of the Hell Creek Project was to learn as much as possible about the geology, flora, and fauna of the formation so they could accurately reconstruct the environment at the end of the Cretaceous Period and the evolution of the creatures, according to the study.
"Most dinosaurs are only known from one or a handful of specimens," Scannella said. "Some dinosaurs are known from a large number of specimens, but they're often found all in one place - on a single stratigraphic horizon. The great thing about Triceratops is that there are a lot of them, and they were found at different levels of the Hell Creek Formation.
The first Triceratops skeleton was discovered in 1887. Researchers originally thought it was a buffalo skeleton, according to CNN.
Scientists at Yale gave the dino its name two years later.
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