Researchers have recently gained new insight into the evolution of the Triceratops after excavating bones from the Hell Creek Formation in the badlands of Eastern Montana.
The research team recorded the precise stratigraphic information for each of about 50 Triceratops and analyzed the morphological details of it skull, Montana State University reported. Stratigraphy looks at layers of rocks.The research was published in the June 30 issue of the journal Proceedings of the National Academy of Sciences (PNAS).
Over about two million years at the end of the Cretaceous Period Triceratops went from having a small nasal horn with a long beak (Triceratops horridu) to a shorter one with a longer beak (Triceratops prorsus). Triceratops prorsus was believed to have only been found near the top of the Hell Creak Formation. Skulls found in the center of the formation showed characteristics of both Triceratops horridus and Triceratops prorsus.
"This study provides a detailed look at shifts in the morphology of a single dinosaur genus over time," Montana State University doctoral candidate John Scannella said.
The team worked to learn as much about the ancient environment as possible. They found the Triceratops were the most abundant dinosaurs in the region at the end of the Cretaceous Period.
"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. So we can compare Triceratops found at different levels," he said. "When you have a larger sample size, you can learn much more about variation, growth and evolution."
The team also found the Triceratops' horn changed shaped as it grew from youth to adult. This change was more dramatic than researchers had previously estimated.
"The study emphasized how important it is to know exactly where dinosaur fossils are collected from," Scannella said. "A beautiful Triceratops without detailed stratigraphic data cannot answer as many questions as a fragmentary specimen with stratigraphic data."
