BOZEMAN — Research by a Montana State University doctoral student and one of the nation’s top paleontologists is upending more than 100 years of thought regarding the dinosaurs known as triceratops and torosaurus.
Since the late 1800s, scientists have believed that triceratops and torosaurus were two different types of dinosaurs. Triceratops had a three-horned skull with a rather short frill, while torosaurus had a much bigger frill with two large holes through it.
However, in the July 14 issue of the Journal of Vertebrate Paleontology, MSU paleontologists John Scannella and Jack Horner said that triceratops and torosaurus are actually the same dinosaur at different stages of growth.
They added that the discovery contributes to an unfolding theory that dinosaur diversity was extremely depleted at the end of the dinosaur age.
The Journal of Vertebrate Paleontology is the official journal of the Society of Vertebrate Paleontology. Scannella is a doctoral student in earth sciences, and Horner is regents professor of paleontology at MSU’s Museum of the Rockies.
Scannella said the confusion over triceratops and torosaurus was easy to understand because juvenile dinosaurs weren’t just miniature versions of adults. They looked very different, and their skulls changed radically as they matured.
The triceratops study suggests that paleontologists should consider ontogeny, or growth from a juvenile to an adult, as a source of major morphological variations before naming new species of dinosaurs to account for variation between specimens, Scannella said.
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Scannella and Horner benefited from an extensive 10-year study of the Hell Creek Formation in Eastern Montana.
As part of the study, field crews collected hundreds of specimens. Forty percent of the specimens came from triceratops at different stages of growth. Some of the skulls belonged to juvenile triceratops and were about the size of footballs. Other skulls are the size of a small car.
Scannella and Horner examined more than 50 triceratops specimens for their study. More than 30 were skulls that came out of the Hell Creek Formation and are housed at the Museum of the Rockies.
The paleontologists also examined skulls from several North American institutions, including the American Museum of Natural History in New York, the National Museum of Natural History at the Smithsonian Institution in Washington, D.C., and the Peabody Museum of Natural History at Yale University in New Haven, Conn.
Scannella said he and Horner tried for three years to look for alternative explanations for their findings. They finally agreed that the triceratops and torosaurus were the same dinosaur.
Scannella said he presented his and Horner’s findings at the Society of Vertebrate Paleontology Conference in Bristol, England, and it was met with equal parts intrigue and skepticism.
“Skepticism is important and a good thing,” Scannella said. “But, so far, all the evidence we have strongly supports the idea.”