Fossils of a certain genus of dinosaur were once thought to be three different species. Recent analysis discovered the specimens actually belong to the same species, but were compressed differently during burial.
"Because of the vagaries of fossilization, no two fossils are the same," senior author Peter Dodson, professor of anatomy in Penn's School of Veterinary Medicine and professor of paleontology in the School of Arts and Sciences' Department of Earth and Environmental Science, said, according to a University of Pennsylvania press release. "Animals are alive and they die, but what's crucial in paleontology is what happens to the animals after they die."
The study focused on fossils from a genus called Psittacosaurus (parrot lizard).
Psittacosaurus had a turtle-like face. The plant-eaters walked the Earth about 120 to 125 million years ago in areas that are now Russia, China, Mongolia, and possibly Thailand.
"Meat-eaters are sexy; plant-eaters are not," Dodson said. "This isn't a flashy dinosaur. But it has an interesting feature in that it's one of the most abundant dinosaurs known to science."
Since so many examples of Psittacosaurus have been found, the team believed it was the perfect genus to use in the study.
"For example, if you have a single dachshund and a single beagle, they may appear to be different species until you found 40 dachshund-beagle mixes of various grades to examine," Brandon Hedrick, a doctoral student in the Department of Earth and Environmental Science and co-leader of the study, said.
The researchers used a technique called "three-dimensional geometric morphometrics" to make the discovery. The system employs lasers to "generate data about the shape of different specimens."
The team looked at skulls from "Psittacosaurus lujiatunensis, P. major or Hongshanosaurus houi."
Old and new technology was used to examine the ancient skulls. The team looked at the 74 fossils "the old fashioned way." They determined if the specimens had certain characteristic associated with their species.
They then used a hand-held stylus to pinpoint "56 'landmarks,' or particular anatomical locations, on each fossil and compared the relative position of those marks between specimens," according to the press release. The lasers were used as well to identify the species.
The team discovered all of the species belonged to the P. lujiatunensis group.
Twisting or crushing of the body over time led to the misidentification of the specimens.
"Our study found all of these false 'species' that are not biological species but are apparent species caused by the process of fossilization," Dodson said.
Researchers hope the study will lead to the re-examination of other fossils that may have been misclassified.
"Hopefully this will open up the paleontological community to using three-dimensional geometrics morphometrics in a variety of ways," Hedrick said. "This technique has limitless applications to understanding dinosaurs."
