Scientists have tracked how a popular dinosaur switched from four feet to two as it grew up.
The Psittacosaurus, or "parrot dinosaur" is known is a well-studied dinosaur, researchers have collected over 1,000 fossils from the ancient creature over time, according to a University of Bristol press release.
The team studied pieces of bone from Psittacosaurus specimens of all ages, from baby to adult.
"Some of the bones from baby Psittacosaurus were only a few millimeters across, so I had to handle them extremely carefully to be able to make useful bone sections," said Dr. Qi Zhao of the Institute for Vertebrate Paleontology in Beijing. "I also had to be sure to cause as little damage to these valuable specimens as possible."
Zhao studies two arm and two leg bone fossils from 16 different dinosaurs within different age ranges.
The scientist noticed the young dinosaurs, which were about one year old, and had long arms but short legs. This led to the belief the babies walked around on all fours. The dino's arms grew faster between the ages of one and three.
Once the Psittacosaurus reached the age of four arm growth slowed down. Then the legs had a massive growth spurt. By the time the dinosaur was full-grown, the legs were twice as long as the arms, allowing it to walk on two legs.
"This remarkable study, the first of its kind, shows how much information is locked in the bones of dinosaurs. We are delighted the study worked so well, and see many ways to use the new methods to understand even more about the astonishing lives of the dinosaurs," said Professor Xing Xu of the Beijing Institute, who supervised Zhao's thesis.
Professor Mike Benton of the University of Bristol, another thesis supervisor, said the findings gave new information on the dinosaur's evolution.
"These kinds of studies can also throw light on the evolution of a dinosaur like Psittacosaurus. Having four-legged babies and juveniles suggests that at some time in their ancestry, both juveniles and adults were also four-legged, and Psittacosaurus and dinosaurs in general became secondarily bipedal," he said.
