New research shows that the "parrot" dinosaur started life crawling on four legs, then moved to two as it grew-much like a human.

New research from Bonn, Bristol, and Berlin has startling findings. The researchers used bio-mechanical analysis and bone histology to demonstrate how the "parrot" dinosaur, Psittacosaurus, moved from four legs to two as it aged.

"These kinds of studies can throw light on the evolution of a dinosaur like Psittacosaurus," said Professor Mike Benton of the University of Bristol, Zhao's PhD supervisor. "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."

Studying ancient, extinct creatures like dinosaurs as they grew throughout the life cycle is difficult.  But the new research published in the journal Nature Communications gives innovative clues. Baby, juvenile, and adult bones were studied-and the results mimic humans in surprising ways.

There have been over 1,000 specimens of psittacosaurus, the 'parrot dinosaur'. It lived during the Cretaceous, 100 million years ago, mostly in China and surrounding areas of East Asia. Qi Zhao led the study as part of his PhD thesis.

A paleontology laboratory in Bonn, Germany sectioned arms and leg bones from sixteen different dinosaurs. They ranged in age from one year to adult, or about ten years old.

The head researcher, Dr. Zhao, told press, "Some of the bones from baby Psittacosaurus were only a few millimetres across, so I had to handle them extremely carefully to be able to make useful bone sections. I also had to be sure to cause as little damage to these valuable specimens as possible."

The one-year-old dinosaurs had relatively long arms and short legs. They moved around on all fours, like a toddler. Later, though, the arm growth slowed; leg bones showed a growth spurt, eventually ending up twice as long as the arms. And, as the legs grew, the parrot dinosaur stood up and walked on two legs, like a human.

"This remarkable study, the first of its kind, shows how much information is locked in the bones of dinosaurs," said Professor Xing Xu of Beijing Institute, another one of Zhao's PhD supervisors. "We are delighted the study worked so well, and see many ways to use the new method to understand even more about the astonishing lives of dinosaurs."