Everyone has seen dinosaur skeletons in museums. You're not supposed to touch them, even on the outside.
Dr. Qi Zhao of the Institute for Vertebrate Paleontology in Beijing got to not only touch some, he got to section two arm and two leg bones from 16 individual dinosaurs, ranging in age from less than one year to 10 years old (fully-grown). He did the sectioning work in a special palaeohistology laboratory in Bonn.
Psittacosaurus, the 'parrot dinosaur' is known from more than 1000 specimens from the Cretaceous, 100 million years ago, of China and other parts of east Asia. The one-year-olds had long arms and short legs, and scuttled about on all fours soon after hatching. The bone sections showed that the arm bones were growing fastest when the animals were ages one to three years. Then, from four to six years, arm growth slowed down, and the leg bones showed a massive growth spurt, meaning they ended up twice as long as the arms, necessary for an animal that stood up on its hind legs as an adult.
Zhao said, "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."
Professor Xing Xu of the Beijing Institute, said, "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."
Professor Mike Benton of the University of Bristol, one of Zhao's PhD supervisors when he was at the University of Bristol, said, "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."
'Histology and postural change during the growth of the ceratopsian dinosaur Psittacosaurus lujiatunensis' by Zhao, Q., Benton, M.J., Sullivan, C., Sander, P.M., and Xu, X. was published in Nature Communications.