Dinosaurs crawled on all fours like toddlers before switching to two feet when they grew up, experts have discovered.
Analysis of bones 100 million years old showed baby Psittacosaurus had long arms and short legs, which were used to scuttle around shortly after hatching.
The arms grew quickly between the ages of one and three, suggesting that the Psittacosaurus continued to move on all fours during their ‘toddler’ years.
But aged four, Psittacosaurus – known as the ‘parrot dinosaur’ – experienced a massive growth spurt in their legs, while development of their arms slowed. This meant legs grew to twice the size of arms and the dinosaur spent its adult life on two feet.
Palaeontologists from Beijing, Bristol and Bonn carried out the intricate study on the bones of babies, juveniles and adults.
Dr Qi Zhao, who conducted the research as part of his PhD thesis at the University of Bristol, 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.”