Like Babies, Dinosaurs Crawled Before Shifting to Using Two-Feet
Since animals appear to be so different from one another, discovering similarities between two species can be very shocking. In a new study, Chinese researchers, headed by Dr. Qi Zhao from the Institute for Vertebrate Paleontology in Beijing, discovered that one particular species of dinosaurs, the Psittacosaurus crawled like human toddlers before learning how to walk on their two hind legs.
The research team analyzed and studied bones that were over 100 million years old. These bones told the researchers that the baby Psittacosaurus dinosaur, also known as the parrot dinosaur, had long arms and short legs. Due to the uneven limb sizes, the baby dinosaurs would not logically be able to walk on their legs, and thus, the researchers concluded that they most likely crawled like human babies. However, this disproportionate ratio quickly shifted once the dinosaurs reached aged four and experienced a massive growth spurt in their legs. This growth spurt was not matched by one in their arms, which lead to the adult dinosaur appearance of long legs with short arms. Due to this growth, the team reasoned that after aged four, the dinosaur must have shifted from crawling on all fours to walking on two feet.
The research team, which was also composed of paleontologists from Bristol and Bonn, used biomedical analysis in conjunction with bone histology to discover how this dinosaur's limbs developed. They looked at bones from babies, juveniles and adults.
"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," Dr. Zhao explained according to The Telegraph. "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."
The findings were published in Nature Communications, titled "Histology and postural change during the growth of the ceratopsian dinosaur Psittacosaurus lujiatunensis."