To see the microstructures of the bones in such fine detail, lead author Dr Fabian Knoll and his team turned to synchrotron radiation. This technology uses "very powerful X-rays that allows for the best imaging resolution using non-intrusive methods," added Chiappe.
They found that the chick’s sternum was still cartilage, not bone, which suggests it was unable to fly. The number of free caudal vertebrae also differed from other juveniles of the same clade.
Based on a few other young fossils, the ossification patterns suggest that the developmental strategies of the ancient avians were more diverse than previously thought. In particular, they varied in size and in the tempo of their skeletal maturation. The chick was found near three other species of Enantiornithes, but to which species this little baby belongs to is difficult to ascertain.
Such research, published in Nature Communications, helps build a picture of how the birds lived during this ancient era. Previous authors have argued that this group of extinct hatchlings were highly precocial – born advanced enough to feed itself soon after birth. That's compared to altricial, which is when the young are relatively helpless for a time being.
For now, the team say that the lack of bone development doesn’t indicate that it was precocial or altricial, as the line between the two is more of a spectrum.
"This new discovery, together with others from around the world, allows us to peek into the world of ancient birds that lived during the age of dinosaurs," said Chiappe. "It is amazing to realize how many of the features we see among living birds had already been developed more than 100 million years ago."